Changes Of RED-Crowned Crane Habitat Connectivity And Recovery Based On Graph Theory In Yancheng Coastal Wetland

Wetland ecosystem is one of the richest biologically diversity ecosystems with richest ecological resources and strong ecosystem services, it is also ecologically sensitive and vulnerable areas. Temporal and spatial change of wetland resources development and utilization has an important impact on the species habitat, distribution and diversity. Yancheng coastal wetland system in Jiangsu Province is one of the international biosphere reserved districts, and it is the only reliable reserved land resources as well. As one of the world’s red-crowned crane most important wintering habitat, frequent changes of wetlands development and utilization in wetland landscape is bound to affect red-crowned crane habitat structure and quality. In recent years, loss of red-crowned cranes wintering habitat is severe, habitat quality decreased significantly, thus resulting in the number of wintering red-crowned cranes proportion decreased. Landscape connectivity plays an important role and has significance in studies of biological migration, species diffusion, as well as ecological flow and other ecological processes, and become one of the hot spots in landscape ecology research content. Graph theory has greatly promoted the development of connectivity-related research, that will be studied by transforming real and specific ecological significant ecological elements into the elements of graph theory parameters, displaying characteristics of natural ecological networks in an intuitive and visual forms. And combined with comprehensive connectivity index, connectivity not only can reflect the structure of connectivity in the landscape, but also can better reflect its function connectivity, that will provide a theoretical and practical framework for analysis of cross-scale and dynamics changes of the regional landscape.This paper firstly reviews the landscape connectivity, the impact of wetland landscape change on biodiversity, the red-crowned crane habitat and other related researches, on the basis of the feasibility, pick Yancheng coastal wetland zone as study area, combined with remote sensing data and field survey data. First of all, this paper analyze temporal changes of crowned crane habitat types and resources in study area, and on the basis of red-crowned crane suitable habitat type map, according to the characteristic of red-crowned crane field and the minimum living space requirements, screened red-crowned crane habitat landscape map in the study area, then use landscape connectivity which is based on graph theory to analyze of Yancheng coastal wetland habitats of the red-crowned crane, to explore spatial and temporal changes of functional connectivity of habitats; Finally, according to the importance of supplement landscape, regard patches with big importance as a potential one to restore habitat and discuss recovery situation in different recovery scenarios. It will be under the broad scale, to help maintain habitat connectivity and ecological landscape flow. The main conclusion of the paper is as follows:(1) In 1991-2010 these 20 years, suitable habitat area continued to decline, a significant increase in supplement habitat and non-habitat area, which indicates that suitable habitat types are constantly being developed to supplement habitat and non-habitat types. From the perspective of land types, reeds and suaeda wetland which are original ecological wetland mainly transformed into aquaculture ponds. In 2003-2010, supplement habitat remains increased, which shows that in this stage, not only suitable habitat was converted to supplement habitat, but considerable non-habitat area was converted to supplement habitats as well. At first growth of non-habitat was greater than supplement habitat, then the growth of supplement habitat is beyond the non-habitat, and forcing non-habitat area changing into supplement habitats in the last stage, which also shows that the aquaculture industry position in Yancheng coastal wetlands have gradually been higher than farming.(2) Red-crowned crane habitat network consisted of a complete network had gradually broken down into several small habitat networks, the red-crowned crane habitat patches at this moment are mainly concentrated in the core protected areas. Landscape Connectivity has great changes in the past 20 years:Integrated connectivity index IIC continued to decline, falling from 0.0991 to 0.0020; other parameters in graph theory indicators show a growing fragmentation of habitat patches, habitat landscape connection degree continues to decline. The important values dIIC of habitat patches shows that most patches contributes little to connectivity of habitat, larger is DIIC, less number of patches. Four periods of time, the importance of red-crowned crane habitat patches classification, the highest importance level of habitat patches has an absolute advantage in the area of patches, lowest importance level of habitat patches has an absolute advantage in the number of patches. Thus for the protection of red-crowned crane population, particular pay attention to and protect these critical areas in Yancheng coastal wetlands. In most cases, the patch area is larger, the greater importance value; But there is a case that very large patch area with not high important value, that means patch area and patch important values does not present a strict proportional relationship.(3) Based on researching landscape connectivity of red-crowned crane habitat restoration, the vast majority and the vast area of supplement habitat have little contribution to enhance landscape connectivity of red-crowned crane habitat, and therefore in restoration of red-crowned crane habitat in Yancheng coastal wetland, should pay more attention to these "very high" and "high" supplement habitat patches. By simulating the recovery scenario S1 and S2, landscape connectivity of red-crowned crane habitat indeed has been significantly improved.