石家庄市域近期植被变化及其驱动因素分析

Vegetation changes and its driving factors in Shijiazhuang City from 2004 to 2010 based on Landsat TM imagine

利用2004年和2010年TM卫星影像数据,对石家庄市域范围的植被变化情况进行了研究,结果表明:石家庄的植被近期变化以改善为主。从时间变化看,在2004-2010年间,全市NDVI的平均值从0.470 7提高到了0.541 6;极低覆盖度、低覆盖度、中覆盖度和高覆盖度植被所占比例分别降低了0.12%、0.7%、4.77%和24.32%,而极高覆盖度的植被面积比例则增加了29.9%;从植被指数差值结果看,全市植被改善面积比例高达83.84%,植被退化面积比例仅为16.16%。从植被变化的区域差异来看,极低覆盖度减幅最大的区域是中部丘陵区和东部平原区;中、高覆盖度的植被盖度等级则以东部平原区减幅最大;西部山区与中部丘陵区这两个区域极高植被盖度等级面积的增加幅度都达5 500 hm2以上。从植被指数差值结果看,改善面积最大的是东部经济林发展区,其改善面积比例达到了91%,改善面积比例最小的为城郊城市林业区,该区域植被改善的面积比例为74.9%。从植被变化的驱动力来看,研究时段的暖干型气候变化特点对于植被的生长于发育十分不利,因此研究时段内植被改善的主导驱动力是人为因素,其中山区的天然林保护工程、退耕还林工程是山区植被变化的主因;平原与丘陵区的植被改善主要得益于该区域的林果产业的发展;城郊城市林业区的植被变化与城区绿化工程的实施与绿地面积的扩大关系最为密切。

Vegetation is a key issue which can play very important role in the globe change research. Along with the progress in the 3S field （especially in the remote sensing）, there are more and more researcher use it in their related study. Moderate landsatellite image is widely used in the resource and environment investigation, as well as LUCC and vegetation changes. Shijiazhuan City has a very important position in the north of China, its changes in ecology and environment not only affect Beijing region, but also has indicating role to the other city which located around it. In this paper, we used the Landsat TM image of August 30,20（O and August 15,2010 which covered all of adminis- trative region of Shijiazhuang City. Consulting the others last related works, the NDVI were calculated by the Band 3 and band 4 data of TM image. Based on the NDVI, we also retrieved the vegetation coverage and NDVI difference value. According to this, the vegetation changes and its driving factors were studied. By comparing the relative data from 2004 to 2009, it was found that the vegetation statue of 2010 is better than that of 2004. There are three aspects are support this results. The first one is that the mean NDVI value is 0.470 7 in 2004, but the same item of that in 2010 is 0.541 6. In the 6 years period, NDVI value has increased 0.0709. The second one is that the area ratio of vegetation coverage in severe low class, low class, medium class and high class had reduced 0.12%, 0.7%, 4.77% and 24.32% respectively, but the severe high class has increased 29.9% at the same time. The third is that the NDVI difference value showed that the ameliorative area of vegetation ratio occupied 83.84% from 2004 to 2010. In different eco-region, the biggest decreasing area of serve low class mainly distributed in the middle hill sub-region, and the low class is in the middle hill sand east plain sub-region. In the east plain sub-region, the reducing degree of medium and high class vegetation coverage was the most remarkable. In the west mountain and the middle hill sub-region, the increasing area of severe high class was above 5 500 hm2 and other classes were all decreasing. From the NDVI difference value, the east economic forest sub-region occupied the biggest area in ameliorative changes, in which the ratio reached 91%, and the smallest area in ameliorative changes appeared in urban forest sub-region. Considering the driving forces of vegetation changes in Shijiazhuang City, we can not infer a direct correlation be- tween vegetation changes and climate changes from 2004 to 2010. We found that the characteristics of the climate changes in this period belong to the warn-dry type, and this is a very disadvantage condition to the vegetation devel- opment. But all related results shows that the state of vegetation is ameliorative, this indicated that the human factors are main driving forces to vegetation changes. The factors include regional green ecological construction projects, ur- ban greening municipal construction projects, and economic forest developing projects in plain region.