Zhang H.,Nanjing Normal University |
Zhang H.,Key Laboratory of Environment Change and Ecology Construction in Jiangsu Province |
Zhang H.,Yancheng Teachers University |
Liu H.,Nanjing Normal University |
And 5 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2012
Wetlands are one of most important ecological systems on earth. Their unique ecosystem function has led to them been sometimes called "the earth's filtration system". Coastal wetland is an important type of wetland, which is not only a rare ecosystem but is also often found in areas disturbed human activities. Landscape changes have become the most significant feature of this fragile zone. Landscape changes inevitably have effects on material circulation and energy flow within the coastal wetland ecosystems, which alter the landscape ecological processes, as well as the coastal wetland pattern and function. In this study, Yancheng coastal wetland was chosen as the study area. The Yancheng coastal wetland, located in the east of Jiangsu Province, is one of the largest mudflats in China and represents one of the most rapidly changing landscapes in the world. Changes to coastal landscapes can have natural causes or result from human activities; the pattern of change greatly differs between the two. We focused on the core area of Yancheng Nature Reserve. This area was divided into two parts based on the type of landscape change: change in the northern area being characterized as from human activities, and that in the southern area characterized as from natural causes. We used remote sensing digitized data from 1987, 1997 and 2007, and applied GIS techniques and methods of landscape ecology to analyze the temporal and spatial changes in landscape pattern caused by natural processes and human activities. In the area affected by human activities, from 1987 to 2007, the landscape pattern was characterized by greater fragmentation, higher dominance and less landscape diversity than those of the other area. The mean vegetation patch area decreased from 205. 31 hm 2 to 55. 60 hm 2 and the landscape diversity index from 1. 4284 to 1. 2928 while the landscape dominance index increased from 0. 3634 to 0 7766. This landscape change resulted in degraded and heterogeneous strips of wetlands. The wetlands showed a one- direction succession from land to sea in the period between 1987 and 1997 but the landscape exhibited a multi-directional succession from 1997 to 2007. In the area that was affected only by natural processes, from 1987 to 2007, the landscape pattern was characterized by greater diversity and less dominance than those of the other area. The landscape dominance index decreased from 0. 4844 to 0. 3164 while the landscape diversity index increased from 0. 9019 to 1. 4754. Strips of wetland development were more evident and there was a one-direction succession from land to sea between 1987 and 2007. The geomorphic deposit process and the succession of plant communities adapting to environmental changes were fundamental factors driving the landscape dynamics of the area not affected by human activities. Whereas human activity, such as dyke construction, was the important driving force behind the changes in landscape pattern in the area with human activities. Through identifying the rules of landscape changes caused by different factors in the Yancheng coastal wetland, we can form a scientific basis for the sustainable exploitation of the coastal wetlands, ensuring protection of the wetland resources while simultaneously achieving social and economic sustainable development in the Yancheng coastal region.
Zhang H.B.,Nanjing Normal University |
Zhang H.B.,Key Laboratory of Environment Change and Ecology Construction in Jiangsu Province |
Zhang H.B.,Yancheng Teachers University |
Liu H.Y.,Nanjing Normal University |
And 3 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2013
As Landscape changes have been the most significant feature of the coastal wetland, we focused on the core area of Yancheng Nature Reserve in the research. Basing on the type of landscape change, we divided this area into two parts: change in the northern area which was characterized as from human activities, and that in the southern area characterized as from natural causes. Using remote sensing digitized data from 2000, 2006 and 2011, and applying GIS techniques and methods of landscape ecology, we analyzed the differences between the temporal and spatial changes in landscape pattern caused by natural and artificial reasons. The result showed us that from the following three aspects. Firstly, in the District by human activities, from the year 2000 to 2011, the area of S. alterniflora marsh increased from 272hm2 to 781hm2; the average dimension tended to decline while the polymerization index showed an increasing tendency, which means the S. alterniflora marsh tended to gather in space and to be regular in pattern form; the growth rate of S. alterniflora marsh first appeared quick and then slow. In terms of spatial landscape evolution, the S. alterniflora marsh extended in both seaside and landside, with its width increasing from 598. 679m to 1719. 002m. Secondly, in the District by natural processes, from 2000 to 2011, on one hand, the area of S. alterniflora marsh increased from 20230hm2 to 39740hm2. On the other hand, the average dimension and polymerization index appeared a decline trend after initial ascent. And thus, the growth rate of S. alterniflora marsh was stable at the speed of 160-180 hm2 / a annually while the coastline increased 15hm2·km-1·a-1 per unit length annually. By comparison, during 2000 to 2011, the growth rate of S. alterniflora marsh in natural wetland district was higher than that in the manual management district. In terms of spatial landscape evolution, the width of S. alterniflora marsh increased from 1625. 586m to 3193. 317m, as it extended to seaside direction from 2000 to 2006 while in both seaside and landside directions from 2006 to 2011. Thirdly, by natural processes, the expansion of S. alterniflora marsh was influenced by the climate, geomorphic processes, hydrological processes, vegetation pattern and competition between species, as a result, it appeared strong zonal characteristic. By human activities, the ecological process changed as the expansion power of seawater was affected, with the dam being blocked. Consequently, the ecological system evolved towards the freshwater wetland and furthermore it restrained the expansion of S. alterniflora marsh, which present inlay pattern to a certain degree.