Base cation concentrations in forest litter and topsoil have different responses to climate and tree species along elevational gradients

Abstract

The forest litter is an essential reservoir of nutrients in forests, supplying a large part of absorbable base cations (BC) to topsoil, and facilitating plant growth within litter-soil system. To characterize elevational patterns of base cation concentrations in the forest litter and topsoil, and explore the effects of climate and tree species, we measured microclimate and collected the forest litter and topsoil (0-10 cm) samples across an elevational range of more than 2000 m (1243 ~ 3316 m a.s.l.), and analyzed the concentrations of BC in laboratory. Results showed that: 1) litter Ca concentration displayed a hump-shaped pattern along the elevational gradients, but litter K and Mg showed saddle-shaped patterns. Soil Ca concentration increased with elevation, while soil K and Mg had no significant changes. 2) Ca concentration in the forest litter under aspen (Populus davidiana) was significantly higher than that in all other species, but in topsoil, Ca concentration was higher under coniferous larch and fir (Larix chinensis and Abies fargesii). Litter K and Mg concentrations was higher under coniferous larch and fir, whereas there were no significant differences among tree species in the concentrations of K and Mg in topsoil. 3) Climatic factors including mean annual temperature (MAT), growing season precipitation (GSP) and non-growing season precipitation (NGSP) determined BC concentrations in the forest litter and topsoil. Soil C/N and C/P also influenced BC cycling between litter and soil. Observation along elevations within different tree species implies that above-ground tree species can redistribute below-ground cations, and this process is profoundly impacted by climate. Litter and soil Ca, K and Mg with different responses to environmental variables depend on their soluble capacity and mobile ability.