地形因子对盐城滨海湿地景观分布与演变的影响

地形作为景观结构和空间格局的重要影响因子,不仅为景观格局的形成提供基础,其空间特征也影响着景观的演变过程.基于2002、2011年地形高程信息和遥感影像,运用GIS技术,并结合分布指数,分析了盐城滨海湿地景观分布与演变对地形因子的响应特征.结果表明:①盐城淤泥质滨海湿地总体地形变化平缓,海拔0-2.5m的区域占整个研究区面积的97％以上.其中,米草带主要分布于0.9-1.5m,碱蓬带主要分布于1.5-2.lm,而芦苇带则主要分布于2.1-2.7m.②2002-2011年9年间湿地景观时间变化明显,其中,芦苇面积增加了3倍,碱蓬面积由26.80％骤降至11.51％,同期,米草面积则增加了50％之多.③湿地景观空间分布特征与地形关系比较明显.其中,米草空间分布向0.6-1.2m区间演变,显示出强烈的向低海拔区间扩张的趋势;碱蓬分布范围随地形的升高总体上呈下降趋势;芦苇在地形较高区间上的分布指数增长迅速,其优势分布区间向2.1-3.0m扩展.

Influences of topographic features on the distribution and evolution of landscape in the coastal wetland of Yancheng

Wetland ecosystems are landscapes of the highest biodiversity in nature and one of the most important environmental resources for human welfares. Their important ecosystem function has led to them been sometimes called "the earth''s filtration system". Yancheng coastal wetland is one of the biggest mudflats in China, and play a important role in protecting wetland biodiversity and adjusting regional climate. Owing to the irrational exploitation in recent years, Yancheng coastal wetland are experiencing significant landscape changes, which has aroused a lot of attention by experts and scholars. Terrain, which serves as an important factor of landscape structure and spatial pattern, not only provides a basis for the formation of landscape pattern, but also affect the evolution of landscape. Yancheng coastal wetland is one of the typical primitive wetlands. In the past, limited to the wetland''s objective conditions, there has been no complete height measurement for Yancheng coastal wetland, which makes terrain''s study become "the blank area of the wetland". As the result, Yancheng coastal wetland was chosen as the study area in this study. Based on the remote sensing images of 2002 and 2011, using GIS techniques and methods of landscape ecology and combining distribution index, we analyze the relationship between landscape types and terrain factors and reveal the response characteristics of terrain factors on the distribution and evolution of Yancheng coastal wetland landscape. The information about spatial distribution of landscape types in Yancheng was obtained through overlay analysis of the terrain factors derived from DEM and the landscape types in different periods based on Arcgis by using the remote sensing images.The result shows that: (1) The overall terrain of Yancheng coastal wetlands changes gently, of which altitude 0-2.5m region accounts for more than 97%. Spartina wetland mainly distributes in 0.9-1.5m, Suaeda wetland mainly distributes in 1.5-2.1m, and Reed wetland in the 2.1-2.7m.(2) During 2002-2011, the time of 9a wetland landscape changes obviously, in which the Reed wetland increases by 3 times, the Suaeda wetland plunges by 26.80% to 11.51%, and at the same period, the Spartina wetland increases by more than 50%.(3) It is found that the topographic distribution pattern of each landscape type also displays the corresponding change based on the statistical analysis on the relationships between the landscape type and the terrain index. Through the analysis, we found that the relationship between the characteristics of wetland landscape spatial distribution and the topography is more obvious. Where the space distribution of Spartina wetland space evolving at the range of 0.6-1.2m, shows strong expansion trend to low altitude interval. At the same time, with terrain increasing, Suaeda wetland distribution range shows downward trend generally. In the higher terrain, the distribution index of Reed wetland rapidly, whose advantage distribution range is extended to 2.1-3.0m. By revealing the terrain and landscape distribution relationship, we can not only provide the basic data for the sustainable exploitation and scientific management of the Yancheng coastal wetlands, but also achieve social and economic sustainable development in the Yancheng coastal wetlands.