Functional Links Between Leaf Traits, Soil Properties, and Aboveground Biomass Along an Altitudinal Gradient in Chitwan, Nepal

ABSTRACT

Altitudinal gradients strongly influence plant species diversity and functional trait expression in forest ecosystems. This study aimed to investigate how leaf traits and environmental variables affect aboveground tree biomass along an altitudinal gradient in Chitwan District, Nepal. We established 90 circular plots (radius 11.3 m), with 30 plots in each of the three altitudinal bands: low (150–600 m), mid (600–1500 m), and high (1500–1930 m). Leaf traits, including leaf thickness, leaf area, specific leaf area (SLA), leaf dry matter content (LDMC), total chlorophyll content, total nitrogen, and phosphorus were measured for nine dominant tree species: Shorea robusta , Trewia nudiflora , Cleistocalyx operculatus , Terminalia alata , Diploknema butyracea , Schima wallichii , Rhododendron arboreum , Quercus semecarpifolia , and Quercus lanata . Mid‐elevation exhibited the highest tree species richness and diversity. Resource‐acquisitive traits (SLA, leaf area, nutrient content, and chlorophyll) were positively associated with biomass, whereas structural traits (LDMC and leaf thickness) were negatively correlated. Structural equation modeling (SEM) revealed that integrated leaf traits had a significant positive effect on biomass accumulation (β = 0.504, p < 0.001). Elevation and soil properties together explained 45.4% of the variation in leaf functional traits and 30.8% of the variation in the above‐ground biomass. These trait–environment relationships reveal adaptive strategies across altitudinal gradients, and provide insights for sustainable forest management under changing environmental conditions.