| Desertification is one of the major global environmental problems that human faced, It has caused serious environmental degradation and economic deprivation and even hazard the survival and development of human society. Desert widely distributed in China and it is one of the countries that damaged seriously by desertification. Therefore, desertification has great significance to China. Vegetation change and sand activity is two major surface processes in semi-arid regions, affecting desertification development. For clarifying the relationship between vegetation changes and sand activities and further explaining the variation of the surface and mechanism in Semi-arid areas, this paper studied the vegetation coverage together with spatial distribution and dynamic Characteristics of the bare sand deeply.Based on the considerations above, it takes sandy grassland in Naiman Banner, which has apparent vegetation change and drift activity, for example. This paper is under the guidance of landscape ecology, using remote sensing and geographic information systems and field investigation to research on the following contents.1. From analysis of remote sensing image in study area combine with the field investigation, it can conclude the sandy grassland vegetation and spatial distribution of the bare sand in Naiman Banner, there are three main types as follows: relatively uniform type, gradient type, geometry type. Relatively uniform type refers to vegetation patches and bare sand patches distribute uniformly in space and the dirtibution is no obvious concentration or gradient characteristics. Gradient-based mainly refers the completely bare sand move to vegetation clusters areas. The distribution of vegetation and bare sand has obvious gradient gradual process.It mainly distributed in the vicinity of rivers and lakes. Geometry type means with geometric shape of the field vegetation and form of the bare sand in the spatial distribution.2. From the reasearch on the vegetation coverage together with spatial distribution and dynamic characteristics of the bare sand in Naiman Banner, we found that: Sandy grassland vegetation - bare sand distribution in Naiman Banner concentrated mainly in a few NDVI values, peak size and half-peak breadths of distribution types vary from unit to unit. Vegetation - bare sand fragmentation occurred mainly in two NDVI sections. The vegetation is basis in patch fragmentation process, bare sand and patchy distribution and patch of High vegetation - bare of sand gradient type distribution similar to their deformation. Plaque deformation in vegetation and uniform density type of bare sand higher than other types. Plaque deformation in Low vegetation - bare patch of sand in the gradient distribution is not relatively significant.3. From the analysis features about the spatial distribution of same NDVI values for plaque we found that: the Area and patch number of the same NDVI values for plaque has power function relationship, index of location parameters is negative; Patch perimeter and area of the same NDVI values for plaque aslo has power function relationship, index of location parameters is Positive.4. From the analysis of area curve about vegetation - the spatial distribution of bare sand, patch density curve, the shape of the dynamic characteristic parameter exponential curve in typical sample with nearly two decades, we found that vegetation - bare sand dynamics has three main modes. Mode 1 for the 1987 to 1992 concentrated fastly between a more narrow NDVI values and took rapid movement to the low NDVI values, simplification of plate was fast. From 1992 to 2002, it focused slowly between the more narrow NDVI values and moved rapidly to high NDVI; From 1992 to 2002, it slower focused between the more narrow NDVI values and moved slowly to low NDVI values, simplification of plate was slow. Mode 2 for the 1987 to 1992 concentrated slowly between a more wide NDVI values and took slow movement to the low NDVI values, simplification of plate was fast. From 1992 to 2002, it focused fastly between the more narrow NDVI values and moved rapidly to high NDVI; simplification of plate was slow.From 2002 to 2009, it focused rapidly between the more wide NDVI values and moved slowly to low NDVI values, simplification of plate was slow. Mode 3 for the 1987 to 1992, it basically unchanged and took slow movement to the low NDVI values, simplification of plate was fast. From 1992 to 2002, it focused fastly between the more wide NDVI values and moved rapidly to high NDVI; simplification of plate was slow.From 2002 to 2009, it focused rapidly between the more narrow NDVI values and moved slowly to high NDVI values, complication of plate was slowish.5. From the analysis on driving force of Sandy grassland vegetation - bare sand dynamics in Naiman Banner, we found that climate change is the the main reason for vegetation - bare sand Changes, In particular, wind, precipitation and evaporation. Human activities on Sandy grassland vegetation - bare sand dynamics in Naiman Banner also has some impact, but not obvious. |
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