基于围垦特征的海滨地区景观格局变化研究——以盐城海岸为例

为探讨滩涂围垦对海滨地区景观格局带来的影响,选取1973—2013年Landsat1、4、5、7、8影像数据,利用GIS(Geographic Information System)、RS(Remote Sensing)和景观指数计算方法,对盐城国家级自然保护区(川东港-新洋港段)已围垦区和未围垦区,以及典型垦区(海丰、海北和金丰垦区)围垦前后景观变化情况进行对比分析。1973—2013年研究区围垦特征如下:以10a为间隔,围垦区域平行于海岸线呈条带状向海推进,且条带逐渐变窄;围垦难度逐渐加大,总体上围垦强度呈减小趋势,过程上围垦面积呈升降交替状态;围垦后垦区利用方式各异,主要以种植业和养殖业为主。受围垦影响该区景观格局变化如下:1973—2013年,未围区(Ⅰ区)自然植被面积增加4762 hm2,斑块形状日益复杂、自然,分维数由1.10上升到1.15,景观破碎化水平较低,在0.17—0.21之间,多样性指数由1.11上升至1.52;已围区(Ⅱ、Ⅲ、Ⅳ区)自然植被面积不断减少,分别减少了9873、13788 hm2和6890 hm2,斑块形状更加简单、规则,分维数分别下降了0.03、0.03和0.02,破碎化程度分别上升了0.21、0.23和0.17,多样性均先升后降,升幅约0.8,降幅约0.5。海北、海丰、金丰垦区自然景观不断向人工景观转移,海北和海丰垦区斑块形状不断趋于简单规则,形状指数分别下降0.8和0.5,而金丰垦区形状指数上升0.4,景观破碎度方面分别呈"升—降—升"、"降—升—降"和"升—降"趋势。围垦前,各垦区景观面积和斑块形状变化差异不大,而景观破碎度变化差异明显;围垦期间各垦区景观格局变化一致;围垦后,各垦区除非受新一轮人类活动干扰,其景观格局基本维持围垦末期状态。

The changes of coastal wetland landscape pattern based on the characteristics of reclamation: a case study in coastal wetland of Yancheng, Jiangsu Province, China

To investigate the impact of reclamation on the landscape pattern of coastal wetlands in Yancheng, northern Jiangsu of China, RS, GIS and FRAGSTATS technologies were applied to analyze the remote sensing data from 1973 to 2013 as basic information resource. Changes of landscape between reclaimed and unreclaimed zones in the national nature reserve of Yancheng, were compared and analyzed from Chuandong Port to Xinyang Port, especially among Haifeng, Haibei and Jinfeng reclamation sites. Characteristics of the reclamation in studied areas from 1973 to 2013 were concluded as follows by a 10-year time interval: Firstly, the ranges of reclamation were stripped in shape, parallel to the coastline, and advanced offshore with width narrowing gradually. Secondly, the difficulty of reclamation increased progressively, and the overall intensity of reclamation showed a decrease tendency while the areas hovered unsteadily during its processes. Thirdly, the land use types diversified remarkably after the reclamation, which were mainly crop cultivation and aquaculture. Consequently, it was found that in the unreclaimed zone I, the natural vegetation area increased by 4762 hm², the patch shape tended to be more complex or irregular, FRAC_AM increased from 1.10 to 1.15, and the degree of landscape fragmentation remained low between 0.17 to 0.21 while the landscape diversity increased from 1.11 to 1.52. On the contrary, in reclamation zones II, III and IV, the natural vegetation area increased by 9873 hm², 13788 hm² and 6890 hm², the patch shape tended to be more simple or regular, FRAC_AM decreased by 0.03, 0.03 and 0.02, and the degree of landscape fragmentation increased by 0.21, 0.23 and 0.17 while the landscape diversity firstly increased and then decreased by 0.8 and 0.5 respectively. Though the changes of landscape areas and the shape of patches in single reclamation sites were similar to that of the whole reclamation zone, landscape fragmentation primarily increased and then decreased. The natural landscape was progressively transformed into artificial landscape, and the patch shape tended to be more simple or regular in Haifeng, Haibei, while more complex and natural in Jinfeng. Meanwhile, the changes of fragmentation were distinctive form each other that, the tend of which were "up-down-up", " down-up- down" and "up-down", respectively. Before reclamation, the differences between the changes of landscape area and patch shape were neglectable, but was significant in the landscape fragmentation. Landscape pattern changes were similar among Haifeng, Haibei and Jinfeng during the period of land reclamation, and that of each site maintained the condition at the end of reclamation, except in the presence of a new round of human disturbance.