黄土高原不同植被覆盖下土壤有机碳的分布特征及其同位素组成研究  

Distribution Characteristics of Soil Organic Carbon and Its Isotopic Composition for Soil Profiles of Loess Plateau under Different Vegetation Conditions

作　　者：李龙波[1,2] 涂成龙[1] 赵志琦[1] 崔丽峰[1,2] 刘文景[2,3] 

机构地区：[1]中国科学院地球化学研究所环境地球化学国家重点实验室,贵阳550002 [2]中国科学院北京研究生院,北京100049 [3]中国科学院地质与地球物理研究所,北京100029

出　　处：《地球与环境》2011年第4期441-449,共9页Earth and Environment

基　　金：中国科学院知识创新工程重要方向项目(KZCX2-EW-102);国家自然科学基金创新群体项目(40721002)

摘　　要：土壤有机碳(SOC)含量及其δ13 C值随深度变化的趋势可以反映植物残体的输入及其在土壤中分解累积特征,有助于揭示SOC循环过程及规律。本研究以黄土高原不同植被类型覆盖条件下的黄土剖面为研究对象,通过测定土壤属性、SOC含量和植物优势种、枯枝落叶、土壤有机质的稳定同位素组成,对该区域SOC深度分布和有机质δ13 C值组成差异进行探讨。研究结果显示SOC含量变化范围在1.1～31.2g/kg之间,且随土层深度增加而逐渐降低。SOC主要集中在表层土壤,其含量变化规律为阔叶林地>针叶林地>灌木林地>草地>荒地。但各剖面SOC在不同土壤层次处出现急剧下降。其中,阔叶林地和针叶林地在10cm深度处、灌木林地和草地在20cm深度处和荒地在5cm深度处,SOC含量急剧减少。但60cm深度以下各剖面SOC含量变化均较小。在枯枝落叶转化为表层土壤有机质的过程中,δ13 Csoc值升高了0.5‰～3.2‰,与其它地区相比13 C富集更大。剖面δ13 Csoc值在-26.3‰～-20.8‰之间变化,均随着土壤深度的加深而增加。但不同植被条件下的变化幅度各不相同,这反映了土壤有机质分解过程中碳同位素分馏效应的强弱程度。剖面有机质碳同位素分馏程度的变化规律为阔叶林地>针叶林地>草地>灌木林地>荒地。这可能是由于阔叶林地上生物量大及微生物对有机质的分解作用强,有机质来源较多且组成、结构不同所致。而荒地剖面坡度很大,地上植被来源较单一,表层枯枝落叶很少,故导致其剖面土壤有机质的分馏效应最低。对比研究表明:不同植被类型覆盖条件下土壤有机质的深度分布特征具有明显差异,土壤有机质的稳定同位素地球化学组成具有地域性特征。Variations in soil organic carbon(SOC) contents and δ13C values of SOC with depth in different soil profiles can provide the information about plant residue and accumulation,which helps to understand the process and mechanism of soil carbon cycle.In this study,five typical soil profiles under different vegetation conditions in loess areas,Northwest China,were selected as a case to study the profile distribution and stable isotopic composition in terms of the physical properties and carbon isotopic composition of foliage,litter and SOC.The results showed that the SOC was mainly enriched in surface soils and decreased with increasing depth.SOC contents varied in the range of 1.1~31.2 g/kg.It was found that the SOC contents of the soils varied according to the vegetation conditions,in the following order:broadleaf plant > coniferous plant > shrub > grassland >wasteland.Rapid changes were noticed at the 10 cm depth for the broadleaf forest and coniferous forest,at the 20 cm depth for the shrubs and grassland and at the 5 cm depth for the wasteland.The SOC contents decreased slowly below the 60 cm depth in the studied soil profiles.Compared with other regions,13C was enriched and δ13Csoc increased by 0.5‰~3.2‰ during litter degrading to SOC in surface soil.The δ13C values of SOC increased with depth,and varied between-26.3‰ to-20.8‰,showing a significant difference in vertical patterns of variation,but the variation ranges were different in different soil profiles.In general,the δ13C values in different soil profiles decreased in the following order:broadleaf plant > coniferous plant >grassland > shrub >wasteland.This may have resulted from the abundant litter materials(e.g.,leaf fall) in broadleaf forest and more active microbial action in its soil,leading to higher carbon isotope fractionation of organic matter.The wasteland seldomly had a vegetation cover and litter was present in a small amount in the topsoil and there occurred less fractionation of SOC.The results indicated that there existed signific

关 键 词：黄土高原 土壤有机碳 稳定碳同位素 

分 类 号：S153.6[农业科学—土壤学] P597[农业科学—农业基础科学]