Research On Vegetation Area Changes In Yanqi Basin In Past Decade

Yanqi basin is a semi-enclosed basin in arid area with relatively largecoverage of vegetation, whose variation directly controls the ecological security,energy, material, ecological system and function in this area. Land vegetation hasbeen significantly influenced by human activity and enlarging human territorycurrently. This paper analyzed the dynamic development of vegetation coverage inYanqi Basin based on TM and ETM remote sensing image, DEM data and vegetationindex. Firstly, the annual average vegetation coverage development was analyzed bythreshold value of vegetation index; Secondly, all vegetation in this basin was gradeduniformly according to the relationship between vegetation index and time. Thedynamic development process of vegetation was then studied assisted byinterconversion among grades; Lastly, conclusion was proofed through spatiotemporalvariation analysis of vegetation coverage in natural vegetation zones, which mainlyare wet land, and the internal variation mechanism of natural vegetation of which wasfurther explored.The spatiotemporal variation analysis indicate that,(a) the gross area ofvegetation in Yanqi basin increases steadily between1998and2011while the smallestis2963.9km2in1999and the largest is3624.1km2in2011;(b) The variation ofvegetation coverage in Yanqi basin, among which the vegetation degradation stage isbetween1998and2006while the vegetation improvement stage is between2006and2011, closely related to natural climate change and human activity;(c) the vegetationin Yanqi basin is mainly of grade two and three, which transfer in large amount andchange prominently;(d) the general variation rule of wet land zone (Xiaohu zone andShuangshuigou zone) is similar to that of Yanqi basin;(e) the vegetation degradedfollowed by improvement between1998and2011in wet land zone (Xiaohu zone andShuangshuigou zone), but the wet land vegetation near Dahu zone is more stable andwill comparatively have quick recovery.