In situ litter decomposition and nutrient release from forest trees along an elevation gradient in Central Himalaya

Abstract Litter plays a central role in the nutrient budgets of forests by supplying inflow to nutrient turnover through decomposition. However, studies of litter decomposition and nutrient dynamics in forest ecosystems are limited, particularly for the central Himalaya forest ecosystems with wide importance for stability and nutrient dynamics under global change. A one-year-long in-situ litter decomposition experiment was conducted with multiple tree species, dominating forests along an elevation gradient from 1300 to 2500 meters above sea level (m.a.s.l.) in central Nepal. The main aim was to examine the litter mass loss, factors affecting the decomposition process and the nutrient dynamics of the studied tree species, based on the litter bag method and physico-chemical analyses of the litter and the soil over time. The results showed that litter mass loss decreased with elevation, being the highest at low elevation (63.65%), followed by middle (46.59%) and high elevation (44.48%). The litter from deciduous tree species decomposed more rapidly than that from evergreen species, with Alnus litter decomposing the fastest (1.42 yr−1) and Pinus litter decomposing the slowest (0.53 yr−1), whereas the other species were in the order of Engelhardia > Castanopsis > Eurya > Lyonia > Quercus > Rhododendron > Schima. The contents of carbon (C), nitrogen (N), phosphorus (P) and potassium (K) in the initial litter (i.e., freshly fallen leaves), as well as weather factors (precipitation and temperature) were the best predictors of litter mass loss. The nutrient release from the litter was not discerned throughout the annual decomposition process, however, the release rate at the end of the study period followed the order of P > K > C > N, indicating that litter is a potential sink of N due to its slow release rate. This study may serve as a baseline for long-term research on nutrient dynamics in forest ecosystems of central and eastern Himalaya, which is imperative for preserving biodiversity and ecosystem stability and for mitigating climate change impacts.