| The desertification caused by wind erosion is seriously in Shanxi Province, especially in the north and northwest that is semi-arid agro-pastoral transitional area. Based on the detailed meteorological data in northern Shanxi, this paper aims to clarify the mutation and temporal-spatial climatic characteristics of sandy desertification and to show the dynamical environment in the past 30 years, the vegetation activities and soil texture distribution in the past 10 years were also investigated. Then, the relationship between climate, land surface environment and desertification were revealed. On this basis, to understand and reveal the past and current desertification, dune mobility index, NDVI and soil erodiable K were put forward to build the desertification index and grading system. After exploring the spatial distribution, area size and dynamic characteristics of desertification land in the past 10 years, the BP artificial neural network was used to simulate and verify the desertification index. The results showed that:(1) In northern Shanxi, the tendency rate of average temperature was 0.48℃/10a, which at a relatively slow rate increased year by year. Mutation test of temperature showed that there was significant warming mutation in each meteorological site. The spatial distribution of annual mean temperature indicated that the high-value area mainly in the northwest of Shanxi and the low-value area mainly in Youyu and Wuzhai county.(2) Results of data analysis indicated that, the precipitation wasn’t outstanding linear trend in study area, and the precipitation mutation test showed that there weren’t significant mutation feature in each meteorological site. However, the precipitation was obviously varies regionally:gradually increased from east to west.(3) The average wind speed gradually increased from west to east in the study area. In addition to Datong, the other meteorological sites were characterized by the mutation. The wind speed along the Northwest of Shanxi, including Hequ, Baode, Pianguan county belonged to a increasing area, while the remaining regions were decreasing.(4)The most intense wind-blown sand activities were occurred in the 1980s, and gradually increased from west to east. Except Baode and Hequ county, the dune mobility index was negative in most areas, which showed the wind-blown sand activities were decreasing in the past 30 years.(5) The vegetation activities in the north Shanxi from 2000 to 2012 showed an increasing trend. The NDVI was obviously varies regionally: gradually decreased from the northwest to the southeast. Vegetation activity in 91.04% of the total study area had increased over the 13 years, especially in the northwest Shanxi, otherwise, the weakened areas are mainly located in the southern part:Daixian and Fansi county. The increasing trend of vegetation activity occurred in the spring, summer and autumn, respectively. Moreover, autumn was the significant increase season, which is consistent with the trends of monthly mean NDVI.(6) Cinnamon soil, alluvial soil and chestnut soil were the main soil types in the north of Shanxi. Besides, aeolian sandy soil and volcanic ash soil which were easily eroded were also scattered. Distribution of soil erodiable K presented that the soil in the northwest of Shanxi was the most prone to soil erosion.(7) The desertification land was mainly distributed in the northwest and central area. From 2001 to 2012, the desertification land exhibited a sustained reversal trend. The "obvious reversal" and "reversal" were mainly concentrated in the northwest of Shanxi and Zuoyun, Huairen, Datong and Yanggao county. The "development" and "serious development" were mainly concentrated in the southern suburb and Tianzhen county of Datong.(8) The BP artificial neural network was used to simulate and verify the desertification index, which showed that the desertification index was feasibility in the north Shanxi, and the BP model can effectively extract the desertification information. |
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