小三江平原湿地东方白鹳(Ciconia boyciana)生境丧失的生态后果

Ecological effects on Oriental White Stork(Ciconia boyciana)with habitat loss in sub-Sanjiang Plain, China

采用生境套娃方法反映水禽——东方白鹳生境需求的层级系统基础上,利用GIS技术建立定量化分析模型,深入探讨了小三江平原生境丧失对东方白鹳生境空间分布的影响。结果显示:与初始状态1954年相比,东方白鹳繁殖生境丧失了81.9%,平均斑块面积缩小了88%;同时,生境面积的丧失是伴随生境破碎化过程发生的。1983之后生境破碎化明显加剧,到2005年生境连通度显著降低,生境处于高度破碎化状态。研究表明,生境丧失对东方白鹳繁殖生境的影响不仅取决于关键生境要素的变化,生境空间异质性改变更为重要。

Since habitat loss poses one of the most serious threats for many species, it is highly important to study the impacts on Oriental White Stork—the endangered species due to the habitat loss. The suh-Sanjiang Plain is recognized as an important breeding area for Oriental White Storks in China, but the population of Oriental White Stork has sharply declined during the last decades apparently due to forest harvesting and loss of natural wetlands. Conservation efforts have been done such as the establishment of wetlands reserves network to assure the persistence of Oriental White Stork at a regional scale. However, little is known about the effects of habitat loss on the distribution of Oriental White Stork. Six key breeding habitat variables have been identified and tested by the field surveys during 2004 and 2005. And GIS model has been applied to evaluate the potential distribution on suitable breeding habitats for Oriental White Storks based on six historical periods. The tests have been made whether habitat loss, size of habitat patches or connectivity between habitatpatches are important in predicting the breeding habitat distribution for Oriental White Stork. Results show that （ 1 ） habitat loss with land use include the loss of habitat area, reduction of habitat quality and the change of habitat structure ; （2） the decline of habitat patches in area and the increase of isolation between patches may result in fragmentation in landscape structure that further leads to the decline of occupancy of patches and population of Oriental White Stork in the study areas ; （3） the decrease in patch number of key habitats such as island-like forest, ponds and marshes as well as spatial isolation have brought serious negative impacts on the breeding habitat of Oriental White Stork with landscape fragmentation, which is the major reason for extinction of breeding population of Oriental White Stork after 1983 ; （4） loss or preservation of habitat spatial structure is also very important to maintain species sustainable survival. Results demonstrate that the original continuous habitat will be segmented in several patches when over 50% habitat is destroyed. The further destruction will decrease the size of mean patches, increase distance of adjacent patches. And when the habitat area is less than 20% of the total landscape area, the isolation will rapidly increase that forms a highly fragmented landscape and lead to the extinction of population of Oriental White Stork in the sub — Sanjiang Plain.