COS 277-3 - Warm season grazing promotes the shallow stratification of soil C, N, and P while cold season grazing sequesters the deep soil C, N, and P in alpine meadow

Background/Question/Methods

Grazing management and climate are known to be important drivers of variations in soil nutrient accumulation. However, how long-term specific grazing management will affect soil nutrient storage and movement under a warm-humid climate trend needs further study. A 20-year grazing management trial was conducted in alpine meadow in the Qilian Mountains on the Qinghai-Tibet Plateau. We sampled and analyzed the soil under a winter pasture (Cold season grazing pasture) and a spring and autumn pasture (Warm season grazing pasture) in August 1999 and August 2019 along grazing gradients at different distances from the pasture entrance (0, 300, 600, 900, 1200, and 1500 m).

Results/Conclusions

The experimental results of 2019 show that warm season grazing increased soil organic carbon density (SOCD), soil total nitrogen density (STND), and soil total phosphorus density (STPD) in the 0–300 m soil, whereas it had the reverse effect in the cold season. Warm and cold season grazing increased the SOCD:STND ratio in the 0–300 m soil, while lower STND:STPD ratio. The comparison found that warm season grazing improved soil total C, N, and P density in the topsoil (0–10 cm), but cold season grazing improved it throughout the profile (0–40 cm) and increased the variability of total C, N, and P density in the deep soil (20–40 cm). These findings indicate that the grazing season and element characteristics jointly affect the accumulation and migration of different elements under long-term grazing. Furthermore, warm and cold season grazing have a positive effect on the accumulation of topsoil and deep soil nutrients, respectively, especially carbon sequestration of deep soil by grazing in the cold season, which can help to explain some of the missing carbon sinks in the global carbon cycle, help to slow global warming, and provide new ideas for designing peak carbon dioxide emissions and carbon neutrality policies.