Estimation Of Soil Respiration From Terrestrial Ecosystems Based On GIS During The Past40Years

Soil respiration is an important process in terrestrial carbon cycle. Concerning the terrestrial ecosystems of China and the world, quantifying the spatial and temporal patterns of soil respiration at the regional scale is critical in providing a theoretical basis for evaluating carbon budget. In this study, we used an empirically based, semi-mechanistic model including climate and soil properties to estimate annual soil respiration from terrestrial ecosystems in China from1970to2009and in the world from1970to2008. We further analyzed the relationship between interannual variability in soil respiration and climatic factors (air temperature and precipitation). Results indicated that the distribution of annual soil respiration showed clear spatial patterns. The highest and lowest annual soil respiration rates and soil heterotrophic rates appeared in southeastern China and northwestern China, respectively, which was in accordance with the spatial patterns of mean annual air temperature and annual precipitation. Although the mean annual air temperature in northwestern China was higher than that in some regions of northeastern china, a greater topsoil organic carbon storage in northeastern China might result in the higher annual soil respiration in this region. By contrast, lower temperature, less precipitation and smaller topsoil organic carbon pool incurred the lowest annual soil respiration in northwestern China. The highest annual soil respiration rates and soil heterotrophic rates appeared near the equator, including northern South America, central Africa, southern Asia and other regions, this was mainly because of the high temperature and the more precipitation of these areas; The highest annual soil respiration and heterotrophic rates appeared near the equator, including northern South America, central Africa and southern Asia. The high soil respiration rates in these regions corresponded to the high temperature and more precipitation. The lowest annual soil respiration and heterotrophic rates appeared in Greenland, northern Africa and central Asia, which was mainly due to the relatively lower temperature or less precipitation. Although the mean annual air temperature in northern Africa and central Asia was high, less precipitation and smaller topsoil organic carbon pool in these areas might result in the low soil respiration rates.Annual soil respiration from terrestrial ecosystems in China varied from4.58to5.19Pg C·yr-1between1970and2009. During this time Period, on average, annual soil respiration was estimated to be4.83Pg C·yr-1. Annual soil respiration in China accounted for4.93%-6.01%of the global annual soil CO2emission. The interannual variability in soil respiration depended on the interannual variability in precipitation and mean air temperature. Annual soil heterotrophic respiration from terrestrial ecosystems in China varied from2.47to2.76Pg C·yr-1between1970and2009. During this time period, on average, annual soil heterotrophic respiration was estimated to be2.60Pg C-yr-1.Annual soil respiration from global terrestrial ecosystems varied from73.53to78.93Pg C·yr-1between1970and2009. During this time period, on average, annual soil respiration was estimated to be75.87Pg C·yr-1. The interannual variability in soil respiration depended on the interannual variability in precipitation and mean air temperature.In this study, the accuracy of estimating the amount of soil respiration depends not only on a large number of climate data but also accurate estimates of soil carbon pool, which reflects the intrinsic link among various carbon cycle variables. In order to reduce the uncertainty in estimating annual soil respiration at regional scale, more in situ measurements of soil respiration and relevant factors (e.g. climate, soil and vegetation) should be made simultaneously and historical soil property data sets should also be established.