广西英罗湾近百年来红树林海岸带变迁及红树林群落演替

发布时间：2018-05-26 05:02

本文选题：广西英罗湾 + ~(210)Pb年代测定　；参考：《华东师范大学》2014年硕士论文

【摘要】：本文首次对广西英罗湾红树林保护区3个典型柱状样进行了高密度的210pb年代测定、粒度测试及孢粉分析。结合粒度特征和孢粉组合了解红树林海岸带沉积环境的变化,通过分析红树林孢粉组合变化特征及孢粉浓度指标了解历史时期红树林群落的发育过程,同时与收集的气象数据进行对比,在210pb测试建立的年代框架中,探讨英罗湾地区近百年来红树林海岸带的变迁和红树林群落的发育、演替及其对环境的响应。通过柱样样品的210pb比活度测试,确立地层的年代框架。利用210pb的CIC模式计年模式计算得到YLW03孔、YLW02孔和018孔的平均沉积速率分别为0.22cm/a,0.21cm/a和0.44cm/a。再结合深度计算得到各层位的年代,各钻孔的底部年龄分别为1810s年代、1670s年代和1810s年代。样品的粒度分析及沉积物微结构表明,YLW02和YLW03孔约在1890s年代之前处于较强的潮沟环境。在此之后水动力逐渐减弱。018孔位于林外光滩,各粒度参数波动较大,反映出该位置复杂的水动力条件。孢粉分析表明,YLW02孔和YLW03孔分别在1890s和1970s年代以前孢粉浓度极低,指示这段时期两地均为潮沟环境。YLW02孔在1890s年代以后孢粉浓度迅速上升,红树植物花粉含量显著增加到红树林记录水平,指示该地在1890s年代之后开始发育红树林。YLW03孔在1970s年代以后孢粉浓度增加,红树植物花粉含量升高,反映出在1970s年代以后该地红树林开始生长。018孔所在地在十九世纪九十年代到二十世纪早期生长过红树林,在此之后海岸线向陆迁移,导致红树林衰退,该地成为低潮带光滩环境。结合主要孢粉种属含量变化和粒度数据,表明近百年来英罗湾地区北部和东部红树林出现以前是水动力较强的潮沟环境,随着滩面高程的增加,潮沟逐渐向潮沟边滩演化,滩面水动力减弱,红树林开始发育。英罗湾周围没有大型河流注入,因而缺乏沉积物来源,所以滩面的升高可能是由于潮沟的横向摆动造成的。英罗湾红树林群落的演替主要受到局地滩面高程的影响,随着滩面高程的变化,英罗湾红树林群落的演替过程大致可分为3个阶段,前期为耐盐耐贫瘠土壤的红树林先锋植物Avicennia marina群落；中期是Aegiceras corniculatum群落、Kandelia candel群落以及Rhizophora stylosa群落；后期是Bruguiera gymnorhiza群落和Excoecaria agallocha群落。红树林群落的演替并没有绝对的界限,常常会出现两种或多种混生的现象。
[Abstract]:For the first time, three typical columnar samples in Yingluowan mangrove reserve in Guangxi were measured by 210pb dating, particle size measurement and pollen analysis. Combined with granularity and sporopollen assemblage, the changes of sedimentary environment in mangrove coastal zone were studied, and the development process of mangrove community in historical period was understood by analyzing the variation characteristics of pollen assemblage and the index of pollen concentration. At the same time, compared with the collected meteorological data, the changes of mangrove coastal zone and the development, succession and response to environment of mangrove coastal zone and mangrove community in Yingluo Bay area were discussed in the framework of 210pb test. Through the 210pb specific activity test of the column sample, the chronological framework of the formation is established. The average deposition rates of YLW02 and 018 holes in YLW03 pore are 0.22 cm / a 0.21 cm / a and 0.44 cm / a, respectively, calculated by 210pb's CIC model. The bottom ages of each borehole are 1810s, 1670s and 1810s, respectively. The grain size analysis and sediment microstructure of the samples show that the YLW02 and YLW03 pores were in a strong tidal trench environment before the 180s. After this, the hydrodynamic force gradually weakened. 018 hole was located in the light beach outside the forest, and the granularity parameters fluctuated greatly, which reflected the complex hydrodynamic conditions in this position. Sporopollen analysis showed that the sporopollen concentrations in the YLW02 and YLW03 holes were very low before 1890 s and 1970 s, respectively, indicating that the concentration of sporopollen increased rapidly after 1890 s in the tidal trench environment. The pollen content of mangrove plants increased significantly to the mangrove record level, indicating that mangrove. YLW03 hole began to develop after 180s, and the pollen concentration of mangrove plants increased after 1970s, and the pollen content of mangrove plants increased. It shows that mangroves began to grow from the 1970s to the early 1900s, where mangroves grew from the 1890s to the early 1900s, after which the coastline moved to the land, leading to the decline of mangroves. This area becomes the environment of low tide zone. Combined with the content change and granularity data of the main sporopollen species, it was shown that mangroves in the northern and eastern parts of Yingluo Bay area had a strong hydrodynamic tidal trench environment before the emergence of mangroves in the last hundred years. With the increase of the beach height, the tidal trench gradually evolved to the tidal gully beach. The beach surface hydrodynamics weakens, the mangrove begins to develop. There are no large rivers around Yingluo Bay, so there is a lack of sediment source, so the elevation of beach surface may be caused by the lateral swinging of tidal trenches. The succession of mangrove communities in Yingluo Bay was mainly affected by the elevation of the local beach. With the change of elevation, the succession of mangrove communities in Yingluo Bay could be divided into three stages. Avicennia marina community of mangrove pioneer plant in salt-tolerant and barren soil, Aegiceras corniculatum community Kandelia candel community and Rhizophora stylosa community in middle stage, Bruguiera gymnorhiza community and Excoecaria agallocha community in late stage. The succession of mangrove communities has no absolute boundary, and there are often two or more mixed phenomena.
【学位授予单位】：华东师范大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：S718.5;P737.1

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