喀斯特二元结构发育，地表水大量漏失，在人类干扰下，原本脆弱的生态系统表现出养分快速流失的特点，然而快速流失的养分是否同样以地下流失为主，受何种产流机制驱动等问题还不清楚，这影响了养分流失阻控技术的提出和石漠化治理工程的深入开展。本项目针对以上问题，依托喀斯特坡地三维水土过程研究平台，将植被-土壤-表层岩溶带作为一个整体考虑，通过三维结构调查，明确土壤-表层岩溶带的相互耦合关系及其结构因子的定量描述方法，结合原位模拟降雨、离子和氢氧同位素示踪、自然降雨监测等技术，对土壤-表层岩溶带结构因子、外部环境因子、土地利用方式影响下的喀斯特坡地三维产流和养分流失过程进行耦合研究，从水文路径、产流机制、水分滞留时间、降雨产流阈值等角度揭示土壤-表层岩溶带养分流失的水文驱动机制，建立基于土壤-表层岩溶带结构和水量平衡方程的喀斯特养分流失模型，为区域生态服务功能的维持和提升提供科学依据。

Karst landforms are the product of dissolution by natural water of surface and subsurface carbonate rock, showing a complex three-dimensional integrated natural system comprised of rock, water, soil, vegetation and atmosphere elements. A network of solution-enlarged joints and cracks results in excessive surface water loss to the underground through deep percolation and seepage. Recent studies found that human disturbance caused rapid nutrients loss in karst environment, which further deteriorated the inherent fragile karstic ecological system. Runoff and soil erosion are the main causes of nutrients loss in non-karst areas. Whether there are some links between rapid surface water loss and rapid nutrients loss in the karst environment, if there are such links, then to what extent, and how do they work? These questions remain to be answered in order to develope effective nutrients loss controling methods as well as to further promote rocky desertification combating projects in southwest China. The aim of this project therefore is to answer these questions from the point of view of considering the vegetation-soil-epikarst system as an integrated whole. Firstly, a three-dimensional structure investigation will be carried out on the karst hillslope experimental plots (each of 100 m2) equipped for three dimensional processes monitoring for both soil and water, to reveal intercoupling features between soil and epikarst within the near-surface karst system from both qualitative and quantitative perspectives. Secondly, various methods, such as in situ rainfall simulation, chemical and hydrogen/oxygen isotope tracers tests, and hydrochemical monitoring under natural weather condition, will be respectively adopted, to evaluate the effects of soil-epikarst's inner structure factors, external environmental factors, and land use patterns on the three dimensional coupling behaviors of runoff generation and nutrients loss. Based on the above experiments, we attempt to reveal how hydrological factors, including flow pathways, runoff generation mechanisms, water residence time, threshold rainfall, affect karstic ecosystem's rapid nutrients loss, and to develop karstic three dimensional nutrients loss models based on soil-epikarst sturcture factors and water balance equations. The results of this project will provide scientific basis for maintaining and promoting the ecosystem service functions in the karst region of southwest China.