Effects of nitrogen addition on C:N:P stoichiometry in moss crust-soil continuum in the N-limited Gurbantunggut Desert, Northwest China

Human-induced nitrogen (N) enrichment contributes to plant nutrient status, which potentially alters the stoichiometry of carbon (C), N, and phosphorus (P) in plants and soil. However, the response of ecological stoichiometry in a moss crust-soil continuum to N enrichment in a N-limited desert ecosystem has not been comprehensively explored. Here, we conducted a four-level N addition experiment [0 (CK), 1.8 (LN), 3.6 (MN), and 7.2 (HN) g N M-2 year(-1)] to elucidate the influence of short-term N input on C:N:P stoichiometry in both the moss crusts (surface) and their underlying soil (subsurface) in the southern margin of the Gurbantunggut Desert, Northwest China. The results showed that N addition increased moss crusts and its underlying soil C, N, and P concentrations and elevated their C:P and N:P ratios. The soil microbial biomass C (SMBC) and N (SMBN) content in soil under moss crusts were shifted across N addition gradient. SMBC and SMBN mean content in May (345.92 mg/kg, 63.21 mg/kg) was higher than July (161.73 mg/kg, 44.38 mg/kg) and October (168.22 mg/kg, 60.73 mg/kg). When MN was added, the mean content of SMBC (288.92 mg/kg) and SMBN (67.95 mg/kg) is higher than that of other N additions levels. N addition treatments showed a significant correlations between moss crusts C, N, and P and associated soil C, N, and P. Redundancy analysis and stepwise multiple linear regression all indicated that moss crusts C:N:P stoichiometry were more sensitive to its underlying soil TP. Soil nutrient traits of moss crusts covered accounted for 68.6% of the variation in C:N:P stoichiometry of the moss crusts, especially soil TP (50.3%), determine the variation of the moss crusts C:N:P stoichiometry. N deposition stimulates the growth of most crusts and their N:P and C:P ratios, resulting in a shift in the desert ecosystem from N to P limitation.