| Mangrove play an important role in ecological function and the value of socioeconomic which grow in tidal zones as a kind of special forest. This paper chose the Gulf of Beibu in southern China as the study area, first, spatial distribution information of coastline in the study site from 1960 to 2010 were extracted by visual interpretation and screen vectorization using multi-sources remote sensing data. Then, analyse the coastline change of the study area in further, aimed to analyze the dynamics of spatial structure of mangrove, we proposed the indices, namely the abundance of mangrove (AM), the evenness of mangrove distribution (EM), the ratio of mangrove coastline length to the total coastline length (RMCL), etc. we analyzed the dynamics of landscape spatial structure of mangrove by bay in the study site from 1960 to 2010. In order to provide the scientific basis for the optimization of spatial distribution, mangrove protection and management. The main conclusions were as follows:(1) The Gulf’s coastline of length decreased at first and then a sustained growth trend, mangrove area was the continued decrease after slightly growth trend, but the number of the patches showed increasing trend after the reduction in the study site from 1960 to 2010. The main cause of the length change of coastline owed to the inning, urban development, aquaculture ponds and saltern, dike, construction. Through the spatial overlay analysis research, the changes in the coastline of the basic forward to the sea. The main cause of the area and patches change of mangrove owed to natural process, afforestation, inning, aquaculture ponds and saltern, dike, construction.(2) Zhenzhu bay, Maowei bay and Dandou bay had the highest EM in 2010, whereas Beilun estuary, western Fangcheng bay and baymouth of Qinzhou bay had the lowest EM. The EM in most bays changed from high to low with the mangrove area decreased from 1960 to 2010, another cause was the length change of coastline owed to the inning, urban development, dike, aquaculture ponds and saltern, construction.(3) The distribution of mangrove were evenness in Jingu easturay and Maowei bay in 2010, which were relative evenness in Dafengjiang eastuary, eastern Fangcheng bay and Dandou bay, but the distribution of mangrove in western Fangcheng bay was concentrated. The evenness of mangrove distribution in most bays changed to better and toward to evenness, reasonable from 1960 to 2010.The evenness had been improved obviously, which were due to the change of the extent and distribution of mangrove and coastline caused by mangrove silviculture, inning, aquaculture ponds and saltern, dike, construction.(4) In 2010, Yingluo bay had the highest RMCL, which were relative ratio in Jingu estuary, Dandou bay and Dafengjiang eastuary, West Fangcheng bay and the baymouth of Qinzhou bay had the lowest RMCL. The dynamic of RMCL in most bays showed a small increase from 1960 to 2010. The cause of RMCL change were relatively complex, the main reason was that large number of aquaculture pond were built on the shallows between the natural coastline and mangrove patches, thus the natural coastline turn to be the mangrove coastline, which lead to the increase of RMCL, other causes include damaged mangroves, afforestation, natural evolution, etc.(5) The overall RAHP of the study site was reached 75.0% from 1960 to 2010, most mangrove patches had the good function of dissipating waves and protect the coastline. The RAHP in Jingu estuary changed from high to low, it changed from low to high and thus to low in west Fangcheng bay, Lianzhou bay, Tieshan bay and Dandou bay, but it showed the opposite trend in Beilun estuary, Maowei bay, and in baymouth of Qinzhou bay, Dafeng estuary and east Beihai coast, they showed the opposite trend as Jingu estuary, it in Yingluo bay, east Fangcheng bay and Zhenzhu bay remained steady from 1960 to 2010. The dynamic of RAHP was difference from that of RMCL, but they shared the similar causes, include the spatial change of coastline and mangrove patch extent caused by patch destruction, afforestation, natural evolution and so on. |
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