Spatially destabilising effect of woody plant diversity on forest productivity in a subtropical mountain forest

Abstract

We used geographically weighted regression to investigate the relationship between biodiversity and the spatial stability of forest productivity (SSFP) in a subtropical mountain forest. We examined the effect of elevation on this relationship and on its spatial non-stationarity. We found that higher woody plant diversity reduced SSPF. Higher woody plant diversity strengthened the asynchrony of species responses to spatial heterogeneity of forest habitats, which contributed to SSFP, but reduced two factors that enhanced SSFP: species dominance and the spatial stability of the dominant species. The percentage of variation in SSFP explained by diversity measures was highest for the Shannon-Wiener index, lowest for functional dispersion, and intermediate for species richness. The correlations of woody plant diversity with SSFP became stronger with elevation and varied among plots, indicating that the spatial non-stationarity existed in the biodiversity-SSFP relationship. These correlations became weaker in most cases after controlling for elevation. Our results suggest that in the subtropical mountain forest higher woody plant diversity has a spatially destabilising effect on forest productivity, particularly at higher elevations.

Environmental filtering drives biodiversity–spatial stability relationships in a large temperate forest region

“…Taxonomic diversity exerted a direct and significantly positive effect on the stability of productivity for the large spatial grains (Figures 3a and 4a). This observation is in line with the portfolio effect assumption that an increase in diversity should increase spatial stability (Tilman et al, 2006; Weigelt et al, 2008; Zhong et al, 2017). However, this finding is in contrast with several recent studies that demonstrated weak or ‘inverse’ portfolio effects on spatial stability of productivity in small‐scale experiments performed in grasslands (Wang et al, 2019) and small‐scale natural forests (Gao et al, 2021; Zhong et al, 2017).…”

“…If facilitation is just sufficient or even insufficient to compensate for competition under very harsh conditions, portfolio effects should remain constant or even decline with increasing stress gradients. Assessing the interplay between larger-scale environmental stress and biodiversity may thus contribute to understanding the biodiversity-spatial stability relationship for different environmental scenarios in temperate forest regions (Gao et al, 2021;Garcia-Palacios et al, 2018;Wilcox et al, 2017;Zhong et al, 2017).…”

“…In addition to spatial scale, environmental stress (e.g. precipitation and elevation) have also been found to influence the strength of portfolio effects (Garcia‐Palacios et al, 2018; Zhong et al, 2017). For example, Garcia‐Palacios et al (2018) observed that the portfolio effects were stronger at water‐limited sites.…”

“…Temporal community stability has been associated with by species asynchrony and species‐level (population) stability (Thibaut & Connolly, 2013; Yan et al, 2021). Analogous to temporal stability, biodiversity stabilizes the spatial ecosystem productivity by increasing species asynchrony (Tilman et al, 2006; Weigelt et al, 2008; Zhong et al, 2017) and/or population stability (Jucker et al, 2014; Romanuk et al, 2006; Roscher et al, 2011). However, negative impacts of diversity on population stability have also been observed (Tilman et al, 2006; Xu et al, 2021; Yan et al, 2021).…”

Size-dependent associations of woody plant structural diversity with soil C:N:P stoichiometry in a subtropical forest

“…By definition, the structural diversity of woody plant community comprises species diversity and tree size diversity (Zlatanov et al, 2013;He et al, 2017), and can be measured and described by species richness, abundance, species diversity indexes, and tree size (Fang et al, 2012;Zlatanov et al, 2013). While a variety of metrics have been used in quantifying species diversity, size diversity is commonly quantified by tree diameter at breast height (DBH) or basal area, a proxy variable of biomass or productivity widely used in forest ecological studies (Nguyen et al, 2012;Zhong et al, 2017). Woody plant structural diversity and soil C:N:P stoichiometry have been widely and yet independently examined for their spatial patterns and changes across environmental gradients, but the interactions and relationship of these biotic and abiotic variables have not been well understood.…”