The Research On Land Use Pattern Evolution Characteristics Of Northern Sand Belt, Along With Windbreak And Sand Fixation Function Change Assessment

Desertification has become one of the outstanding problems those damage the ecological environment of our country, Anti-desertification become an urgent matter to improve the ecological environment.the Northern Sand Belt is located in the north of China, Including Xinjiang, Gansu, Inner Mongolia and other provinces. It is an important part of the "two Barrier three Belt" ecological Security Strategy pattern.. In this study, we analyzed the land use pattern evolution and variation characteristics of macro ecological condition of the northern sand belt based on GIS, from the aspects of the transfer matrix, dynamic degree, land cover change index and landscape pattern index, etc.. On this basis, we evaluated the Sand-fixing Effect of the northern sand belt during2000to2010, with Revised Wind Erosion Equation (RWEQ). The main conclusions are as follows:(1)The descending order of the area of the ecosystem first classification during2000to2010is:Grassland> Desert> farmland> shrub> Forest> Wetlands> Towns> glacier/snow. The proportion of grassland is approximately39%, which of desert and farmland are25%and30%respectively.(2)In the conversion of land use types, the shrub and Grassland converted a lot to other types. They are mainly converted to farmland and towns. There are many other types converted into farmland, while a lot of farmland occupied by towns.(3)Land cover change index of the Northern Sand Belt are-0.11,0.16and0.05in the three period of2000—2005、2005—2010and2000—2010respectively. Visible, the macro ecological condition in northern sand belt deteriorated during2000to2005. And it changed for the better during2005to2010. Overall, the macro ecological condition is getting better during2000to2010.(4) With the method of landscape ecology, the patch number of Northern Sand Belt increased during2000to2010. Meanwhile, the average patch area decreased, the edge density increased and the aggregation index decreased. It shows that the structure of landscape pattern tend to be complicated, and plaque tends to be fragmented.(5)The northern Sand belt in2000—2010wind erosion intensity in the "light" grade regional distribution area is the largest, about50%of the total area of the north sand belt,The area of the other five wind erosion intensity level ratio is small. From its change trend, wind erosion intensity "severe" levels decreased from21%in2000to16.6%in2010. And "moderate","strong" and "very strong" trend to increase the percentage of area.(6)The lower the windbreak and sand fixation in each level is, the greater the proportion of its distribution area is. The proportion of the total area is biggest for "low" level, more than60%. Followed by "low" level, accounting for20%,other grades area is smaller. From the point of its change trend,"low" level for windbreak and sand fixation decreased from65.7%in2000to61.2%in2010, All other types of area percentage present a growth trend.(7)The north sand belt vegetation ecosystem has important function to prevent soil erosion, ecological service value of soil fertility. Area in2010more than the total value of40billion yuan a year for windbreak and sand fixation, accounts for about3.3%of GDP. From the point of the value structure of windbreak and sand fixation ecological system, maintain the highest proportion of the value of soil fertility,75%; Second to keep the value of soil loss.