红树林湿地土壤有机碳库动态与变化研究

Soil organic carbon (SOC), the most important carbon pool on land, its'changes are crucial to global carbon cycle. Mangrove wetlands, occurring along ocean coastlines throughout the tropics and subtropics, are usually characterized by high SOC storage and complex incoming and outgoing process; despite its' vital function in global carbon sequestration, little has been know about it's dynamic and changes, less the impacts which anthropic factor imposed on it..Based on our previous NSFC studies about ecological function alterations in degraded mangrove wetlands, this study will focus on the dynamic rules and change trends of soil organic carbon (SOC) in different mangrove in Hainan Islands. With the help of modern monitoring instrument, data from field's monitoring and lab analysis will be achieved.The amount of biomass returning, including litters and roots, the rate of carbon emissions, including CO2 and CH4, and the movement of dissolved soil organic carbon (DOC) in mangrove soil will be determined by various methods.With carbon income and outgoing results, periodic dynamic rules and change trends of SOC pool will be discussed, and the driver will be analysed. Comparative analysis will be also carried out among the data of soil samples from natural mangrove, degraded mangrove and recovered mangrove；different results will explain the influnces of anthropic factors on SOC pool in mangrove..The main purposes of the study are to understand the changing rules of SOC dynamic in mangrove, discover the natural and anthropic factors which effect mangrove SOC dynamics, and reveal the consequence which anthropic factors imposed on mangrove carbon sequestration functions. The vital function of DOC was before ignored for the first will be considered in mangrove carbon cycle in this study, and different methods, which including water quality monitoring, experimental analysis, and outdoor simulation, will be conducted in determining DOC in mangrove soil; Fast Greenhouse Gas Analyser (FGGA) will be firstly used in monitoring CO2 and CH4 emission in the fields work of wetlands. Results of this study will do great help in evaluating carbon sequestration function and environmental effect of artificial recovering of mangroves; it will be also useful in forecast the responds of mangrove carbon sequestration to global changes.

土壤有机碳（SOC）库是陆地上最大的碳库，其微小变化影响全球碳循环。红树林湿地SOC储量高，收支过程复杂，是热带、亚热带海岸最重要的SOC库；但是目前关于红树林SOC研究较少，其动态规律和变化趋势以及人类活动对其产生的影响尚未阐明。.本项目拟以海南红树林湿地为研究对象，在前项国家基金关于红树林退化评价研究基础上，结合野外监测和实验分析，掌握红树林生物归还量、SOC矿化分解释放温室气体速率和可溶性土壤有机碳（DOC）含量在不同环境下的动态特征，分析其变化趋势及影响因素；同时通过比较天然、退化和人工恢复三种不同状态红树林SOC库储量和动态，揭示并预测人类活动对其产生的影响。研究首次考虑DOC在红树林碳循环中的重要作用，且首次采用温室气体分析仪FGGA进行湿地的野外监测。研究结果可为合理评价红树林固碳功能和人工恢复的环境效应提供理论基础，为预测红树林固碳对人类活动和全球气候变化的响应提供依据。

红树林是热带、亚热带海岸潮间带特殊的湿地类型，具有重要的生态功能，其中碳储功能得到人们广泛关注。本研究以海南东寨港红树林湿地为研究对象，在群落调查的基础上，对不同群落类型林下1米深的土壤进行分层取样，测定土壤中TC、SOC、DOC及各项土壤理化指标的含量，分析和测定红树林土壤碳储量及其空间分布规律，而且对主要群落类型进行了为期两年的温室气体排放（二氧化碳和甲烷）监测，探讨了影响红树林土壤碳循环的主要因素。研究结果表明，红树植物群落生物量、潮位是影响红树林土壤碳储量的主要因素；而群落类型、淹水时间、潮位、温度、土壤理化性质等因素是影响土壤碳排放的主要因素。总结出了如下规律：在土壤碳储量方面，在垂直方向上差异显著，土壤有机碳含量最大值出现在20~40 cm，土壤有机碳密度最大值出现在0~20 cm；不同群落类型土壤有机碳含量存在明显差异，以东寨港红树林为例，土壤单位面积碳储量排序靠前的群落依次为海莲群落、海桑群落、角果木群落和桐花树群落，海莲群落土壤有机碳含量最高，为20.89±6.75 g kg-1，人工无瓣海桑林最低，为12.71±3.62 g kg-1，进一步相关分析显示，土壤有机碳含量与群落植株胸径和基盖度呈显著正相关，与株高无关；主要与淹水时间、潮汐动态过程以及群落的结构组成特征具有显著的相关性；从温室气体排放速率来看，在所有群落中二氧化碳排放量大于甲烷的排放量，且夏季的排放量大于冬季的排放量；有凋落物覆盖的的排放量大于无凋落物的地表；根系发达的小于根系不发达的排放量；红树林湿地土壤CO2和CH4年均排放通量分别为1.62 µmol•m-2•s-1和0.56 µmol•m-2•s-1； 温室气体排放通量在各群落及不同月份间呈显著差异，且人工林与天然林差异显著。土壤理化性质与排放通量相关分析表明，土壤温度、土壤有机碳含量、含水率与排放通量显著相关。通过本研究，不仅可以为研究和探讨红树林湿地在全球碳循环中的作用提供基础数据，也可为红树林的恢复和保护提供理论借鉴。