黄河中下游典型河岸缓冲带植被景观连接度及其网络构建

植被作为河岸缓冲带生态系统服务形成与维持的基础,在维持生物多样性方面,能为多种物种提供栖息地和迁移廊道。因此,本文以黄河中下游典型河岸缓冲带植被为对象,采用遥感解译、景观连接度指标、斑块重要性评价和廊道网络分析相结合的方法,分析2003年、2009年和2015年研究区的植被景观连接度和斑块重要值变化,并构建河岸缓冲带植被廊道网络,以期为黄河中下游河岸缓冲带生物多样性保护提供支持。结果表明,研究区植被斑块的连接度在2003—2015年呈增加趋势,且随距离阈值的增大而增大;不同距离阈值下,斑块重要值随斑块面积增大而增大,且随距离阈值增大的而增大;小型斑块(0~5 hm~2)重要值呈增加趋势,中型斑块(5~10 hm~2)重要值呈先增加后降低趋势,而大型斑块(10 hm~2)重要值呈降低趋势。植被廊道网络分析表明,基于重要生态节点同时考虑沟渠和道路廊道可作为研究区植被廊道网络构建的重要参考。

Landscape connectivity and network construction of riparian vegetation in typical reach of the middle and lower reaches of Yellow River

Riparian ecosystems form the linkages and exchange zones of matter,energy and information between aquatic and terrestrial ecosystems.The characteristics of such zones significantly influence integrated landscape ecosystem functions from land to riparian regions.Riparian vegetation as an important component of riparian ecosystem,is the basis of the formation and maintenance of riparian buffer zone ecosystem services.However,riparian vegetation has now been widely recognized as fragile and sensitive system requiring conservation as it undergoes strong disturbances and great alteration by anthropogenic activities globally.Conservation activities have largely focused on the restoration or creation of natural areas to facilitate the movement of organisms.This is often based on reliable measurement of landscape connectivity and patch importance.In this study,a typical riparian buffer zone in the middle and lower reaches of Yellow River was analyzed for landscape connectivity and importance of riparian vegetation in 2003,2009 and 2015 using remote sensing,landscape connectivity indexes,patch importance evaluation and corridor-network analysis.Also the study constructed a riparian vegetation corridor-network in order to provide support for maintaining biodiversity in riparian buffer zones in the middle and lower reaches of Yellow River.The results indicated that landscape connectivity of riparian vegetation increased both from 2003 to 2015 and with increasing threshold distance.Thus the number of links (NL) and the number of the largest component (NLC) of vegetation patches increased from 2003 to 2015 and they increased with increasing threshold distance.However,the number of components decreased from 2003 to 2015 and with increasing threshold distance.The integral index of connectivity (IIC) and the probability of connectivity (PC) increased with increasing threshold distance.Under different threshold distances,the importance value increased with increasing patch area.Thus with increasing threshold distance,the importance value of small patches (0-5 hm²) increased gradually,that of middle patches (5-10 hm²) initially increased and then decreased,while those of large patches (>10 hm²) decreased gradually.When the threshold distance was more than 1 000 m,the importance values of small,middle and large patches became stable,indicating that 1 000 m was the optimal threshold distance for the analysis of landscape connectivity in the study area.Ultimately,the corridor-network analysis proved to be important reference for the construction of riparian vegetation corridor-network.It sim-ultaneously considered important ecological nodes,ditches and road corridors in the study area as the established vegetation network system had high corridor node number,network closure and connection degree.In addition,riparian vegetation corridor-network construction should not only prioritize the connection between large patches,but also emphasize the stepping-stone role of small and middle patches between the large patches.