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1.	Felton, Adam, et al. (author) Keeping pace with forestry : Multi-scale conservation in a changing production forest matrix 2020 In: Ambio. - : Springer. - 0044-7447 .- 1654-7209. ; 49:5, s. 1050-1064 Journal article (peer-reviewed)abstract The multi-scale approach to conserving forest biodiversity has been used in Sweden since the 1980s, a period defined by increased reserve area and conservation actions within production forests. However, two thousand forest-associated species remain on Sweden's red-list, and Sweden's 2020 goals for sustainable forests are not being met. We argue that ongoing changes in the production forest matrix require more consideration, and that multi-scale conservation must be adapted to, and integrated with, production forest development. To make this case, we summarize trends in habitat provision by Sweden's protected and production forests, and the variety of ways silviculture can affect biodiversity. We discuss how different forestry trajectories affect the type and extent of conservation approaches needed to secure biodiversity, and suggest leverage points for aiding the adoption of diversified silviculture. Sweden's long-term experience with multi-scale conservation and intensive forestry provides insights for other countries trying to conserve species within production landscapes.
2.	Hultberg, Tove, et al. (author) The late-Holocene decline of Tilia in relation to climate and human activities - pollen evidence from 42 sites in southern Sweden 2017 In: Journal of Biogeography. - : Wiley. - 0305-0270 .- 1365-2699. ; 44:10, s. 2398-2409 Journal article (peer-reviewed)abstract Aim: The dominant role of Tilia in primeval forests of Scandinavia has long been recognized, but the timing and mechanisms for its decline have not been completely unravelled. A particular uncertainty involves the balance between climate and human activities as the drivers of the change. One reason for the uncertainty is the challenge in evaluating the past cover of the genus owing to its poorly dispersed pollen; another is that a multi-site study would be required to trace subregional differences. To overcome these obstacles, we here apply two different analytical methods to pollen data from 42 sites in two distinct vegetation zones of Sweden. Location: Temperate and hemi-boreal vegetation zones of southern Sweden. Methods: Generalized additive mixed models (GAMM) were used to model the development of Tilia and cereal pollen percentages over time. Twelve sites were used for reconstruction of local cover of Tilia using the landscape reconstruction algorithm (LRA). Results: Before 4000 cal. bp the Tilia mean pollen percentages were similar in the two vegetation zones. Thereafter, values in the hemi-boreal zone declined, with less Tilia since around 3000 cal. bp. In contrast, Tilia did not decrease in the temperate zone until this past millennium. The LRA application revealed that in some forests a large cover of Tilia remained considerably longer than has traditionally been estimated by pollen percentages alone. Main conclusions: By using a large coherent dataset we found significant differences in how the abundance and distribution of Tilia changed through time between two adjacent vegetation zones. We interpret the initial decline in the northern hemi-boreal zone to be driven by cooling climate, and the later decline in the southern temperate zone to be driven more by human land-use.
3.	Brunet, Jörg, et al. (author) Bumblebees mediate landscape effects on a forest herb's population genetic structure in European agricultural landscapes 2024 In: Ecology and Evolution. - 2045-7758. ; 14 Journal article (peer-reviewed)abstract Spatially isolated plant populations in agricultural landscapes exhibit genetic responses not only to habitat fragmentation per se but also to the composition of the landscape matrix between habitat patches. These responses can only be understood by examining how the landscape matrix influences among-habitat movements of pollinators and seed vectors, which act as genetic linkers among populations. We studied the forest herb Polygonatum multiflorum and its associated pollinator and genetic linker, the bumblebee Bombus pascuorum, in three European agricultural landscapes. We aimed to identify which landscape features affect the movement activity of B. pascuorum between forest patches and to assess the relative importance of these features in explaining the forest herb's population genetic structure. We applied microsatellite markers to estimate the movement activity of the bumblebee as well as the population genetic structure of the forest herb. We modelled the movement activity as a function of various landscape metrics. Those metrics found to explain the movement activity best were then used to explain the population genetic structure of the forest herb. The bumblebee movement activity was affected by the cover of maize fields and semi-natural grasslands on a larger spatial scale and by landscape heterogeneity on a smaller spatial scale. For some measures of the forest herb's population genetic structure, that is, allelic richness, observed heterozygosity and the F-value, the combinations of landscape metrics, which explained the linker movement activity best, yielded lower AICc values than 95% of the models including all possible combinations of landscape metrics.Synthesis: The genetic linker, B. pascuorum, mediates landscape effects on the population genetic structure of the forest herb P. multiflorum. Our study indicates, that the movement of the genetic linker among forest patches, and thus the pollen driven gene flow of the herb, depends on the relative value of floral resources in the specific landscape setting. Noteworthy, the population genetic structure of the long-lived, clonal forest herb species correlated with recent land-use types such as maize, which have been existing for not more than a few decades within these landscapes. This underscores the short time in which land-use changes can influence the evolutionary potential of long-lived wild plants.Bumblebees can connect isolated populations of forest herbs within agricultural landscapes by moving between forest patches. These movements are influenced by specific aspects of the landscape. These same landscape aspects also partly explain the population genetic structure of a forest herb species associated with bumblebees as pollinators.image
4.	Brunet, Jörg, et al. (author) Disturbance of the herbaceous layer after invasion of an eutrophic temperate forest by wild boar 2016 In: Nordic Journal of Botany. - : Wiley. - 0107-055X. ; 34, s. 120-128 Journal article (peer-reviewed)abstract Disturbances of the soil and the tree canopy are crucial factors determining the diversity, composition and biomass of the herbaceous layer in forests. This study presents a detailed account of ground vegetation in permanent plots surveyed before and after invasion of wild boar (Sus scrofa) to a temperate deciduous broadleaf forest. Specifically, we aimed to quantify the effect of wild boar rooting on cover, richness and composition of spring ephemerals, summer green herbs and saplings of woody species in relation to tree canopy cover. Rooting frequency in sample plots increased from 0% in 2010 to 61% in 2013. In heavily rooted plots, the mean cover of spring ephemeral geophytes (mainly Anemone nemorosa, A. ranunculoides and Ranunculus ficaria) decreased from 75% to 39% between 2010 and 2013. Species richness of summer green herbs generally increased between 2010 and 2013 and was additionally positively affected by heavy rooting and low canopy cover. Rooting also caused heterogenization of the herbaceous layer and amplified ongoing compositional changes induced by changing light conditions. Frequency and richness of spring ephemeral and woody species remained unchanged. We conclude that overall species richness of the herbaceous layer may increase in the short-term as a result of increased plant recruitment and seed dispersal. However, wild boar rooting can greatly reduce the ground cover of spring ephemerals in eutrophic broadleaf forests, thereby threatening their important ecological function. To avoid long-term losses of characteristic spring flora elements, local population control of wild boar is necessary to reduce abundance and frequency of soil rooting.
5.	Brunet, Jörg, et al. (author) Immigration credit of temperate forest herbs in fragmented landscapes—Implications for restoration of habitat connectivity 2021 In: Journal of Applied Ecology. - : Wiley. - 0021-8901 .- 1365-2664. ; 58:10, s. 2195-2206 Journal article (peer-reviewed)abstract In many agricultural landscapes, it is important to restore networks of forests to provide habitat and stepping stones for forest specialist taxa. More knowledge is, however, needed on how to facilitate the immigration of such taxa in restored forest patches. Here, we present the first chronosequence study to quantify the dynamics of immigration credits of forest specialist plants in post-arable forest patches.We studied the distribution of herbaceous forest specialist plant species in 54 post-arable broadleaved forest patches along gradients of age (20–140 years since forest establishment), distance from ancient forest (0–2,600 m) and patch area (0.5–9.6 ha). With linear mixed models, we estimated the effects of these factors on species richness, patch means of four dispersal-related plant traits and with generalized linear models on the occurrence of 20 individual species.Post-arable forest patch age and spatial isolation from ancient forest, but not patch size, were important predictors for species richness of forest specialists, suggesting that also small patches are valuable for habitat connectivity. Compared to species richness in ancient forest stands, the immigration credit was reduced by more than 90% after 80 years in post-arable forest patches contiguous to ancient forest compared to 40% after 80 years and 60% after 140 years in isolated patches (at least 100 m to next forest). Tall-growing species with adaptations to long-distance dispersal were faster colonizers, whereas species with heavy diaspores and clonal growth were slower to colonize.Synthesis and applications. We show that post-arable oak plantations have a high potential for restoration of forest herb vegetation. Dispersal-related plant traits play a key role in explaining interspecific differences among forest specialists. To facilitate forest herb immigration across all functional groups in agricultural landscapes, we suggest to create clusters of relatively small new forest patches nearby older forest with source populations.
6.	Brunet, Jörg, et al. (author) Klimatförändringar, kvävenedfall och skogsbruk : effekter på floran i Sveriges skogar under de senaste 20 åren 2015 In: Fakta. Skog. - 1400-7789. Other publication (pop. science, debate, etc.)
7.	Brunet, Jörg, et al. (author) Pathogen induced disturbance and succession in temperate forests: Evidence from a 100-year data set in southern Sweden 2014 In: Basic and Applied Ecology. - : Elsevier BV. - 1439-1791 .- 1618-0089. ; 15, s. 114-121 Journal article (peer-reviewed)abstract Major tree species arc declining in many temperate forests due to changing disturbance regimes, including invasive pests and pathogens. We examined the interaction of secondary succession and Dutch elm disease in the Swedish temperate forest reserve Dal by Soderskog, based on five tree surveys made between 1909 and 2011. The forest is characterized by the coexistence of four major European tree species: wych elm (Ulmm glabra), European ash (Fraxinus excelsior), European beech (Fagus sylvotica) and pedunculate oak (Quercus robur). After protection of the forest in 1918, lack of disturbance mainly favoured elm, while the oak population declined due to mortality of old oaks and lack of regeneration. Dutch elm disease has caused high and continuous elm mortality since 1988. As a result, increased light availability at the forest floor favoured abundant regeneration of ash, beech, and lately also oak. The recent arrival of an invasive fungal pathogen causing ash dieback may once again change the course of succession. Open space emerging from loss of elm and ash in forest reserves may be used by reserve managers in favour oak regeneration and biodiversity of semi-open woodlands once lost during succession to closed forest. We conclude that winners and losers change places as an effect of invasive pathogens, resulting in unexpected successions and both losses, id gains in valuable ecological niches and habitat structures in temperate broadleaf forests,
8.	Brunet, Jörg, et al. (author) Pollinator movement activity influences genetic diversity and differentiation of spatially isolated populations of clonal forest herbs 2022 In: Frontiers in Ecology and Evolution. - : Frontiers Media SA. - 2296-701X. ; 10 Journal article (peer-reviewed)abstract In agricultural landscapes, forest herbs live in small, spatially isolated forest patches. For their long-term survival, their populations depend on animals as genetic linkers that provide pollen- or seed-mediated gene flow among different forest patches. However, whether insect pollinators serve as genetic linkers among spatially isolated forest herb populations in agricultural landscapes remains to be shown. Here, we used population genetic methods to analyze: (A) the genetic diversity and genetic differentiation of populations of two common, slow-colonizing temperate forest herb species [Polygonatum multiflorum (L.) All. and Anemone nemorosa L.] in spatially isolated populations within three agricultural landscapes in Germany and Sweden and (B) the movement activity of their most relevant associated pollinator species, i.e., the bumblebee Bombus pascuorum (Scopoli, 1,763) and the hoverfly Melanostoma scalare (Fabricus, 1,794), respectively, which differ in their mobility. We tested whether the indicated pollinator movement activity affected the genetic diversity and genetic differentiation of the forest herb populations. Bumblebee movement indicators that solely indicated movement activity between the forest patches affected both genetic diversity and genetic differentiation of the associated forest herb P. multiflorum in a way that can be explained by pollen-mediated gene flow among the forest herb populations. In contrast, movement indicators reflecting the total movement activity at a forest patch (including within-forest patch movement activity) showed unexpected effects for both plant-pollinator pairs that might be explained by accelerated genetic drift due to enhanced sexual reproduction. Our integrated approach revealed that bumblebees serve as genetic linkers of associated forest herb populations, even if they are more than 2 km apart from each other. No such evidence was found for the forest associated hoverfly species which showed significant genetic differentiation among forest patches itself. Our approach also indicated that a higher within-forest patch movement activity of both pollinator species might enhance sexual recruitment and thus diminishes the temporal buffer that clonal growth provides against habitat fragmentation effects.
9.	Brunet, Jörg, et al. (author) Små lövskogars betydelse i jordbrukslandskapet 2019 Reports (other academic/artistic)abstract I svenska jordbrukslandskap finns en varierande mängd restbiotoper medmer eller mindre naturlig vegetation, som små våtmarker, gräsmarker ellerlövskogar.För att kunna utveckla fungerande ekologiska nätverk, grön infrastruktur,i våra jordbrukslandskap behöver vi förstå funktionen av och samspeletmellan småbiotoper bättre. Vi behöver veta om olika arter kan användaisolerade restbiotoper som spridningsöar (stepping stones) eller om vi behöverskapa sammanhängande nätverk av livsmiljöer. Inom detta projekt har vistuderat kärlväxtfloran, med fokus på fältskiktet, och flera grupper av denmarklevande faunan i små lövskogar i fyra svenska jordbrukslandskap medvarierande naturförhållanden, Skabersjö och Västerstad i Skåne, samt Selaönoch Tobo i Sörmland. Vi har särskilt fokuserat på hur markanvändningshistoriaoch fragmenteringen av livsmiljöer har påverkat mångfalden avkärlväxteroch jordlöpare.Kärlväxter bygger upp skogsmiljöers vegetation och skapar därmed flertaletlivsmiljöer för andra organismgrupper. Bland jordlöparna finns både växtätareoch rovdjur och gruppen spelar en viktig roll i skogens näringskedja.Båda grupperna innehåller även arter med varierande spridningsförmågaochär därför lämpliga för undersökningar av effekter av livsmiljöers fragmentering.Få studier har jämfört dynamiken av dessa två artrika och funktionellt viktigagrupper i samma undersökningsområden. Sådana jämförande studier avväxter och djur är emellertid viktiga om man ska kunna bedöma effekternaav bevarande- och restaureringsåtgärder i fragmenterade landskap.Våra resultat visar följande:• Småskogars markhistorik och markförhållanden varierar mellan olikajordbrukslandskap i södra Sverige. I områden med sedimentberggrund,till exempel i Skåne, är jordarna ofta djupa, fuktigare och därmed merproduktiva. Skogarna här blir snabbt täta och förutsättningar för typiskaskogsarter är goda. I områden på urberg, till exempel i Sörmland, liggersmåskogarna ofta på åkerholmar och nära hällmarker. Jordarna är oftagrunda, torra och mindre bördiga. Här kan hävd- och ljusberoende arterleva kvar länge även utan tamdjursbete och skogarna förblir halvöppna.• Markens bördighet i lövskogarna är högst i Skabersjö, följt av Västerstad,Selaön och Tobo. Längs denna gradient minskar markens kol/kvävekvotoch mängden växttillgänglig fosfor, vilket resulterar i en mer näringsgynnadvegetation i Skåne. Skillnader i markens bördighet påverkaräven den förnalevande lägre markfaunan. Våra resultat visar till exempelatt både mängden förnaätande (detritivora) djur (gråsuggor, tusenfotingar,vissa jordlöpare) och rovdjur (vissa jordlöpare, spindlar, lockespindlar)ökar med markens bördighet.• En fungerande grön infrastruktur för växter och djur behöver inte nödvändigtvisbestå av ett nätverk av sammanhängande livsmiljöer utan ettsystem av spridningsöar kan också vara effektivt för att skogslevandearter ska kunna förflytta sig genom landskapet och kolonisera nya livsmiljöer,som till exempel lövskogsplanteringar på tidigare åkermark.• Små (0,5–2 hektar) isolerade skogsområden med skoglig kontinuitet kanhysa en stor mångfald av specialiserade skogsarter även lång tid efter attområdena har blivit isolerade. De är ofta de enda återstående öarna mednaturlig vegetation i ett intensivt brukat landskap, och det är av stor viktatt deras naturvärden bevaras.• Nyetablerad isolerad lövskog som är helt omgiven av öppen mark koloniserasav typiska skogsarter av både kärlväxter och jordlöpare. Dennaprocess går dock betydligt snabbare för kärlväxter om den nya skogenplanteras direkt intill äldre skogsmark, medan närheten till äldre skoginte är lika viktig för jordlöparna. Våra resultat tyder på att många arterav skogslevande jordlöpare, inklusive sådana som saknar flygförmåga,har en oväntat bra förmåga att förflytta sig relativt stora sträckor genomöppna marker för att nå isolerade skogsområden.• Nyetablerad lövskog på åkermark är värdefull för kalkgynnade skogsartersom historiskt sett har förlorat en stor del av sin ursprungliga livsmiljötill jordbruket. I denna grupp ingår rödlistade arter såsom desmeknopp,skogsveronika och strävlosta som alla koloniserar åkermarksplanteringar.• Den tidigare markanvändningen och skogarnas täthet har stor betydelseför vilka arter som idag finns i små lövskogar i jordbrukslandskapet. Meröppna småskogar med ett större ljusinsläpp och tidigare betade småskogarkan hysa en blandning av skogsarter och hävdberoende typiska gräsmarksarter,medan tätare skogar med längre skogskontinuitet kännetecknas avtypiska skogsarter.• Småskogar i jordbrukslandskapet är känsliga för olika typer av störningarsom snabbt kan spoliera deras naturvärden. Exempel från våra landskapär kalavverkning, nedskräpning, granplantering, tamdjursbete i områdensom inte lämpar sig för bete, eller utebliven hävd i områden med en värdefullgräsmarksflora.Vi drar följande slutsatser för hur små lövskogar i jordbrukslandskap kan bidratill en fungerande grön infrastruktur för skogslevande arter:• Små lövskogar med lång kontinuitet och en flora och fauna med typiskaskogsarter bör ges högre prioritet i natur- och landskapsvården. Markägaremed litet skogsinnehav som domineras av små lövskogar bör få regelbundenrådgivning om dessa skogars naturvärden och bevarande. I deflesta fall kan småskogar brukas för virkesproduktion med generell ellerförstärkt naturvårdshänsyn utan att befintliga naturvärden äventyras.I andra fall kan upprättande av naturvårdsavtal eller biotopskydd varaangeläget, särskilt om naturvärden är knutna till gamla ädellövträd.Generellt bör naturvårdande myndigheter rikta mer fokus på lämpligförvaltning av jordbrukslandskapets små lövskogar. Det är viktigt attjordbrukare får upp ögonen för sina småskogars naturvärden, till exempelgenom kostnadsfri rådgivning.• Om småskogar sköts på ett lämpligt sätt kan utdöenderisken för typiskaskogsarter minskas betydligt. Ett försiktigt virkesuttag har förmodligeninga negativa effekter utan kan snarare vitalisera små populationer avlundväxter i småskogar och öka mångfalden av träd och buskar. En stordel av lundfloran består av långlivade arter med utlöpare och/eller underjordiskaövervintringsorgan som både kan överleva länge i små beståndoch expandera lokalt när tillfälle ges.• Vissa öppna småskogar har en historia som betesmark där naturvärdenaidag delvis är knutna till en hävdberoende flora och insektsfauna. Fördessa bör det avgöras från fall till fall om områdena kan restaureras ochingå i en större betesmark, eller om utvecklingen till en mer sluten skogsmiljöska få fortsätta.• Genom att etablera nya småskogar på jordbruksmark kan man skapaspridningsöar som kan koloniseras av typiska skogsarter och därmedförbättra förutsättningar att gamla småskogar kan behålla livskraftigapopulationer av dessa arter. Många av de mer kortlivade lundväxternahar å andra sidan en bra spridningsförmåga då fröna sprids över störreavstånd, och genom öppna marker, med hjälp av däggdjur, fåglar och vind.• Vi föreslår att man vid nyetablering av lövskog i jordbrukslandskap hellreplanterar fler skogar med en storlek mellan 1–5 hektar än att satsa påfärre och större skogar. Dessa skogar bör etableras nära äldre artrik skogmen även utspritt i det öppna jordbrukslandskapet.• Resultaten från vår tidsserie av ekplanteringar på åkermark visar tydligtatt dessa efter 60–80 år kan ha utvecklat en flora och jordlöparfaunasom till stor del liknar den i ekskog på gammal skogsmark.• Våra resultat tyder på att etablering av ek- eller aspbestånd som röjs ochgallras regelbundet är bäst för biologisk mångfald då sådana bestånderbjuder optimala ljusförhållanden för etablering av lundfloran. Beståndenär tillräckligt ljusa för att lundväxter kan etablera sig och bygga upp sinabestånd, medan de är för mörka för att störningsgynnade arter som halloneller brännässla ska kunna konkurrera i längden. Ek- eller aspbestånderbjuder även bättre förutsättningar för spontan etablering av andraträd- och buskarter än till exempel täta bokplanteringar eller alltför ljusabjörkplanteringar med tät och högväxt undervegetation som hindraretableringav både ved- och lundväxter.
10.	Brunet, Jörg, et al. (author) Små lövskogars funktion för biologisk mångfald i jordbrukslandskap 2019 Reports (other academic/artistic)abstract Vi har studerat hur markanvändningshistoria och fragmenteringen av livsmiljöer har påverkat mångfalden av kärlväxter och jordlöpare i små lövskogar i fyra svenska jordbrukslandskap med varierande naturförhållanden.Resultat1) Ett system av stepping stones kan vara effektivt för att skogslevande arter kan förflytta sig genom landskapet och kolonisera nya livsmiljöer.2) Små isolerade skogsområden med skoglig kontinuitet (0.5-1 ha) kan hysa en stor mångfald av specialiserade arter lång tid efter att områdena har blivit isolerade.3) Nyetablerad lövskog koloniseras av många typiska skogsarter. Närheten till äldre skog är viktigare för skogsväxter än för jordlöpare.4) Nyetablerad lövskog på åkermark är en livsmiljö för kalkgynnade skogsarter som har förlorat en stor del av sin ursprungliga livsmiljö till jordbruket.5) Den tidigare markanvändningen och skogarnas täthet har stor betydelse för vilka naturvårdsintressanta arter som idag finns i små lövskogar i jordbrukslandskapet.6) Småskogars naturvärden är känsliga för störningar som t ex kalavverkning, skräpdumpning, barrskogsplantering och olämpligt tamdjursbete.Slutsatser1) Små lövskogar med habitatkontinuitet och en flora och fauna av typiska skogsarter bör ges högre prioritet i natur- och landskapsvård.2) Om småskogar sköts på ett lämpligt sätt kan utdöenderisken för typiska skogsarter minskas betydligt.3) För ljusöppna småskogar med en hävdberoende restflora och -fauna kan återupptagen beteshävd vara lämplig.4) Nya småskogar kan vara stepping stones som koloniseras av typiska skogsarter och därmed förbättrar förutsättningar för gamla småskogar att behålla sina skogsarter.5) Plantera hellre fler små skogar (1-4 ha) än färre och större. Dessa skogar bör både etableras nära intill äldre artrik skog men även fördelat i det öppna jordbrukslandskapet.6) Etablering av ek- eller aspbestånd skapar de bästa ljus- och markförhållanden för utvecklingen av en artrik lundflora, jämfört med andra lövträdslag.
11.	Brunet, Jörg, et al. (author) Temperature effects on forest understorey plants in hedgerows: a combined warming and transplant experiment 2021 In: Annals of Botany. - : Oxford University Press (OUP). - 0305-7364 .- 1095-8290. ; 128, s. 315-327 Journal article (peer-reviewed)abstract Background and Aims Hedgerows have been shown to improve forest connectivity, leading to an increased probability of species tracking the shifting bioclimatic envelopes. However, it is still unknown how species in hedgerows respond to temperature changes, and whether effects differ compared with those in nearby forests. We aimed to elucidate how ongoing changes in the climate system will affect the efficiency of hedgerows in supporting forest plant persistence and migration in agricultural landscapes.Methods Here we report results from the first warming experiment in hedgerows. We combined reciprocal transplantation of plants along an 860-km latitudinal transect with experimental warming to assess the effects of temperature on vegetative growth and reproduction of two common forest herbs (Anemone nemorosa and Geum urbanum) in hedgerows versus forests.Key Results Both species grew taller and produced more biomass in forests than in hedgerows, most likely due to higher competition with ruderals and graminoids in hedgerows. Adult plant performance of both species generally benefitted from experimental warming, despite lower survival of A. nemorosa in heated plots. Transplantation affected the species differently: A. nemorosa plants grew taller, produced more biomass and showed higher survival when transplanted at their home site, indicating local adaptation, while individuals of G. urbanum showed greater height, biomass, reproductive output and survival when transplanted northwards, likely owing to the higher light availability associated with increasing photoperiod during the growing season.Conclusions These findings demonstrate that some forest herbs can show phenotypic plasticity to warming temperatures, potentially increasing their ability to benefit from hedgerows as ecological corridors. Our study thus provides novel insights into the impacts of climate change on understorey plant community dynamics in hedgerows, and how rising temperature can influence the efficiency of these corridors to assist forest species' persistence and colonization within and beyond their current distribution range.
12.	Brunet, Jörg, et al. (author) Visst gör små lövskogar nytta! 2020 In: Svensk Botanisk Tidskrift. - 0039-646X. ; 114, s. 116-121 Journal article (pop. science, debate, etc.)abstract Varför behöver vi biologisk mångfald? Jessica Lindgren och medförfattare använder ett naturvetenskapligt angreppssätt för att visa hur små lövskogar har förvånansvärt stor betydelse för människor och annat levande.
13.	De Pauw, Karen, et al. (author) Forest understorey communities respond strongly to light in interaction with forest structure, but not to microclimate warming 2022 In: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 233:1, s. 219-235 Journal article (peer-reviewed)abstract Forests harbour large spatiotemporal heterogeneity in canopy structure. This variation drives the microclimate and light availability at the forest floor. So far, we do not know how light availability and sub-canopy temperature interactively mediate the impact of macroclimate warming on understorey communities.We therefore assessed the functional response of understorey plant communities to warming and light addition in a full factorial experiment installed in temperate deciduous forests across Europe along natural microclimate, light and macroclimate gradients. Furthermore, we related these functional responses to the species’ life-history syndromes and thermal niches.We found no significant community responses to the warming treatment. The light treatment, however, had a stronger impact on communities, mainly due to responses by fast-colonizing generalists and not by slow-colonizing forest specialists. The forest structure strongly mediated the response to light addition and also had a clear impact on functional traits and total plant cover.The effects of short-term experimental warming were small and suggest a time-lag in the response of understorey species to climate change. Canopy disturbance, for instance due to drought, pests or logging, has a strong and immediate impact and particularly favours generalists in the understorey in structurally complex forests.
14.	De Pauw, Karen, et al. (author) Taxonomic, phylogenetic and functional diversity of understorey plants respond differently to environmental conditions in European forest edges 2021 In: Journal of Ecology. - : Wiley. - 0022-0477 .- 1365-2745. ; 109:7, s. 2629-2648 Journal article (peer-reviewed)abstract Forest biodiversity world-wide is affected by climate change, habitat loss and fragmentation, and today 20% of the forest area is located within 100 m of a forest edge. Still, forest edges harbour a substantial amount of terrestrial biodiversity, especially in the understorey. The functional and phylogenetic diversity of forest edges have never been studied simultaneously at a continental scale, in spite of their importance for the forests' functioning and for communities' resilience to future change.We assessed nine metrics of taxonomic, phylogenetic and functional diversity of understorey plant communities in 225 plots spread along edge-to-interior gradients in deciduous forests across Europe. We then derived the relative effects and importance of edaphic, stand and landscape conditions on the diversity metrics.Here, we show that taxonomic, phylogenetic and functional diversity metrics respond differently to environmental conditions. We report an increase in functional diversity in plots with stronger microclimatic buffering, in spite of their lower taxonomic species richness. Additionally, we found increased taxonomic species richness at the forest edge, but in forests with intermediate and high openness, these communities had decreased phylogenetic diversity.Functional and phylogenetic diversity revealed complementary and important insights in community assembly mechanisms. Several environmental filters were identified as potential drivers of the patterns, such as a colder macroclimate and less buffered microclimate for functional diversity. For phylogenetic diversity, edaphic conditions were more important. Interestingly, plots with lower soil pH had decreased taxonomic species richness, but led to increased phylogenetic diversity, challenging the phylogenetic niche conservatism concept.Synthesis. Taxonomic, phylogenetic and functional diversity of understorey communities in forest edges respond differently to environmental conditions, providing insight into different community assembly mechanisms and their interactions. Therefore, it is important to look beyond species richness with phylogenetic and functional diversity approaches when focusing on forest understorey biodiversity.
15.	Díaz-Calafat, Joan, et al. (author) From broadleaves to conifers : The effect of tree composition and density on understory microclimate across latitudes 2023 In: Agricultural and Forest Meteorology. - 0168-1923 .- 1873-2240. ; 341 Journal article (peer-reviewed)abstract Forest canopies buffer the macroclimate and thus play an important role in mitigating climate-warming impacts on forest ecosystems. Despite the importance of the tree layer for understory microclimate buffering, our knowledge about the effects of forest structure, composition and their interactions with macroclimate is limited, especially in mixtures of conifers and broadleaves. Here we studied five mixed forest stands along a 1800 km latitudinal gradient covering a 7°C span in mean annual temperature. In each of these forests we established 40 plots (200 in total), in which air and soil temperatures were measured continuously for at least one year. The plots were located across gradients of forest density and broadleaved proportions (i.e. from open to closed canopies, and from 100% conifer to 100% broadleaved tree dominance). Air minimum, mean and maximum temperature offsets (i.e. difference between macroclimate and microclimate) and soil mean temperature offsets were calculated for the coldest and warmest months. Forest structure, and especially forest density, was the key determinant of understory temperatures. However, the absolute and relative importance of the proportion of broadleaves and forest density differed largely between response variables. Forest density ranged from being independent of, to interacting with, tree species composition. The effect of these two variables was independent of the macroclimate along our latitudinal gradient. Temperature, precipitation, snow depth and wind outside forests affected understory temperature buffering. Finally, we found that the scale at which the overstory affects soil microclimate approximated 6-7 m, whereas for air microclimate this was at least 10 m. These findings have implications for biodiversity conservation and forest management in a changing climate, as they facilitate the projection of understory temperatures in scenarios where both forest structure and macroclimate are dynamic. This is especially relevant given the global importance of ongoing forest conversion from conifers to broadleaves, and vice versa.
16.	Felton, Annika, et al. (author) Forage availability, supplementary feed and ungulate density : Associations with ungulate damage in pine production forests 2022 In: Forest Ecology and Management. - : Elsevier. - 0378-1127 .- 1872-7042. ; 513 Journal article (peer-reviewed)abstract Populations of large herbivores, including members of the deer family Cervidae, are expanding across and within many regions of the northern hemisphere. Because their browsing on trees can result in economic losses to forestry and strongly affect ecosystems, it is becoming increasingly important to understand how best to mitigate resultant damage. Previous research has highlighted the importance of regulating deer density and the availability of alternative forage to reduce browsing damage levels in conifer production stands. However, often only one or two proxies of forage availability have been used instead of applying a broad foodscape approach and more knowledge is needed to understand which types of alternative forage best mitigate damage. We conducted field inventories of damage that occurred during the previous fall/winter in 112 production stands in southern Sweden, while also measuring forage availability and cervid faecal pellets in the surrounding landscape (16 ha). Local landowners provided data on supplementary feeding. We found that variation in cervid (Alces alces, Capreolus capreolus, Cervus elaphus and Dama dama) browsing damage to top shoots or stems of young Scots pine trees (Pinus sylvestris, hereon pine), was better explained by the availability of alternative natural forage (using several indices and species of trees and shrubs) than by supplementary feeding. The proportion of damaged pine trees was higher in stands with a lower density of pine stems; in landscapes with a lower density of key broadleaf tree species (genera Sorbus, Salix, Populus and Quercus); and in landscapes with more open land (agricultural fields and paddocks). Damage was also higher in stands where relatively large amounts of moose faeces was found, while not related to the amount of faeces from other cervid species. The amount of supplementary feed (silage or other types such as root vegetables) did not explain variation in pine damage, but the result was possibly affected by relatively few study areas supplying sufficient data on supplementary feeding. The results from our inventory illustrate the efficacy of using naturally growing forage to mitigate browsing damage to young pine trees in managed landscapes. Creation of such forage is also recommended over supplementary feeding because of co-benefits to forest biodiversity and ecosystem services.
17.	Felton, Adam, et al. (author) Forest biodiversity and ecosystem services from spruce-birch mixtures : The potential importance of tree spatial arrangement 2022 In: Environmental Challenges. - : Elsevier BV. - 2667-0100. ; 6 Research review (peer-reviewed)abstract There is increasing empirical support for the biodiversity and ecosystem service (ES) benefits of mixed-species production forests. However, few studies control for the spatial arrangement of the trees within mixtures to determine the influence that clustering the tree species (patch scale mixtures), versus evenly dispersing them (intimate scale mixtures), may have for biodiversity and ES outcomes. To highlight the potential implications of altering tree spatial arrangement in mixtures, and the need to fill related knowledge gaps, here we provide a qualitative multi-disciplinary overview of ecological and socio-economic drivers with the potential to alter biodiversity, ecosystem services, and management-related outcomes from patch versus intimate scale mixtures. We focused our overview on even-aged mixtures of Norway spruce (Picea abies) and birch (Betula pendula or B. pubescens) in Sweden, which enabled us to contrast findings within a biogeographical and silvicultural setting. Specifically, we targeted implications for biodiversity (understory vascular plants, epiphytic lichens, saproxylic beetles, birds), biomass production, harvesting costs, management ease, recreation and aesthetics, cervid game, as well as abiotic and biotic risks (wind, fire, pathogens, pests, browsing damage). In the absence of direct empirical evidence, we primarily relied on expert inference from theory and relevant empirical studies sourced from the Fennoscandian region, and further afield if needed. Collectively these efforts allowed us to develop a number of informed hypotheses indicating that for spruce-birch mixtures in this region, patch scale mixtures may have the potential to favour the diversity of several forest dependant taxonomic groups, cervid game and reduce harvesting costs, whereas intimate mixtures may have the potential to reduce pathogen and pest damage, and likewise, potentially benefit production outcomes. Current knowledge was too limited, inconsistent or context dependant to even tentatively infer outcomes for fire risk, wind damage, browsing damage, management ease, recreational and aesthetic outcomes. We emphasize that our hypotheses require testing, but are sufficient to (1) highlight the likely importance of spatial-scale to biodiversity and ecosystem services outcomes in mixed-species production forests, (2) caution against generalization from mixture studies that lack scale considerations, and (3) motivate the targeted consideration of spatial grain in future mixture studies.
18.	Felton, Adam, et al. (author) From mixtures to monocultures: Bird assemblage responses along a production forest conifer-broadleaf gradient 2021 In: Forest Ecology and Management. - : Elsevier BV. - 0378-1127 .- 1872-7042. ; 494 Journal article (peer-reviewed)abstract Increasing the prevalence of broadleaf trees in conifer-dominated production forests is a recommended means of improving habitat availability for broadleaf and mixed-forest species. The implications for biodiversity are often measured by contrasting broadleaf-conifer mixtures with conifer-dominated stands. However, few studies include broadleaf-dominated stands in these assessments. Here we contrasted the bird assemblages of even-aged production forests along a mixture gradient from Norway spruce (Picea abies) dominated, to birch (Betula spp.) dominated stands in southern Sweden. We conducted point count surveys of bird individuals exhibiting breeding behaviour within 30 stands varying from <0.5% to over 98.5% broadleaf by basal area. A total of 355 birds were detected, comprising 36 bird species, seven of which are classified as near threatened by the Swedish Red-list. Our results indicate i) a distinct shift in bird community composition linked to the percentage of broadleaf trees at stand and landscape scales, ii) significantly higher bird species richness, evenness, and abundance in stands with a higher proportion of birch, iii) higher bird abundance in birch-dominated stands than in mixtures, and iv) shifts in bird species guilds as related to stand basal area, the amount of shrubs in the understory, and quantities of dead wood. All of these results have implications for the ways in which production forest management could be altered to enhance avian diversity, and we discuss these with respect to the use of broadleaf versus mixed-species stands.
19.	Felton, Annika M., et al. (author) Increased intake of tree forage by moose is associated with intake of crops rich in nonstructural carbohydrates 2024 In: Ecology. - : John Wiley & Sons. - 0012-9658 .- 1939-9170. Journal article (peer-reviewed)abstract Animals representing a wide range of taxonomic groups are known to select specific food combinations to achieve a nutritionally balanced diet. The nutrient balancing hypothesis suggests that, when given the opportunity, animals select foods to achieve a particular target nutrient balance, and that balancing occurs between meals and between days. For wild ruminants who inhabit landscapes dominated by human land use, nutritionally imbalanced diets can result from ingesting agricultural crops rich in starch and sugar (nonstructural carbohydrates [NCs]), which can be provided to them by people as supplementary feeds. Here, we test the nutrient balancing hypothesis by assessing potential effects that the ingestion of such crops by Alces alces (moose) may have on forage intake. We predicted that moose compensate for an imbalanced intake of excess NC by selecting tree forage with macro-nutritional content better suited for their rumen microbiome during wintertime. We applied DNA metabarcoding to identify plants in fecal and rumen content from the same moose during winter in Sweden. We found that the concentration of NC-rich crops in feces predicted the presence of Picea abies (Norway spruce) in rumen samples. The finding is consistent with the prediction that moose use tree forage as a nutritionally complementary resource to balance their intake of NC-rich foods, and that they ingested P. abies in particular (normally a forage rarely eaten by moose) because it was the most readily available tree. Our finding sheds new light on the foraging behavior of a model species in herbivore ecology, and on how habitat alterations by humans may change the behavior of wildlife.
20.	Felton, Annika, et al. (author) Macronutrient balancing in free-ranging populations of moose 2021 In: Ecology and Evolution. - : Wiley. - 2045-7758. ; 11, s. 11223-11240 Journal article (peer-reviewed)abstract At northern latitudes, large spatial and temporal variation in the nutritional composition of available foods poses challenges to wild herbivores trying to satisfy their nutrient requirements. Studies conducted in mostly captive settings have shown that animals from a variety of taxonomic groups deal with this challenge by adjusting the amounts and proportions of available food combinations to achieve a target nutrient balance. In this study, we used proportions-based nutritional geometry to analyze the nutritional composition of rumen samples collected in winter from 481 moose (Alces alces) in southern Sweden and examine whether free-ranging moose show comparable patterns of nutrient balancing. Our main hypothesis was that wild moose actively regulate their rumen nutrient composition to offset ecologically imposed variation in the nutritional composition of available foods. To test this, we assessed the macronutritional composition (protein, carbohydrates, and lipids) of rumen contents and commonly eaten foods, including supplementary feed, across populations with contrasting winter diets, spanning an area of approximately 10,000 km(2). Our results suggest that moose balanced the macronutrient composition of their rumen, with the rumen contents having consistently similar proportional relationship between protein and nonstructural carbohydrates, despite differences in available (and eaten) foods. Furthermore, we found that rumen macronutrient balance was tightly related to ingested levels of dietary fiber (cellulose and hemicellulose), such that the greater the fiber content, the less protein was present in the rumen compared with nonstructural carbohydrates. Our results also suggest that moose benefit from access to a greater variety of trees, shrubs, herbs, and grasses, which provides them with a larger nutritional space to maneuver within. Our findings provide novel theoretical insights into a model species for ungulate nutritional ecology, while also generating data of direct relevance to wildlife and forest management, such as silvicultural or supplementary feeding practices.
21.	Felton, Adam, et al. (author) The biodiversity contribution of wood plantations: Contrasting the bird communities of Sweden's protected and production oak forests 2016 In: Forest Ecology and Management. - : Elsevier BV. - 0378-1127 .- 1872-7042. ; 365, s. 51-60 Journal article (peer-reviewed)abstract The oak-dominated woodlands and forests of northern Europe have experienced dramatic declines due to agriculture, urbanization, and conifer-dominated production forestry. These losses have had a substantial negative impact on biodiversity due to the large number of forest species which depend on oak and the environments oak-dominated forests provide. Production oak stands may serve as a means of supplementing or complementing the habitat provided by the limited remaining natural oak remnants in this region. Here we evaluate the extent to which oak plantations in temperate southern Sweden provide habitat and resources for bird communities, by surveying and contrasting the bird species composition and diversity found in mature and young production oak stands (5 and 8 replicates respectively) and protected oak-dominated remnant forests (5 replicates). The mature production stands possessed a bird community partially overlapping in bird species composition, and comparable in species richness (34 species) to that found within protected oak forests (39 species). Furthermore, the production oak forests surveyed hosted threatened or near threatened bird species, including black woodpecker (Dryocopus martius), goldcrest (Regulus regulus), starling (Sturnus vulgaris), and yellowhammer (Emberiza citrinella). Though production oak forests cannot replace the habitat provided by protected oak forests, these stands do appear to provide conditions consistent with the habitat and resource requirements of a diverse cross-section of bird species in this region, including species of substantial conservation concern. Production oak forests thus have the capacity to make a positive contribution to biodiversity conservation, as well as providing a diverse range of goods and services to society. (C) 2016 Elsevier B.V. All rights reserved.
22.	Felton, Annika, et al. (author) The Nutritional Balancing Act of a Large Herbivore: An Experiment with Captive Moose (Alces alces L) 2016 In: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 11 Journal article (peer-reviewed)abstract The nutrient balancing hypothesis proposes that, when sufficient food is available, the primary goal of animal diet selection is to obtain a nutritionally balanced diet. This hypothesis can be tested using the Geometric Framework for nutrition (GF). The GF enables researchers to study patterns of nutrient intake (e.g. macronutrients; protein, carbohydrates, fat), interactions between the different nutrients, and how an animal resolves the potential conflict between over-eating one or more nutrients and under-eating others during periods of dietary imbalance. Using the moose (Alces alces L.), a model species in the development of herbivore foraging theory, we conducted a feeding experiment guided by the GF, combining continuous observations of six captive moose with analysis of the macronutritional composition of foods. We identified the moose's self-selected macronutrient target by allowing them to compose a diet by mixing two nutritionally complementary pellet types plus limited access to Salix browse. Such periods of free choice were intermixed with periods when they were restricted to one of the two pellet types plus Salix browse. Our observations of food intake by moose given free choice lend support to the nutrient balancing hypothesis, as the moose combined the foods in specific proportions that provided a particular ratio and amount of macronutrients. When restricted to either of two diets comprising a single pellet type, the moose i) maintained a relatively stable intake of non-protein energy while allowing protein intakes to vary with food composition, and ii) increased their intake of the food item that most closely resembled the self-selected macronutrient intake from the free choice periods, namely Salix browse. We place our results in the context of the nutritional strategy of the moose, ruminant physiology and the categorization of food quality.
23.	Fernández-Fernández, P., et al. (author) Different effects of warming treatments in forests versus hedgerows on the understorey plant Geum urbanum 2022 In: Plant Biology. - : Wiley. - 1435-8603 .- 1438-8677. ; 24:5, s. 734-744 Journal article (peer-reviewed)abstract The effectiveness of hedgerows as functional corridors in the face of climate warming has been little researched. Here we investigated the effects of warming temperatures on plant performance and population growth of Geum urbanum in forests versus hedgerows in two European temperate regions.Adult individuals were transplanted in three forest–hedgerow pairs in each of two different latitudes, and an experimental warming treatment using open-top chambers was used in a full factorial design. Plant performance was analysed using mixed models and population performance was analysed using Integral Projection Models and elasticity analyses.Temperature increases due to open-top chamber installation were higher in forests than in hedgerows. In forests, the warming treatment had a significant negative effect on the population growth rate of G. urbanum. In contrast, no significant effect of the warming treatment on population dynamics was detected in hedgerows. Overall, the highest population growth rates were found in the forest control sites, which was driven by a higher fecundity rather than a higher survival probability.Effects of warming treatments on G. urbanum population growth rates differed between forests and hedgerows. In forests, warming treatments negatively affected population growth, but not in hedgerows. This could be a consequence of the overall lower warming achieved in hedgerows. We conclude that maintenance of cooler forest microclimates coul, at least temporarily, moderate the species response to climate warming.
24.	Gasperini, Cristina, et al. (author) Soil seed bank responses to edge effects in temperate European forests 2022 In: Global Ecology and Biogeography. - Stockholm : Wiley. - 1466-822X .- 1466-8238. ; 31:9, s. 1877-1893 Journal article (peer-reviewed)abstract Aim: The amount of forest edges is increasing globally due to forest fragmentation and land-use changes. However, edge effects on the soil seed bank of temperate forests are still poorly understood. Here, we assessed edge effects at contrasting spatial scales across Europe and quantified the extent to which edges can preserve the seeds of forest specialist plants.Location: Temperate European deciduous forests along a 2,300-km latitudinal gradient.Time period: 2018-2021.Major taxa studied: Vascular plants.Methods: Through a greenhouse germination experiment, we studied how edge effects alter the density, diversity, composition and functionality of forest soil seed banks in 90 plots along different latitudes, elevations and forest management types. We also assessed which environmental conditions drive the seed bank responses at the forest edge versus interior and looked at the relationship between the seed bank and the herb layer species richness.Results: Overall, 10,108 seedlings of 250 species emerged from the soil seed bank. Seed density and species richness of generalists (species not only associated with forests) were higher at edges compared to interiors, with a negative influence of C : N ratio and litter quality. Conversely, forest specialist species richness did not decline from the interior to the edge. Also, edges were compositionally, but not functionally, different from interiors. The correlation between the seed bank and the herb layer species richness was positive and affected by microclimate.Main conclusions: Our results underpin how edge effects shape species diversity and composition of soil seed banks in ancient forests, especially increasing the proportion of generalist species and thus potentially favouring a shift in community composition. However, the presence of many forest specialists suggests that soil seed banks still play a key role in understorey species persistence and could support the resilience of our fragmented forests.
25.	Govaert, Sanne, et al. (author) Edge influence on understorey plant communities depends on forest management 2020 In: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 31:2, s. 281-292 Journal article (peer-reviewed)abstract Questions: Does the influence of forest edges on plant species richness and composition depend on forest management? Do forest specialists and generalists show contrasting patterns?Location: Mesic, deciduous forests across Europe.Methods: Vegetation surveys were performed in forests with three management types (unthinned, thinned 5-10 years ago and recently thinned) along a macroclimatic gradient from Italy to Norway. In each of 45 forests, we established five vegetation plots along a south-facing edge-to-interior gradient (n = 225). Forest specialist, generalist and total species richness, as well as evenness and proportion of specialists, were tested as a function of the management type and distance to the edge while accounting for several environmental variables (e.g. landscape composition and soil characteristics). Magnitude and distance of edge influence were estimated for species richness per management type.Results: Greatest total species richness was found in thinned forests. Edge influence on generalist plant species richness was contingent on the management type, with the smallest decrease in species richness from the edge-to-interior in unthinned forests. In addition, generalist richness increased with the proportion of forests in the surrounding landscape and decreased in forests dominated by tree species that cast more shade. Forest specialist species richness, however, was not affected by management type or distance to the edge, and only increased with pH and increasing proportion of forests in the landscape.Conclusions: Forest thinning affects the plant community composition along edge-to-interior transects of European forests, with richness of forest specialists and generalists responding differently. Therefore, future studies should take the forest management into account when interpreting edge-to-interior because both modify the microclimate, soil processes and deposition of polluting aerosols. This interaction is key to predict the effects of global change on forest plants in landscapes characterized by the mosaic of forest patches and agricultural land that is typical for Europe.
26.	Govaert, Sanne, et al. (author) Trait–micro-environment relationships of forest herb communities across Europe 2024 In: Global Ecology and Biogeography. - 1466-822X .- 1466-8238. ; 33:2, s. 286-302 Journal article (peer-reviewed)abstract Aim: The microclimate and light conditions on the forest floor are strongly modified by tree canopies. Therefore, we need to better consider the micro-environment when quantifying trait–environment relationships for forest understorey plants. Here, we quantify relationships between micro-environmental conditions and plant functional traits at the community level, including intraspecific trait variation, and their relationship with microclimate air temperature, light and soil properties.Location: Deciduous temperate forests across Europe.Time period: 2018.Major taxa studied: Herbaceous vegetation.Methods: We sampled 225 plots across 15 regions along four complementary gradients capturing both macro- and microclimatic conditions including latitude, elevation, forest management and distance to forest edges. We related the community-weighted mean of five plant functional traits (plant height, specific leaf area [SLA], plant carbon [C], plant nitrogen [N] and plant C:N ratio) across 150 vascular plant species to variation in local microclimate air temperature, light and soil properties. We tested the effect of accounting for intraspecific variation in trait–environment relationships and performed variation partitioning to identify major drivers of trait variation.Results: Microclimate temperature, light availability and soil properties were all important predictors of community-weighted mean functional traits. When light availability and variation in temperature were higher, the herb community often consisted of taller plants with a higher C:N ratio. In more productive environments (e.g. with high soil nitrogen availability), the community was dominated by individuals with resource-acquisitive traits: high SLA and N but low C:N. Including intraspecific trait variation increased the strength of the trait–micro-environment relationship, and increased the importance of light availability.Main conclusions: The trait–environment relationships were much stronger when the micro-environment and intraspecific trait variation were considered. By locally steering light availability and temperature, forest managers can potentially impact the functional signature of the forest herb-layer community.
27.	Grelle, Achim, et al. (author) From source to sink : recovery of the carbon balance in young forests 2023 In: Agricultural and Forest Meteorology. - : Elsevier. - 0168-1923 .- 1873-2240. ; 330 Journal article (peer-reviewed)abstract We analyzed ecosystem carbon fluxes from eddy-covariance measurements in five young forests in southernSweden where the previous stand had been harvested by clear-cutting or wind-felled: three stands with Norwayspruce (Picea abies (L.) Karst.), one with Scots pine (Pinus sylvestris) and one with Larch (Larix x eurolepis A.Henry). One of the spruce stands had the stumps harvested, one was fertilized and one without any specialtreatments. These stands returned from positive (sources) to negative (sinks) annual carbon fluxes 8–13 yearsafter disturbance, depending on site productivity and management. This corresponds to approximately 15% ofthe rotation periods at these sites. Extrapolation in combination with chronosequence data suggests thatconventionally regenerated stands reach a neutral carbon balance after approximately 30% of the rotationperiod. The lowest carbon emissions and shortest recovery time was observed in a stand where the stumps of thetrees, in addition to the stems and logging residues, were removed after harvest. This stand not only returned to acarbon sink within this time period but the total carbon gains since disturbance also equaled the total losses afteronly 11 years. These results stress that production stands in southern Sweden are carbon sources during arelatively small part of the rotation period, and that this part can be considerably shortened by measures thatincrease productivity or reduce the amount of woody debris left after disturbance.
28.	Hedwall, Per-Ola, et al. (author) Can thinning alleviate negative effects of fertilization on boreal forest floor vegetation? 2013 In: Forest Ecology and Management. - : Elsevier BV. - 0378-1127 .- 1872-7042. ; 310, s. 382-392 Journal article (peer-reviewed)abstract Society's increased interest in renewable energy and materials put pressure on forest biomass production. Intensive fertilization of young Norway spruce (Picea abies) forest has a considerable potential to increase the production of tree biomass, but there are concerns about negative side-effects on forest ecosystem structure and function. Fertilization of young forest has a strong negative impact on light availability below the tree canopy and reduces the abundance of the forest floor vegetation. The silvicultural practice of thinning has been shown to affect composition and diversity of forest floor vegetation, and it has been proposed, but rarely tested, that the effects of fertilization are interdependent on the type of thinning performed. Here we present responses on the forest floor vegetation following 25 years of fertilization and eighth years after thinning (removing 30% or 60% of the tree basal area) in a Norway spruce forest in northern Sweden. Fertilization without thinning led to a considerable reduction in abundance of most forest floor plants. It did not affect species richness but resulted in an increased evenness. Thinning reduced the fertilization effects so that the total abundance of the vegetation was comparable to the unfertilized control plots. A considerable change in species composition had, however, taken place. Thinning favored early-successional species and pteridophytes on the account of dwarfshrubs. Thinning also increased species richness and functional richness, while none, or negative effects were seen on evenness and functional evenness, respectively. A comparison with data from the National Forest Inventory revealed that the type of vegetation generated by fertilization, without or in combination with thinning, is a type of vegetation very uncommon in Swedish boreal forests. First, we conclude that the effects of fertilization on forest floor vegetation in young stands of Norway spruce are largely dependent on thinning regime. Secondly, fertilization will, independently of thinning, lead to considerable changes in the vegetation, including a functional shift from dwarf-shrubs with ericoid mycorrhiza to ferns and grasses with arbuscular mycorrhiza, resulting in a functional type of vegetation that is rare in this part of the boreal forest biome. Finally, in contrast to what previously has been suggested for unfertilized forests, thinning of fertilized forests may not promote late-successional species.
29.	Hedwall, Per-Ola, et al. (author) Changes in the abundance of keystone forest floor species in response to changes of forest structure 2013 In: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 24, s. 296-306 Journal article (peer-reviewed)abstract Question Does the abundance of keystone forest floor species change in response to changes in the forest structure? Location Sweden Methods We used data from the Swedish National Forest Inventory to investigate changes in the abundance of three common species, as well as the total abundance of all understorey vascular plants (the field layer) in forests in the boreal and temperate parts of Sweden. GLMs and GAMs were used to relate species abundance and temporal changes in abundances to forest structure and forest structural change. Results Productivity, measured as the site index, was the most important determinant of individual species' abundance. The volume of Picea abies, the density of tree stems and forest age were among the most important forest structural variables. We found that the dwarf shrub Vaccinium myrtillus, the narrow-leaved grasses (mainly Avenella flexuosa) and the total field layer cover decreased in boreal Sweden from 1994 through 2010 and that these changes coincided with an increase in forest density and with a reduction in forest age. Conclusions Changes in Swedish forests to higher tree layer density and younger age appear to contribute significantly to current changes in forest floor vegetation. The use of more intensive thinning practices to reduce the total density of the forest and to increase the proportion of broad-leaved tree species and Pinus sylvestris would favour the forest floor species in this study. Moreover, increasing forest age (i.e. the length of rotation periods) might favour V. myrtillus in particular, for which the time since disturbance is important for the recovery of pre-disturbance abundance. However, increased thinning intensity and forest age will reduce the potential for wood production, implying a trade-off between production of wood and maintenance of well-developed forest floor vegetation.
30.	Hedwall, Per-Ola, et al. (author) Compositional changes of forest-floor vegetation in young stands of Norway spruce as an effect of repeated fertilisation 2010 In: Forest Ecology and Management. - : Elsevier BV. - 0378-1127 .- 1872-7042. ; 259, s. 2418-2425 Journal article (peer-reviewed)abstract Forestry practices that aim to increase biomass production may mitigate climate change through increased carbon sequestration and the potential of substituting fossil fuels with renewable biofuels. Fertilising young stands of Norway spruce in Sweden have shown to increase tree growth by more than 200%. Fertilisation, however, also has other effects on forest ecosystems. Here, we studied the response of the species composition of forest-floor vegetation to three different frequencies of fertilisation in young stands of Norway spruce. Fertiliser was applied every year, every second year or every third year. The total amount of N ranged from 425 kg ha(-1) to 625 kg ha(-1), in combination with P, K. Ca, Mg, S, Mn, Zi, B and Cu. The largest effects of the fertilisation were found among bryophytes and lichens, which lost substantial cover. Unexpectedly, Deschampsia flexuosa, commonly known to be favoured by fertilisation, was negatively affected. Species that increased in frequency were Oxalis acetosella, Brachythecium sp. and Plagiothecium sp. Decreased availability of light, as an indirect effect of fertilisation through increased tree canopy cover, was found to be the most important factor behind the change in species composition of vascular plants. The total cover of bryophytes, however, did not show any significant response to the changes in canopy cover, indicating that the effects seen in this group may be a result of more direct effects of the fertiliser. Few significant differences were found between the two most intensive fertilisation frequencies, although fertilisation every third year was often distinguished from both the control and the other fertilised treatments. Even though the effects at the stand level were substantial, the effects on biodiversity and function of ecosystems on a landscape or regional level need further investigation. (C) 2010 Elsevier B.V. All rights reserved.
31.	Hedwall, Per-Ola, et al. (author) Concealed by darkness: How stand density can override the biodiversity benefits of mixed forests 2019 In: Ecosphere. - : Wiley. - 2150-8925. ; 10 Journal article (peer-reviewed)abstract Higher tree species richness often increases the diversity of other taxonomic groups and is promoted in many managed forest systems. The reason for the higher diversity is due to, for example, inter-specific differences in resource filtering of the trees. Resource filtering also depends on the total density of the tree layer, but the interaction between tree species composition and density is, so far, unexplored. Likewise, few studies have addressed whether mixtures of tree species host higher diversity, or support higher productivity, of other taxa than monocultures of the same tree species. We use a gradient in overstory tree species composition, ranging from pure Norway spruce (Picea abies) to pure Birch (Betula sp.), combined with a gradient from open to closed forest, to assess the joint effects of tree species mixture and forest density on the understory vegetation. The cover and species richness of understory vascular plants increased with an increasing proportion of birch and decreased with increasing forest density, while the cover of bryophytes decreased with an increasing proportion of birch and increasing forest density. There were clear interactions between tree species composition and forest density; the decrease in vascular plants with forest density was stronger in forest dominated by spruce than in forests dominated by birch, and the positive effect of an increasing proportion of birch was smaller in dense than in open forests. There were no indications of mixed forests supporting a higher species richness or plant cover than any of the two monocultures. Additionally, few species (10%) showed tendencies toward a higher probability of occurrence in mixed forests, and most of these also occurred in open pure stands. Our results indicate a potential conflict between goals for diversified forests and increased biomass production, as the positive effects for understory vegetation from mixtures may be lost to concomitant increases in forest density. Furthermore, the limited number of species benefiting from mixtures per se indicates that similar biodiversity benefits for understory vegetation may be obtained at landscape levels from the increased use of broadleaf and lower-density production stands, as from mixtures.
32.	Hedwall, Per-Ola, et al. (author) Decreased variation of forest understory vegetation is an effect of fertilisation in young stands of Picea abies 2011 In: Scandinavian Journal of Forest Research. - : Informa UK Limited. - 0282-7581 .- 1651-1891. ; 26, s. 46-55 Journal article (peer-reviewed)abstract The substitution of fossil fuels with biofuels to mitigate climate change has caused increased interest in enhancing forest biomass production through fertilisation. We investigated the effects of different fertilisation frequencies on the diversity of understory vegetation in young stands of Picea abies on five sites distributed in regions in the middle and south of Sweden. The treatments included fertilisation conducted annually, every second year or every third year, as well as an unfertilised control. A lower number of vascular plant species was observed on fertilised plots than on control plots, whereas the number of bryophyte species remained unchanged. Fertilised plots also showed a lower variance in species composition and a lower Shannon's diversity index than unfertilised plots. Fertilised plots were more similar to each other than unfertilised plots were to each other over the geographical range. The two most intensive fertilisation treatments had similar effects on the vegetation, whereas the effects of fertilisation conducted every third year were not as substantial. However, the treatment in which fertilisation occurred every third year implies a lower stem-wood production, and there is little knowledge of the long-term differences between the treatments. We conclude that fertilisation of young stands will lead to long-term changes in understory vegetation at the stand scale, whereas the effects at the landscape level are still largely unknown.
33.	Hedwall, Per-Ola, et al. (author) Does background nitrogen deposition affect the response of boreal vegetation to fertilization? 2013 In: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 173, s. 615-624 Journal article (peer-reviewed)abstract Forest floor vegetation is an important component of forest biodiversity, and numerous studies have shown that N input alters the vegetation. In some cases, however, the effects of experimental N addition have been small or absent. Two alternative hypotheses have been suggested: (a) competition from the tree layer confounds the response to N, or (b) N response in areas with high background deposition is limited by N saturation. Neither of these hypotheses has so far been explicitly tested. Here, we compile data on forest floor vegetation from N addition experiments, in which the forest had been clear-cut, along an N deposition gradient ranging from 4 to 16 kg ha-1 year-1 in Sweden. We analyzed the effects of N addition and its interaction with N deposition on common species and thereby tested the second hypothesis in an environment without the confounding effects of the tree layer. The results show that the effects of the experimental N addition are significantly influenced by background N deposition: the N addition effects are smaller in areas with high N deposition than in areas with low N deposition, despite the fact that the highest N deposition in this study can be considered moderate from an international perspective. The results are important when assessing the reliability of results from N addition experiments on forest floor vegetation in areas with moderate to high background N deposition. We conclude that the interacting effects of N addition and N deposition need to be included when assessing long-term N sensitivity of plant communities.
34.	Hedwall, Per-Ola, et al. (author) Effects of clear-cutting and slash removal on soil water chemistry and forest-floor vegetation in a nutrient optimised Norway spruce stand 2013 In: Silva Fennica. - : Finnish Society of Forest Science. - 0037-5330 .- 2242-4075. ; 47 Journal article (peer-reviewed)abstract Fertilisation with nutrient optimisation has in Sweden resulted in large increases in volume growth in young stands of Norway spruce. There are, however, environmental concerns about repeated fertilisation and one is the risk of nutrient leakage to ground water resources and aquatic ecosystems after clear-cutting of such forests. The present study followed soil-water chemistry in optimised fertilised stands after clear-cutting, as well as effects of harvest of slash on nutrient leakage. Parts of a 30-year-old stand of Norway spruce, which had been subject to a nutrient optimisation experiment for 17 years, were clear-cut. A split-plot design with whole-tree harvesting as the sub-plot treatment was applied. Lysimeters were installed and soil-water sampled at nine occasions during the following four years. No significant effects of fertilisation on nitrate leaching were found, while harvest of slash affected the concentration of Ca, DOC, DON, K, Mg, ammonium and nitrate, as well as pH in the soil solution. While no effects of fertilisation could be seen on the soil water concentration of N, the results indicate an interaction between fertilisation and harvest of slash on the concentration of nitrate in the soil solution. The results indicate that forest-floor vegetation plays an important role in the retention of N after clear-cutting of fertilised forests.
35.	Hedwall, Per-Ola, et al. (author) Fertilization in Boreal and Temperate Forests and the Potential for Biomass Production 2013 In: Forest bioenergy production: management, carbon sequestration and adaptation. - New York, NY : Springer. - 9781461483908 ; , s. 95-110 Book chapter (peer-reviewed)abstract Forest fertilization is one of the most efficient methods in forest management to increase the short-term production of biomass. In this context, this chapter provides a brief background of the physiological response of trees to fertilization and increased nutrient availability. Furthermore, we shall describe different fertilization regimes and demonstrate the potentials of fertilization in enhancing biomass production, which will be performed by presenting relevant literature and some unpublished results. This chapter will also elaborate on some ideas for developing fertilization in operational forestry.
36.	Hedwall, Per-Ola, et al. (author) Fertilization in northern forests - biological, economic and environmental constraints and possibilities 2014 In: Scandinavian Journal of Forest Research. - : Informa UK Limited. - 0282-7581 .- 1651-1891. ; 29:4, s. 301-311 Research review (peer-reviewed)abstract Forests of northern ecosystems respond slowly to management activities and the possibilities to increase the growth in a short-term perspective and meet swift increases in society's demand for biomass are small. An exception among the silvicultural measures is fertilization which can be applied in combination with present management systems and, almost instantly, enhances forest productivity. There may, however, be both economic and environmental constraints to large-scale applications of fertilizers in forest. Here we review the literature concerning biomass production of forests under different fertilization regimens, environmental constraints and possibilities in northern forests on mineral soils. Further on we discuss the implications of both extensive and more intensive fertilization in relation to the developing bioeconomy, which encompasses the production and conversion of renewable biological resources into food, health and industrial products and energy. Fertilization in Sweden and Finland is currently practiced by extensive fertilization regimens where nitrogen fertilizers are applied once, or up to three times, during a rotation period, mainly in mature forest. This type of fertilization gives, in most cases, a small and transient effect on the environment as well as a high rate of return to the forest owner with low-economic risk. The increase in biomass production, however, is relatively small and consequently the impact on the processing industry and the bioeconomy is limited. More intensive fertilization regimens implying intensive fertilization starting in young forests may, on the other hand, considerably increase the biomass supply and value for the industry. The economic and environmental risks of this type of fertilization may, however, be larger and more research is needed on the effects on the stand level, and especially on the landscape level, including late rotation management of the forest.
37.	Hedwall, Per-Ola, et al. (author) Forest density and edge effects on soil microbial communities in deciduous forests across Europe 2022 In: Applied Soil Ecology. - : Elsevier BV. - 0929-1393 .- 1873-0272. ; 179 Journal article (peer-reviewed)abstract Forest fragmentation increases the proportion of edge area and this, in turn, induces changes in forest structure, species composition and microclimate. These factors are also strongly determined by the forest management regime. Although the interactive effects of edges and density on forest plant communities have been extensively studied, little is known about the response of the belowground communities. Here we investigated the variation of soil microbiota in 45 deciduous broadleaved forests along a latitudinal gradient from Italy to Norway at a continental scale across Europe. Phospholipid fatty acid (PLFA) and neutral lipid fatty acid (NLFA) were used to map the microbial community in the forest edge and interior across three forest densities (dense, intermediate, open forest). Microbial community composition was only affected by forest edge effects and not by forest density. We did not find any interaction effects between forest density and distance-to-edge. Arbuscular mycorrhizal fungi (AMF) were significantly more abundant in edges and Gram-negative bacteria more abundant in interiors, respectively. The microbial community composition was closely related to soil pH, soil potassium and nitrogen, texture (percent sand) and soil temperature. Soil pH was positively correlated with the saprotrophic fungi and potassium was positively correlated with Gram-negative bacteria but negatively correlated with Actinobacteria. In sum, we reveal the notable effects of forest edges on the soil AMF abundance. This result indicated that AMF could possess a stronger affinity with species growing in the edges, which may help to improve plant perfor-mance under hostile conditions herein.
38.	Hedwall, Per-Ola (author) Forest floor vegetation in Sweden : impacts of intensified forestry, nutrient addition and changes in forest structure 2012 Doctoral thesis (other academic/artistic)abstract In boreal forests, dwarf-shrubs (Vaccinium spp.) often dominate the forest floor and are key-stone species in ecosystems due to their importance for nutrient cycling and as a major food source for herbivores. Forestry affects the vegetation both directly through management and indirectly by altering the forest structure. Forest fertilization with N at the end of the rotation period is a common practice in Swedish boreal forests. Even higher timber production can be achieved if fertilization with multi-nutrient fertilizer is applied early in the rotation period, but the effects on forest floor vegetation have not been studied. The objectives of this thesis were to increase knowledge regarding how 1) intensive fertilization in young forest affects forest floor vegetation; 2) background deposition of N influences the effects of N addition; and 3) to relate observed changes in common species abundances to changes in forest structure. Fertilization decreased the abundance of many common forest plant species while only few species increased (I). Surprisingly, also species known as nitrophilous decreased in abundance. Paper I shows that the decrease in availability of light induced by fertilization is a crucial factor behind this change. Consequently, fertilization reduced both species richness, species diversity and the between site (β) diversity (II). In areas where the background N deposition was low (4 kg ha-1 yr-1), the effects of N addition were larger than in areas with intermediate (16 kg ha-1 yr-1) deposition (III). Key-stone species among the forest floor vegetation of boreal Sweden (e.g. Vaccinium myrtillus) were found to decrease in abundance (IV). These species are strongly dependent on aspects of forest structure, such as forest density and age, and likewise, temporal changes in species abundance coincided with corresponding changes in forest structure (IV). In conclusion, in large parts of Sweden the prevailing forest management is incompatible with a productive forest floor vegetation possessing a high diversity of plant species, and this situation will only be exacerbated by more intensive use of fertilization regimes. To avoid associated cascading effects from the decreased abundance of key-stone species, forestry intensity needs to be relaxed on the landscape level which would likely result in a considerable loss of timber production. Compensation for this loss through intensified forestry on other areas would indicate the need for altered forest zoning.
39.	Hedwall, Per-Ola (author) Functional composition of temperate forest trees under chronic ungulate herbivory 2018 In: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 29, s. 179-188 Journal article (peer-reviewed)abstract Question: Functional plant traits often express consistent changes along ecological gradients and, hence, are often used as indicators of environmental change (e.g. nutrient availability, temperature changes). Besides being driven by edaphic conditions, functional plant composition is filtered by herbivory, and traits responsive to nutrient availability often coincide with those related to palatability or resistance to browsing. We hypothesized that herbivory may distort the ways in which traits are expressed along environmental gradients.Location: Bialowieza National Park, Poland.Methods: We used a long-term controlled, exclosure experiment in the Bialowieza National Park to study tree functional trait expression and plant indicator values, with and without large ungulate browsing, along a natural soil fertility gradient.Results: Browsing largely reduced the functional diversity of regenerating trees, indicated by multivariate analysis and Rao's Quadratic Entropy (RQE), and altered how several traits change with increasing fertility. Browsing led to an increase in specific leaf area (SLA) on poorer sites. RQE showed a hump-backed trend along the fertility gradient, indicating the largest functional diversity at intermediate fertility. However, this pattern was not affected by browsing. Unlike the morphological tree traits, trends of light and N plant indicator values along the gradient were unaffected by browsing.Conclusions: These results highlight how the expression of plant traits resulting from one driver (soil fertility) can be modified by another driver (herbivory,) and stress the importance of taking herbivory into account when using plant traits as indicators of large-scale processes (e.g. climate change). Furthermore, the results suggest that plant indicator values may be more robust towards these effects, while compiled indices such as RQE could mask considerable functional turnover. Several traits (e.g. SLA) are strongly connected to nutrient cycling. The development, driven by browsing, towards higher SLA on poorer sites may thus cause a positive feedback effect on site fertility that drives an increase in nutrient availability. This may in turn have implications for ecosystem functionality. Hence, the large reduction in functional diversity revealed at the scale of this study may in the long term have implications on multiple ecosystem processes.
40.	Hedwall, Per-Ola, et al. (author) Half a century of multiple anthropogenic stressors has altered northern forest understory plant communities 2019 In: Ecological Applications. - : Wiley. - 1051-0761 .- 1939-5582. ; 29 Journal article (peer-reviewed)abstract Boreal forests form the largest and least disturbed forest biome in the northern hemisphere. However, anthropogenic pressure from intensified forest management, eutrophication, and climate change may alter the ecosystem functions of understory vegetation and services boreal forests provide. Swedish forests span long gradients of climate, nitrogen deposition, and management intensity. This makes them ideal to study how the species composition and functions of other, more pristine, boreal forests might change under increased anthropogenic pressure. Moreover, the National Forest Inventory (NFI) has collected systematic data on Swedish forest vegetation since the mid-20th century. We use this data to quantify changes in vegetation types between two periods, 1953-1962 and 2003-2012. The results show changes in forest understory vegetation since the 1950s at scales not previously documented in the boreal biome. The spatial extent of most vegetation types changed significantly. Shade-adapted and nutrient-demanding species (those with high specific leaf area) have become more common at the expense of light-demanding and nutrient-conservative (low specific leaf area) species. The cover of ericaceous dwarf shrubs decreased dramatically. These effects were strongest where anthropogenic impacts were greatest, suggesting links to drivers such as nitrogen deposition and land-use change. These changes may impact ecosystem functions and services via effects on higher trophic levels and faster plant litter decomposition in the expanding vegetation types. This, in turn, may influence nutrient dynamics, and consequently ecosystem productivity and carbon sequestration.
41.	Hedwall, Per-Ola (author) Intensive management with fertilisation of Picea abies – changes in the composition and diversity of ground vegetation in young stands 2009 Conference paper (other academic/artistic)
42.	Hedwall, Per-Ola, et al. (author) Interactions between local and global drivers determine long-term trends in boreal forest understorey vegetation 2021 In: Global Ecology and Biogeography. - : Wiley. - 1466-822X .- 1466-8238. ; 30, s. 1765-1780 Journal article (peer-reviewed)abstract Aim Global change effects on forest ecosystems are increasingly claimed to be context dependent, indicated by interactions between global and local environmental drivers. Most examples of such context dependencies originate from temperate systems, while limited research comes from the boreal biome. Here we set out to test if interactions between climate warming, nitrogen deposition, land-use change resulting in increasing forest density, and soil pH drive long-term changes in understorey vegetation in boreal forests. Location Sweden. Time period 1953-2012. Major taxa studied Vascular plants. Methods We used long-term (50 years) National Forest Inventory data on forest understorey vegetation in Sweden to model the combined effects of climate warming, nitrogen deposition, increase in forest density (tree basal area), and soil pH. Results Our results identify increasing temperature, nitrogen deposition and denser, shadier forest conditions as the main drivers of understorey vegetation changes during this time period. More importantly, we found that these effects varied with local conditions, that is, that the change towards a more nitrophilic understorey vegetation was more pronounced at low than high soil pH. Forest density was an important modulator of nitrogen deposition and temperature increase, with effects generally decreasing with density. Decreased cover of ericaceous dwarf shrubs was driven by both forest density and nitrogen deposition, with a stronger effect at low than at high pH. Main conclusions Our results highlight that to understand forest ecosystems' response to global change, and to make adequate management decisions to mitigate the effects of global change, we need to understand how changes in local environmental factors (forest density and soil pH) interact with global-scale drivers (nitrogen deposition and climate warming). Neglecting such interactions will lead to incorrect estimations of effects. In our case, we would for example, have underestimated the eutrophication effects on acid soils, which constitute a considerable part of the boreal biome.
43.	Hedwall, Per-Ola, et al. (author) Interactions with successional stage and nutrient status determines the life-form-specific effects of increased soil temperature on boreal forest floor vegetation 2015 In: Ecology and Evolution. - : Wiley. - 2045-7758. ; 5, s. 948-960 Journal article (peer-reviewed)abstract The boreal forest is one of the largest terrestrial biomes and plays a key role for the global carbon balance and climate. The forest floor vegetation has a strong influence on the carbon and nitrogen cycles of the forests and is sensitive to changes in temperature conditions and nutrient availability. Additionally, the effects of climate warming on forest floor vegetation have been suggested to be moderated by the tree layer. Data on the effects of soil warming on forest floor vegetation from the boreal forest are, however, very scarce. We studied the effects on the forest floor vegetation in a long-term (18years) soil warming and fertilization experiment in a Norway spruce stand in northern Sweden. During the first 9years, warming favored early successional species such as grasses and forbs at the expense of dwarf shrubs and bryophytes in unfertilized stands, while the effects were smaller after fertilization. Hence, warming led to significant changes in species composition and an increase in species richness in the open canopy nutrient limited forest. After another 9years of warming and increasing tree canopy closure, most of the initial effects had ceased, indicating an interaction between forest succession and warming. The only remaining effect of warming was on the abundance of bryophytes, which contrary to the initial phase was strongly favored by warming. We propose that the suggested moderating effects of the tree layer are specific to plant life-form and conclude that the successional phase of the forest may have a considerable impact on the effects of climate change on forest floor vegetation and its feedback effects on the carbon and nitrogen cycles, and thus on the climate.
44.	Hedwall, Per-Ola, et al. (author) Interplay between N-form and N-dose influences ecosystem effects of N addition to boreal forest 2018 In: Plant and Soil. - : Springer Science and Business Media LLC. - 0032-079X .- 1573-5036. ; 423, s. 385-395 Journal article (peer-reviewed)abstract Nitrogen (N) addition effects on boreal forest ecosystem are influenced by an interplay between N-form and N-dose. We hypothesize that trees take up organic N more efficiently than inorganic N and that unwanted side-effects of organic N are smaller. We predicted that 1) the tree growth response to arginine (ARG) addition is larger than to ammonium-nitrate (AN) and, 2) understory vegetation and ectomycorrhizal (EcM) changes following ARG addition are smaller than following AN addition.We investigated the effects of AN and ARG addition (50 and 150 kg N ha(-1)) during five years on tree growth, understory vegetation and EcM fungi in a Pinus sylvestris L. forest (c 50 years old) in northern Sweden.N addition increased tree growth and changed understory vegetation composition with few significant differences between AN and ARG. Differences in responses mainly occurred for the bryophyte Pleurozium schreberi which decreased more from ARG, and for EcM sporocarps, which sharply declined from AN, but not from ARG.We found very few differences in responses between AN and ARG addition with the exception of EcM and bryophytes. These species groups have several key functions in boreal forests and the differences in responses merits further investigations.
45.	Hedwall, Per-Ola, et al. (author) Nitrogen-retention capacity in a fertilized forest after clear-cutting - the effect of forest-floor vegetation 2015 In: Canadian Journal of Forest Research. - : Canadian Science Publishing. - 0045-5067 .- 1208-6037. ; 45, s. 130-134 Journal article (peer-reviewed)abstract Forest fertilization with nitrogen (N) has several benefits to society such as increased wood production and carbon sequestration. There are, however, concerns about N leakage, particularly following clear-cutting. The forest-floor vegetation may increase the N retention of forest ecosystems; however, very few studies have quantified the amount of vegetation required. We studied the relationship between vegetation cover and risk of N leakage, estimated by the amounts of ammonium-N and nitrate-N retained on ion-exchange capsules in the soil, during 4 years following the clear-cutting and harvesting of logging residues in a previously fertilized forest in southern Sweden. Previous fertilization increased the amount of nitrate-N captured on the capsules, whereas the amount of ammonium-N decreased. The vascular vegetation cover increased from almost zero to approximately 25% independent of fertilization. The amount of ammonium-N and nitrate-N retained on the capsules was already reduced by 50%-75% at 20% vegetation cover, and by 30%-40% cover, it approached zero, independent of the number of years since clear-cutting. The vegetation may impede tree-seedling establishment, implying a trade-off between seedling growth and N-retention capacity. However, our results indicate that maximum N retention may be achieved at a relatively low vegetation cover, which could be accomplished with less intrusive scarification methods than currently used.
46.	Hedwall, Per-Ola, et al. (author) Peatland plant communities under global change : negative feedback loops counteract shifts in species composition 2017 In: Ecology. - : Wiley. - 0012-9658 .- 1939-9170. ; 98:1, s. 150-161 Journal article (peer-reviewed)abstract Mires (bogs and fens) are nutrient-limited peatland ecosystems, the vegetation of which is especially sensitive to nitrogen deposition and climate change. The role of mires in the global carbon cycle, and the delivery of different ecosystem services can be considerably altered by changes in the vegetation, which has a strong impact on peat-formation and hydrology. Mire ecosystems are commonly open with limited canopy cover but both nitrogen deposition and increased temperatures may increase the woody vegetation component. It has been predicted that such an increase in tree cover and the associated effects on light and water regimes would cause a positive feed-back loop with respect to the ground vegetation. None of these effects, however, have so far been confirmed in large-scale spatiotemporal studies. Here we analyzed data pertaining to mire vegetation from the Swedish National Forest Inventory collected from permanent sample plots over a period of 20 yr along a latitudinal gradient covering 14 degrees. We hypothesized that the changes would be larger in the southern parts as a result of higher nitrogen deposition and warmer climate. Our results showed an increase in woody vegetation with increases in most ericaceous dwarf-shrubs and in the basal area of trees. These changes were, in contrast to our expectations, evenly distributed over most of the latitudinal gradient. While nitrogen deposition is elevated in the south, the increase in temperatures during recent decades has been larger in the north. Hence, we suggest that different processes in the north and south have produced similar vegetation changes along the latitudinal gradient. There was, however, a sharp increase in compositional change at high deposition, indicating a threshold effect in the response. Instead of a positive feed-back loop caused by the tree layer, an increase in canopy cover reduced the changes in composition of the ground vegetation, whereas a decrease in canopy cover lead to larger changes. Increased natural disturbances of the tree layer due to, for example, pathogens or climate is a predicted outcome of climate change. Hence, these results may have important implications for predictions of long-term effects of increased temperature on peatland vegetation.
47.	Hedwall, Per-Ola, et al. (author) Phosphorus and nitrogen co-limitation of forest ground vegetation under elevated anthropogenic nitrogen deposition 2017 In: Oecologia. - : Springer. - 0029-8549 .- 1432-1939. ; 185:2, s. 317-326 Journal article (peer-reviewed)abstract Plant growth in northern forest ecosystems is considered to be primarily nitrogen limited. Nitrogen deposition is predicted to change this towards co-limitation/limitation by other nutrients (e.g., phosphorus), although evidence of such stoichiometric effects is scarce. We utilized two forest fertilization experiments in southern Sweden to analyze single and combined effects of nitrogen and phosphorus on the productivity, composition, and diversity of the ground vegetation. Our results indicate that the productivity of forest ground vegetation in southern Sweden is co-limited by nitrogen and phosphorus. Additionally, the combined effect of nitrogen and phosphorus on the productivity was larger than when applied solely. No effects on species richness of any of these two nutrients were observed when applied separately, while applied in combination, they increased species richness and changed species composition, mainly by promoting more mesotrophic species. All these effects, however, occurred only for the vascular plants and not for bryophytes. The tree layer in a forest has a profound impact on the productivity and diversity of the ground vegetation by competing for both light and nutrients. This was confirmed in our study where a combination of nitrogen and high tree basal area reduced cover of the ground vegetation compared to all the other treatments where basal area was lower after stand thinning. During the past decades, nitrogen deposition may have further increased this competition from the trees for phosphorus and gradually reduced ground vegetation diversity. Phosphorus limitation induced by nitrogen deposition may, thus, contribute to ongoing changes in forest ground vegetation.
48.	Hedwall, Per-Ola, et al. (author) Sprucification in protected forests: myth or veracity? - Clues from 60 yrs survey data 2016 In: Applied Vegetation Science. - : Wiley. - 1402-2001. ; 19, s. 371-380 Journal article (peer-reviewed)abstract Questions: The purpose of this study was to examine how compositional characteristics of forest reserves in production landscapes change over time and to explore the local site conditions that drive these processes. Our hypothesis was according to the general paradigm that suppression of natural disturbance regimes and lack of active management causes protected forest areas (PFAs) to develop into forests of high density dominated by late successional tree species.Location: Boreal and hemiboreal forests of Sweden.Methods: We used long-term (60 yrs) data from the Swedish National Forest Inventory (NFI), representing all the PFAs in Sweden, to study changes in tree species composition in relation to site factors and the initial state of the forest.Results: During the period of our study the average density expressed by the growing stock (GS) increased from 70 to 140 m(3).ha(-1). This increase concerned both early and late successional tree species and there was no evidence for a faster increase of the late successional species Norway spruce (Picea abies) and the species composition was stable over time. A net volume increment (NVINCR) in spruce was mostly related to sites where spruce already was present, sites with high productivity and forest of high age. The probability of an increase in Scots pine (Pinus sylvestris) was negatively linked to productivity and stand age, while the NVINCR was higher on more productive sites. The NVINCR of deciduous trees was unrelated to site productivity and age but positively affected by the initial GS, increasing slope and soil depth.Conclusions: Our results suggest that the relative composition of species is stable over time and balanced by site productivity, which is in accordance with the resource-ratio hypothesis. An important cause of this stability could be the low number of tree species in northern Europe, which limits the number of potential successional pathways.
49.	Hedwall, Per-Ola, et al. (author) Structural changes in protected forests in Sweden: implications for conservation functionality 2015 In: Canadian Journal of Forest Research. - : Canadian Science Publishing. - 0045-5067 .- 1208-6037. ; 45, s. 1215-1224 Journal article (peer-reviewed)abstract Protected forest areas (PFAs) are key features of biodiversity conservation, and knowledge about long-term development is crucial in evaluating their efficiency and management needs. Longitudinal data on forest structure in PFAs is uncommon and often from small areas. Here we use data from the Swedish National Forest Inventory to study changes in more than 750 000 ha of PFAs over 60 years. Structures important for biodiversity, e.g., number of large trees and the volume of hard deadwood, including both standing and down wood, have more than doubled. The initial volume of deadwood, however, was very low. The overall tree species composition was stable over time, and only among the largest trees were there indications of a shift towards the late successional Norway spruce (Picea abies (L.) Karst.). Deadwood increased independent of species, size of wood, and site characteristics. This increase was positively related to the volume of living trees and forest age. We conclude that Swedish PFAs, in the absence of active management and under fire suppression at the landscape scale, develop structural components that are crucial for conservation of biodiversity. However, although tree species composition appears stable, present disturbance regimes in the PFAs are considerably different from those in naturally dynamic forests, which may have implications for long-term biodiversity maintenance.
50.	Hedwall, Per-Ola, et al. (author) Trait variations of ground flora species disentangle the effects of global change and altered land-use in Swedish forests during 20 years 2016 In: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 22, s. 4038-4047 Journal article (peer-reviewed)abstract Northern forest ecosystems are exposed to a range of anthropogenic processes including global warming, atmospheric deposition, and changing land-use. The vegetation of northern forests is composed of species with several functional traits related to these processes, whose effects may be difficult to disentangle. Here, we combined analyses of spatio-temporal dynamics and functional traits of ground flora species, including morphological characteristics, responses to macro- and microclimate, soil conditions, and disturbance. Based on data from the Swedish National Forest Inventory, we compared changes in occurrence of a large number of ground flora species during a 20-year period (1994-2013) in boreal and temperate Sweden respectively. Our results show that a majority of the common ground flora species have changed their overall frequency. Comparisons of functional traits between increasing and declining species, and of trends in mean trait values of sample plots, indicate that current floristic changes are caused by combined effects of climate warming, nitrogen deposition and changing land-use. Changes and their relations with plant traits were generally larger in temperate southern Sweden. Nutrient-demanding species with mesotrophic morphology were favored by ongoing eutrophication due to nitrogen deposition in the temperate zone, while dwarf shrubs with low demands on nitrogen decreased in frequency. An increase of species with less northern and less eastern distribution limits was also restricted to temperate Sweden, and indicates effects of a moister and milder macroclimate. A trend toward dense plantation forests is mirrored by a decrease of light-demanding species in both vegetation zones, and a decrease of grassland species in the temperate zone. Although denser tree canopies may buffer effects of a warmer climate and of nitrogen deposition to some extent, traits related to these processes were weakly correlated in the group of species with changing frequency. Hence, our results indicate specific effects of these often confounded anthropogenic processes.

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