喀斯特坡耕地浅层孔（裂）隙水文过程及土壤侵蚀响应机制

Hydrological process in underground pore fissure directly determines types of soil erosion on karst hillslope farmland. For the key scientific issues of hydrology process and soil erosion in karst region, taking typical karst hillslope farmland as example, we analyzed characteristics of hydraulic parameters on soil, underground pore fissure and soil-rock interface through hydrological process observations and experiments based on understanding its erosion environment of two element three-dimensional structures. We simulate runoff plots for karst hillslope farmlands by combination of concretes simulated underground pore fissure and a steel tank in which underground pore fissure degrees and slopes could be adjusted. Moreover, we study the hydrological processes in underground pore fissure using artificial simulated rainfall experiments, and revel its erosion processes and mechanisms on slope scale. At the same time, we build many standard runoff plots on typical karst hillslope farmlands for verifying simulated tests. We mainly study hydrological processes and erosion process in underground pore fissure from the view of water-soil-rock/pole (fissure) using isotope tracer and natural rainfall observation method, in order to reveal its response mechanism, and then construct response models of soil and water loss. Results not only would make a theory breakthrough in revealing response mechanism and driving force between hydrological processes and soil erosion on karst hillslope farmlands, but also will promote development of hydrology and soil erosion, those could provide scientific basis for the realization of health sustainable development in ecological environment in karst regions.

喀斯特坡耕地浅层孔（裂）隙水文过程直接决定其土壤流失形式。针对喀斯特区水文过程与土壤侵蚀研究的核心科学问题，以喀斯特坡耕地为研究对象，在弄清其二元三维结构的侵蚀环境基础上，从探索水文过程入手，明确土壤、孔（裂）隙及岩-土界面水力参数。利用可调坡度、孔（裂）隙度的试验钢槽及混凝土模拟的地下孔（裂）隙基岩，建立喀斯特坡耕地径流小区，采用人工模拟降雨试验研究坡面尺度浅层孔（裂）隙水文过程，揭示其土壤侵蚀过程与机理；同时，在典型喀斯特坡耕地上建立标准径流小区，采用同位素示踪及自然降雨观测法，研究以水-土-岩/孔（裂）隙为基础的喀斯特坡耕地浅层孔（裂）隙水文过程与侵蚀特征，以揭示二者的响应机制，构建水土流失量与水文过程参数响应模型。研究不仅在揭示喀斯特坡耕地水文过程和土壤侵蚀响应机制及其驱动力上取得理论突破，同时也将推动水文学和土壤侵蚀学的发展，为实现喀斯特地区生态环境健康持续发展提供科学依据。

加强以水为纽带的水-土壤-岩石/孔（裂）隙等界面的水文过程及其与土壤侵蚀响应机制研究，是喀斯特地区农业环境科学领域亟待解决的关键科学问题之一。针对喀斯特区水文过程与土壤侵蚀研究及生态环境建设中的核心科学问题，本项目以喀斯特坡耕地为研究对象，基于野外实地调查和地统计学分析，系统分析喀斯特坡耕地二元三维结构侵蚀环境的类型及结构特征。在此基础上，从水文过程入手，结合野外原位监测、同位素示踪等方法，开展了喀斯特坡耕地浅层孔(裂)隙水文过程及驱动力、土壤水分调蓄功能等研究。与此同时，通过室内模拟、野外同位素示踪、定位观测相结合的方法，研究了浅层孔(裂)隙土壤机械组成对降雨的响应特征、裂隙水土漏失过程等，重点揭示了喀斯特坡地浅层裂隙土壤漏失机制。研究结果表明：喀斯特坡地岩溶裂隙类型剖面形态受地质构造、岩性等因素影响发育特征存在高度异质性。不同石漠化强度等级下裂隙均有发育和分布，其形态类型可分为漏斗型裂隙、竖长方裂隙、梯形裂隙和斜长方裂隙等。不同裂隙的土壤水分入渗过程可分为迅速降低和趋于稳定阶段两个阶段。裂隙优先流主要发生在20 cm土层范围，优先流路径主要为两侧岩石界面，两侧岩-土界面流能穿过渗透性较差的黄色粘土层。浅层岩溶裂隙为土壤赋存提供“容器”功能，其组成的“裂隙-土壤”系统成为喀斯特石漠化坡地主要的水分储存库和植物水分供应来源。大雨强、缓坡条件、裂隙发育及严重石漠化强度均会加重水分裂隙漏失, 暴雨或大暴雨是裂隙土壤发生漏失的关键因素。水分裂隙漏失是坡面主要的流失方式之一，不同雨强、坡度、岩石裸露率下水分裂隙漏失比例总体高于50.8%。土壤蠕移是其漏失的主要形式，发生层次和粒级具有偶然性，岩-土界面与裂隙土层内土壤颗粒均有向下漏失的可能。研究重点揭示了喀斯特坡耕地水文过程和土壤侵蚀驱动力及二者响应机制。研究结果丰富了喀斯特土壤侵蚀学科体系，为实现喀斯特地区生态环境健康持续发展提供科学依据。