A B S T R A C TEcological projects are an important and vital method to help ecosystem adaptation and restoration in response to the environment change and human interference. The accurate and objective assessment of ecological projects will assist ecosystem management and adaption. This study took the central Tibetan Plateau as the study area, where a series of ecological projects has been implemented since 2005 to prevent grassland degradation by protecting and restoring the grasslands. Our aim is to explore where and to what extent the ecological projects influenced the grassland variation, using SPOT NDVI-based residual trend as an indicator. The results indicated that before the projects (between 1998 and 2004), human-induced degradation characterized the grassland. However, a general grassland restoration was detected after the projects from 2005 to 2012. Moreover, over 60% of project plots had positive trends in the NDVI residuals. From the spatial patterns, project-induced restoration was detected in the western and northern regions, such as Maduo, Dongde and Xinghai counties. For the eastern regions, the human-induced degradation has been generally mitigated and yet not reversed after the projects. Our results indicated that ecological protection and restoration projects in the central Tibetan Plateau have mitigated the grassland degradation and even reversed the degradation in some areas, and also suggested that the NDVI-based residual trend is a useful indicator for assessing the effectiveness of the ecological projects in alpine regions.

Abstract:The Southwest China Karst, the largest continuous karst zone in the world, has suffered serious rock desertification due to the large population pressure in the area. Recent trend analyses have indicated general greening trends in this region. The region has experienced mild climate change, and yet significant land use changes, such as afforestation and reforestation. In addition, out-migration has occurred. Whether climate change or human-induced factors, i.e., ecological afforestation projects and out-migration have primarily promoted forest restoration in this region was investigated in this study, using Guizhou Province as the study area. Based on Moderate-Resolution Imaging Spectroradiometer (MODIS) Normalized Difference Vegetation Index (NDVI) data, we found general greening trends of the forest from 2000 to 2010. About 89% of the forests have experienced an increase in the annual NDVI, and among which, about 41% is statistically significant. For the summer season, more than 65% of the forests have increases in summer NDVI, and about 16% of the increases are significant. The strongest greening trends mainly occurred in the karst areas. Meanwhile, annual average and summer average temperature in this region have increased and the precipitation in most of the region has decreased, although most of these changes were not statistically significant (p > 0.1). A site-based regression analysis using 19 climate stations with minimum land use OPEN ACCESS Remote Sens. 2014, 6 9896 changes showed that a warming climate coupled with a decrease in precipitation explained some of the changes in the forest NDVI, but the results were not conclusive. The major changes were attributed to human-induced factors, especially in the karst areas. The implications of an ecological afforestation project and out-migration for forest restoration were also discussed, and the need for further investigations at the household level to better understand the out-migration-environment relationship was identified.

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