Agricultural uses reshape soil C, N, and P stoichiometry in subtropical ecosystems

Abstract

Changes in elemental stoichiometry, in most cases, attributed to land use alterations may cause vital impacts on the nutrient status and environmental quality of ecosystems. Here, we studied the stoichiometry and spatial distribution patterns of soil organic carbon (SOC), total soil nitrogen (TN), and total soil phosphorus (TP) in topsoil (0–20 cm; 1207 samples) ecosystems in a representative catchment of subtropical hilly region of China. Its main land uses are woodland, paddy fields, and tea farmlands. Data obtained show that the medians of SOC, TN, and TP were 16.97, 1.83, and 0.52 g kg−1, and medians of C : N, C : P, and N : P molar ratios were 10.0, 78.6 and 7.9, respectively. The best-fitting model were exponential models for SOC, TN, TP, C : N, and N : P, while for C : P was Gaussian model. The nugget values for SOC, TN, TP, C : N, C : P, and N : P were 1.0, 0.06, 0.01, 6.0, 56.0, and 1.0, respectively. And their ranges were 750, 1290, 570, 2970, 810, and 720, respectively. The nugget-to-sill ratio (NSR) for SOC, TN, TP, C : P, and N : P were 2.7 %, 14.3 %, 20.0 %, 4.0 %, and 10.0 %, respectively, and showed strong spatial autocorrelation. While C:N molar ratios had a moderate spatial correlation, with NSR of 49.95 %. Spatial analyses showed that agriculture derived land use changes alter largely the spatial distribution and stoichiometry of C, N, and P elements in individual landscapes and entire catchment. For woodland ecosystems, topography factors (elevation and slope) determined the elemental spatial distributions and stoichiometry (C : N, C : P, and N : P molar ratios). However, this status had been merged in agricultural ecosystems, due to the relative similarity in cropping and managing (N and P inputs through fertilization). Agriculture significantly increases N, and P contents but narrows C : N, C : P, and N : P molar ratios. Thus, our findings demonstrate that agricultural activities can affect carbon and nutrient stoichiometry at the catchment scale.