自然和人工管理驱动下盐城海滨湿地景观格局演变特征与空间差异

将盐城国家级自然保护区核心区划分为人工管理区和自然湿地区两种模式,根据1987年、1997年、2007年3个时相的景观资料,运用RS、GIS技术和景观生态学方法,分析不同驱动力下湿地景观格局的变化差异。结果表明:(1)人工管理区,景观斑块平均面积由205.31 hm2降至55.60 hm2,景观多样性指数1.4284降低到1.2928,优势度从0.3634上升到0.7766,表明景观破碎化明显,景观多样性呈降低趋势,优势度则呈上升趋势。景观变化的结果导致景观带状特征变弱,镶嵌性特征十分明显;1987—1997年期间,景观格局空间演变表现为从陆地向海洋的单向演替;而1997—2007年,景观演替呈现多向性特征。(2)自然湿地区,景观优势度呈下降趋势,从0.4844下降到0.3164;而景观多样性呈上升趋势,其指数从0.9019上升到1.4754。景观带状格局发育更加明显,各景观带宽趋于均匀,并且景观从陆地向海洋呈单向演替特征。(3)影响海滨湿地景观格局演变的驱动因素是:自然湿地区主要受海洋潮汐作用影响,其主要自然过程如地貌过程和植物群落演替过程等呈连续性变化,从而导致景观演变呈带状连续性发展;人工管理区主要受人为管理影响,人为管理往往使生态过程的连续性发生突变,从而使景观演变呈多向性特征。

Spatiotemporal characteristics of landscape change in the coastal wetlands of Yancheng caused by natural processes and human activities

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 hm² to 55.60 hm² 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.