Change in Vegetation Cover as Affected by Grain for Green Project in Gansu

Based on the 2000-2015 MODIS-NDVI remote sensing data, spatio-temporal variation of land vegetation cover in Gansu Province was explored with the aid of the GIS technology, and linear regression analysis methods. Then, on such a basis, the relationship between vegetation coverage and the total area involved in the Grain-for-Green project was analyzed. Results show that the annual NDVI value of Gansu Province continued to increase during the study period, with an annual growth rate of 0.43%, indicating that vegetation coverage was generally improved in Gansu Province. Although vegetation coverage in some regions still showed a decreasing trend, the areas with vegetation coverage improving formed the majority of the province. Among them, the highly-improved regions, moderately-improved regions, and slightly-improved regions accounted for about 20.62%, 14.67% and 33.05% of the province in area, respectively, while the regions with vegetation cover degrading only held 2.87%. In general, however, the total effective vegetation coverage in Gansu is still lower, compared with many other provinces in China, with the mean of 16 years being only 50.98%. The areas medium and low in vegetation coverage in total accounted for over half of the total area, and unevenly distributed. The southeast part of the province was the highest in vegetation coverage, reaching 75.43%, followed by the central part and the northwest part, with coverage of 47.84% and 31.77%, respectively, indicating that the distribution of vegetation cover varied spatially in the province. The area of lands involved in the Grain-for-Green project better explains the changes of vegetation coverage. The annual mean vegetation coverage of the years from 2000-2015 of the province was significantly related to the area of lands affected by the "Grain for Green" project in the region east to the Yellow River, with a determination coefficient of 0.7218.