發(fā)布時間：2018-05-26 05:02

  本文選題：廣西英羅灣 + ~(210)Pb年代測定��； 參考：《華東師范大學(xué)》2014年碩士論文

【摘要】：本文首次對廣西英羅灣紅樹林保護(hù)區(qū)3個典型柱狀樣進(jìn)行了高密度的210pb年代測定、粒度測試及孢粉分析。結(jié)合粒度特征和孢粉組合了解紅樹林海岸帶沉積環(huán)境的變化,通過分析紅樹林孢粉組合變化特征及孢粉濃度指標(biāo)了解歷史時期紅樹林群落的發(fā)育過程,同時與收集的氣象數(shù)據(jù)進(jìn)行對比,在210pb測試建立的年代框架中,探討英羅灣地區(qū)近百年來紅樹林海岸帶的變遷和紅樹林群落的發(fā)育、演替及其對環(huán)境的響應(yīng)。 通過柱樣樣品的210pb比活度測試,確立地層的年代框架。利用210pb的CIC模式計(jì)年模式計(jì)算得到Y(jié)LW03孔、YLW02孔和018孔的平均沉積速率分別為0.22cm/a,0.21cm/a和0.44cm/a。再結(jié)合深度計(jì)算得到各層位的年代,各鉆孔的底部年齡分別為1810s年代、1670s年代和1810s年代。 樣品的粒度分析及沉積物微結(jié)構(gòu)表明,YLW02和YLW03孔約在1890s年代之前處于較強(qiáng)的潮溝環(huán)境。在此之后水動力逐漸減弱。018孔位于林外光灘,各粒度參數(shù)波動較大,反映出該位置復(fù)雜的水動力條件。 孢粉分析表明,YLW02孔和YLW03孔分別在1890s和1970s年代以前孢粉濃度極低,指示這段時期兩地均為潮溝環(huán)境。YLW02孔在1890s年代以后孢粉濃度迅速上升,紅樹植物花粉含量顯著增加到紅樹林記錄水平,指示該地在1890s年代之后開始發(fā)育紅樹林。YLW03孔在1970s年代以后孢粉濃度增加,紅樹植物花粉含量升高,反映出在1970s年代以后該地紅樹林開始生長。018孔所在地在十九世紀(jì)九十年代到二十世紀(jì)早期生長過紅樹林,在此之后海岸線向陸遷移,導(dǎo)致紅樹林衰退,該地成為低潮帶光灘環(huán)境。 結(jié)合主要孢粉種屬含量變化和粒度數(shù)據(jù),表明近百年來英羅灣地區(qū)北部和東部紅樹林出現(xiàn)以前是水動力較強(qiáng)的潮溝環(huán)境,隨著灘面高程的增加,潮溝逐漸向潮溝邊灘演化,灘面水動力減弱,紅樹林開始發(fā)育。英羅灣周圍沒有大型河流注入,因而缺乏沉積物來源,所以灘面的升高可能是由于潮溝的橫向擺動造成的。 英羅灣紅樹林群落的演替主要受到局地灘面高程的影響,隨著灘面高程的變化,英羅灣紅樹林群落的演替過程大致可分為3個階段,前期為耐鹽耐貧瘠土壤的紅樹林先鋒植物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。紅樹林群落的演替并沒有絕對的界限,常常會出現(xiàn)兩種或多種混生的現(xiàn)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.
【學(xué)位授予單位】：華東師范大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：S718.5;P737.1

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相關(guān)期刊論文 前10條

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本文編號：1936040