Species identity and resource availability explain variation among above and below-ground functional traits in Himalayan temperate forests

Abstract

Trait variation across spatial and temporal scales allows plants to adapt to changing environments. Understanding the mechanisms driving trait variability, it is important to unravel how plant functional traits adapt to changing climates. Plant chemical traits (C, N, P, K, S, Ca, Mg, Mn, Zn, Fe, Cu, and Na) for leaf, stem, and root were studied for ten dominant evergreen tree species along increasing elevation (1500–3000 m asl) for three seasons (summer, monsoon, and winter) in temperate forests of western Himalaya, India. We also collected five soil samples from each plot to analyze chemical trait variation with respective soil nutrient concentrations. Our results suggested that temperature significantly (P < 0.05) affected leaf traits, whereas stem and root traits were maximally driven by light and water availability (P < 0.05). Maximum trait variance was observed at species level (∼48%) followed by individual level (∼45%). Coniferous species displayed strong trait coordination among organs, whereas broad-leaved species showed strong correlation with environmental resources. Trait correlation with respective soil nutrient concentration was found strongest for the root, followed by stem, and ultimately got lost for leaf traits (except Ca, Mg, and Mn). Weaker plant–soil interaction for leaf traits showed external factors such as lopping alter plant-soil relationship. We provide evidence of varying degrees of trait conservatism within broad-leaved and coniferous trees that leads to increased trait variability. We also emphasize the importance of considering major abiotic and biotic stresses exerted on different plant organs when investigating trait variation along environmental gradients.