Variations of NPP and Carbon Stock Benefits before and after the Grain for Green Project in Northern Shaanxi

Northern Shaanxi is one of the pilot zones for implementating of Grain for Green Project. Monitoring the net primary production (NPP) change before and after the project would help understand the spatial patterns and the accomplishment of the Grain for Green project, and also be propitious to calibrate the projects benefits. Using the improved Carnegie-Ames-Stanford Approach (CASA) modeling, the terrestrial NPP was estimated. Meanwhile, the carbon (C) stock benefits of Grain for Green Project were analyzed through the different land cover types and slope gradients. The results are as follows: (1) There was an apparently increase of average NPP in Northern Shaanxi from 2000 to 2007. Based on the trend analysis, the areas with high NPP growth rate (more than 20%) account for about 75% area of the whole Northern Shaanxi. (2) The C stock increased significantly from 2000 to 2007 in Northern Shaanxi. The total C stock of vegetation was 7169.4 t and the C stock per unit area was 121.2 t Ckm-2a-1. The total C stock of sloping farmland was more than 2000 t, which account for 31.3% of the whole C stock in Northern Shaanxi. (3) The main districts of the Grain for Green Project, such as the sloping farmland, open forest and lands with slope 15° to 35°, gained better C stock benefits than other areas. The results in this study indicated that the Grain for Green project resulted in good C stock benefits.