Background
The authors introduce their study by noting that climate change has altered China's vegetation growth environment to the point that it has "impacted vegetation dynamics, composition and functions," which is extremely important in light of the fact that they say that "grassland is the biggest terrestrial ecosystem type in China" and that it plays an important role in the country's "national ecological environmental protection plans," citing Ren et al. (2011).

What was done
Working with GIMMS (Global Inventory Modeling and Mapping Studies) and MODIS (Moderate Resolution Imaging Spectroradiometer) NDVI (Normalized Difference Vegetation Index) data from 1982 to 2006 and from 2001 to 2010, respectively, Zhou et al. blended the two data sets together to determine the degree of change and the spatial pattern of China's grass coverage over the 1982-2010 period.

What was learned
The six Chinese scientists report that (1) "for 78.9% of the total grassland area of China, its grass coverage is increasing," that (2) "the mean coverage increased by 0.17% per year," that (3) the "area percentage of grass coverage with extremely significant (P<0.01) and significant (P<0.05) increase trends were 46.03% and 11%, respectively," while (3) the "area percentage of grass coverage with extremely significant and significant decreases were only 4.1% and 3.24%."

What it means
In discussing their findings, Zhou et al. remark that "at the annual time scale, there are no significant correlations between grass coverage and annual mean temperature and precipitation," which pretty much makes the ongoing rise in the atmosphere's CO2 concentration the most likely driver of the long-term increase in China's grassland coverage.

Reference
Ren, J, Liang, T., Lin, H. et al. 2011. Study on grassland's response to global climate change and its carbon sequestration potentials. Acta Prataculturae Sinica 20: 1-22.