三峡库区1988～2007年植被覆盖动态变化研究

VEGETATION COVER CHANGE IN THE THREE GORGES RESERVOIR AREA DURING 1988～2007

长时期植被覆盖变化研究有助于揭示区域陆地生态系统的动态变化特征。以1988、2000和2007年3期遥感影像为基础数据,结合森林资源二类清查数据库,应用非监督分类的方法提取三峡库区植被覆盖信息,通过面积转移矩阵、动态度及动态变化趋势状态指数和土地利用程度分析了库区近20 a来的植被覆盖变化。结果表明:(1)三峡库区20 a来植被覆盖总面积呈下降趋势,下降速度在减缓。但库区内乔木林(针叶林、阔叶林、针阔混交林)面积减少且变化量较大,而灌木林面积呈现上升趋势。(2)1988~2000年植被覆盖类型转移趋势主要表现为:针叶林主要转入类型为阔叶林和耕地,转出类型为耕地和灌丛;阔叶林主要转入类型为灌丛和耕地,转出类型为针叶林;针阔混交林主要转入类型是针叶林,转出类型是耕地;灌丛主要转入类型和转出类型均为耕地。(3)2000~2007年植被覆盖类型转移趋势主要表现为:针叶林、阔叶林、针阔混交林及灌丛对耕地的转移率分别为8.27%、60.33%、47.24%和29.11%,贡献率分别为3.92%、10.15%、1.04%和13.18%。这一时期内同时,各植被类型向城镇村及工矿用地的转移率及贡献率均明显高于上一研究期。(4)三峡库区整体土地利用程度处于中等以上水平,高于全国平均水平,三峡库区土地利用的强度呈明显增大的趋势。三峡库区植被覆盖变化的3个驱动力因子分别为三峡工程建设、国家政策、经济发展与城市化建设。

Long period research of vegetation cover change will help to reveal the dynamic characteristics of regional terrestrial ecosystem.Based on the imageries of three periods in 1988,2000 and 2007,we analyzed the vegetation cover change combined with forest inventory database in the Three Gorges Reservoir Area.The Unsupervised Classification was used to classify the vegetation cover types,and some mathematic models were applied to study the spatio-temporal changes of vegetation cover during the 20 years in the Three Gorges Reservoir Area,such as vegetation cover type transferring matrix model,land use dynamic model and land use degree model.The main results showed that the area of the vegetation cover decreased continuously during the past 20 years in the Three Gorges Reservoir Area,but the rate had a slower decrease.The area of the arbor forest(including coniferous forest,broadleaved forest and mixed wood) had reduced and the change quantity was very large,however,the area of the shrubbery had increased constantly.The main transfer direction during the period of 1988~2000 was the mutual transfer in various vegetations cover type and between the vegetation cover types and the cropland.Coniferous forest transferred mainly into cropland and shrubbery,broadleaved forest transferred into coniferous forest mainly,mixed wood transferred into cropland mainly,and shrubbery into cropland mainly.The main tendency during 2000~2007 was the mutual transfer between the vegetation cover types and the cropland.The rate of the transferring of coniferous forest,broadleaved forest,mixed wood and shrubbery into cropland were 8.27%,60.33%,47.2% and 29.11% respectively;and the rate of contribution were 3.92%,10.15%,1.04% and 13.18% respectively.And it was also found that the transferring rate and contribution rate of the vegetation cover type changing into the residential land in 2000~2007 had been higher than that in 1988~2000.The total land use degree index of Three Gorges Reservoir Area was above the medium level and higher than the national average level.And the tendency of the land use degree in the Three Gorges Reservoir Area increased obviously.The driving forces for vegetation cover change in the Three Gorges Reservoir Area were the Three Gorges Project,national policy,economic development and urbanized construction.