The Vegetation Cover Change Analysis Of The Loess Plateau Ecological Fragile Areas Based On Object Oriented

There are obvious ecological vulnerability and ladder evolution in China’s western loess plateau. Time and space dynamic analysis to the vegetation change, we can offer references to the development of the area, such as reasonably developing the resource, protecting and establishing the ecological environment and promoting the sustainable development of resource and society economy. This paper takes Yulin city as an example and extracts six period vegetation information from 1990 to 2014 of Yulin city using object-oriented classification technology. Then this paper perform binarization processing, compositing and difference operation to the vegetation information, and analyze the spatial distribution and quantity statistics of the vegetation change of Yulin city over 25 years from multiple aspects: such as overall change, regional horizontal, vertical space and vegetation types. After that, we got the conclusions as follows:(1)The spatial distribution of vegetation change in Yulin city is approximately bounded in ancient Great Wall and presents obvious district transitivity from northwest to southeast; the overall changing trend of Yulin’s vegetation presents linear positive correlation, which can be divided to 3 phases: slow, fast and sluggish, the cover area increases as an annual rate of 0.62%, which rants at average level, the net cover area increased 5090.96 km2 and the coverage increased 11.93% till 2014.(2)The major districts that suffered the vegetation coverage lost are locate in of the Wubao county, Mizhi county and Suide county of southeast direction of Yulin city, and the net area reducing is 0.17 km2, 0.13 km2 and 4.76 km2, which are all below 3%. Most of the nine counties that achieved area increase are situated in the west and the northwest of Yulin city, including five county that the proportion of net vegetation coverage area reached more than 9%, the order of the degree of change from high to low was: Shenmu county > Yuyang district > Hengshan county > Jingbian county > Dingbian county.(3) The vegetation coverage area of Yulin city increased within each elevation level, and the region of most distinguish increase distributes in the elevation of 1000 m ~ 1400 m range which total area increased of 4338.15 km2-- accounting for 10.17% of the whole city`s area increase; As to the slope distribution, the vegetation variation of Yulin decreases with the increase of the slope, they were negative correlation, and the turning point is the interval of 15° ~ 20°, flat area with slope less than this interval are of great vegetation variation, and also sharp increase of vegetation coverage, but in the region of more steep slope the variation levels remain low and the ecological structure is in a stable state.(4)During the last 25 years, the arable land in Yulin showed a declining trend with the rate of 0.86%. The changes of the forest area was in a linear growth, with a growth oriented performance which is total about 1.94%. The change rate of the grass land in different phase was seriously divergence, with an average rate of 0.36%. The ecological structure was unstable. The change rate of the grass land was the slowest above all.(5)The government policy and the urbanization is the main reason of the changes in vegetation differences of Yulin city. The results showed that the ecological structure of Yulin city tends to be stable, ecological environment construction effect is better.