关键词: 喀斯特环境, 环境退化, 自然恢复, 遥感

Abstract: The land cover, vegetation cover, biological product, biological delivery and soil physical chemical features were regarded as indexes mainly representing Karst environment degradation and its rehabilitation, and remote sensing and survey are used to study them. A study area was in Zhiyun district, Guizhou Province. The study method is as follows: (1) The imageries of Landsat MSS in 1973, TM in 1990 and TM in 1995 were chosen to classify the land cover. (2) The TM imageries data, which were obtained at the same time at the end of October in 1994 and 1995, were chosen to calculate their NDVI (Normalized Difference Vegetation Index. Its formulation is (TM 4-TM 3)/(TM 4+TM 3)). (3) According to the degradation, the sample plots were chosen. The plot of forest is 25 m², the shrub is 5 m² and the grass is 1 m². The production and the number of vegetation were surveyed at four corners and in the middle which is 1 m² to forest and shrub. To grass, all in the plot were surveyed. (4) In the same plot of vegetation survey, the soil samples were analyzed in the experiment. The analysis led to the following conclusions: (1) After analyzing the complex Karst environment, the three aspects of land cover, the vegetation and soil are chosen to reflect the degradation and natural rehabilitation of Karst area. (2) Because of human activities, the area showing vegetation degradation is estimated to be 1 63%. The impact of human exploitation makes the degradation rate of vegetation cover reach 1 88%. (3) The area of the forest and shrub cover is the main object for human cultivation due to its environmental quality. Therefore policies on environmental conservation are recently executed and the degradation rate has been dropped by 1 9%, but estimation shows that there is still 0 48% of the forest and shrub degraded per year. (4) When vegetation becomes shrub from grass, the increasing rate of vegetation delivery is three times per year until vegetation is rehabilitated to forest. The annual rate of vegetation turned from grass to shrub reaches 2 5% and the rate of vegetation cover from shrub to forest reaches 3 5% until vegetation becomes forest. The annual rate of vegetation production from shrub to forest reaches 50% until forest appears. Lastly, the soil becomes fertile during natural rehabilitation, the annual rate of soil organic constituent turned from grass to shrub is 1 5% and the rate from shrub to forest is 2 5%.

Key words: Karst environment, environmental degradation, natural rehabilitation