Characterizing the dynamics of soil organic carbon in grasslands on the Qinghai-Tibetan Plateau

Abstract

Carbon dynamics of grasslands on the Qinghai-Tibetan Plateau may play an important role in regional and global carbon cycles. The CENTURY model (Version 4.5) is used to examine temporal and spatial variations of soil organic carbon (SOC) in grasslands on the Plateau for the period from 1960 to 2002. The model successfully simulates the dynamics of aboveground carbon and soil surface SOC at the soil depth of 0-20 cm and the simulated results agree well to the measurements. Examination of SOC for eight typical grasslands shows different patterns of temporal variation in different ecosystems in 1960-2002. The extent of temporal variation increases with the increase of SOC of ecosystem. SOC increases first and decreases quickly then during the period from 1990 to 2000. Spatially, SOC density obtained for the equilibrium condition declines gradually from the southeast to the northwest on the plateau and showed a high heterogeneity in the eastern plateau. The results suggest that (i) SOC density in the alpine grasslands shows remarkable response to climate change during the 42 years, and (ii) the net carbon exchange rate between the alpine grassland ecosystems and the atmosphere increases from 1990 to 2000 as compared with that before 1990. carbon cycle, CENTURY model, climate change, global warming, soil organic carbon.

Intense methane ebullition from open water area of a shallow peatland lake on the eastern Tibetan Plateau

“…On the Tibetan Plateau, soil organic carbon (SOC) density decreases gradually from east to west, which is mainly due to the transition of climate from warm and wet to cold and dry, with the spatial heterogeneity of SOC density in the eastern part much stronger than that in western part (Zhang et al, 2006). Lake Medo is situated in the eastern edge of the Tibetan Plateau and in the peatland area with the highest SOC density .…”

Ecosystem carbon stocks and their changes in China’s grasslands

“…Since then, a number of studies have been conducted to evaluate SOC stocks in grassland ecosystems at regional and national scales [7,8,17,19,29,[39][40][41]. However, large differences exist among previous studies ( Table 2).…”

“…Previous estimates were usually based on data from the Second National Soil Survey [19,40] or were ground-based measurements at large spatial scales [7,8,40]. In addition, a global soil C dataset [17] or biogeochemical model [29,41] was used for the estimate. Although the Second National Soil Survey provided the most comprehensive soil information, few soil profiles were sampled from core areas of China's grasslands, such as the Tibetan Plateau and Xinjiang regions [42][43][44].…”

“…Recently, a number of studies reported changes in soil C in Tibetan alpine grasslands [14,41] and China's grasslands [6,7,19]. However, both the magnitude and direction of the soil C changes differed among these studies.…”

Impacts of altitude and position on the rates of soil nitrogen mineralization and nitrification in alpine meadows on the eastern Qinghai–Tibetan Plateau, China

“…The plateau ecosystem is very fragile and sensitive to changes in climate, and may act as an "indicator region" for early climate change in China and East Asia (Tang et al 1986). An alpine meadow, covering about 42% of the plateau area, is a representative vegetation type and the major grazing (alpine yak and sheep) land of this region (Zhang et al 2007). The alpine ecosystem may be a major C and N sink because of its high productivity and the low rate of decomposition resulting from low temperature (annual mean temperature below 2.4°C from 1958 to 2008).…”