Contrasting patterns of leaf trait variation and soil associations in two alpine grassland species across land-use histories

Understanding adaptive variation in leaf traits is essential for revealing ecological processes and resource acquisition strategies of grassland plants in alpine ecosystems. This study investigated leaf functional traits in two common alpine grassland species, Elymus nutans Griseb. and Medicago archiducis-nicolai Širj., across four sites with contrasting land-use histories (grazing, enclosure, restoring farmland to forest and restoring farmland to grassland) in Guinan County, Qinghai Province, China. We measured 13 structural and chemical leaf traits and 11 soil properties. Linear mixed-effects models (LMMs) were used to evaluate differences in leaf traits among species and land-use histories, while spearman correlation analysis was applied to examine relationships among leaf traits and soil variables. Principal component analysis (PCA) was used to identify the major factors of leaf traits variation, and redundancy analysis (RDA) was conducted to explore associations between leaf traits and soil properties. The results revealed significant variation in leaf functional traits among species and land-use histories. In E. nutans , leaf density, leaf thickness, leaf dry matter content, leaf area and leaf phosphorus content exhibited relatively high variation, whereas leaf area, leaf length and leaf thickness showed greater variation in M. archiducis-nicolai . Correlation analysis revealed strong associations among structural, chemical of leaf traits and soil-related variables. RDA indicated that soil nutrient availability and moisture were important environmental variables associated with trait variation. The two species exhibited contrasting patterns of trait variation, with E. nutans showing greater variation in structural and nutrient-related traits, while M. archiducis-nicolai varied primarily in size-related traits. These findings highlight species-specific patterns of leaf trait variation and their associations with soil properties across contrasting land-use histories, contributing to a better understanding of plant functional ecology in alpine grasslands.