Effects of litter quality and climate change along an elevation gradient on litter mass loss in an alpine meadow ecosystem on the Tibetan plateau

Knowledge of the response of litter mass loss to climate warming and litter quality in alpine ecosystems is still sparse. Here, we conducted a 507-day litter decomposition experiment along an elevation gradient from 3200 to 3800 m using different litter types to determine the influences of litter quality and climate change on the elemental mass losses and on the temperature sensitivity of litter mass losses (annual percentage decomposition (%) per 1°C temperature difference). Mass losses of C, nitrogen (N), phosphorus (P), potassium (K), sodium (Na), calcium (Ca), and Magnesium (Mg) decreased with an increase in elevation. In general, N and Na concentrations in litter and ratios of C:N and lignin:N were the best predictors of C mass losses. A higher N concentration and C:N ratio in litter caused greater C mass losses, but higher lignin:N ratio in litter resulted in lower C mass losses. Litter decomposition occurred in a two-stage process. Carbon mass loss in litter was mainly limited by soil temperature in the first growing season of the decomposition period, whereas N concentration and ratios of C:P and N:P limited carbon mass loss in the remaining litter during the second growing season of the decomposition period. Soil moisture appeared not to affect litter mass loss and the temperature sensitivity of litter mass loss of grass litter was greater than that of shrub litter in the alpine region.