Interactions among trees: A key element in the stabilising effect of species diversity on forest growth

Aussenac, Raphaël; Bergeron, Yves; Gravel, Dominique; Drobyshev, Igor

doi:10.1111/1365-2435.13257

Cited by 44 publications

(29 citation statements)

References 39 publications

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“…Previous studies often conclude that the weak or negative associations between climatic change and tree growth are attributable to warming‐induced water deficits (Chen & Luo, ; Chen, Luo, Reich, Searle, & Biswas, ; Girardin et al, ; Restaino et al, ) or reaching the maximum capacity of carbon assimilation of a tree (Hararuk et al, ) or changes in carbon allocation strategies (Giguere‐Croteau et al, ). Interspecific interactions, which we did not quantify in our study, can also determine boreal tree growth responses to climate change (Aussenac, Bergeron, Gravel, & Drobyshev, ; Aussenac et al, ). In our study area, water availability increased during the study period.…”

Section: Discussionmentioning

confidence: 87%

Climatic change only stimulated growth for trees under weak competition in central boreal forests

et al. 2019

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Global change ecologists have often used trees under weak competition (e.g. dominant/codominant trees) to examine relationships between climatic change and tree growth. Scaling up these results to a forest relies on the assumption that the climatic change–tree growth relationship is not affected by tree‐level competition. Using permanent sample plot data from the central Canadian boreal region where warming did not result in water deficit, we tested the above‐mentioned assumption by looking at whether the relationship between climatic change and tree growth varied with tree‐level competition, which was quantified using a modified Hegyi competition index. We found that tree growth increased over time for trees under weak competition, but decreased for those under strong competition. The divergent temporal trends among trees under different levels of competition led to a non‐significant change in growth for our study plots. Growth increased with regional warming, atmospheric [CO2] and water availability for trees under weak competition, but not for those under strong competition. Synthesis. Our results suggest that upscaling the growth responses of dominant/codominant trees to climate change to a forest or a region can lead to biased estimates. Tree‐level competition should be taken into account when expressing climatic change and tree growth relationships.

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Section: Discussionmentioning

confidence: 87%

Climatic change only stimulated growth for trees under weak competition in central boreal forests

et al. 2019

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“…In grassland ecosystems, there is abundant evidence that interannual fluctuations of community‐level productivity are smaller in more diverse compared to less diverse communities, resulting in a net positive DSR (Hautier et al, ; Isbell et al, ). The few studies that have analysed temporal stability in temperate and boreal forest ecosystems support the hypothesis that diversity can stabilize community‐level productivity (Aussenac, Bergeron, Gravel, & Drobyshev, ; del Río et al, ; Jucker, Bouriaud, Avacaritei, & Coomes, ; Morin, Fahse, de Mazancourt, Scherer‐Lorenzen, & Bugmann, ). For seasonally dry tropics undergoing supraseasonal drought cycles, where the contrast between favourable and unfavourable growth conditions is likely stronger, there has been some evidence from the Sardinilla experiment that species mixing decreases the climatic sensitivity of tree growth and hence stabilizes productivity (Hutchison et al, ) but no detailed analysis of the underlying drivers of this phenomenon exist.…”

Section: Introductionmentioning

confidence: 91%

Drivers of productivity and its temporal stability in a tropical tree diversity experiment

Schnabel

Schwarz

Dănescu

et al. 2019

Global Change Biology

111

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There is increasing evidence that mixed-species forests can provide multiple ecosystem services at a higher level than their monospecific counterparts. However, most studies concerning tree diversity and ecosystem functioning relationships use data from forest inventories (under noncontrolled conditions) or from very young plantation experiments. Here, we investigated temporal dynamics of diversityproductivity relationships and diversity-stability relationships in the oldest tropical tree diversity experiment. Sardinilla was established in Panama in 2001, with 22 plots that form a gradient in native tree species richness of one-, two-, three-and five-species communities. Using annual data describing tree diameters and heights, we calculated basal area increment as the proxy of tree productivity. We combined tree neighbourhood-and community-level analyses and tested the effects of both species diversity and structural diversity on productivity and its temporal stability.General patterns were consistent across both scales indicating that tree-tree interactions in neighbourhoods drive observed diversity effects. From 2006 to 2016, mean overyielding (higher productivity in mixtures than in monocultures) was 25%-30% in two-and three-species mixtures and 50% in five-species stands. Tree neighbourhood diversity enhanced community productivity but the effect of species diversity was stronger and increased over time, whereas the effect of structural diversity declined. Temporal stability of community productivity increased with species diversity via two principle mechanisms: asynchronous responses of species to environmental variability and overyielding. Overyielding in mixtures was highest during a strong El Niño-related drought. Overall, positive diversity-productivity and diversity-stability relationships predominated, with the highest productivity and stability at the highest levels of diversity. These results provide new insights into mixing effects in diverse, tropical plantations and highlight the importance of analyses of temporal dynamics for our understanding of the complex relationships between diversity, productivity and stability. Under climate change, mixed-species forests may provide both high levels and high stability of production.

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“…Consequently, BPRs at the local neighbourhood scale should become stronger during periods of water deficits, meaning that the relative importance of biodiversity effects increases during drought (Figure a,b). The few evidence on climate–growth relationships in response to local neighbourhood conditions comes from observational studies performed in less diverse temperate forests with a limited taxonomic tree diversity (Jourdan, Kunstler, & Morin, ), and most of these studies accounted for neighbourhood diversity using a contrast of neighbourhood composition (conspecific vs. heterospecific neighbours; Mölder & Leuschner, ; Vitali, Forrester, & Bauhus, ) or neighbourhood competition (intraspecific vs. interspecific competition; Aussenac, Bergeron, Gravel, & Drobyshev, ). Similarly, one recent experimental study explored drought resistance of tropical tree seedlings in response to neighbourhood composition (conspecific vs. heterospecific neighbours; O’Brien, Reynolds, Ong, & Hector, ).…”

Section: Introductionmentioning

confidence: 99%

Neighbourhood diversity mitigates drought impacts on tree growth

et al. 2020

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1. Biodiversity is considered to mitigate detrimental impacts of climate change on the functioning of forest ecosystems, such as drought-induced decline in forest productivity. However, previous studies produced controversial results and experimental evidence is rare. Specifically, the biological mechanisms underlying mitigation effects remain unclear, as existing work focuses on biodiversity effects related to the community scale.2. Using trait-based neighbourhood models, we quantified changes in above-ground wood productivity of 3,397 trees that were planted in a large-scale tree diversity experiment in subtropical China across gradients of neighbourhood diversity and climatic conditions over a 6-year period. This approach allowed us to simultaneously assess to what extent functional traits of a focal tree and biodiversity at the local neighbourhood scale mediate the growth response of individual trees to drought events.3. We found that neighbourhood tree species richness can mitigate for droughtinduced growth decline of young trees. Overall, positive net biodiversity effects were strongest during drought and increased with increasing taxonomic diversity of neighbours. In particular, drought-sensitive species (i.e. those with a low cavitation resistance) benefitted the most from growing in diverse neighbourhoods, suggesting that soil water partitioning among local neighbours during drought particularly facilitated most vulnerable individuals. Thus, diverse neighbourhoods may enhance ecosystem resistance to drought by locally supporting droughtsensitive species in the community. 4. Synthesis. Our findings demonstrate that mechanisms operating at the local neighbourhood scale are a key component for regulating forests responses to drought 866 | Journal of Ecology FICHTNER ET al. and improve insights into how local species interactions vary along stress gradients in highly diverse tree communities. K E Y W O R D S biodiversity, climate change, drought resistance, ecosystem functioning, forest, functional traits, species interactions, stress-gradient hypothesis | 867 Journal of Ecology FICHTNER ET al.

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Interactions among trees: A key element in the stabilising effect of species diversity on forest growth

Cited by 44 publications

References 39 publications

Climatic change only stimulated growth for trees under weak competition in central boreal forests

Climatic change only stimulated growth for trees under weak competition in central boreal forests

Drivers of productivity and its temporal stability in a tropical tree diversity experiment

Neighbourhood diversity mitigates drought impacts on tree growth

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