Study On The Distribution And Influencing Factors Of Forest And Grass Vegetation Cover In Wuqi County

In the past few decades,a series of forestry ecological projects have been implemented in the Loess Plateau area,which is conducive to improving the coverage of its forest and grass vegetation,but has caused the problem of uneven spatial distribution of forest and grass vegetation.This article takes Wuqi County as a research area,and interprets the Landsat remote sensing images from 1997 to 2018 through remote sensing technology to explore the spatial and temporal changes of vegetation coverage in the past 20 years.Combining the transfer rate and state index to dynamically analyze the mutual transformation trend of land area with different vegetation coverage.Explore the correlation between terrain factors,meteorological factors,man-made factors and vegetation coverage through multivariate statistical analysis methods;Through the point pattern method,analyze the correlation between the vegetation coverage value of each sample point and the distance to the nearest water system,main road,and residential point;Use mathematical statistical methods to explore the change trend of the area occupied by various land-use types in the study area in the past 20 years.The main conclusions are as follows:(1)The spatial distribution of vegetation coverage values shows a gradual decreasing trend from southeast to northwest;in terms of interannual changes,the area of land with various levels of vegetation coverage changes frequently.The land area of low-grade vegetation coverage is mainly transfer-out,the land area of medium and medium-high vegetation coverage is mainly transfer-in,and the average vegetation coverage increases year by year.(2)In the terrain factor analysis,the land with medium and above vegetation coverage is mainly distributed in the altitude of 1300-1400 m,1400-1500 m and the shaded and semi-shaded slopes.The average vegetation coverage on the sunny slope was the lowest,and the average change in vegetation coverage on the slope and steep slope was the most dramatic in 2005.Meteorological factors have a strong correlation between autumn and winter precipitation and vegetation coverage.In the long run,the overall annual temperature will affect the vegetation coverage more than precipitation,and there is a certain degree of lag.The mean value of the vegetation coverage for many years is consistent with the fitting curve of the cumulatively confirmed qualified area of the project of returning farmland to forest.(3)In the study area,the construction land increased more from 2000-2009-2018,and the main types were urban land and public transport construction land.The grassland area is reduced.The proportion of forest area in the east and south increased.The forest and grass vegetation is mainly distributed in the range of 500-2500 m from the residential area,0-800 m from the main road and 0-400 m from the main water system.And it has the greatest impact on the distribution of forest and grassland with moderate vegetation coverage,and has almost no effect on forest and grassland with low vegetation coverage.(4)Among the influences of meteorological factors and forest and grass vegetation location factors on vegetation coverage,meteorological factors(air temperature and precipitation)have a greater influence on vegetation coverage,followed by the closest distance to roads and water systems,and less influence to the nearest distance to residential areas.