Mycorrhizal status and type dominate global fine root C:N:P stoichiometry

Fine root stoichiometry characterizes nutrient cycling in terrestrial ecosystems. Mycorrhizae are major regulators of plant carbon (C), nitrogen (N) and phosphorus (P) nutrients. However, our understanding of the fine root stoichiometry at the global scale and their driving role by mycorrhizae is extremely limited. This study used global data to explore the stoichiometry of fine root C, N, P and their relationships with climatic factors across different mycorrhizal statuses and types. The results showed that obligately mycorrhizal (OM) species (always form mycorrhizae) had significantly higher fine root N contents (12.66 mg/g), while non-mycorrhizal (NM) species had significantly higher fine root P contents (1.50 mg/g). Arbuscular mycorrhizal (AM) plants had significantly lower fine root C contents (443.11 mg/g) and higher fine root N contents (13.55 mg/g). AM + ECM plants had significantly higher fine root C/N, root C/P, and root N/P. Mycorrhiza had a positive effect on fine roots N, with AM having the most pronounced positive effect. The correlation between the elements of fine roots was more pronounced among OM and AM plants. Mean annual precipitation (MAP) and mean annual temperature (MAT) had positive effects on C in OM plants, with the most pronounced positive effects on C in ECM plants. MAP and MAT had negative effects on C in FM plants. MAT had a positive effect on N in NM plants, but a negative effect on P in OM plants. Our study revealed biogeographic patterns of global fine root C:N:P stoichiometry and advanced our understanding of fine root biogeochemical cycling.