The Western Part Of Hainan Land Desertification In The Past 20 Years Associated With Climate Change Research,

The west of Hainan Island is the only sandy desertification district of the tropical dry grasslands with sparse trees in my country, and it is very typical of the sandy desertification types and course. By interpreting the 1986 TM and 2003 TM remote sensing image based on background database and expert information, we have achieved the tow periods vector data of sandy desertification of the research area. Based on field research and the dynamic analysis of remote sensing data of tow times, using multi-information of research area (including data of geology, geography, hydrology, meteorology, economy, human culture) and existing research results, the paper discusses drive factors of sandy desertification and the relationships between drive factors and sandy desertification with the help of CIS tool and some mathematical method such as probability statistics, factor analysis and degree of association. In addition, the rule of temporal and spatial variation of sandy desertification in the west of Hainan Island is researched.In this paper, the background database of geography data, social economic data, midway data during the research course, and the research results database are established, which are needed for the sandy desertification research. The desertification land is classified as gently desertification, medium desertification, severe desertification land and the severest desertification land. The sandy desertification distributing scope and degree of the research area are evaluated, based on the desertification research area and the collected remote sensing information, using the TM data, the background database of sandy desertification research and the method of man-computer, interactive identification based on knowledge system.The overall temporal and spatial variation characteristics of sandy desertification in the recent 20 years in the west of Hainan Island are that: the main types of sandy desertification are changed from medium and severest sandy desertification types to gently and medium sandy desertification types. The area of gently sandy desertification land is increasing. The area of severe-severest sandy desertification is decreasing. The area of medium sandy desertification is decreasing, too.The overall temporal and spatial variation trends in the recent 20 years are that: the total area of desertification land is decreasing, the reverse trend of sandy desertification is greater than the evaluative trend.The temperature in the west of Hainan Island for the past 20 years appears to be going up, especially during the period of 1990s, the precipitation in the period of 1980s appears to be descending, but the precipitation in 1990s appears to ascending. According to the association of the temperature and the precipitation, we know that 1980s is the warm-dry period, but the 1990s is warm-humid period, the climatic variability trend is becoming warm-humid in the west of Hainan Island in recent 20 years.With the method of mathematical statistics and degree of association analysis, the relationship between the temporal-spatial variations of sandy desertification and the climatic variations is researched, the association degree of the desertification and the climatic factors is analyzed, too. The results show that: the climatic factors which have greater association degree with sandy desertification are mean annual temperature, mean annual relative humidity and annual evaporation. The climatic factors interact and interference with sandy desertification thus forms a positive feedback mechanism. In a word, the warm and humid trend of climatic exerts a fairly influence on the sandy desertification.