导　　师： 高全洲

学科专业： 070501

授予学位： 博士

作　　者： ;

机构地区： 中山大学

摘　　要： 作为碳循环的一个环节，河流对流域起着物质输移、环境改造的重要作用，其强大的碳汇功能已引起学者的广泛关注。本研究选择典型亚热带气候条件下的梅江流域为研究对象，采用野外调查、取样和室内实验分析相结合的方法，对湿热山地典型森林类型土壤碳储量及其分配特征进行研究，剖析土壤有机碳积累的主要影响因素。同时通过对河流水化学组成的分析，查明河水主要离子的来源，推断梅江流域主要化学风化过程，定量估算三大类岩石和大气降水对河水主要离子的贡献率，对梅江江流域化学风化过程的碳汇效应进行了相关性分析。主要研究结果如下： （1）研究区5种林分土壤有机碳平均含量在4.14～22.14g·kg-1之间，常绿阔叶林最高，其次为针阔混交林，桉树人工林最小。SOC含量随剖面深度增加而减少，但林分不同其递减幅度有所差异，其中常绿阔叶林递减率最大，SOC表聚性明显。5种林分土壤碳密度差异显著，其各土层变化范围为1.57～5.74kg·m-2，自然地带性植被类型各个土层土壤碳密度均高于次生植被类型对应的碳密度。 （2）5种林分土壤碳储量整体较低，平均为148.76t·hm-2，低于我国一些相似气候带或植被类型的研究结果。人为干扰活动对森林土壤碳储量影响明显，是制约土壤碳储量大小的重要因素。相关性分析表明，5种林分SOC含量与粘粒含量、质量含水率、养分和水稳性团聚体数量之间整体上呈正相关关系，与土壤容重、pH值呈负相关关系，森林土壤有机碳积累及其影响因子之间关系密切。 （3）梅江流域河流主离子组成以Ca2+、Na+、和HCO3-为主，其次是SO42-和Cl-，水化学类型为重碳酸盐类钙组Ⅰ型。pH值在6.03～8.54之间，总体上表现出较低的电导率。据GibbS图和离子三角形图分析，研究区河水化学组成属“岩石风化型”，水化学成分主要来自以碳酸盐岩化学风化为主、硅酸盐为辅的混合风化作用，同时也受大气降水的影响，大气降水对河水溶解质的贡献率为22.85/%，远高于世界平均值。河流Cl-//Na+摩尔浓度比低于1.17，河流总体上受人类活动影响微弱。 （4）主成分和因子分析表明，硅酸盐类对研究区河流离子的贡献比例较高，为19.7/%。流域化学风化反应主要以碳酸岩风化为主，硅酸盐岩风化次之。各流域年均化学风化速率为32.21t//km2.a，低于世界和长江的化学风化速率。岩石化学风化对大气CO2的消耗量为2.32×108mol//yr，消耗率为194.29×103mol//km2.yr,与世界平均水平比较接近。 （5）各河流DIC含量介于4.14~87.59mg//L之间，年均值为28.38mg//L，高于亚马逊河和刚果河，但低于黄河、印度河等世界大河。河流全年DIC侵蚀通量为23.67×106g//km2.y。河流DOC含量年均值达2.72mg//L，全年DOC侵蚀通量为2.27×106106g//km2.y，与世界主要大河碳通量的比较，DOC通量属于中等产出水平。 （6）相关性分析表明，研究区河流DIC碳汇效应受岩性、土壤、气候等自然因子影响明显，而5种林分SOC含量与河流DOC含量则没有呈现明显的相关关系，这与流域内自然与人为因素综合作用下的扰动有关。根据关联度分析，5种林分SOC对河流DOC的贡献率以马尾松林为最高，混交林、桉树林次之，竹林最小，这关联度顺序在某种程度上反映了5种林分对整个研究区生态效应影响的显著程度。 As a part of the global surface water cycle, the river has the important function ofsubstance transportation and environment transformation and its carbon sink arousedconsiderable attention from scholars. Based on the status of the international research,in this paper, we take the Meijiang River Basin under typical subtropical climateconditions as the research object. Using the research method of field investigation,soil sampling and laboratory analysis, it has been discussed for the storage,distribution of soil organic carbon and the main factors affecting soil organic carbonaccumulation of the fiver main forest types in the humid mountainous area. At thesame time, using the main chemical composition of river water, we investigated thesource of major ions in river water and its formation mechanism, discussd the mainchemical weathering processes of the river basin and determined the distribution ofthe three different rock, Atmospheric Precipitation and human activities. We analysefinally the correlation of chemical weathering process and its carbon sink effect. Theresults are showed as follow: /(1/) The average soil organic carbon content for the five forest types was4.14g·kg-1～22.14g·kg-1, the soil organic carbon content in evergreen broad-leaved forestwas highest but lowest in eucalypt forest. Soil organic carbon contents generallydecreased with depth, but decrease range was different for the five forest types. Thesoil organic carbon assembled obviously in surface layer soils. Soil carbon density inthe five forest types change greatly, with a range of1.57kg·m-2～5.74kg·m-2for fivesoil depth intervals. Soil carbon density under natural vegetation was significantlyhigher than that under secondary vegetation. /(2/) The total mean value of carbon storage was148.76t·hm-2in the five foresttypes. By comparisons, soil carbon storage of the main forest types in mountain areaof Northeast Guangdong was lower than that of other regions. These results showedthat human impact was one of factors that exert a tremendous influence on soil carbonstorage. The correlation analysis showed5kinds of forest SOC and the content ofclay, water, nutrient or the number of water stable aggregates were positivelycorrelated, but negatively correlated with soil bulk density, pH. The relationshipbetween the influencing factors forest soil organic carbon accumulation is close. /(3/) The main chemical composition of river water in Meijiang river basin is Ca2+,Na+and HCO3-，Secondly by SO42-and Cl-. Water chemistry type is heavy carbonatecalcium type Ⅰ. The value of pH is6.03~8.54, but EC is relatively low. Accordingto the analysis of Gibbs graph and Temary diagram, Meijiang river basin belongs torock weathering controlling type, and chemical compositions of water are mainlyfrom weathering of carbonate rocks, secondly from silicate rocks, it is show thatprecipitation influenced them obviously. The contribution rate of precipitation is22.85/%for dissolved solids in river water, and it is higher than the mean value of theworld. But molar concentration rate of Cl-//Na+of river water is less than1.17, thisshowed that the rivers are affected faintly by artificial actions overall. /(4/) On the basis of factor analysis and principal composition analysis, thecontributions of silicate rock to the total dissolved solids of river water is19.7/%, it ishigh relatively. The primary weathering processes is the carbonate rock dissolutionand the second is the weathering of silicate rocks in Meijiang river basin. Annual ratesof chemical weathering in river basin is32.21t//km2.a, it is lower than Yangtze Riverand mean value of the world. Based on contribution rate of atmospheric CO2to theHCO3-in the river water, the quantity of CO2consumption by rock weathering isestimated to be2.32×108mol//yr，and the rates of CO2consumption by rockweathering is194.29×103mol//km2.yr, close to the world average level. /(5/) DIC contents of river water in Meijiang river basin are between4.14~87.59mg//L, the annual mean value is28.38mg//L, higher than that of the YellowRiver and the Indus River. The annual denudation flux of DIC is calculated to be 23.67×106g//km2.y. The Annual mean value of DOC content of river water is2.72mg//L, annual denudation flux of DOC is calculated to be2.27×106g//km2.y, whichis medium level of output compare with the main large rivers in the world. /(6/) According to the correlation analysis of influence factors, DIC carbon sinkeffect is significantly affected by lithology, soil, climate and other natural factors inMeijiang river basin, whereas SOC content of the5kinds of forest and DOC contentof rivers did not show significant correlation, this maybe connected with the naturalfactors and artificial disturbance. The correlation analysis show that contribution rateof the5types of forest SOC for the river DOC was the highest in Masson pine forest,secondly is coniferous and broad-leaved mixed forest and Eucalypt forest, bambooforest is the minimum. The relational sequence represents the influence level of the5kinds of forest for the ecological effect of the whole study area.

关 键 词： 土壤碳积累 化学风化 大气 消耗 碳汇效应 湿热山地

分 类 号： [S153.6 P512.12]

领　　域： [农业科学] [农业科学] [天文地球]