On models for landscape connectivity: a case study of the new-born wetland of the Yellow River Delta

The models for landscape connectivity are distinguished into models for line connectivity, vertex connectivity, network connectivity and patch connectivity separately. Because the models for line connectivity, for vertex connectivity, and for network connectivity have long been studied and have become ripe, the model for patch connectivity is paid special attention in this paper. The patch connectivity is defined as the average movement efficiency (minimizing movement distance) of animal migrants or plant propagules in patches of a region under consideration. According to this definition, a model for landscape connectivity is mathematically deduced to apply to GIS data. The application of model for patch connectivity in the new-born wetland of the Yellow River Delta shows patch connectivity has a negative interrelation with human impact intensity and landscape diversity.

Spatial connectivity and distribution of landscape type in the natural secondary forests of eastern mountainous region,northeast China——a case study of Mao'ershan region in Heilongjiang Province

Mao'ershan region is representative in the natural secondary forested region of the eastern mountainous region, northeast China. The landscape nearest neighbor index and landscape connectivity index were calculated with ARC/INFO software for Mao'ershan region. The spatial distribution of the landscape of the region was analyzed. The results showed that the landscape connectivity index of non-woodland was significantly higher than that of woodland. The landscape connectivity index of natural forest was nearly equal to zero, which means its fragmentation degree is high. The nearest neighbor index of plantation was lower than that of natural forest and non-forestland. Among the man-made forests, the distance index of the coniferous mixed plantation is the lowest, and its pattern is nearly glomeration. The landscape pattern of natural forest presented nearly random distribution. Among non-forest land, the distance index of cut blank was the lowest, and its pattern was also nearly glomeration. Keywords Landscape type - Landscape pattern - Nearest neighbor index - Landscape connectivity index - Natural secondary forest - Northeast China CLC number S759.92 Document code A Foundation item: This paper was supported by the Key Project of State Department of Science Technology (2002BA515B040).Biography: LI SHu-juan (1977), female. Lecture in Ocean University of China, Qingdao 266003, P. R. China.Responsible editor: Zhu Hong

Application of landscape connectivity in habitat suitability evaluation——case study in Wolong Nature Reserve,Sichuan,China

Landscape connectivity is a parameter of landscape function, which measures the processes by which the sub populations of organisms are interconnected into a functional demographic unit. It is a landscape phenomenon which describes the relationships between landscape subunits. Landscape connectivity can be measured by measuring the degree to which the landscape pattern facilitates or impedes movement of animals among resource patches, particularly for conserved animal species. In this paper, the landscape connectivity for Giant Panda in Wolong Nature Reserve was evaluated by using landscape ecological model on the base of choosing three natural affecting factors on Giant Panda and using geographic information system. The results demonstrate that only about 90 36 km 2 (c.a.4 47%) of total area 2023 31 km 2 is most suitable for Giant Panda survival, the suitable area is about 226 42 km 2 (11 19%), the moderately suitable area is 286 09 km 2 (14 13%), as much as 1236 51 km 2 is completely unsuitable for Giant Panda living. The result will be helpful for making a decision on improving eco environment and protecting Giant Panda in Wolong Nature Reserve.

Optimization of Urban Ecological Network Based on MSPA-MCR Model: A Case Study of Jingzhou City

As a key carrier supporting urban ecological health and living environment quality,urban ecological network is a key focus of current urban green space research.Jingzhou City of Hubei Province is taken as the research object.Relying on GIS technology platform,MSPA method is used to analyze the landscape pattern of Jingzhou City.On this basis,the landscape connectivity evaluation method is used to accurately identify and extract the source areas with important ecological value in Jingzhou City.Then,the normalization method and weighting method are combined to create a resistance factor evaluation system to construct the resistance surface.Based on the MCR model,the ecological network of Jingzhou City is successfully constructed,and targeted spatial optimization strategies and development suggestions are proposed.

Landscape Network Approach to Assess Ecological Impacts of Road Projects on Biological Conservation

Awareness of the adverse ecological effects of road and other large construction projects has resulted in a rapidly growing demand to quantitatively predict and evaluate the effects on gene flow among plants and animals in natural habitats.In this study,we evaluated the effects of different road construction scenarios on animal species movement by using the methods of ecological landscape connectivity in the typical regions of Yunnan Province,China.The results showed landscape connectivity levels(Probability of Connectivity(PC))decreased after road construction and species with lower dispersal abilities were more affected to the subsequent habitat fragmentation.First level roads affected landscape connectivity most significantly.At a distance of 100 m,the PC index decreased more than 50%.Further analysis suggested that the use of landscape connectivity to assess landscape processes revealed the adverse effects on the species movement more effectively compared with the traditional landscape pattern analysis.In addition,we conducted a graph theory and a least-cost modeling discussion,it is obvious that they are powerful tools to represent and analyze landscape networks with respect to related species movement.Network analysis offers a quantitative and simple but effective tool for ecological process assessment and biological conservation on large scales.

Are local plague endemicity and ecological characteristics of vectors and reservoirs related? A case study in north-east Tanzania

The pattern of plague endemicity in Tanzania is characterized by continuous re-appearance of the disease in some locations, while in other neighbouring villages the disease has never or seldom been observed. To understand the reasons for this pattern, we studied small mammal and flea species composition, diversity and relative abundances in two plague-endemic and two plague-free locations. We asked （a） whether fleas more abundant in plague-endemic locations differ in their characteristic abundance and the degree of their host specificity from fleas more abundant in plague-free locations and （b） whether hosts most abundant in p/ague-endemic locations differ in the diversity of their flea assemblages from hosts most abundant in p/ague-free locations. We characterized （a） each host species by species richness and degree of taxonomic relatedness of its flea assemblages and （b） each flea species by its mean abundance and size, and degree of taxonomic relatedness of its host spectrum and compared their relative abundances between locations. No significant difference between plague-endemic and plague-free locations in either host density or any variable related to flea abundance or diversity was found. However, there was marginally significant effect of taxonomic distinctness of a flea assemblage barboured by a host on its probability to be more abundant in either plague-endemic or plague-free locations. Furthermore, hosts more abundant in plague-endemic locations tended to harbour closely-related fleas. Finally, while opportunistic and specialist fleas were equally distributed in both sets of locations, fleas exploiting distantly-related hosts were found mainly in plague-free locations during the rainy season. We suggest that the observed patterns might arise due to seasonal and spatial differences in local microclimatic conditions and landscape connectivity [ Current Zoology 55 （3） ： 200 - 211, 2009].

Ecological connectivity in fragmented agricultural landscapes and the importance of scattered trees and small patches

Background:Fragmentation and habitat loss can restrict species movement and reduce connectivity,negatively impacting biodiversity.Characterising the overall connectivity of an area can inform better management of human modified landscapes.Contemporary connectivity modelling methods seldom incorporate fine-scale movement patterns associated with movement between fine-scaled structural connectivity elements such as scattered trees,roadside corridors and small patches of habitat.This study aims to characterise connectivity within the Karuah-Myall catchments,a typical woodland ecosystem that is fragmented by agriculture,using least-cost path analysis and a graph-theoretic approach;it focuses on how fine-scaled vegetation such as scattered trees support connectivity.We mapped scattered(and paddock)trees within this agricultural landscape where the main human modified land use was pasture.We modelled connectivity for a general representative woodland species using an interpatch dispersal distance and gap crossing threshold,and resistance from different land cover types.The gap crossing distance threshold was used to model movement between fine-scaled vegetation features.We compared the least-cost paths modelled with and without scattered trees.Results:Our results show that by excluding scattered trees,least-cost paths across the cleared pasture landscape did not reflect the types of movement patterns typically observed from field studies,such as those associated with a foray-search strategy used by small and medium mammals and birds.The modelling also shows that the KaruahMyall catchments are well connected and provide value to biodiversity beyond the catchment borders,by connecting coastal vegetation to the Great Eastern Ranges national wildlife corridor initiative.Conclusion:Connectivity models that exclude fine-scale landscape features such as scattered trees and small,linear patches risk misrepresenting connectivity patterns.Models of regional-scale connectivity can be influenced by the presence or absence of even the smallest features,such as scattered trees.

Quantifying landscape linkages among giant panda subpopulations in regional scale conservation

Understanding habitat requirements and identifying landscape linkages are essential for the survival of isolat­ed populations of endangered species.Currently,some of the giant panda populations are isolated,which threat­ens their long-term survival,particularly in the Xiaoxiangling mountains.In the present study,we quantified niche requirements and then identified potential linkages of giant panda subpopulations in the most isolated re­gion,using ecological niche factor analysis and a least-cost path model.Giant pandas preferred habitat with co­nifer forest and gentle slopes(>20 to≤30°).Based on spatial distribution of suitable habitat,linkages were iden­tified for the Yele subpopulation to 4 other subpopulations(Liziping,Matou,Xinmin and Wanba).Their lengths ranged from 15 to 54 km.The accumulated cost ranged from 693 to 3166 and conifer forest covered over 31%.However,a variety of features(e.g.major roads,human settlements and large unforested areas)might act as barriers along the linkages for giant panda dispersal.Our analysis quantified giant panda subpopulation connec­tivity to ensure long-term survival.

On the effects of spatial resolution on effective distance measurement in digital landscapes

Background:Connectivity is an important landscape attribute in ecological studies and conservation practices and is often expressed in terms of effective distance.If the cost of movement of an organism over a landscape is effectively represented by a raster surface,effective distances can be equated with the cost-weighted distance of least-cost paths.It is generally recognized that this measure is sensitive to the grid’s cell size,but little is known if it is always sensitive in the same way and to the same degree and if not,what makes it more(or less)sensitive.We conducted computational experiments with both synthetic and real landscape data,in which we generated and analyzed large samples of effective distances measured on cost surfaces of varying cell sizes derived from those data.The particular focus was on the statistical behavior of the ratio—referred to as‘accuracy indicator’—of the effective distance measured on a lower-resolution cost surface to that measured on a higher-resolution cost surface.Results:In the experiment with synthetic cost surfaces,the sample values of the accuracy indicator were generally clustered around 1,but slightly greater with the absence of linear sequences(or barriers)of high-cost or inadmissible cells and smaller with the presence of such sequences.The latter tendency was more dominant,and both tendencies became more pronounced as the difference between the spatial resolutions of the associated cost surfaces increased.When two real satellite images(of different resolutions with fairly large discrepancies)were used as the basis of cost estimation,the variation of the accuracy indicator was found to be substantially large in the vicinity(1500 m)of the source but decreases quickly with an increase in distance from it.Conclusions:Effective distances measured on lower-resolution cost surfaces are generally highly correlated with—and useful predictors of—effective distances measured on higher-resolution cost surfaces.This relationship tends to be weakened when linear barriers to dispersal(e.g.,roads and rivers)exist,but strengthened when moving away from sources of dispersal and/or when linear barriers(if any)are detected by other presumably more accessible and affordable sources such as vector line data.Thus,if benefits of high-resolution data are not likely to substantially outweigh their costs,the use of lower resolution data is worth considering as a cost-effective alternative in the application of least-cost path modeling to landscape connectivity analysis.

Evolution Characteristics of the Ecological Space Network of Resource-Based Cities:A Case Study on Xuzhou

The territorial and spatial planning is an essential tool for ecological civilization construction in spatial development and urban governance.Since ecological space has been an important part of the territorial and spatial planning,this study established a spatial structural pattern of"ecological source-ecological corridor-ecological node"along with methods including landscape connectivity analysis and ecological resistance surface analysis.Taking the ecological space of Xuzhou City,a typical resource-based city,as a case study,this research analyzed the ecological spatial network structure and evaluated the evolution characteristics before judging the breadth threshold value of the ecological corridor and providing planning control strategy.The study found that since the urbanization of Xuzhou City resumed its growth,the quantity of ecological sources,corridors,and nodes have grown along.The resistance of the ecological corridor increases year by year,with the proper breadth threshold value around 100–200 m.The development of an ecological network structure shows a single-polarization evolution characteristic that is high quality and high resistance.