寻乌水流域景观格局演变及其生态环境效应

土地利用变化引起的景观格局演变及其生态环境效应研究已成为诸多学者广泛关注的研究热点。为正确认识和评价土地利用变化对景观格局和生态环境的影响,以寻乌水流域为研究对象,选取1995、2005年Landsat5 TM影像和2015年Landsat8 OLI影像进行遥感解译,得到3期的土地利用数据,借助ArcGIS10.2和Frgstats4.2软件,分析土地利用动态变化与景观格局演变特征。同时运用遥感生态指数(RSEI)对寻乌水流域1995—2015年期间生态环境质量时空演变进行评价。结果表明:(1)近20年寻乌水流域园地(增加40.14%)和林地(减少33.91%)面积占比变化幅度最大,水域(减少0.1%)变化幅度最小。土地利用变化单向转换频繁,园地"涨势"和林地"落势"十分明显,整体处于不平衡状态。(2)景观水平上,流域的香农多样性指数(SHDI)、修正Simpon均匀度指数(MSIEI)分别由1995年的0.7083、0.2423上升至2015年的1.114、0.5247,景观聚集度指数(CONTAG)由1995年的72.93下降至2015年的58.13。流域的景观异质性增强,破碎化程度提高。(3)寻乌水流域1995、2005和2015年RSEI均值分别为0.554、0.544和0.550,呈先下降后上升趋势,生态环境状况恶化后得到改善。寻乌果业发展引起的园地快速扩张对林地的占用是生态环境恶化的主因,后期退果(耕)还林、保护生态林及植树造林等是生态环境改善的主因。研究成果可为流域的土地利用规划、良好的生态格局建立和生态环境保护提供重要科学依据。

Landscape pattern evolution and ecological environment effect of Xunwu watershed

Landscape pattern evolution and ecological environment responses were intensively affected by land use change. This research field has become the study hotspot of many scholars. In order to exactly evaluate the impact of land use change on landscape pattern and eco-environment, this paper takes Xunwu watershed as the research object. Both landsat5 TM images in 1995 and 2005, and Landsat8 OLI images in 2015 were selected for remote sensing interpretation. Therefore, land use data of three periods were obtained. Meanwhile, the dynamic change of land use and the evolution characteristics of landscape pattern were analyzed by ArcGIS10.2 and Frgstats4.2. In addition, remote sensing ecological index (RSEI) was used to evaluate the temporal and spatial evolution of eco-environment quality in Xunwu watershed from 1995 to 2015. Firstly, the results indicated that the area of orchard land (increased by 40.14%) and forest land (decreased by 33.91%) in the Xunwu watershed changed the most in the past 20 years. The area of water body changed the least with a decrease of 0.1%. Land use change is frequent with one-way characteristics. The "rising trend" of orchard land and "falling trend" of forest land are very obvious. Overall, changes were revealed as an unbalanced state. Secondly, the shannon''s diversity index (SHDI) and modified simpson''s evenness index (MSIEI) increased from 0.7083 and 0.2423 in 1995 to 1.114 and 0.5247 in 2015 at the landscape level, respectively. Index of CONTAG decreased from 72.93 in 1995 to 58.13 in 2015. Thus, landscape heterogeneity of the watershed is enhanced, and the fragmentation degree is also increased. Thirdly, the mean values of Xunwu watershed RSEI were 0.554, 0.544 and 0.550 in 1995, 2005 and 2015. It showed a trend of first decline and then increase. Eco-environment was improved suffering from degradation. The occupation of forest land is the main cause of the deterioration of eco-environment by the rapid expansion of orchard land. The primary causes of eco-environment improvement include returning orchard (cultivated) to forest, protecting ecological forest, and afforestation. This study would provide important scientific basis for land use planning, lucid waters and lush mountains pattern establishment, and ecological environment protection.