CR 71:187-201 (2017)  -  DOI: https://doi.org/10.3354/cr01429

ABSTRACT: Grassland productivity change, along with the factors driving this change, is central to the study of terrestrial ecosystems. To date, few studies have examined these factors in grassland areas in southern China. In this study, we investigated grassland productivity change in an area in southern China that constitutes nearly 25% of the country’s total terrestrial area. Pairing GIMMS NDVI3g data with meteorological data from between 1982 and 2012, we estimated grassland net primary productivity (NPP) using the Carnegie-Ames-Stanford-Approach model. We then investigated the spatiotemporal changes in grassland NPP in response to several climate factors. Overall, we found an average annual grassland NPP of 309.6 g C m^-2 with a relatively large annual variation of 198.3 to 365.1 g C m^-2. Annual NPP exhibited an increasing trend, from 288 g C m^-2 yr^-1 in the 1980s to 323 g C m^-2 yr^-1 in the 2010s, with a mean annual increase rate of 0.39%. More than two-thirds of the grasslands (70.69%) showed relatively small fluctuations in annual NPP change. Collectively, our results indicate that grasslands in southern China were a relatively productive and stable ecosystem over the study period, accounting for approximately 1.8 to 5.5% of total annual Chinese terrestrial NPP. Our results also indicate interesting correlations between NPP and climate factors. During the study period, and across the study area, solar radiation and precipitation were positively correlated with NPP, while temperature was negatively correlated with NPP. Increases in NPP due to increasing radiation and precipitation combined with the decreases in NPP resulting from increasing temperature yielded an insignificant change in NPP overall.

KEY WORDS: Net primary production · Grasslands · Spatiotemporal variations · Climatic effect · Carnegie-Ames-Stanford-Approach · CASA · Southern China