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The components of root exudates released from healthy and unhealthy black locust (Robinia pseudoacacia L.) root were determined by GC-MS. The results showed that the kinds and contents of root exudates released from Black Locust are different for healthy and unhealthy plants, so it may be evaluated whether the Black Locust plants are healthy or unhealthy by the root exudates. Healthy plants can release more kinds of exudates than unhealthy plants, especially the kinds of acids, alcohol and ester. There are 46 kinds of compounds in the healthy Black Locust, but only 24 kinds in the unhealthy Black Locust. Many compounds are released from healthy plant but not from unhealthy, while many kinds of compounds are released from unhealthy plant but not from healthy one.

With the deterioration of the global ecology, the eco-environment fragility has been an important topic of the ecological environment research. The Northwest Yunnan is a typical area of abundant biological resources and vulnerable ecological environment. The ecological environment vulnerability is more initiated by the human disturbances except its special natural basic factors such as the geological structure, the terrain ,the geomorphology, the climate and hydrology conditions and so on. The paper analyses the human disturbances factors which impress the ecological environment vulnerability of the region from the negative interferences and positive interferences in order to enhance the research of the ecological environment to protect the ecological environment better in this area.

The semiarid loess area in north Shaanxi Province is one of the most serious areas of water erosion of China. Vegetation, rainfall, soil, and topography are the most dominant natural factors affecting soil erosion; and land disturbance/restoration is a significant factor influencing runoff and sediment yield in this area. According to the research, the results showed: (1) the relative impacts of the four factors on runoff were rainfall > soil > topography > vegetation, and the relative impacts of the factors on sediment yield were soil > runoff > rainfall > topography > vegetation; (2) during a period of the preliminary stage after land disturbance, topography was the most critical factor for the runoff, while sediment yield was soil. During a period of land restoration after land disturbance, runoff was primarily affected by vegetation, while sediment yield was rainfall; (3) this study showed Hippophae rhamnoides + Pinus tabulaeformis and Hippophae rhamnoides were the best vegetation type for reducing runoff and sediment yield, especially if the slope is less than 20°. Land disturbance is caused by human activities in semiarid regions, and in order to reduce the runoff and sediment yield quickly and effectively, artificial measures should be taken for rehabilitation of the disturbed lands.