| 1. |
- De Pauw, Karen, et al.
(författare)
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Forest understorey communities respond strongly to light in interaction with forest structure, but not to microclimate warming
- 2022
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Ingår i: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 233:1, s. 219-235
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Tidskriftsartikel (refereegranskat)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.
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| 2. |
- Díaz-Calafat, Joan, et al.
(författare)
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From broadleaves to conifers : The effect of tree composition and density on understory microclimate across latitudes
- 2023
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Ingår i: Agricultural and Forest Meteorology. - 0168-1923 .- 1873-2240. ; 341
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Tidskriftsartikel (refereegranskat)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.
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| 3. |
- Hedwall, Per-Ola, et al.
(författare)
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Interactions between local and global drivers determine long-term trends in boreal forest understorey vegetation
- 2021
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Ingår i: Global Ecology and Biogeography. - : Wiley. - 1466-822X .- 1466-8238. ; 30, s. 1765-1780
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Tidskriftsartikel (refereegranskat)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.
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| 4. |
- Meeussen, Ccamille, et al.
(författare)
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Initial oak regeneration responses to experimental warming along microclimatic and macroclimatic gradients
- 2022
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Ingår i: Plant Biology. - : Wiley. - 1435-8603 .- 1438-8677. ; 24:5, s. 745-757
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Tidskriftsartikel (refereegranskat)abstract
- Quercus spp. are one of the most important tree genera in temperate deciduous forests in terms of biodiversity, economic and cultural perspectives.However, natural regeneration of oaks, depending on specific environmental conditions, is still not sufficiently understood.Oak regeneration dynamics are impacted by climate change, but these climate impacts will depend on local forest management and light and temperature conditions.
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| 5. |
- Pommerening, Arne, et al.
(författare)
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Do large forest trees tend towards high species mingling?
- 2017
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Ingår i: Ecological Informatics. - : Elsevier BV. - 1574-9541 .- 1878-0512. ; 42, s. 139-147
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Tidskriftsartikel (refereegranskat)abstract
- Effects caused by human management and natural disturbances as well as by ecological mechanisms such as those described, for example, by the Janzen-Connell and the herd immunity hypotheses play an important role in maintaining species diversity. These processes are often accompanied by local size-hierarchy effects and as a likely consequence of them we hypothesised that large plants generally have a tendency to show high species mingling, where plants and their nearest neighbours are heterospecific. To carry out a first benchmark study in forests from different parts of Europe, Africa and North America, we selected spatial data from twelve forest ecosystems and analysed the mingling situation based on an index of spatial species mingling. Using stem diameter at breast height and stem diameter differentiation among the nearest neighbours as explanatory variables we then applied logistic regression to explain mingling probability. Overall we found significant support for the expectation that large trees and trees growing at low local densities often (75% of all analysed forest stands) have indeed a tendency towards high species mingling. This supports our expectation that the tendency of larger trees towards high species mingling generally is either a consequence of disturbances/forest management or of the aforementioned ecological processes, although a few forest stands also deviated from the expected pattern. We also found that size differentiation and species mingling are strongly related in local neighbourhoods. Thus the results of our study strongly support the view that local species richness promotes local size hierarchy irrespective of climate zone. This leads to situations where in local neighbourhoods with large size diversity there is also high mingling and vice versa. This allows conservation to focus on maintaining or improving one diversity aspect, e.g. size diversity, whilst obtaining the other, e.g. species mingling, as a byproduct.
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| 6. |
- Sanczuk, Pieter, et al.
(författare)
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Microclimate and forest density drive plant population dynamics under climate change
- 2023
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Ingår i: Nature Climate Change. - 1758-678X .- 1758-6798. ; 13:8, s. 840-847
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Tidskriftsartikel (refereegranskat)abstract
- Macroclimatic changes are impacting ecosystems worldwide. However, a large portion of terrestrial species live under conditions where impacts of macroclimate change are buffered, such as in the shade of trees, and how this buffering impacts future below-canopy biodiversity redistributions at the continental scale is unknown. Here we show that shady forest floors due to dense tree canopies mitigate severe warming impacts on forest biodiversity, while canopy opening amplifies macroclimate change impacts. A cross-continental transplant experiment in five contrasting biogeographical areas combined with experimental heating and irradiation treatments was used to parametize 25-m resolution mechanistic demographic distribution models and project the current and future distributions of 12 common understorey plant species, considering the effects of forest microclimate and forest cover density. These results highlight microclimates and forest density as powerful tools for forest managers and policymakers to shelter forest biodiversity from climate change.The impacts of microclimate on future plant population dynamics are poorly understood. The authors use large-scale transplant climate change experiments to show the contribution of forest microclimates to population dynamics and project the distributions of 12 common understorey plants.
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| 7. |
- Uria Diez, Jaime, et al.
(författare)
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Crown plasticity in Scots pine (Pinus sylvestris L.) as a strategy of adaptation to competition and environmental factors
- 2017
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Ingår i: Ecological Modelling. - : Elsevier BV. - 0304-3800 .- 1872-7026. ; 356, s. 117-126
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Tidskriftsartikel (refereegranskat)abstract
- Competition for canopy space is a major ecological process in forest dynamics and some tree species are able to shift their crowns away from competition pressure to improve light capture. As a result canopy structure is an expression of the spatial pattern of resource acquisition. A novel combination of spatial analysis, tessellations and computer simulations of crown movements allowed us to disentangle the main processes that govern crown movements in Pinus sylvestris L forests. By applying spatial point process statistics to three sets of coordinates (stem, crown and tessellation centre points), we analysed and modelled the interaction between individuals along different tree-crown development stages in Valsain forest, Sierra of Guadarrama (Spain). Overall we found that Scots pine trees were able to respond to the presence of neighbours in monospecific stands. The trees involved tended to avoid competition by shifting their crowns towards empty spaces. Mature trees showed more crown displacement than smaller trees and made an effective use of canopy space. The efficient use of space in older stands was indicated by more regular crown patterns compared to those of younger stands, which usually were more clustered. We also found that crown asymmetry was often a combination of some minor abiotic and biotic ecological processes. In our study, wind and slope did not have a big effect on crown displacement, while biotic interactions showed a strong effect on canopy structure causing trees to be regularly distributed and thus using canopy space more efficiently. (C) 2017 Elsevier B.V. All rights reserved.
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| 8. |
- Uria Diez, Jaime
(författare)
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Fertilization triggers 11 yr of changes in community assembly in Mediterranean grassland
- 2016
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Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 27, s. 728-738
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Tidskriftsartikel (refereegranskat)abstract
- QuestionFertilization, i.e. nutrient addition, and changes in grazing intensity are important factors associated with global change that threaten grasslands worldwide. How does the plant community assembly in Mediterranean grasslands respond after 11yr to a single fertilization event?LocationSpecies-rich Mediterranean grassland, Navarra, northern Spain.MethodsIn 2003, 11 permanent plots were established in a Mediterranean grassland: six plots were fertilized and five were used as controls. Fertilization consisted in the addition of sewage sludge on the soil surface. Grazing was excluded during the course of the experiment. Changes in vegetation abundance were monitored from 2004 to 2014. In 2012, key plant functional traits (height, leaf area, SLA, LDMC) of the most frequent species were collected. We measured taxonomic and functional species composition and diversity. Niche overlap compared to null models was used to assess the mechanisms influencing community assembly.ResultsSpecies composition changed markedly in the fertilized plots. These changes were accompanied by a reduction in taxonomic diversity. One yr after starting the experiment there were no differences in functional composition (i.e. CWM trait values) between fertilized and control plots (excluding SLA), but 11yr later fertilized plots were composed of taller plants with larger SLA and lower LDMC. We found a major reduction in niche overlap in plant height andSLA after fertilizing associated with a replacement in several species that could be indicative of competitive exclusion (principle of limiting similarity). Conversely, we found an increase in niche overlap in leaf area indicating that competition increases similarity among species (weaker competitor exclusion or abiotic filtering). At the end of the experiment, we found large differences in SLA and LDMC between fertilized and control plots.ConclusionsA single fertilization event that occurred 11yr ago triggered a wave of changes in grassland community assembly that are still on-going. Fertilization enhanced the establishment of taller species with larger leaf areas, which displaced, by competitive exclusion, the species that had previously been present. Community assembly patterns in Mediterranean grassland are highly sensitive to abrupt changes in resource availability.
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| 9. |
- Uria Diez, Jaime
(författare)
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Spatial distribution and association patterns in a tropical evergreen broad-leaved forest of north-central Vietnam
- 2016
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Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 27, s. 318-327
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Tidskriftsartikel (refereegranskat)abstract
- Questions: What are the prevailing types of intraspecific spatial distributions and interspecific association patterns at species and life stage levels of trees in a tropical rain forest? Which ecological processes could structure these patterns? Possible processes include dispersal limitation, self-thinning, facilitation and competition between species and life stages. Location: A tropical broad-leaved forest in north-central Vietnam. Methods: We used univariate and bivariate pair-correlation functions to investigate the spatial distribution and association patterns of 18 abundant tree species. To disentangle first- and second-order effects, we used a scale separation approach with the heterogeneous Poisson process as nullmodel. Results: (1) Sixteen of 18 species had aggregated patterns at various scales and regardless of their abundance. (2) Significant and aggregated patterns were found in 64% of all specific life stages. (3) At scales up to 15 m, 12.4% species pairs showed significant associations, among that 71% were spatial attractions, 5% were spatial repulsions and 24% were non-essential interactions. (4) In different life stage associations, attractions (81%) predominated over repulsions (19%) at small scales of up to 15 m. Conclusions: Our findings provide evidence that dispersal limitation may regulate the spatial patterns of tree species. Moreover, positive spatial associations between tree species and life stages suggest the presence of species herd protection and/or facilitation in this forest stand, while the persistence of intraspecific aggregation through life stages suggests a very late onset or even absence of selfthinning. Habitat heterogeneity plays an important role for species distribution patterns, and the spatial segregation occurs at a scale around 15 min this forest.
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| 10. |
- Uria Diez, Jaime
(författare)
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Within‐community environmental variability drives trait variability in species‐rich grasslands
- 2017
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Ingår i: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 28, s. 303-312
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Tidskriftsartikel (refereegranskat)abstract
- AimsSpatial environmental heterogeneity has been considered an important co-existence mechanism because environmental variation enables different species to co-occur. We predict that if functional differences are important for co-existence, then both species and functional diversity should be positively related to environmental heterogeneity.LocationThirty three dry calcareous grassland sites in Estonia.MethodsIn each site, we established a transect (10.0mx0.1m), consisting of 100 quadrats (10cmx10cm). In each quadrat, we recorded species richness and composition, and measured soil depth, moisture and light availability. We collected data on eight traits from most of the species found across the sites. We calculated functional diversity (FD) at the quadrat scale, and compared the observed FD to that expected at random using two null models. The first null model used all the species that occurred in the transect in the randomizations to determine environmental filtering from the transect to the quadrat. The second null model restricted the species used in the randomizations to those species whose trait range was within the range of the observed values in the quadrat, to detect evidence for niche partitioning. Quadrat mean trait values and variability in functional composition were then related to small-scale mean environmental conditions and heterogeneity, respectively.ResultsWe found convergent patterns in biomass, specific leaf area, specific root length and clonality compared to randomized communities that included all species occurring in the transect, and found divergence in height and leaf area using the range-restricted null model. Hence, we found patterns consistent with environmental filtering and niche partitioning depending on the traits considered. Quadrat mean traits were significantly correlated with the measured environmental variables, with the main trend being a positive relationship between size-related traits and soil resources, and a negative relationship between these traits and light availability. Trait variability in height, leaf area, leaf dry matter content, specific root length and clonality was positively related to soil depth heterogeneity. There was a trend for species richness to be negatively related to environmental heterogeneity.ConclusionsCo-occurring species were more similar in several traits partly due to micro-environmental filtering in response to variability in soil depth. While environmental heterogeneity increased trait variability, negative relationships with species richness were observed. Hence, niche partitioning does not appear to be important for the maintenance of high small-scale species richness in these grasslands.
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