陕北榆阳区1978年至2005年植被覆盖率变化分析

本文以榆阳区遥感影像、数字高程(DEM)等资料为依据,运用地学信息图谱理论和方法,在RS和GIS的支持下生成了榆阳区1978年～2005年植被覆盖率变化图谱,分析了该区近30年来植被覆盖率的时空变化特征.研究表明:①1978年～2005年问,榆阳区植被覆盖率由3.22%增加到了10.35%;②各坡度段的植被覆盖率都有较大幅度增加.其中1989年～2005年问明显呈现出植被覆盖率增速随坡度增加而加大的变化态势;③黄土丘陵沟壑区在各时段的植被覆盖率及其增速均大于风沙草滩区,前者在1978年～1989年及1989年～2005年两时段植被覆盖率增速相近,而风沙草滩区前时段的增速则约为后时段的1.77倍;④榆阳区研究期各时段内的植被覆盖率都是城区＞近郊＞远郊,覆盖率增速在1978年～1989年段表现为:城区＞近郊＞远郊,1989年～2005年段体现为:远郊＞近郊＞城区.

Images Analysis of the Vegetation Coverage Changes in Yuyang District of Northern Shaanxi Province in the Recent 30 Years

Based on the remote sensing images, the digital elevation model (DEM), and other information of Yuyang District, suitable models, the theory of geographic information images, as well as RS and GIS are used to, analyze temporal-spatial changes of the vegetation coverage in Yuyang District from 1978 to 2005. It is concluded that in the recent 30 years, the proportion of the vegetation coverage in Yuyang District has gone up from 3.22% to 10.35%- about 7.13% total increase and the annual average growth rate of 0.26%, while that in loess hilly-gully region has increased from 3.74% to 14.17% and that in wind drift sand region has increased from 3.02% to 8.86%. The proportions of the vegetation coverage in all the different slops of Yuyang District have increased in the research period. The steeper the slops are, the faster the vegetation coverage has increased between 1989 and 2005. The vegetation coverage and its increasing speed in loess hilly-gully region are higher than those in wind drift sand region in the research period. The increasing velocity of vegetation coverage has been similar between 1978~1989 and 1989~2005 in the loess hilly-gully region, while that in the wind drift sand region between 1978 and 1989 has been about 1.77 times more than between1989 and 2005. Among the urban, the suburban and the outer suburban areas of Yuyang District, the vegetation coverage in urban areas has been the highest and that in the outer suburb the lowest from 1978 to 2005. The increasing velocity of the vegetation coverage in the urban areas has been the fastest while that in the outer suburb has been the slowest between1978 and1989, but the status has reversed between1989 and 2005. Plant growth and vegetation development can be affected by climate factors, topography, soil conditions and land-use types. Natural and non-natural disturbances, such as global climate changes, deforestation, afforestation and other human activities can also impact vegetation development. However, the change of vegetation coverage can be mainly attributed to human activities in a short period.