Soil respiration and human effects on global grasslands

摘要

Grasslands comprise approximately 40% of the earth's land area (excluding areas of permanent ice cover) and play a critical role in the global carbon cycle. In this paper, by reviewing literature, we quantify annual soil CO_2 efflux, contribution of root respiration to total soil respiration, apparent temperature sensitivity of soil respiration (indicated by Q_(10)), and turnover rates of soil organic carbon (SOC). We discuss effects of human activities (grazing, land-use changes, and fertilization) on soil respiration rates of global natural grasslands. The soil CO_2 efflux from temperate and tropical natural grasslands is 389.8 ± 45.5 g C m~(-2) yr~(-1) and 601.3 ± 45.6 g C m~(-2) yr~(-1) (mean±S.E.), respectively. The contribution of root respiration to total soil respiration averages 36%, ranging from 8% to 64%. Annual soil CO_2 efflux increases with temperature and precipitation, but increased precipitation can cause a decrease in soil respiration rate in rainy regions. Mean turnover rates of SOC are 71 years in temperate grasslands and 15 years in tropical grasslands. The average Q_(10) value is 2.13, with 2.23 for temperate grasslands and 1.94 for tropical grasslands. Human activities significantly affect soil respiration but the extent varies among sites.