南方岩溶区峰丛土壤自然风化演替过程中微结构变化及其应变机理

Good soil structure plays important role to sustain the ecosystem stability in south karst area in China. As we known, soil aggregate can well index soil structure. However, transformation mechanism of soil aggregate within different natural weathering stages is still lacking in this area. In this project, the researching area is planning at Mulun nature reserve in Huanjiang county, Guangxi province. The experimental material is collecting typical topsoil, which locates at karst peek-cluster depression. The temporal scale of weathering process is adopted with the method of time trading space, that is, along with time axis, the topsoil is gathering at peak, mid-slope and depression, respectively. After characterizing the soils on physical and chemical features and incubating one at constant temperature, meanwhile using modern analytical technique (like as polarizing microscope, SEM/EDS and CT scanning and so on), the results will clearly demonstrate that 1) internal change on stability of soil aggregate due to different weathering intensities, 2) response between microscopic structure of soil aggregate and cements (organic matter, oxide, calcium carbonate), 3) kinetic of cementation effect on organic matter in soil aggregating process. All of this, can provide scientific basis for the forming theory of soil aggregate and the ecological recovery in karst area in south of China.

良好的土壤结构是维持南方岩溶区生态系统稳定的关键，但该区域土壤自然风化演替过程中团聚体形成因素及其胶结机制尚不明确。本项目拟以广西环江县木论自然保护区为研究区域，选择典型岩溶峰丛洼地，以空间换时间的方法，分别于峰顶、坡面中部、坡麓自然林下采取风化程度各异的表层土壤。结合土壤理化性质分析（团聚体组成及其稳定性指标、颗粒组成、矿物组成、有机质组分、碳酸钙、铁铝氧化物等）及室内恒温培养试验，运用偏光显微镜、电镜扫描（SEM/EDS）、CT扫描和电子探针技术等手段，阐述岩溶区不同风化强度土壤微结构特征，解析土壤团聚体稳定性的变化及其内部主控因素，揭示团聚体微结构及胶结物（有机质、氧化物、碳酸钙）之间的耦合关系，并明确土壤团聚化过程中有机物胶结效应大小的变化。从而为丰富土壤团聚体形成理论、维护南方岩溶区生态系统安全提供科学依据。

土壤结构是南方岩溶区生态系统稳定与重建的关键，为探明该区域土壤自然风化演替过程中团聚体形成的主控因素及有机物的胶结机理，本研究从土壤微形态的响应特征切入，选择广西环江县木论自然保护区典型岩溶峰丛洼地为研究区域，以空间换时间的方法，分别于峰顶、坡面中部、坡麓自然林下采取风化程度各异的表层土壤进行研究。研究结果显示：（1）典型岩溶岩溶峰丛洼地不同石灰岩土壤中>2mm（干筛）、>0.25mm（湿筛）的大团聚体占绝对优势，微团聚体含量较少，不同粒级团聚体含量表现为随粒径减小而减少的趋势，黑色石灰土以粗大团聚体为主，稳定性较好，红色石灰土以细大团聚体为主，棕色石灰土两者比例相近。研究区石灰岩土壤团聚体稳定性与土壤有机质、游离铁含量关系显著。（2）通过CT扫描数据显示，不同石灰岩土壤微形态受有机质及其组分含量、游离铁含量影响大，利用缺陷占比率分析得到的分形维数变化趋势与团聚体稳定性分析结果一致，表现为黑色石灰土>红色石灰土>棕色石灰土；土壤孔隙度表现为棕色石灰土>黑色石灰土>红色石灰土。（3）通过对去除有机质后的不同石灰岩土壤进行室内培养，发现有机碳含量增加与土壤大团聚体形成呈明显正相关关系。