我国西南喀斯特地区土层浅薄，持水保水能力弱，因此，研究该区广泛分布的林地地表凋落物的水文功能具有重要意义。林下凋落物影响降雨截留、入渗，土壤蒸发和土壤储水量，同时也对水分具有较强的吸持能力，是植被利用的一个重要水分来源，但其中的水分被植被利用的比例尚不明确。为此，项目选择喀斯特洼地典型林地为研究对象，通过野外定位观测，结合氢氧稳定同位素技术，研究林下凋落物对水分入渗和蒸发的影响，分析凋落物覆盖下土壤水分动态特征及其对植被耗水的影响，阐明植被对不同厚度和分解程度凋落物层水分的利用比例及干湿季节变化，探究林下凋落物对植被的供水机制。研究结果一方面有助于深化认识林下凋落物的生态水文功能，另一方面可为西南喀斯特地区植被建设调控提供科学参考。

Karst landscape is widely distributed in southwest China with extensive outcrops, and shallow soils. Therefore, it is of importance to study the hydrological functions of forest floor litter in this area. Floor litter can affect rainfall interception, infiltration, soil evaporation, soil water storage, and also has strong water holding capacity. Though floor litter is an important water source for vegetation, the utilization ratio of water in which is unclear. This project will be conducted in a typical forest land in karst depression, using field monitoring and hydrogen and oxygen stable isotope technique. We aim (1) to study the effect of floor litter on water infiltration and evaporation; (2) to analyze the dynamics of soil moisture and its influence on vegetation water consumption under the condition of litter coverage; (3) to clarify water utilization ratio and its seasonal change of floor litter with different thicknesses and decomposition degrees; (4) to explore the water supply mechanism of forest litter for vegetation. This research will be conductive to deepen understanding the eco-hydrological functions of floor litter. This research will also provide scientific reference for regulating vegetation construction in karst area of southwest China.