Net ecosystem productivity of temperate grasslands in northern China: An upscaling study

Abstract

a b s t r a c tGrassland is one of the widespread biome types globally, and plays an important role in the terrestrial carbon cycle. We examined net ecosystem production (NEP) for the temperate grasslands in northern China from 2000 to 2010. We combined flux observations, satellite data, and climate data to develop a piecewise regression model for NEP, and then used the model to map NEP for grasslands in northern China. Over the growing season, the northern China's grassland had a net carbon uptake of 158 ± 25 g C m −2 during 2000-2010 with the mean regional NEP estimate of 126 Tg C. Our results showed generally higher grassland NEP at high latitudes (northeast) than at low latitudes (central and west) because of different grassland types and environmental conditions. In the northeast, which is dominated by meadow steppes, the growing season NEP generally reached 200-300 g C m −2 . In the southwest corner of the region, which is partially occupied by alpine meadow systems, the growing season NEP also reached 200-300 g C m −2 . In the central part, which is dominated by typical steppe systems, the growing season NEP generally varied in the range of 100-200 g C m −2 . The NEP of the northern China's grasslands was highly variable through years, ranging from 129 (2001) to 217 g C m −2 growing season −1 (2010). The large interannual variations of NEP could be attributed to the sensitivity of temperate grasslands to climate changes and extreme climatic events. The droughts in 2000, 2001, and 2006 reduced the carbon uptake over the growing season by 11%, 29%, and 16% relative to the long-term (2000-2010) mean. Over the study period (2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010), precipitation was significantly correlated with NEP for the growing season (R 2 = 0.35, p-value < 0.1), indicating that water availability is an important stressor for the productivity of the temperate grasslands in semi-arid and arid regions in northern China. We conclude that northern temperate grasslands have the potential to sequester carbon, but the capacity of carbon sequestration depends on grassland types and environmental conditions. Extreme climate events like drought can significantly reduce the net carbon uptake of grasslands.

Effects of Precipitation Intensity and Temperature on NDVI-Based Grass Change over Northern China during the Period from 1982 to 2011

“…The northeast of the study region (NE) is strongly influenced by temperate monsoon climate, where the rain season occurs in summer (June-August). The annual precipitation is about above 450 mm and the annual mean temperature varies from −3 °C to 9 °C in NE [34]. The altitude was lower than 1000 m and grassland is dominated by meadow steppes.…”

Data-driven diagnostics of terrestrial carbon dynamics over North America

“…To date, significant advances have been made in the upscaling of EC flux observations . A number of studies have upscaled EC flux observations to large regions using satellite remote sensing data and modeling approaches (Xiao et al, 2008(Xiao et al, , 2011aJung et al, 2009;Ryu et al, 2011), and some of these studies have also used the resulting flux estimates to assess regional terrestrial carbon and water budgets (Sun et al, 2011;Xiao et al, 2010Xiao et al, , 2011aZhang et al, 2014).…”

Daily and seasonal patterns of CO2 fluxes and evapotranspiration in maize-grass intercropping

“…), the type of plant (C3 or C4 metabolism), pasture condition, soil water storage, among others. For example, Zhang et al (2014) showed, in a study of 11 years in temperate grasslands in China, that carbon sequestration occurred, but the ability of the grassland to sequester carbon depended on the type of the pasture and the environmental conditions. In addition, an extreme climate event, such as drought, can significantly reduce carbon sequestration, as observed in periods of lower rainfall and soil water storage ( Figures 1B and 4) in this research.…”

“…During the experimental period, the average value of CO 2 fluxes was -0.78 µmol m -2 s -1 , which corresponded to a carbon sequestration of 2.9 t C ha -1 and 8.0 kg C ha -1 d -1 . Several studies (Randow et al, 2004;Wolf et al, 2011;Zhang et al, 2014) have shown that the CO 2 flux values in pastures tend to be negative (i.e., pastures usually act as a sink for CO 2 ).…”

“…However, most studies have focused on forest ecosystems and grasslands (Aires et al, 2008;Merbold et al, 2009;Otieno et al, 2010;Wolf et al, 2011;Krishnan et al, 2012;Zhang et al, 2014) and only a minority has concentrated on croplands, as example maize and soybean (Béziat et al, 2009;HernandezRamirez et al, 2011;Moreira et al, 2015).…”