Mycorrhizal associations drive the tradeoff between plant biomass and soil carbon accumulations in forest ecosystems under N deposition and warming

Abstract Forest ecosystems store ca. 80% of the carbon (C) in terrestrial ecosystems 1–2 , but their long-term C sequestration partly depends on how plant biomass and soil C stocks will respond to global changes. Although the stimulation of plant growth by global change drivers such as nitrogen (N) deposition, elevated CO 2, and warming has been widely observed 3–5 , the response of soil C stock to global changes remains uncertain. Here, we conducted a meta-analysis on 3050 pairwise observations of plant and soil C-related data from 372 experiments worldwide. We found that plant biomass and soil C stock increased more under elevated CO 2 than under N deposition and warming. Under N deposition and warming, soil C stock depended on mycorrhizal associations, decreasing in forests dominated by arbuscular mycorrhizal (AM) tree species while increasing in forests dominated by ectomycorrhizal (ECM) tree species. These results suggest a mycorrhizae-mediated tradeoff between plant biomass and soil C sequestration in forest ecosystems under N deposition and warming conditions.