Spatial patterns of litter density and their controlling factors in forests and grasslands of China

Abstract

Litter is an important component of terrestrial ecosystems and plays significant role in nutrient cycles. The accumulation of litter (or litter density) on the soil surface depends on the balance of the process of litter input and decomposition. Theoretically, any factors influencing the processes of litter input or decomposition will affect the accumulation of litter. Therefore, the accurate assessment of litter density is important in illustrating the ecosystem response of carbon (C) and nitrogen (N) cycles to global climate change. However, to date in China, spatial patterns of litter density and their influencing factors have not been reported. In this study, we collected the litter density data of forests and grasslands in China, published from 2000 to 2014; the data of 1864 sampling sites, including litter density, mean annual precipitation, mean annual temperature, climate, soil, and productivity, were obtained to explore the spatial patterns of litter density and their main controlling factors. In addition, we estimated the C and N storages of litter at different scales and the total C and N contents of forests and grasslands in China. Our results showed that the litter density in the forests and grasslands of China exhibited weak latitudinal and longitudinal distribution patterns; however, after the division with a different latitudinal and longitudinal interval, it showed significant spatial distribution. Litter density in the forests increased with increasing latitude and longitude and was mainly controlled by temperature. Litter density in the grasslands increased with increasing longitude; the main controlling factor of spatial patterns was precipitation. Apparent variations in the litter density were observed at the local or regional scale for forests and grasslands, which attenuated the expected spatial patterns of litter density. The total estimated amount of litter in the forests was 1135.56 Tg, and the C and N storages were 517.93 TgC and 15.33 TgN, respectively. The total amount of litter in the grasslands was 119.63 Tg, with 47.11 TgC and 1.59 TgN. To the best of our knowledge, this is the first study to evaluating the spatial patterns and C and N storages of litter in the forests and grasslands of China, which provide important information on the significance of litter in ecosystem nutrient cycles, especially for the accurate estimation of C and N storages in terrestrial ecosystems at the national scale.