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从消浪护岸角度,研究景观尺度红树林空间结构动态变化,提出了红树林丰度、红树林空间分布均匀度、红树林岸线比重和高效护岸红树林面积比例4个指标及其计算方法。以广西北部湾(不含七十二泾)为研究区,采用航空图像和高分辨率卫星遥感图像,提取1960/1976年、1990年、2001年、2007年和2010年的红树林空间分布和海岸线信息;通过GIS叠合分析,计算各个海湾的4个指标,对研究区各个时期的红树林空间结构进行动态分析,结果表明,12010年,茅尾海、丹兜海和珍珠港的红树林丰度最高,钦州湾外湾、防城港西湾和北仑河口的最低;1960/1976~2010年,大多数海湾的红树林丰度由高变低,但北仑河口和茅尾海的红树林丰度呈低、高、低的变化,廉州湾的红树林丰度呈高、低、高的变化,丹兜海的红树林丰度逐渐升高,英罗港的红树林丰度基本保持稳定。红树林丰度变化的主要原因是红树林面积逐期减少,另一个原因是由于围垦、盐田和养殖塘及海堤建设、城市发展、港口码头建设等导致海岸线长度发生了变化;22010年,金鼓江口和茅尾海的红树林空间分布最均匀,大风江口、英罗港和丹兜海的红树林次之,防城港西湾的红树林则高度集中;总体上,1960/1976~2010年,研究区大多数海湾的红树林空间分布表现为由高度集中或较集中向基本均匀发展的趋势,均匀度得到较大改善,人工造林、海堤和养殖塘及港口码头建设引起的红树林数量和空间分布变化及海岸线变迁,是红树林空间分布均匀度发生变化的主要原因;32010年,英罗港、金鼓江口和丹兜海的红树林岸线比例最高,防城港西湾和钦州湾外湾的最低;1960/1976~2010年,大多数海湾红树林岸线比例在小幅度上升,但一些海湾的红树林岸线比例表现为波动变化,金鼓江口则由高逐渐变低;红树林岸线比例变化原因较复杂,最主要的原因是原有自然岸线与红树林之间的滩涂修建了大量养殖塘,自然岸线变成了与红树林斑块接近的红树林岸线,故红树林岸线比例升高,其他原因包括人工造林、红树林毁损等;42010年,研究区高效护岸红树林面积比例为76.7%,绝大数红树林都具有良好的消浪护岸作用;1960/1976~2010年,珍珠港和防城港东湾高效护岸红树林面积比例基本上保持稳定;北仑河口、茅尾海、廉州湾、铁山港和丹兜海的高效护岸红树林面积比例波动变化;金鼓江口的高效护岸红树林面积比例由高逐渐变低;防城港西湾、钦州湾外湾、大风江口、北海东海岸和英罗港的高效护岸红树林面积比例由低逐渐升高;高效护岸红树林面积比例的变化趋势与红树林岸线比例变化趋势相同,其变化原因也基本相似,包括海岸线空间位置发生较大变化、人工造林和自然演变引起红树林斑块扩大及红树林毁损等。
The dynamic changes of mangrove spatial structure at landscape scale were studied from the view point of waves breaking revetment. Four indices of mangrove forest abundance, spatial distribution uniformity of mangrove forest, proportion of mangrove shoreline and mangrove area of high-efficiency revetment were put forward and their calculation methods were proposed. Taking the Beibu Gulf of Guangxi (excluding Qi’dianjing) as the study area, aerial images and high resolution satellite remote sensing images were used to extract the spatial distribution of mangrove forests in 1960, 1976, 1990, 2001, 2007 and 2010 According to GIS overlap analysis, four indexes of each bay were calculated and the spatial structure of mangroves in each period of the study area was dynamically analyzed. The results showed that in 12010 mangroves of Maowai, Dandou and Pearl Harbor The highest abundance, Qinzhou Bay Outer Bay, Fangchenggang West Bay and Beilun estuary minimum; from 1960 to 1976 to 2010, most of the Gulf mangrove abundance from high to low, but the Beilun estuary and Maowei mangrove abundance Low, high and low. The abundance of mangroves in Lianzhou Bay showed high, low and high changes. The abundance of mangroves in Danubehai Sea gradually increased. The mangrove abundance in Yingluo Port basically remained stable. The main reason for the change in the abundance of mangroves is the period-by-period decrease of mangrove area. Another reason is that the coastline length has been changed due to reclamation, construction of salt fields and aquaculture ponds and sea walls, urban development and construction of port terminals. In 22010, Mangrove estuary and Mawei sea mangrove distribution of the most uniform, the windy estuary, Yingluo Hong Kong and Dandong sea mangroves followed, the Fangchenggang West Bay mangrove are highly concentrated; Overall, from 1960/1976 to 2010, The spatial distribution of mangroves in most of the gulfs in the study area showed a tendency of becoming more or less uniform from a high level or from a high level to a high level. The evenness was greatly improved. The number of mangrove forests caused by afforestation, seawalls, aquaculture ponds and port harbors The change of spatial distribution and the change of coastline are the main reasons for the change of spatial distribution uniformity of mangroves. In 32010, the ratio of mangroves shoreline of Yingluo Harbor, Jinjiang River estuary and Danduhai Sea is the highest, that of Fangchenggang Bay and Qinzhou Bay The proportion of the coastline of most mangroves in the Gulf increased slightly from 1960 to 1976 to 2010, but the ratio of the shoreline of some mangroves in some of the Gulf showed fluctuant changes, while that of the Jinguang estuary was increased from high The gradation is low; the reason for the change in the proportion of mangrove shoreline is more complicated, the most important reason is that a large number of aquaculture ponds are built on the beach between the original natural shoreline and mangrove forest, and the natural shoreline becomes red The proportion of mangroves in the study area increased by 76.7% in 42010. The vast majority of mangroves have good anti-wave activities And the revegetation effect. From 1960 to 1976 to 2010, the proportion of mangroves of Pearl River Harbor and Fangchenggang East Bay high-efficiency revetment basically remained stable; the high-efficiency revetment mangrove forests of Beilun estuary, Maowei sea, Lianzhou bay, Tieshangang and Danduhai Area ratio fluctuated. The ratio of mangrove area of high-efficiency revetment in Jinguang estuary gradually decreased from high to high. The proportion of mangrove area of high-efficiency revetment in Fangchenggang Bay, Qinzhou Bay Outer Bay, Great Wind River Estuary, East China Sea and Yingluo Port gradually decreased from low The trend of mangrove area proportion of high revetment revetment is the same with that of mangrove afforestation, and the reason for its change is basically the same, including the great change of spatial position of coastline, afforestation Caused by natural evolution and expansion of mangrove patches of mangroves and other damage.