Grassland is the indispensable natural resources which covers a large area of terrestrial China and plays an important role in the ecological construction, ecological security, and food security of the country. The size of the grassland, i.e. grassland area, is its important natural property, which is the basis to estimate total grassland biomass and productivity. Therefore, an accurate estimate of the grassland area is of great importance in reasonable protection and utilization of the grassland resources.
However, the estimated area of China’s grasslands varies greatly among different studies due to different data sources and grassland definitions.Climate determines geographical distribution of natural vegetation, and thus the distribution of a vegetation type can be retrieved based on regional characteristics of climate. In the semi-arid and arid regions of northern China, precipitation is the major limiting factor of vegetation distribution, especially for grassland. On the other hand, Normalized Difference Vegetation Index (NDVI) data well reflects the vegetation coverage and is strongly correlated with precipitation in the arid and semi-arid regions. Therefore, the distribution and area of grasslands can be retrieved using the relationship between precipitation and NDVI in the recognized regions of the grassland.
Results/Conclusions
Finally we document an estimate of the total grassland area of 293×104 km2 in China, with a small variation of 290~295×104 km2 over the past 30 years. Uncertainties remain in our estimations because the area might be overestimated or underestimated at regional scale. Nevertheless, our estimate is generally consistent with that from the vegetation map of China and land cover data of China in 2010. Overall, this study develops a useful methodology which estimates the range and area of the grasslands based on the thresholds of precipitation and NDVI values and generates reliable estimates of the total grassland area in China.