广西钦州湾百年来红树林演变的有机碳同位素和孢粉示踪及其影响因素

气候变化和人类活动制约下的红树林演变是一种长时间尺度效应,而沉积物则是记录这种响应的最佳档案。采用古生态学研究思路,选择有效的示踪参数是解读这一档案的有效途径。本文通过广西钦州湾红树林区1根柱状沉积物中有机碳同位素(δ13C)、C/N分析和孢粉鉴定,以沉积物中的红树林源有机碳贡献和红树植物孢粉组合为示踪参数,在210Pb年龄框架构建的基础上,通过对比研究红树林源有机碳贡献和红树孢粉组合特征,揭示百年来钦州湾红树林兴衰和群落演替规律;进而重塑其红树林演变历史:兴盛期(1864-1918年)、衰退期(1918-1968年)和低谷期(1968-2007年),这与土地替代、遥感分析和现场勘测数据较为吻合。结合气候变化和人类活动资料,发现钦州湾红树林的近期衰退主要源于人类活动的影响,尤其是虾塘围垦;而与气候变化关系不大。

Historical retrospection on mangrove development using stable carbon isotopes and pollen analysis,and its response to climate change and human activity

Mangrove evolution is the long time-scale process under the condition of climate change and human activity,and is clearly recorded by the surrounding sediments. It is a new palaeoecological approach to trace mangrove evolution using organic carbon isotopes and mangrove pollen from sedimentary records. In the study,a sediment core was collected from a mangrove swamp of the Qinzhou Bay,Guangxi. Based on the three end-number model,δ13C and C/N analysis were used to calculate the contribution of mangrove-derived organic carbon. Compared with mangrove pollen assemblage and 210Pb dating,it revealed the temporal evolution of mangrove development and its community succession in the recent 150 years. The mangrove evolution could be divided into three major stages: flourish (1864-1918 A.D.),degradation (1918-1968 A.D.) and low-level period (1968-2007 A.D.),which was consistent with the previous reports. An significantly degradation in mangrove ecosystem recently corresponded to the increase of reclamation area (especially for the shrimp-pond reclamation) and artificial seawalls,rather than the climate change as recorded in the region.