| 1. |
- De Pauw, Karen, et al.
(författare)
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Nutrient-demanding and thermophilous plants dominate urban forest-edge vegetation across temperate Europe
- 2024
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Ingår i: Journal of Vegetation Science. - 1100-9233 .- 1654-1103. ; 35:1
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Tidskriftsartikel (refereegranskat)abstract
- QuestionsForests are highly fragmented across the globe. For urban forests in particular, fragmentation increases the exposure to local warming caused by the urban heat island (UHI) effect. We here aim to quantify edge effects on herbaceous understorey vegetation in urban forests, and test whether these effects interact with forest structural complexity.LocationWe set up a pan-European study at the continental scale including six urban forests in Zurich, Paris, Katowice, Brussels, Bremen, and Stockholm.MethodsWe recorded understorey plant communities from the edge towards the interior of urban forests. Within each urban forest, we studied edge-to-interior gradients in paired stands with differing forest structural complexity. Community composition was analysed based on species specialism, life form, light, nutrient, acidity and disturbance indicator values and species' thermal niches.ResultsWe found that herbaceous communities at urban forest edges supported more generalists and forbs but fewer ferns than in forests' interiors. A buffered summer microclimate proved crucial for the presence of fern species. The edge communities contained more thermophilous, disturbance-tolerant, nutrient-demanding and basiphilous plant species, a pattern strongly confirmed by corresponding edge-to-interior gradients in microclimate, soil and light conditions in the understorey. Additionally, plots with a lower canopy cover and higher light availability supported higher numbers of both generalists and forest specialists. Even though no significant interactions were found between the edge distance and forest structural complexity, opposing additive effects indicated that a dense canopy can be used to buffer negative edge effects.ConclusionThe urban environment poses a multifaceted filter on understorey plant communities which contributes to significant differences in community composition between urban forest edges and interiors. For urban biodiversity conservation and the buffering of edge effects, it will be key to maintain dense canopies near urban forest edges. The urban environment poses a multifaceted filter on understorey plant communities which contributes to significant differences in community composition between urban forest edges and interiors. For urban biodiversity conservation and the buffering of edge effects, it will be key to maintain dense canopies near urban forest edges.image
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| 2. |
- De Pauw, Karen, et al.
(författare)
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Taxonomic, phylogenetic and functional diversity of understorey plants respond differently to environmental conditions in European forest edges
- 2021
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Ingår i: Journal of Ecology. - : Wiley. - 0022-0477 .- 1365-2745. ; 109:7, s. 2629-2648
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Tidskriftsartikel (refereegranskat)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.
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| 3. |
- De Pauw, Karen, et al.
(författare)
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The urban heat island accelerates litter decomposition through microclimatic warming in temperate urban forests
- 2024
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Ingår i: Urban Ecosystems. - 1083-8155 .- 1573-1642.
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Tidskriftsartikel (refereegranskat)abstract
- Forests worldwide are experiencing fragmentation, with especially important consequences for ecosystems bordering urbanized areas. Urban forests are exposed to local warming due to the urban heat island which affects their biodiversity and ecosystem functioning. A key ecosystem function affecting carbon and nutrient cycling in forests is litter decomposition, a process driven by the local microclimate. Thus, our aim was to clarify the impact of the urban heat island on litter decomposition in urban forests. We studied soil microclimate and litter decomposition in six urban forests across Europe and along local gradients from the urban forest edge to the interior. To quantify decomposition independent from local forest composition and litter quality, we used standardized green tea and rooibos tea litterbags. We determined the role of the soil microclimate and other environmental drivers for litter decomposition. Secondly, we assessed effects of edge proximity and landscape context on the soil microclimate. Soil characteristics were only driving green tea and not rooibos tea decomposition. On the contrary, higher soil temperatures resulted in faster rates of litter decomposition for both green and rooibos tea and were related to the proximity to the forest edge and the proportion of built-up area in the landscape. Via structural equation modelling we detected cascading effects of the urban heat island on litter decomposition. Such changes in litter decomposition have the potential to alter the soil food web, nutrient cycling and carbon drawdown in urban forests, and could result in significant interactions between urbanisation and ongoing climate change.
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| 4. |
- De Pauw, Karen, et al.
(författare)
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Urban forest microclimates across temperate Europe are shaped by deep edge effects and forest structure
- 2023
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Ingår i: Agricultural and Forest Meteorology. - 0168-1923 .- 1873-2240. ; 341
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Tidskriftsartikel (refereegranskat)abstract
- The urban heat island (UHI) causes strong warming of cities and their urban forests worldwide. Especially urban forest edges are strongly exposed to the UHI effect, which could impact urban forest biodiversity and functioning. However, it is not known to what extent the UHI effect alters edge-to-interior microclimatic gradients within urban forests and whether this depends on the forests' structure.Here we quantified gradients of air temperature, relative air humidity and vapour pressure deficits (VPD) along urban forest edge-to-interior transects with contrasting stand structures in six major cities across Europe. We performed continuous hourly microclimate measurements for two consecutive years and analysed the magnitude and depth of edge effects, as well as forest structural drivers of microclimatic variation.Compared to edge studies in rural temperate forests, we found that edge effects reached deeper into urban forests, at least up to 50 m. Throughout the year, urban forest edges were warmer and drier compared to forest interiors, with the largest differences occurring during summer and daytime. Not only maximum, but also mean and minimum temperatures were higher at the urban forest edge up to large edge distances (at least 85 m). Denser forests with a higher plant area index buffered high air temperatures and VPDs from spring to autumn.We conclude that urban forest edges are unique ecotones with specific microclimates shaped by the UHI effect. Both forest edges and interiors showed increased buffering capacities with higher forest canopy density. We advocate for the conservation and expansion of urban forests which can buffer increasingly frequent and intense climate extremes. To this end, urban forest managers are encouraged to aim for multi-layered dense forest canopies and consider edge buffer zones of at least 50 m wide.
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| 5. |
- Gasperini, Cristina, et al.
(författare)
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Soil seed bank responses to edge effects in temperate European forests
- 2022
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Ingår i: Global Ecology and Biogeography. - Stockholm : Wiley. - 1466-822X .- 1466-8238. ; 31:9, s. 1877-1893
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Tidskriftsartikel (refereegranskat)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.
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| 6. |
- Govaert, Sanne, et al.
(författare)
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Edge influence on understorey plant communities depends on forest management
- 2020
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Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 31:2, s. 281-292
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Tidskriftsartikel (refereegranskat)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.
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| 7. |
- Govaert, Sanne, et al.
(författare)
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Trait–micro-environment relationships of forest herb communities across Europe
- 2024
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Ingår i: Global Ecology and Biogeography. - 1466-822X .- 1466-8238. ; 33:2, s. 286-302
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Tidskriftsartikel (refereegranskat)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.
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| 8. |
- Meeussen, Camille, et al.
(författare)
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Drivers of carbon stocks in forest edges across Europe
- 2021
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 759
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Tidskriftsartikel (refereegranskat)abstract
- Forests play a key role in global carbon cycling and sequestration. However, the potential for carbon drawdown is affected by forest fragmentation and resulting changes in microclimate, nutrient inputs, disturbance and productivity near edges. Up to 20% of the global forested area lieswithin 100 m of an edge and, even in temperate forests, knowledge on howedge conditions affect carbon stocks and howfar this influence penetrates into forest interiors is scarce. Here we studied carbon stocks in the aboveground biomass, forest floor and the mineral topsoil in 225 plots in deciduous forest edges across Europe and tested the impact of macroclimate, nitrogen deposition and smaller-grained drivers (e.g. microclimate) on these stocks. Total carbon and carbon in the aboveground biomass stock were on average 39% and 95% higher at the forest edge than 100 m into the interior. The increase in the aboveground biomass stock close to the edgewas mainly related to enhanced nitrogen deposition. No edge influence was found for stocks in the mineral topsoil. Edge-to-interior gradients in forest floor carbon changed across latitude: carbon stocks in the forest floor were higher near the edge in southern Europe. Forest floor carbon decreased with increasing litter quality (i.e. high decomposition rate) and decreasing plant area index, whereas higher soil temperatures negatively affected the mineral top soil carbon. Based on high-resolution forest fragmentation maps, we estimate that the additional carbon stored in deciduous forest edges across Europe amounts to not less than 183 Tg carbon, which is equivalent to the storage capacity of 1 million ha of additional forest. This study underpins the importance of including edge influences when quantifying the carbon stocks in temperate forests and stresses the importance of preserving natural forest edges and small forest patches with a high edge-to-interior surface area.
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| 9. |
- Meeussen, Camille, et al.
(författare)
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Microclimatic edge-to-interior gradients of European deciduous forests
- 2021
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Ingår i: Agricultural and Forest Meteorology. - : Elsevier BV. - 0168-1923 .- 1873-2240. ; 311
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Tidskriftsartikel (refereegranskat)abstract
- Global forest cover is heavily fragmented. Due to high edge-to-surface ratios in small forest patches, a large proportion of forests is affected by edge influences involving steep microclimatic gradients. Although forest edges are important ecotones and account for 20% of the global forested area, it remains unclear how biotic and abiotic drivers affect forest edge microclimates at the continental scale. Here we report soil and air temperatures measured in 225 deciduous forest plots across Europe for two years. Forest stands were situated along a latitudinal gradient and subject to a varying vegetation structure as quantified by terrestrial laser scanning. In summer, the average offset of air and soil temperatures in forest edges compared to temperatures outside the forest amounted to -2.8 degrees C and -2.3 degrees C, respectively. Edge-to-interior summer temperature gradients were affected by the macroclimate and edge structure. From the edge onwards, larger offsets were observed in dense forest edges and in warmer, southern regions. In open forests and northern Europe, altered microclimatic conditions extended deeper into the forest and gradients were steeper. Canopy closure and plant area index were important drivers of summer offsets in edges, whereas in winter also the forest-floor biomass played a key role. Using high-resolution maps, we estimated that approximately 10% of the European broadleaved forests would be affected by altered temperature regimes. Gradual transition zones between forest and adjacent lands are valuable habitat types for edge species. However, if cool and moist forest interiors are desired, then (i) dense and complex forest edges, (ii) an undisturbed forested buffer zone of at least 12.5 m deep and (iii) trees with a high shade casting ability could all contribute to an increased offset. These findings provide important guidelines to mitigate edge influences, to protect typical forest microclimates and to adapt forest management to climate change.
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| 10. |
- Meeussen, Camille, et al.
(författare)
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Structural variation of forest edges across Europe
- 2020
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Ingår i: Forest Ecology and Management. - : Elsevier BV. - 0378-1127 .- 1872-7042. ; 462
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Tidskriftsartikel (refereegranskat)abstract
- Forest edges are interfaces between forest interiors and adjacent land cover types. They are important elements in the landscape with almost 20% of the global forest area located within 100 m of the edge. Edges are structurally different from forest interiors, which results in unique edge influences on microclimate, functioning and biodiversity. These edge influences have been studied for multiple decades, yet there is only limited information available on how forest edge structure varies at the continental scale, and which factors drive this potential structural diversity. Here we quantified the structural variation along 45 edge-to-interior transects situated along latitudinal, elevational and management gradients across Europe. We combined state-of-the-art terrestrial laser scanning and conventional forest inventory techniques to investigate how the forest edge structure (e.g. plant area index, stem density, canopy height and foliage height diversity) varies and which factors affect this forest edge structural variability. Macroclimate, management, distance to the forest edge and tree community composition all influenced the forest edge structural variability and interestingly we detected interactive effects of our predictors as well. We found more abrupt edge-to-interior gradients (i.e. steeper slopes) in the plant area index in regularly thinned forests. In addition, latitude, mean annual temperature and humidity all affected edge-to-interior gradients in stem density. We also detected a simultaneous impact of both humidity and management, and humidity and distance to the forest edge, on the canopy height and foliage height diversity. These results contribute to our understanding of how environmental conditions and management shape the forest edge structure. Our findings stress the need for site-specific recommendations on forest edge management instead of generalized recommendations as the macroclimate substantially influences the forest edge structure. Only then, the forest edge microclimate, functioning and biodiversity can be conserved at a local scale.
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