Relative contributions of climate and grazing to forage supply in the Yellow River source area

Grassland ecosystems, critical for ecosystem services like forage supply, face threats from climate change and grazing pressure. This study investigates the spatiotemporal dynamics of forage supply and grazing intensity in the Yellow River Source Area (YRSA) from 2000 to 2020, focusing on the relative contributions of climate factors and grazing. Our result revealed that forage supply exhibited a southeast-to-northwest decline and increased slightly overall, with variability among grassland types. Using a Livestock Carrying Pressure Index (LCPI), which incorporating seasonal grazing practices and supplementary feeding, we found that grazing intensity showed spatial heterogeneity, with moderate grazing pressure (1.5<LCPI<2.5) to heavy grazing pressure (LCPI>2.5) in the northeast, and understocked (LCPI<0.9) in central and southern regions. Precipitation was identified as the dominant factor positively influencing forage supply in northern and western YRSA, while grazing intensity negatively affected forage supply in most area. We further quantified the relative contributions of these factors, revealing that precipitation played the most significant role in the north and west, while grazing intensity was the primary driver in specific central and southern areas. Grazing intensity dominates 42.4% of grasslands, surpassing precipitation (40.7%) and temperature (16.9%). These findings underscore the need for climate-adaptive grazing management strategies to optimize forage production and safeguard the YRSA's ecological functions.