Topography mediated effect of canopy cover and light intensity explain trait variability among shrub species in Western Himalayan Forest ecosystem

This study examines how topography (elevation and slope aspect) shapes shrub diversity and functional traits in Western Himalayan Forests. We recorded 777 individuals from nine species across 90 plots between 1500–3000 m asl. Shrub density declined significantly with elevation on north-facing slopes, while species richness and diversity peaked at mid-elevations (∼2226 m asl), with higher beta diversity at higher elevations and northern aspects. Six dominant shrub species (Sarcococca saligna, Prinsepia utilis, Berberis aristata, Cotoneaster bacillaris, Rubus ellipticus and Daphne papyraceae) were selected to identify important environmental factor(s) affecting twelve plant functional traits. Trait variation revealed distinct strategies between deciduous and evergreen shrubs. Deciduous species exhibited acquisitive traits, including higher Specific Leaf Area (SLA), Leaf Phosphorus Content (LPC), and Leaf Potassium Content (LKC), while evergreen species showed conservative traits such as higher Leaf Thickness (LT), Leaf Dry Matter Content (LDMC), and Leaf Relative Water Content (LRWC), while evergreen species showed conservative traits (higher LT, LDMC, LRWC), especially at higher elevations, reflecting adaptation to environmental stress. Linear mixed-effects models explained 5–61 % of trait variability through fixed effects (stand canopy cover, light intensity, soil moisture). Structural equation models revealed that deciduous traits were more indirectly shaped via vegetation and soil feedback, while evergreen traits were tightly constrained by topography and stand canopy cover. Environmental predictors explained 63 % of vegetation structure and 50 % of trait variation. Our findings highlight the role of topography and associated environmental variables in shaping shrub communities and highlight the importance of functional trait perspectives for conservation planning in mountain ecosystems.