岔口小流域植被覆盖度时空变化特征分析

Analysis on temporal and spatial variation of vegetation coverage in Cha-Kou small watershed

[目的]本研究旨在为岔口小流域的生态环境评价和改良提供参考,同时为该地区的坡改梯、荒坡绿化等工程提供决策依据。[方法]基于Landsat-7ETM影像数据反演2001-2010年岔口小流域植被覆盖度时序变化与空间格局,并结合流域同时期的气象数据和地形数据,分析流域植被覆盖度的年际变化对气候变化的响应及空间分布对地形变化的响应。[结果]结果表明:(1)2001-2010年研究区的平均植被覆盖度为0.51。研究区西部的植被覆盖度普遍高于东部,林地、沟川地和沟坝地的植被覆盖度相对较高。(2)2001-2010年研究区植被覆盖度总体上呈上升趋势,平均变化速率为0.013/年。研究区东部和南部地区植被覆盖度升上趋势较为明显。(3)研究区植被生长与温度和降雨量之间均呈正相关,并且降雨量是限制植被生长的主要气候因子。温度对植被生长的影响无明显的时滞性,而降雨量对植被生长的影响存在时滞效应。(4)研究区的最高海拔并未达到限制植被生长的临界值,随着海拔的升高,植被覆盖度增加。研究区植被覆盖度随着坡度的升高而增加,达到一定坡度时,随着坡度的升高而减少。[结论]2001-2010年岔口小流域植被覆盖度呈上升趋势,气候变化和退耕还林工程的实施是其增加的主要原因,地形变化则影响其分布。

[Objective]The study aimed to provide a reference for the ecological environment evaluation and improvement in Cha-Kou Small Watershed while providing decision-making basis for the Slope-to-Terrace Project and slope greening project. EMethod]Landsat-7 ETM data can be used to invert vegetation coverage change. With meteorological data and topography data during the same period, we analyzed the response of vegetation coverage to the climate change and the topography change, f-Results]It found that the average vegetation coverage of study area was 0.51 during 2001-2010. The vegetation coverage in the west of study area was higher. Moreover, the vegetation coverage of wood land, plain land and dam land were relatively higher than the rest. During 2001-2010 the vegetation coverage of study area, whose average rate of change was 0. 013/year, exhibited an increasing trend, especially in eastern and southern regions. There was a positive correlation between vegetation growth and temperature or rainfall, and rainfall was the main eli- mate factor limiting vegetation growth. The influence of rainfall but not temperature on the vegetation growth showed an obvious time lag. As the highest altitude in study area was not up to the critical value limiting vegetation growth, vegetation coverage increased with the increase of altitude. And vegetation coverage increased with the increase of slope until the slope was up to the critical value when vegetation coverage decreases with the increase of slope. [Conclusion] During 2001-2010 the vegetation coverage of study area exhibited an increasing trend, climate change and the implementation of Grain-to-Green Project were major causes of its increase, and the topography change affected its distribution.