Effect of grazing exclusion on the temperature sensitivity of soil net nitrogen mineralization in the Inner Mongolian grasslands

Abstract

Grazing exclusion (GE) is an efficient management practice that prevents grassland degradation. The temperature sensitivity (Q10) of soil net nitrogen (N) mineralization (Nmin) is an important parameter of N cycles, and it directly influences the feedback between the primary productivity of grassland ecosystems and climate warming. However, information remains limited about how GE affects the Q10 of Nmin in N-limited grasslands. In this study, we conducted a laboratory incubation experiment at six temperatures (−10, 0, 5, 15, 25, and 35 °C) and three soil moisture contents (15%, 25%, and 35%) for 35 days by using intact soil cores from three different GE periods grassland (0, 4 and 24 years). The results showed that long-term GE decreased the Q10 of Nmin, which was highest in GE0 (2.62), followed by GE4 (2.36) and GE24 (2.42). In addition, Q10 declined in 15% soil moisture content under all three GE treatments. Furthermore, activation energy (Ea) was negatively correlated with the substrate quality index (Q) in all three GE grasslands. These results support the carbon quality-temperature (CQT) hypothesis, showing that is can be applied to soil N mineralization in grasslands after long-term GE. This study demonstrated that GE potentially reduces the sensitivity of Nmin to increasing temperature under global warming scenarios, which might help prevent N losses in these N-limited grasslands.