Coupling and decoupling of soil carbon, nitrogen and phosphorus stocks following grazing exclusion in temperate grasslands

Abstract

Grazing exclusion is considered a crucial measure for improving ecosystem structure and function, including elements such as soil carbon and nutrients. However, little is known about the relationships of soil organic C (SOC), total nitrogen (TN), and total phosphorous (TP) stocks during long-term grazing exclusion. This study examined the SOC, TN, and TP stocks after 0–33 years of grazing exclusion in temperate grasslands on the Loess Plateau, China. The results showed that long-term grazing exclusion significantly increased SOC and TN stocks but declined TP stocks compared to those in grazing grasslands. In addition, grazing exclusion was more favorable for SOC and TN accumulations than TP accretion, and SOC and TN stocks were decoupled from TP stock. Overall, changes in SOC stock were determined by plant productivity, and TN stocks were also driven by soil microbial activities (i.e., N-acquiring enzymes). Nevertheless, plant and microbial characteristics had no effects on TP stocks following grazing exclusion. This study emphasizes the positive effect of grazing exclusion on SOC and TN accumulations, further, it is needed to explore soil phosphorus stabilization mechanisms during grassland restoration after grazing exclusion.