Spatiotemporal dynamic simulation of grassland carbon storage in China

Based on the Terrestrial Ecosystem Model (TEM 5.0), together with the data of climate (temperature, precipitation and solar radiation) and environment (grassland vegetation types, soil texture, altitude, longitude and latitude, and atmospheric CO2 concentration data), the spatiotemporal variations of carbon storage and density, and their controlling factors were discussed in this paper. The results indicated that: (1) the total carbon storage of China's grasslands with a total area of 394.93x10(4) km(2) was 59.47 Pg C. Among them, there were 3.15 Pg C in vegetation and 56.32 Pg C in soil carbon. China's grasslands covering 7.0-11.3% of the total world's grassland area had 1.3-11.3% of the vegetation carbon and 9.7-22.5% of the soil carbon in the world grasslands. The total carbon storage increased from 59.13 to 60.16 Pg C during 1961-2013 with an increasing rate of 19.4 Tg C yr(-1). (2) The grasslands in the Qinghai-Tibetan Plateau contributed most to the total carbon storage during 1961-2013, accounting for 63.2% of the total grassland carbon storage, followed by Xinjiang grasslands (15.8%) and Inner Mongolia grasslands (11.1%). (3) The vegetation carbon storage showed an increasing trend, with the average annual growth rate of 9.62 Tg C yr(-1) during 1961-2013, and temperature was the main determinant factor, explaining approximately 85% of its variation. The vegetation carbon storage showed an increasing trend in most grassland regions, however, a decreasing trend in the central grassland in the southern China, the western and central parts of the Inner Mongolian grasslands as well as some parts on the Qinghai-Tibetan Plateau. The soil carbon storage showed a significantly increasing trend with a rate of 7.96 Tg C yr(-1), which resulted from the interaction of more precipitation and low temperature in the 1980s and 1990s. Among them, precipitation was the main determinant factor of increasing soil carbon increases of China's grasslands.