红树林潮滩沉积速率测量与研究

THE MEASUREMENT AND STUDY ON SEDIMENTATION RATES IN MANGROVE TIDAL FLATS

红树林捕沙促淤功能是红树林防浪护岸效益的主要表现之一。本文用标志桩法与（２１０）Ｐｂ同位素定年法测定红树林潮滩沉积速率。海南东寨港林市村岸段标志桩试验显示：红海榄Ｒｈｉｚｏｐｈｏｒａｓｔｙｌｏｓａ密林区普遍淤积，平均速率４．１ｍｍ·ａ（－１）；白滩与疏林区侵蚀，平均速率８．２ｍｍ·ａ（－１）。沉积速率随滩地高程增加或潮水浸淹频率的减小而减小。冬春淤积为主而夏季冲刷为主。区域性淤积速度受区域泥沙来源与海岸动态影响。在粤西廉江高桥镇凤地村岸段的（２１０）Ｐｈ测试显示，０—９０ｃｍ段沉积历时为１４５（１８４７—１９９２）ａ，平均沉积速率为６．２ｍｍ·ａ（－１）。其中０—４０ｃｍ段１９６６—１９９２年沉积速率１５．４ｍｍ·ａ（－１）最大，４０—５０ｃｍ段１９３０－１９６６年沉积速率２．８ｍｍ·ａ（－１）最小。

ne of the coastal protection functions of the mangrove is its ability of trapping silt and accelarating sedimentation of mangrove tidal flats. This research studied the sedimentation rates of magrove tidal flats, both modern and of a hundred years period, based on stakes and 210pb dating. At Linshicun study area of Dongzhaigang Harbor in Hainan Island, 12 stakes were arranged and measured for & times during Nov. 1992-Nov. 1994.9 stakes in the dense forest showed obvious siltation with a mean rate of 4. 1 mm. a-1,and other 3 stakes in a sparse forest and bare flat showed erosion with a mean rate of 8. 2 mm. a-1. Sedimentation rates in the dense forest decreased with increasing flat altitude or decreasing tidal inudation frequency. The seasonal change of sedimentation showed siltation in winter and spring and erosion in summer. Regional sedimentation intensity depends on regional sediment. sources and tidal flat dynamics. At Fengdicun study area of Gaoqiaozhen Town in Lianjiang County of east Guangdong, 12 sediment samples were taken from 12 layers of a 1 m core and its 210Pb activity measured. The results showed that mean sedimentation rate of the 0-90cm section was 6. 2 mm· a-1 and sedimentation duration was 145 a (1847-1992). The sedimentation rate of the 0-40cm section was faster (15. 5mm·a-1, duration 1966-1992) than that of the 40-50cm section (2. 8 mm. a-1, duration 1930-1966).