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Luan, China

Sun X.-B.,Wanxi University | Liu H.-Y.,Nanjing Normal University
Journal of Ecology and Rural Environment | Year: 2014

Expansion process of alien species is an important content of the study on management and control of ecological invasion. Based on the 1991, 1997 and 2007 remote sensing images of the coast of Yancheng, Jiangsu, expansions of Spartina alterniflora under different conditions were simulated and factors affecting the expansion and their intensities were identified with the aid of GIS technology and the Markov-CA model. Results show that (1) the actual annual expansion rate of S. alterniflora was 24.39% during the period of 1991-1997 and 7.76% during the period of 1997-2007, indicating that the species expanded rapidly in the former period and the expansion slowed down during the latter period; (2) the annual expansion rate of S. alterniflora, when the plants were let grow freely, was the highest, reaching 9.40% and 6.78% during the two periods, separately, and declined to 7.10% and 5.49%, separately, when growth of the plants was affected by competition of other species in the community and to 7.10% and 5.24%, separately, when growth of the plants was affected by both competition of other species in the community and artificial disturbance; (3) affected by competition of other plant species in the community, the annual expansions rate of S. alterniflora decreased by 2.30 and 1.29 percentage point, respectively, and affected by artificial disturbance, it did by 0 and 0.25 percentage point, respectively; and (4) the Markov-CA model built in this study can be used to get some valuable insights into the relationships between the expansion processes of exotic plant species and its affecting factors, which may provide some scientific basis for rational exploitation of wetland resources and conservation of biodiversity in the coastal zone of Yancheng. Source


Li Y.,Nanjing Normal University | Liu H.,Nanjing Normal University | Sun X.,Nanjing Normal University | Sun X.,Wanxi University | Zhu L.,Nanjing Normal University
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2010

Understanding the spatial differences of ecological functions of the coastal wetlands in the Yancheng is of great importance for wetlands protection and exploitation. Hydrogeomorphic unit (HGMU) is a base condition for ecological function assessment. Based on the distribution of wetland types abstracted from Alos imagery in 2006 - 2007 and field surveying on hydrological condition and DEM (1:25000), the hydrogeomorphic units were determinated for evaluation of wetland ecological functions in the study area. The results showed that the coastal wetlands of yancheng can be classified 7 HGMUs. Each HGMU has similar ecological functions, and different HGMU has clear different ecological functions. Among these HGMUs, the double direction of freshwater-flooding area (estuary area), daily tide-mud and sand flat area and monthly tide-mudflat, as well as annual tide-grass flat area had better ecological functions than other areas in the coastal wetlands of Yancheng. Therefore, to conservation these HGMU wetlands are of significant importance for maintaining regional ecological functions in the coastal area. Source


Sun X.,Nanjing Normal University | Sun X.,Wanxi University | Liu H.,Nanjing Normal University
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2010

Identification of the relationships between landscape and ecological processes is one of key issues of landscape ecology. Landscape pattern aims to build optimized landscape which could make landscape eco-efficiency maximization and stabilization. The Yancheng coastal wetlands were chosen for the study. Based on application of remote sensing (RS) and geographical information system (GIS), the functions of wetlands landscape ecosystem services were evaluated firstly, then applying the resistance model, some key ecological function zones were identified, and the optimization of wetlands landscape pattern were put forward in the study area. The research findings include: (1) Ecological process and functions of wetlands in the coastal area were different in spatial distribution. (2) Based on an accumulative cost intensity model, and the calculation of the cost intensity, and the sources identification, the critical ecological positions, corridors, and sources were designed in the study area, and the landscape pattern optimization further discussed. The conclusions includes: (3) Optimization of wetlands landscape pattern improved connectivity of landscape. The critical ecological positions for connectivity of landscape near the bays of the Old Huanghe River estuary and Dafeng Port was the most important, and it was the first primary object to be optimized. (4) The optimized landscape pattern for the Yancheng coastal area is to strengthen protection of nature resources, maintain high landscape connectivity, and promote the sustainable development in land-use and environmental protection. Source


Sun X.-B.,Nanjing Normal University | Sun X.-B.,Wanxi University | Liu H.-Y.,Nanjing Normal University
Journal of Ecology and Rural Environment | Year: 2011

Based on the data of the three phases of wetland landscape evolution, the CA-Markov model was used to simulate temporal and spatial evolution processes of wetland landscape of the core area of Yancheng Nature Reserve as affected by different conditions, with a view to exploring impacts of natural and anthropogenic factors on the landscape of the area and trend of its evolution. Results show that human management altered the evolution processes of the wetland landscape in the northern section of the core area. During the period from 1987 to 2007, the reed marsh belt and the Spartina alterniflora marsh belt expanded rapidly in width, with their proportion in area increasing from 5.62% to 60.20%, and from 1.91% to 7.78%, respectively, thus cutting the proportion of seepweed marsh from 67.50% to 7.21%. Its wetland landscape gradually changed in composition from four distinct belts (reed marsh - seepweed marsh - Spartina alterniflora marsh - mudflat) to tree (reed marsh - Spartina alterniflora marsh - mudflat) and by 2013, the belt of seepweed marsh will have disappeared in the northern section. In the southeastern section of the core area, natural succession dominated the evolution of the landscape in structure. Dotted patches of Spartina alterniflora marsh in 1987 expanded and merged into a belt in 2007, with its proportion in area increasing from 2.75% to 36.54%. The belt of reed marsh increased steadily in area and the areas of seepweed marsh and rivers remained almost unchanged thus cutting the proportion of mudflat from 65.44% to 26.85%. In the years to follow, the expansion of Spartina alterniflora marsh will slow down, while the other types of wetlands will keep going along their course of evolution. The wetland landscape will evolve in composition from three belts (reed marsh - seepweed marsh - mudflat) to four belts (reed marsh - seepweed marsh - Spartina alterniflora marsh - mudflat). Source

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