Assessment of grassland degradation in Guinan county, Qinghai Province, China, in the past 30 years

Abstract In this study, the quantity, quality and spatial changes of grassland in Guinan County, Qinghai Province, China, were assessed by means of interpreting remote sensing satellite imagery during four key periods (1976, 1996, 2001 and 2006) as well as by applying various methods of analysis such as a transition matrix, fractal dimension, dynamic degree modelling and a spatial model of land use change. The assessment results were summarized from three positions. First, grassland area decreased and grassland quality degraded in the past 30 years. The decreased rate of area and the degraded degree of quality were significantly different during different time periods. Both the decline in grassland area and the degradation in grassland quality were determined to be most severe from 1976 to 1996 (especially for high density grassland) and moderate from 1996 to 2001 and from 2001 to 2006. Second, the grassland centre of gravity trended to move along a general southeastern direction; however, the direction of movement of grassland centre of gravity displayed multidirectional and irregular tendencies during different time periods. The primary reason that caused this situation was that the cultivation and protection of grasslands occurred during successive turns. Third, the change observed in grassland behaviour was shaped by a range of factors including natural forces as well as human‐induced disturbances. The dominant factor was primarily human activity. The transition matrix method, the fractal dimension method and the spatial model of land use change method showed similar results. Copyright © 2008 John Wiley & Sons, Ltd.