Degradation and spatial variability of soil organic matter at different scales in grazed semi-arid grasslands of Northern China

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The Eurasian steppe, one of the largest grassland ecosystems globally, has supported nomadic pastoralism for thousands of years. However, the shift from extensive grazing management to sedentary, intensive livestock production in Northern China since the 1950s has led to severe grassland degradation. Approximately 30% of these grasslands, covering nearly 4 million km², are degraded, impacting around 400 million people. Overgrazing has resulted in a decline of soil organic matter (SOM) stocks, crucial for carbon storage, as semi-arid grasslands hold about 15% of total soil organic carbon (SOC) stocks. Understanding SOC levels in steppe soils and the effects of intensive grazing is vital amid increasing agricultural land demand and ongoing soil degradation. The Sino-German research unit MAGIM was established in 2004 to study the effects of intensified grazing and the potential benefits of grazing exclusion in a semi-arid grassland ecosystem in Inner Mongolia. This region features Leymus chinensis and Stipa grandis dominated communities, typically grazed by sheep and goats. The research aimed to estimate SOM in grassland soils at various spatial scales and to investigate degradation processes and SOM loss due to heavy grazing. Additionally, the study evaluated short-term indicators for early grassland desertification through a controlled grazing experiment.