岷江流域三江交汇区景观格局变化研究

本文以生态景观理论为基础,地理信息与遥感技术为支撑,对岷江流域三江交汇区三期遥感数据,1990年TM、2002年TM、2014年ETM+数据进行图像分类、景观指数提取、空间分析,同时采用面积转移矩阵统计各景观面积的转移情况,分析景观格局变化的影响因素,研究结果表明:(1)1990—2014年三江交汇区景观类型面积排序为:农田林地草地水域居民地裸地。优势景观为耕地,所占比例由72.83%下降到63.32%,面积减少了3480hm2。草地所占比例呈现波动变化,总体增加了2.81%。林地比例由15.98%上升到18.79%,增加了700hm2。居民地所占比例升高了4.1%;(2)1990年研究区内草地景观易受到外部干扰,其分布形状复杂。林地景观整体聚合度较高同时具有较低的异质性,分布通透性好、规模连续。农田分布较为分散且斑块较小。2002年农田斑块分布复杂化,同时具有聚集度高的特点。2014年研究区内农田优势地位下降。此时农田分布比较破碎并且呈现集中的态势。草地分布规模性较好、分布较为完整,但是内部存在一定的破碎性;(3)三江交汇区景观类型相互转化的主要原因:一是,退耕还林、还草政策实施,海拔超过500m的丘陵山地区域,建立生态保护区。二是,成绵乐铁路和高速路网的完善,使得三江交汇区的土地类型向建设用地转化加快,主要集中在乐山市中区和周围城镇。

The Change of Landscape Pattern in Middle and Lower of the Minjiang River

GIS and remote sensing technology has played an important role in change monitoring in the field of geographic and ecological landscape. In this paper, data of three times remote sensing, TM in 1990 and 2002, ETM+ in 2014 were usd to detect the land use cover change, extract the index of different types of landscape, and calculate the transfer matrix to count the landscape area, and point out the driving force of landscape pattern change in the Minjiang River. The results showed that: (1) The landscape area sort: farmland >woodland > grassland > water > residential land > bare land in the study area. The dominant landscape was farmland and its proportion fell to 63.32% from 72.83%, farmland area decreased 3480 ha. But the overall proportion of grassland, woodland and residential land was raised in the study period. (2) The grassland landscape was susceptible to external interference in 1990, and its distribution shape was complex. The distribution of forest land is concentrated and continuous, and the permeability is good; the farmland is scattered and the patches are smaller. In 2002, the distribution of farmland patches was complicated, and it was characterized by high aggregation. The dominance of farmland declined in the study area in 2014. At this time, farmland distribution was broken, and showing a concentrated situation. The grassland distribution scale was better, but there was a certain fragmentation in the interior. (3) The main reasons for the landscape change in study area are as follows: first, the policy of returning farmland to forests and grassland has been put into effect, and an ecological reserve has been set up in hilly areas over 500m above sea level. Second, the land types transformation to construction land has been accelerated due to the improvingrailway and highway network, mainly concentrated in the central district of Leshan city and surrounding towns.