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

Highlights

• Long-term grazing exclusion decrease the soil nitrogen mineralization rate.

• Temperature sensitivity decrease with the duration of grazing exclusion.

• Carbon quality-temperature hypothesis is applicable to soil N mineralization.

Abstract

Grazing exclusion (GE) is an efficient management practice that prevents grassland degradation. The temperature sensitivity (Q₁₀) of soil net nitrogen (N) mineralization (N_min) 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 N_min 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 N_min, 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 (E_a) 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 N_min to increasing temperature under global warming scenarios, which might help prevent N losses in these N-limited grasslands.