近20年福建红树林和互花米草群落时空变化及景观特征

Analysis of Spatio-temporal Dynamical Change and Landscape Characteristics of Mangroves and Spartina alterniflora in Fujian Based on Satellite Imageries From 1999 to 2018

红树林和互花米草是福建沿海重要的滩涂湿地植被群落,其分布与变化直接影响福建沿海的生态环境安全。基于多源多时相Landsat影像和高空间分辨率Quickbird及GF-1影像,利用3S技术和野外实地调查结果对1999—2018年近20 a福建红树林和互花米草群落分布格局和变化特征进行研究,采用斑块-廊道-基质景观模式和景观指数分析不同时相福建主要海域景观结构的变化特征。结果表明:(1)1999—2018年近20 a红树林和互花米草增长迅速,面积分别增加477.3和2647.81 hm^2,年增长率下降趋势明显,红树林保护区内互花米草年增长率大于红树林年增长率。(2)在斑块特征上,近20 a面积>20 hm^2的大斑块数量减少3.39%,≤20 hm^2的小斑块数量增加18.03%,斑块破碎度在增大,不稳定性在增加。(3)除三沙湾由于基质改变而表现为同质化趋势外,福建其他海域基质所占比例均逐年降低,异质化趋势不断增强。研究显示近20 a互花米草在福建北部海域占据绝对优势地位,在南部海域互花米草与红树林形成竞争状态,并已入侵部分红树林保护区核心区,对红树林构成严重威胁,需要采取相应的治理措施。

Mangroves and Spartina alterniflora are important coastal wetland vegetation resources in Fujian.Identifying the spatio-temporal distribution and evolution characteristics of mangroves and Spartina alterniflora is of great significance for the safety of coastal ecological environment.Based on the data of multi-source satellite imageries such as Landsat-5 TM,Landsat-7 ETM+,Landsat 8 OIL,Quickbird and GF-1 imageries from 1999 to 2018,the spatial distribution and dynamical change of mangroves and Spartina alterniflora were studied and analyzed using the methods of image processing,geographic information systems(GIS),global positioning system(GPS)technology and field investigations.The changes of landscape structure and characteristics were analyzed and evaluated by adopting the aspects of“patch-corridor-matrix”pattern and landscape ecology index.The results show that:(1)The total areas of mangroves and Spartina alterniflora in Fujian grew rapidly from 1999 to 2018,the increased area of mangroves and Spartina alterniflora was 477.3 and 2647.81 hm^2,respectively.The annual growth rate of mangroves and Spartina alterniflora were dropped significantly,the annual growth rate of Spartina alterniflora was greater than that of mangroves in the mangrove reserve.(2)The number of the big patches(≥20 hm^2)was decreased by 3.39%between 1999 and 2018,while that of the small patches(<20 hm^2)was increased by 18.03%.The degree of fragmentation of wetland landscape had increased and the instability of wetland landscape construction increased gradually during the past 20 years.(3)The proportions of based pattern in most main sea were decreased except for Sansha Bay,and the wetland landscape pattern tended to be heterogeneous(i.e.,increased fragmentation and decreased aggregation of tidal flat).In the past 20 years,Spartina alterniflora occupied the dominant position in the northern sea of Fujian,and Spartina alterniflora competed with mangroves in southern sea of Fujian.Moreover,Spartina alterniflora had invaded the core areas of mangroves in nature reserve,and actions should be taken to clean it away.The research results can provide foundational data and theoretical support for mangrove protection and Spartina alterniflora management.