喀斯特坡耕地土壤养分地下孔（裂）隙流失特征与机理

In the Karst area，Soil erosion and rock desertification as key scientific problems have attracted widespread attentions. Therefore, it is critically important to study the characteristics of soil nutrients loss followed shallow underground fissure, establish loss equation and reveal the mechanism of soil nutrient loss followed underground fissure flow. The experiment of the artificial rainfall was conducted by using a steel flume (the slope and subsurface porosity would be adjusted) with series combinations between subsurface porosity and microgeomorphic units in this study based on the characters of shallow underground fissure. Meanwhile, to verify the feasibility of variable slope and porosity flume, the validated experiments will applied at15-20 typical runoff plots located Dalongwan watershed located in Dafang county, Bijie district, College of Forestry experimental field and Libo Nature Reserve. This new study method would help us deep understanding the process and mechanism of soil erosion and nutrient loss. Also, it would be provided sound theoretical basis for improving the soil and water conservation science theory and the area of rocky desertification, the eco-environmental sustainable development in Karst area.

针对喀斯特地区水土流失、石漠化等关键科学问题，在系统探索喀斯特坡耕地地下浅层（地表以下2-3m）孔（裂）隙发育特征和坡耕地微地貌类型的基础上，选择其典型组合（地下浅层孔裂隙度和微地貌类型），利用可调坡度、可调裂隙试验钢槽建立喀斯特坡耕地模拟径流小区，进行人工降雨试验，开展坡耕地土壤养分随地下浅层孔（裂）隙流流失特征研究，建立地下浅层孔（裂）隙土壤养分流失方程，揭示其土壤养分地下浅层孔（裂）隙流失机理。同时，在贵大林学院试验场、毕节市大方县大湾、荔波茂南自然保护区建立15-20个典型坡耕地野外径流小区，利用其地表土壤养分流失检验与印证可调坡度、可调裂隙试验钢槽模拟喀斯特坡耕地径流小区研究方法的可靠性；为完善水土保持科学理论和该区石漠化治理，实现喀斯特高原生态环境健康持续发展提供科学依据。

喀斯特坡耕地严重的水土流失会造成大量的土壤养分流失，从而制约当地的农业生产。本文以喀斯特坡耕地为研究对象，采用人工模拟降雨试验，对喀斯特裸坡土壤溶质迁移及养分流失特征进行了研究，揭示喀斯特坡耕地养分流失的主要影响因素，结果表明：（1）喀斯特高原石漠化区的浅层岩溶裂隙倾角主要分布在60°~90°，浅层岩溶裂隙垂面形态可分为H型、A型、V型、Y型和O型5种类型。（2）喀斯特坡耕地地下泥沙全氮、全磷、全钾、速效钾、土壤有机碳随地下孔裂（隙）度的增大而增大。（3）降雨强度与地表泥沙全氮、全磷、全钾、有效磷、土壤有机碳成极显著正相关关系（P＜0.01）；坡度与地表径流磷素迁移量成极显著正相关关系（P＜0.01），与地表水解氮迁移量成显著正相关关系（P＜0.05）；地下孔（裂）隙度与地表氮素、钾素和水溶性有机碳成极显著负相关关系（P＜0.01）。（4）降雨强度与地下泥沙中全氮、全磷、全钾、土壤有机碳呈极显著正相关关系（P＜0.01）；坡度与地下水溶性有机碳成显著负相关关系（P＜0.05），与地表泥沙中水解氮及有效磷迁移量成显著正相关关系（P＜0.05）；地下孔（裂）隙度与地下泥沙全氮、全磷、全钾和土壤有机碳成极显著正相关关系（P＜0.01），与地下水解氮成正相关关系。（5）喀斯特裸露坡耕地土壤溶质迁移线性回归分析表明：降雨强度与泥沙各养分迁移量之间的线性关系相对较好拟合程度较高；坡度仅与地表水解氮与地下有效磷的拟合程度较好；地下孔（裂）隙度与泥沙各个养分之间的拟合效果相对较好。本研究可为喀斯特区坡耕地养分流失防治提供理论依据。