关键词: 土地沙化, 沙化程度, 演变, 特征, 若尔盖高原

Abstract: [Objective] The situation of land desertification in Zoige County of southwest China is severe. In order to provide scientific basis for prevention and control of futher desertification in this area, it is necessary to explore the evolution trend of land desertification in Zoige County. [Method] The process of evolution dynamics of land desertification was studied with the transfer matrix of biostatistics based on the data of four land desertification monitoring data from 1994, 1999, 2004, and 2009 in Zoige County. [Result] Desertification expansion was at a rate of 11.08% per year in Zoige County during the period from 1994 to 2009, as a result,the sand area in 2009 was 4.5 times higher than that in 1994. The average annual rate of the expansion of desertification in diverse degrees of desertification was in a regular sequence of 24.49%, 12.03%, 7.80% and 6.68% for extremely severe desertification, mild desertification, severe desertification and moderate desertification land, respectively. On the whole, the degree of arenaceous desertification in sandy land was still in the initial stage for the mild sand land accounting for 75.69% of the total desertification area, suggesting that it was the favorable period for the management of desertification. After 15 years of desertification evolution, the structure of different degree of arenaceous desertification had been changed with a trend of decreasing ratio of the moderate and severe desertification land and an increasing one of the mild and very severe desertification land in terms of desertification area ratio. The proportion of desertification degree remained stable,and that was 61.53%, 68.77% and 83.06% for the period from 1994 to 1999, 1999 to 2004 and 2004 to 2009, respectively. This proportion suggested the desertification degree was in a gradually stabilized trend in time series. The sandy land area in mitigating desertification degree was 2.23 times of the land area proportion in deterioration of desertification during the period from 2004 to 2009. The trend of sandy desertification was in the direction of mitigation. The land desertification evolution, had both gradual change and jumping process at the 5 years' scale. Due to the presence of jumping process, non-desertified land is not necessarily the safest and would evolve into the severe desertified land under certain conditions. In contrast, the severe desertification can jump into a non-desertified land under the control of human resources. In recent decades desertification evolutionary trend had been improved under the background of combat desertification. [Conclusion] Nevertheless, the land desertification in Zoige County is still quite harsh and there will still a long and arduous approach to take in the sand control task for the future.

Key words: land desertification, degree of desertification, evolution, characteristics, Zoige Plateau