白洋淀湿地景观斑块时空变化研究

Spatial and Temporal Changes of Landscape Patches in Baiyangdian Wetlands,China

景观格局变化可以深刻地反映人类活动对生态环境的影响,研究白洋淀湿地景观格局时空变化对于明晰湿地水环境质量的恶化原因具有重要意义。通过综合运用GIS技术和景观格局指数法,对白洋淀1987、1999和2007年LandsatTM遥感影像进行解译分析,研究了白洋淀20年间景观格局动态变化。结果表明：苇地、耕地和水域是淀区主导景观类型,所占比例高达86.62%~93.06%,苇地为42.74%~58.02%。淀区斑块数和密度增加了23.01%,景观破碎化程度加剧。景观均匀度指数由0.74降至0.67,多样性指数由1.44降至1.25。苇地和耕地面积增加最多,分别为18.08%和28.05%;水域和干草地减少最多,分别为35.78%和76.53%景观分维数范围为1.05~1.27,受人类影响较大;苇地从1.27降至1.19,水域从1.16降至1.09,人为影响明显增强;裸地、林地和干草地的分维数最小,分别为1.06~1.08,1.05~1.09和1.07~1.09。根据主导景观类型时空变化,将白洋淀划分为G、WG和WS区。G和WG区主导景观类型均表现出从水域到苇地再到耕地转化趋势,WS区的水面和苇地在外源调水的作用下得以维持,水域整体向东部转移。建议白洋淀湿地保护以水域、苇地和草地为核心,控制淀内及周边人类活动对自然景观的扰动。调水要充分考虑白洋淀的景观时空特征,尽量降低对重要景观类型和生物多样性的影响。

The changes of landscape pattern profoundly reflect effect of human activities on the ecology and environment.The spatio-tempo-ral changes of Baiyangdian wetland landscape pattern from 1987 to 2007 were studied through the analysis of remote sensing images in 1987,1999 and 2007.Variations of landscape metrics were analyzed using GIS and Fragstats3.3 software package.Results showed that：reed bed,farmland and waters were the main landscape types in Baiyangdian,and they accounted for a proportion of 86.62%～93.06% of the total area,of which the reed bed was 42.74%～58.02%.The patch numbers and density increased by 23.01%,indicating the aggravation of landscape frag-mentation.The evenness index and diversity index declined from 0.74 to 0.67,and 1.44 to 1.25,respectively.Areas of reed and cultivated land were increased significantly,by the respective 18.08% and 28.05%,while water and dry grass were reduced greatly,by 35.78% and 76.53%,respectively.Landscape fractal dimension of this region ranged from 1.05 to 1.27,demonstrating the strong human impacts.The fractal dimen-sions of the reed bed and waters were much higher,ranging from 1.27 to 1.19 and from 1.16 to 1.09,showing the largest magnitude of decrease.While the fractal dimensions of bare lands,dry grasslands and woodland were all the lowest during the studied period,indicating the intense human impacts.According to the spatio-temporal changes of dominate landscape patterns,the wetland could be divided into three parts：part G,WG and WS.The dominate types in part G and WG exhibited a changing trend from water to farmlands via the state of reed bed.While in part WS reed bed and waters were preserved due to inter-basins water transfer.Consequently,the whole water area displayed an eastward transference.Accordingly we suggest that the protection of waters,reed and other natural patches should be taken as the core objects,and disturbance to these landscapes especially that from farming,construction and domestic pollution should be controlled strictly.Additionally,in water transfer projects,the spatio-temporal characters of the wetlands should also be taken into deep consideration,in order to minimize the influence on local natural landscapes and biodiversity,further more to assure the integrity and eco-healthy of the wetland.