Grassland degradation track based on remote sensing technology in Daqing,northestern China.

Daqing is a resource-based city rising with the development of mineral resources.With the exploitation of petroleum resource and exploitation management of grassland,the grassland is getting degraded.As an important factor that maintains the ecological balance,grassland degradation prevents the economic development and the improvement of ecological environment.Based on TM images in 1988,1992,1996,2001 of Daqing using GIS,RS,GPS technology,the track of grassland degradation in Daqing was analyzed.The degree of grassland degradation was reflected by two indicators,grassland fraction and proportion of edible pasture grass.The two indicators were calculated by qualifying remote sensing inversion model based on vegetation index.Certain weights were given to the above two indicators to draw the picture of grassland degradation degree.The calibrated multi-temporal images were input to the GIS to monitor the characteristics and the track of grassland degradation in Daqing in 13 years.The results show that undegraded grassland and lightly degraded grassland were decreasing,moderately degraded grassland and seriously degraded grassland were increasing.The change of adjacent grassland degradation degree exceeded that of non-adjacent grassland from 1988 to 2001,showing that grassland degradation was a gradual process in Daqing.The change of grassland degradation degree was slow,and the slow-velocity change was predominant.The grassland changes included retrieval and degraded changes,but generally the degraded change was dominant.There was 1 461.4 km grassland changing into cropland,and 342.32 km changing into saline-alkali land.The track of grassland degradation in Daqing shows the process is from undegraded grassland to lightly degraded grassland,moderately degraded grassland,seriously degraded grassland,and finally to the non-grassland types.