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Multi-strata forests can enhance ecosystem functioning, with interactions between overstorey trees and understorey shrubs playing a pivotal role. However, how the structure and composition of neighbouring trees, together with shrub traits, influence shrub growth remains poorly understood.
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In a large-scale subtropical biodiversity experiment manipulating tree and shrub species richness, we inventoried 4411 shrubs and their surrounding trees after 11 years of interactions.
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We found that individual shrub biomass declined with increasing neighbour tree species richness, basal area and functional diversity, but exhibited a U-shaped trend with the proportion of ectomycorrhizal-associated neighbour tree individuals. Shrubs with more conservative resource-use strategies attained higher biomass, particularly when surrounded by trees with low functional diversity and a high proportion of ectomycorrhizal associations. Biomass was also greater when shrubs were more resource-conservative and functionally distinct from the neighbouring trees.
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Our findings highlight how shrub functional traits, combined with tree diversity, competition and functional traits, shape tree–shrub interactions, with shrubs benefiting more from resource-conservative and functionally distinct traits relative to their neighbouring trees.
Figure 1. Overview of experimental design and hypotheses.
Figure 2. The effects of tree neighbourhood characteristics on individual shrub biomass.
Figure 3. The effects of shrub trait PC1 on individual shrub biomass across tree neighbourhood characteristics.
Figure 4. The effects of trait differences between shrub and neighbour trees on individual shrub biomass.
Literature:
Sai Peng, Chen Chen, Helge Bruelheide, Pablo Castro Sánchez‐Bermejo, Anpeng Cheng, Xianglu Deng, Sylvia Haider, Shan Li, Yi Li, Ting Tang, Yujie Xue, Haoru Yan, Bo Yang, Bernhard Schmid, Keping Ma, Xiaojuan Liu*. 2026. Shrubs benefit from being functionally more conservative and distinct from neighbour trees. Functional Ecology. Online. https://besjournals.onlinelibrary.wiley.com/doi/10.1111/1365-2435.70466.
