黄土高原典型干旱区退耕还林后植被覆盖变化研究

Study on changes of land cover in the typical arid region of the Loess Plateau after the Grain for Green Project

以MODIS NDVI为数据源,选择退耕还林意义最为典型的甘肃省会宁地区为示范区,应用像元二分模型计算该地区2000—2010年11 a的植被覆盖度,分析了退耕还林后该地区植被覆盖度动态变化特征及趋势。结果表明:从实施退耕还林还草政策以来,会宁县植被覆盖度虽然年际间有较大波动,但总体上呈微弱的增加趋势,并以低植被覆盖度类型和中低植被覆盖度类型为主,11 a监测期植被覆盖度增加的面积达到70.60%,且植被覆盖度主要向10%—45%范围内转化。空间上植被覆盖度差异较大,南部高、中部和北部显著偏低。人类活动与气候变化是影响植被覆盖度变化的主要因素。

Huining county is located in the southern Loess Plateau in China.As a very typical arid/semi-arid area in hilly andgully regions of the Loess Plateau,it seems to be a very significant test area for evaluation of Grain for Green Project.In thispaper,MODIS NDVI was selected as the data source to track the variation of vegetation coverage in Huining from2000to2010and vegetation coverage maps from different periods using the two sub-pixel model.In this study,results show that thevegetation coverage exhibits higher in the southern region,but lower in the central and northern regions in Huining county.Since the policy of Grain for Green Project was put into force,the vegetation coverage in the county has increased andmaintained above20%in most years whereas it has reached to peak value of36.60%in2005.During11monitoring years,theland is dominated by low and medium-low vegetation coverage type with a large spatial variation.The increased areas of thevegetation coverage are about70.60%,where the transformation of vegetation coverage is mainly focused on the range from10%to45%.Both human activities and climate changes are the main factors to induce the changes of vegetation coverage.Meanwhile,there is a significant correlation(R2=0.688)between precipitation and vegetation coverage.