Dynamic Change of Land Cover of Qinling Mountains Based on MODIS NDVI

摘要

Taking the Qinling Mountains in Shaanxi Province as the research area, based on the MODIS NDVI data after time series reconstruction, combined with the land-use status data ,DEM data, and forest resources survey results, the change-vector analysis method and overlay segmentation method were used to analyze the degree of change in land cover and the type of change were explored in the Qinling Mountains from 2000 to 2015. The results showed that: 1)The most significant change of the land use map unit in the Qinling Mountains in 2000-2015 was the "deciduous forest to mingled forest", "cultivated land to deciduous forest" is the second largest unit type, accounting for 46.32% and 12.74% of the changeable area respectively. The other land use types have the smallest change to the water body, accounting for less than 0.01% of the area. 2) According to the NDVI cumulative change rate and the segmentation threshold, the NDVI change vector intensity types are determined: increasing, fluctuating, decreasing and stable. The area of increasing type accounted for 35.53%, and distributed around Shangluo in the northeast of the study area, Ankang in the southwest of Hanzhong and the south of the city mainly. The fluctuating type and decreasing area accounted for 5.46% and 0.85%, respectively. The fluctuating type was mixed among other types of changes, and the decreasing type were mainly distributed along the gentle slopes along the Luo River, Han River and Danjiang River, and around the city. The stable type has a dominant position and is distributed over a large area outside the areas of increasing, decreasing, and fluctuating, with an area ratio of 58.16%. In the areas with an altitude elevation of less than 1000m in the Qinling Mountains, the NDVI change vector increase dominates. With the increase of altitude, the NDVI change vector type within the range of 1500-2700m altitude is dominated by the stable type, and the proportion of the increasing type is reduced by the altitude; In the areas with a high altitude of 2700m, the NDVI change slowly increases year by year, showing an increase in the proportion of increased pixel area. Based on the dynamic analysis of vegetation cover change intensity in mountainous regions of Qinling Mountains, this paper reveals the intensity and regularity of vegetation changes in mountainous regions, provideing a basis for rapid monitoring of large-scale land cover changes, and has practical significance for the ecological protection of the Qinling Mountains.