Dynamics of Multiple Elements in Particulate and Mineral-Associated Organic Matter Across Varying Soil Depths Following 13 years of Nitrogen and Water Addition in an Agro-Pastoral Ecotone Grassland - Huiqi Ke; Shilin Wang; Guoxiang Niu; Ruzhen Wang; Yibo Li; Yanan Ning; Canran Yang; Yinliu Wang; Yong Jiang; Jianhui Huang (Ecosystems, 2026)