Soil Stoichiometry Influenced the Soil Aggregates C, N, P Contents Due to Land Use Change in Surface Degenerated Soil.

Land use change could markedly change the soil C:N:P stoichiometry ratios, and soil carbon (C), nitrogen (N), and phosphorus (P) contents in soil aggregates. To understand how soil C:N:P stoichiometry ratios influence soil C, N, and P contents in soil aggregates, we investigated the changes in soil C:N:P stoichiometry and soil C, N, and P contents in soil aggregates from 0- to 20- and 20- to 40-cm depths after slope croplands (SC) converted to forests on the Loess Plateau (China). We hypothesize that after land use change soil C, N, and P contents in soil water-stable aggregates would be affected by soil C:N:P ratios, especially in surface soil. We found that both SOC, TN, TP and soil C:N, C:P, and N:P ratios increased after land use change. Compared with SC, the SOC, TN and TP content in soil aggregates were also increased, especially in small macro-aggregates (0.25–5 mm). Furthermore, the ‘Best’ model results indicate that SOC, TN, and TP contents in soil aggregates were significantly affected by soil C:N, C:P, and N:P ratios, and redundancy analysis (RDA) indicates that soil C:P and N:P ratios were the main factors to influence SOC, TN, and TP contents in small macro-aggregates in surface soil (0-20 cm) after land use change. The results suggest that SOC accumulation in afforested soils was due to its accumulation in small macro-aggregates and this increase was largely affected by soil C:N:P stoichiometry ratios in surface soil after land use change.