Climate and mycorrhizae mediate the relationship of tree species diversity and carbon stocks in subtropical forests

Abstract

It is increasingly being recognized that tree species diversity has positive effects on forest ecosystem carbon (C) stock. However, at broad spatial scales, this relationship may depend on climate conditions and species mycorrhizal associations. Here, observations from 667 forest plots in subtropical China were used to investigate the effects of species diversity, mean annual precipitation (MAP), mean annual temperature (MAT) and mycorrhizal type (arbuscular or ectomycorrhizal) on the forest C stock and its components (tree C stock, shrub layer C stock, herb layer C stock, litter layer C stock, root C stock and soil C stock). We found positive effect of tree species diversity on total forest C stock. MAP had positive effects on total forest C stock and its components, while MAT had consistently negative effects on total forest C stock and most of its components. Different levels of MAP and MAT did modulate the strength of effect of species diversity on forest C stock and its components. In addition, species diversity, MAT and MAP showed a significant positive relationship with arbuscular mycorrhiza‐associated tree C stock but had no or negative relationship with ectomycorrhiza‐associated tree C stock. Synthesis. Our results indicate that maintaining high level of species diversity may support the buffering of negative effects resulting from climate warming. Furthermore, under climate warming the specific C stock of AM trees can increase, which can potentially promote forest C stock. Taken together, our study suggests that afforestation policies should consider not only tree species diversity to increase forest C stock but also the effects of different tree mycorrhizal types.

Scale‐dependent diversity–biomass relationships can be driven by tree mycorrhizal association and soil fertility

“…Second, AM tree species often possess strong conspecific negative density dependence or negative plant–soil feedback (Bennett et al, 2017; Jiang et al, 2021; Pu et al, 2022), promoting species coexistence and thus improving species diversity in AM‐dominated communities (Tedersoo et al, 2020). These facts support the hypothesis that communities with more AM trees (i.e., AM‐dominated) tend to possess higher species diversity, which has been proposed by Allen et al (1995) and supported by recent empirical studies (e.g., Gerz et al, 2016; Jiang et al, 2021; Mao et al, 2019; Yan, Bongers, et al, 2022; also see Deng et al, 2023 for new nutrient‐acquiring strategy perspective). However, since some other studies did not find evidence that AM‐dominated communities are more diverse (Bahram et al, 2020; Carteron et al, 2022), this hypothesis still needs to be tested by more empirical studies especially including data across spatial scales, such as the present study.…”

Tree diversity and mycorrhizal type co‐determine multitrophic ecosystem functions

“…Besides effects on the life strategies of the host, the two types of mycorrhizal fungi largely shape the soil microbial communities (Heděnec et al, 2020;Singavarapu et al, 2022) as well as higher trophic groups in the soil food web (Peng et al, 2022). Taken together, mycorrhizal types are likely to co-determine forest BEF relationships, as indicated by recent work (Deng et al, 2023;Dietrich et al, 2023;Luo et al, 2023;Yan et al, 2022). Due to the cascading effects across trophic levels (Eisenhauer et al, 2013;Schuldt et al, 2018), mycorrhizal association types can potentially shape the relationship between tree diversity and multitrophic ecosystem functions; however, empirical evidence is lacking thus far.…”

Elevational Patterns of Tree Species Richness and Forest Biomass on Two Subtropical Mountains in China

“…Species diversity has been found to facilitate ecosystem biomass (productivity) in natural forests, plantations, and manipulated biodiversity experiments [3][4][5][6]. However, discrepancies have been commonly observed in different forest types or at different spatial scales, given the complex interactive impacts of numerous biotic and abiotic factors on species diversity and stand biomass, respectively [6][7][8][9][10]. Thus, exploring the underlying drivers of forest biodiversity and biomass still remains a key issue in ecological research.…”

“…Climatic factors, especially temperature and precipitation, have been well recognized as key drivers of species richness across wide spatial gradients [11][12][13][14], while their impacts on forest biomass may vary depending on the climatic region or forest type [15][16][17][18]. In addition to the direct effects due to increased energy input or water availability, the climate could also indirectly modulate species richness and biomass through other factors, such as soil properties, stand structures, and mycorrhizal associations [8,10,19]. In recent decades, attention has been paid to the roles of aboveground stand structures [7,[20][21][22] and belowground mycorrhizal associations [6,10,23,24] in shaping species diversity and stand biomass, as well as their relationship.…”

“…In addition to the direct effects due to increased energy input or water availability, the climate could also indirectly modulate species richness and biomass through other factors, such as soil properties, stand structures, and mycorrhizal associations [8,10,19]. In recent decades, attention has been paid to the roles of aboveground stand structures [7,[20][21][22] and belowground mycorrhizal associations [6,10,23,24] in shaping species diversity and stand biomass, as well as their relationship. However, few studies have considered the aboveground and belowground biotic interactions as well as climate simultaneously, which can help us better understand the mechanisms underpinning species diversity and biomass patterns.…”