Tree mycorrhizal associations determine how biodiversity, large trees,
and environmental factors drive aboveground carbon stock in temperate
forests
Abstract
Experimental and observational studies have elucidated that an
amalgamation of biotic (e.g., biodiversity, large trees) and abiotic
factors (e.g., climate, soil) jointly determine tree aboveground carbon
stock within forest ecosystems. Yet, a pivotal factor potentially
influencing these carbon repositories might be the specific tree
mycorrhizal associations, especially given that ectomycorrhizal (EM)
tree species frequently comprise more large-sized trees, translating to
an augmented carbon reserve, as opposed to arbuscular mycorrhizal (AM)
counterpart. However, how biotic and abiotic factors determine forest
carbon through regulating AM vs. EM tree carbon stock is still elusive
across large regions. Here, we examined a forest inventory data
consisting of over 90,000 trees from 631 forest plots (30m × 30m each).
Our objective was to explore how biodiversity (i.e., species diversity
and ecological uniqueness), large trees (top 1% tree diameters), and
environmental factors (e.g., climate and soil nutrients) differently
regulate AM and EM, and thus, total tree aboveground carbon stock of
temperate forests in northeast China. Our findings illuminated that
large trees had consistent enhancement effect on AM and EM tree carbon
repositories. However, the effects of biodiversity and environmental
factors on carbon stock were opposite between AM and EM trees.
Specifically, the two components of biodiversity were positively
associated with AM tree carbon stock while negatively associated with EM
tree carbon stock. Environment heterogeneity (i.e. mean annual
temperature and soil nutrients) also exhibited contrasting impacts on AM
and EM tree carbon stock. Consequently, when integrating AM and EM tree
carbon stock into total carbon stock, the consistent effect of large
trees on AM vs. EM trees was strengthened and most important, while the
opposite effect of biodiversity or environment factors was diluted. In
summary, this study emphasized a mycorrhizal viewpoint to better
understand the determinants of overarching aboveground carbon profile
across regional forests.