Local edaphic factors influence leaf nutrient resorption efficiency of evergreen and deciduous trees: a case study from montane subtropical old-growth and regenerating forests of Meghalaya

Variation in soil nutrient availability can influence the functional traits and performance of tree species in a forested landscape. We tested this hypothesis by studying the variations in leaf-traits, and N- and P-resorption efficiencies of a few evergreen (Myrica esculenta, Rhododendron arboretum and Lithocarpus dealbatus) and deciduous (Quercus griffithii, Engelhardtia spicata and Lyonia ovalifolia) tree species growing in montane subtropical old-growth and regenerating forests of Meghalaya, northeast India, varying in their soil characteristics. Trees of the old-growth forest stand, having greater soil total N and P, proved to be much efficient in their foliar nutrient resorption (mean = 42.0% for N and mean = 82.1% for P) and showed higher leaf nutritional quality compared to the regenerating forest stand. Deciduous species had greater N-resorption efficiencies (45.3–49.7%) than the evergreen species (23.6–56.9%) in the old-growth stand. However, in the regenerating stand, the evergreen species were better at resorbing both N (30.6–55.9%) and P (67.9–76.4%) from their leaves than the deciduous species (23.2–40.9% for N and 33.2–52.0% for P). Overall, phosphorus was the limiting nutrient for growth in both the functional groups, with relatively low concentrations in the soils of the two forest stands. The evergreen and deciduous trees in the old-growth forest are found to tightly conserve nutrients with higher leaf N and P concentrations and higher N- and P- resorption efficiencies than the regenerating forest stand. The study clearly indicates that soil fertility has profound effect on the internal nutrient cycling of evergreen and deciduous tree species.