Soil stoichiometry influence C, N, and P distribution in soil aggregates after afforestation

Soil carbon stabilization depends on its distribution in structural aggregates, and nutrient ratios in soils (mainly carbon (C), nitrogen (N), and phosphorus (P)). However, The relationship between the soil C:N:P stoichiometry and soil C, N, and P content in soil aggregates after afforestation are poorly understood. We investigated changes in soil C:N:P stoichiometry and soil C, N, and P content in soil aggregates at 0-20 cm and 20-40 cm depths on lands that were converted from slope croplands (SC) to forests on the Loess Plateau in China. Our results showed that soil organic carbon (SOC), soil total nitrogen (STN), soil total phosphorous (STP), and soil C:N, C:P, and N:P increased after afforestation. Compared with SC, the SOC, STN, and STP content in soil aggregates greatly increased in small macro-aggregates (0.25-5 mm). Furthermore, Beerkan Estimation of Soil Transfer (BEST) model results indicated that SOC, STN, and STP contents in soil aggregates were significantly affected by soil C:N, C:P, and N:P ratios. Likewise, redundancy analysis (RDA) showed that soil C:P and N:P ratios were the main factors to influence SOC, STN, and STP contents in small macro-aggregates in surface soil (0-20 cm). These results suggested that SOC accumulation after afforestation was due to its accumulation in small macro-aggregates and this increase was largely affected by soil C:N:P stoichiometry in surface soil. © 2021 University of Sao Paolo. All rights reserved.