Ecosystem carbon stocks and their changes in China’s grasslands

Abstract

The knowledge of carbon (C) stock and its dynamics is crucial for understanding the role of grassland ecosystems in China's terrestrial C cycle. To date, a comprehensive assessment on C balance in China's grasslands is still lacking. By reviewing published literature, this study aims to evaluate ecosystem C stocks (both vegetation biomass and soil organic C) and their changes in China's grasslands. Our results are summarized as follows: (1) biomass C density (C stock per area) of China's grasslands differed greatly among previous studies, ranging from 215.8 to 348.1 g C m(-2) with an average of 300.2 g C m(-2). Likewise, soil C density also varied greatly between 8.5 and 15.1 kg C m(-2). In total, ecosystem C stock in China's grasslands was estimated at 29.1 Pg C. (2) Both the magnitude and direction of ecosystem C changes in China's grasslands differed greatly among previous studies. According to recent reports, neither biomass nor soil C stock in China's grasslands showed a significant change during the past 20 years, indicating that grassland ecosystems are C neutral. (3) Spatial patterns and temporal dynamics of grassland biomass were closely correlated with precipitation, while changes in soil C stocks exhibited close associations with soil moisture and soil texture. Human activities, such as livestock grazing and fencing could also affect ecosystem C dynamics in China's grasslands.

Estimation and uncertainty analyses of grassland biomass in Northern China: Comparison of multiple remote sensing data sources and modeling approaches

“…This result was in the range of previously reported results (479.56-2551.56 g/m 2 , Fan et al, 2007;Fang et al, 2010;Ni, 2002;Piao et al, 2007). We noticed that the previous estimations were subject to large differences.…”

“…Due to the large spatial heterogeneity and temporal dynamics of grassland across complex regions, the regional model simulations of grassland biomass inevitably suffered from deficiencies and uncertainties. Previous grassland biomass estimations were usually with large difference and short of quantitative uncertainty analysis (Fan et al, 2007;Fang et al, 2010;Ni, 2002;Piao et al, 2007). Hence, a more comprehensive grassland biomass assessment, including its magnitude and uncertainty is needed.…”

Carbon management in dryland agricultural systems. A review

“…Proper grazing management should maintain a favorable C balance in the ecosystem versus haymaking or combined practices (Oates and Jackson 2014;Ziter and MacDougall 2013). For example, the use of conservative practices to avoid overgrazing or to fence plots has represented a solution to erosion damages in Chinese grasslands (Fang et al 2010;Han et al 2008).…”

Determination of green aboveground biomass in desert steppe using litter-soil-adjusted vegetation index

“…Grassland is one of the most widespread ecosystem types, and accurate estimation of grassland green aboveground biomass is increasingly needed to reduce uncertainty of this terrestrial carbon sink [Scurlock and Hall, 1998;Scurlock et al, 2002], especially in arid and semiarid areas [Cui et al, 2011;Fang et al, 2010;Eisfelder et al, 2012]. Green aboveground biomass is also a key ecological variable in arid and semiarid grassland [Eisfelder et al, 2012], and influences important environmental processes, such as soil erosion, environmental degradation, and desertification [Verstraete, 1986;Eswaran et al, 2001;Hirata et al, 2001;Moleele et al, 2001;Mulligan, 2009].…”