Patterns and drivers of leaf carbon, nitrogen, and phosphorus stoichiometry in the desert steppe of the Ili River Basin

Leaf carbon (C), nitrogen (N), and phosphorus (P) stoichiometry serves as a critical indicator of plant nutrient utilization strategies, underpinning grassland management and maintaining ecosystem stability in desert steppes. However, the spatiotemporal variations and multi-factor driving mechanisms of leaf stoichiometry in arid desert steppes remain insufficiently explored, leaving regional adaptive mechanisms poorly understood. Here, we investigated the leaf C, N, and P stoichiometric traits of desert steppe vegetation in the Ili River Basin across May, July, and September and evaluated their spatiotemporal patterns along with their responses to hydrothermal, edaphic, and topographic factors. The results showed that the mean concentrations of leaf C, N, and P were 420.93 ± 81.59 g·kg⁻¹, 19.40 ± 5.94 g·kg⁻¹, and 1.73 ± 0.77 g·kg⁻¹, with average C/N, C/P, and N/P mass ratios of 24.92 ± 8.66, 292.13 ± 127.69, and 13.60 ± 7.44, respectively. Seasonally, leaf C continuously declined throughout the growing season, leaf N peaked in May before decreasing, and leaf P presented a unimodal trend. Spatially, leaf C was concentrated in the central and western regions; leaf N was higher in the west and lower in the east, while leaf P displayed the reverse spatial gradient. Mechanistically, leaf P response to temperature and light conditions supported the Temperature-Plant Physiology Hypothesis (TPPH). Meanwhile, topography shaped regional nutrient patterns, supporting the Biogeochemical Hypothesis (BGH). Soil pH was identified as the primary driver regulating stoichiometric ratios by modulating nutrient bioavailability. Furthermore, plant competition and soil nutrient buffering jointly stabilized stoichiometric homeostasis. This study deepens our understanding of leaf stoichiometry in the desert steppe and serves as a reference for nutrient regulation and ecological conservation in fragile arid grasslands.