Atmospheric nitrogen deposition affects forest plant and soil system carbon:nitrogen:phosphorus stoichiometric flexibility: A meta-analysis
Xiyan Jiang, Xiaojing Wang, Yaqi Qiao, Yi Cao, Yan Jiao, An Yang, Mengzhou Liu, Lei Ma, Mengya Song, Shenglei Fu
Abstract
Nitrogen (N) deposition affects forest stoichiometric flexibility through changing soil nutrient availability to influence plant uptake. However, the effect of N deposition on the flexibility of carbon (C), N, and phosphorus (P) in forest plant-soil-microbe systems remains unclear. We conducted a meta-analysis based on 751 pairs of observations to evaluate the responses of plant, soil and microbial biomass C, N and P nutrients and stoichiometry to N addition in different N intensity (0–50, 50–100, >100 kgha−1 year−1 of N), duration (0–5, >5 year), method (understory, canopy), and matter (ammonium N, nitrate N, organic N, mixed N). N addition significantly increased plant N:P (leaf: 14.98%, root: 13.29%), plant C:P (leaf: 6.8%, root: 25.44%), soil N:P (13.94%), soil C:P (10.86%), microbial biomass N:P (23.58%), microbial biomass C:P (12.62%), but reduced plant C:N (leaf: 6.49%, root: 9.02%). Furthermore, plant C:N:P stoichiometry changed significantly under short-term N inputs, while soil and microorganisms changed drastically under high N addition. Canopy N addition primarily affected plant C:N:P stoichiometry through altering plant N content, while understory N inputs altered more by influencing soil C and P content. Organic N significantly influenced plant and soil C:N and C:P, while ammonia N changed plant N:P. Plant C:P and soil C:N were strongly correlated with mean annual precipitation (MAT), and the C:N:P stoichiometric flexibility in soil and plant under N addition connected with soil depth. Besides, N addition decoupled the correlations between soil microorganisms and the plant. N addition significantly increased the C:P and N:P in soil, plant, and microbial biomass, reducing plant C:N, and aggravated forest P limitations. Significantly, these impacts were contingent on climate types, soil layers, and N input forms. The findings enhance our comprehension of the plant-soil system nutrient cycling mechanisms in forest ecosystems and plant strategy responses to N deposition.