土壤大孔隙形态对喀斯特区水土漏失过程的影响

在岩溶作用下，喀斯特土壤—表层岩溶带耦合发育，上覆土壤中大孔隙与下伏表层岩溶带中裂隙、管道存在密切的水力联系，然而土壤大孔隙影响土壤—表层岩溶带系统中水土漏失的过程机理尚不清楚。通过人工模拟降雨试验，采用试验微区模拟不同土壤大孔隙形态（出露型、浅埋型、深埋型），并以全土微区为对照，探讨了土壤大孔隙对喀斯特地区水土漏失过程的影响。结果表明：与全土微区相比，土壤大孔隙的存在明显加速了水分的垂直渗漏，其对水分渗漏量的影响表现在峰值不同（出露型 > 浅埋型 > 深埋型 > 全土）。土壤大孔隙也给土壤漏失带来风险性，不同形态土壤大孔隙间土壤漏失存在显著差异，表现为出露型 > 浅埋型 > 深埋型 > 全土。本研究中土壤漏失量总体较少（<10 g），土壤强烈漏失现象只在极端状况下发生（雨强为120 mm/h的出露型土壤大孔隙微区）。漏失泥沙主要以粒径<2 mm的小颗粒为主， > 5 mm的大颗粒仅出现在出露型土壤大孔隙微区。土壤漏失因子（土壤漏失量、漏失土壤细颗粒含量）与水分渗漏因子（水分垂直渗漏出流时间、水分渗漏量）存在显著相关关系，说明土壤漏失主要受到水文过程的驱动。土壤大孔隙形态和降雨强度控制了水分渗漏过程，进而影响到土壤漏失过程。研究结果可为该区石漠化治理和地下水污染防控提供科技支撑。

Effect of Soil Macropore Structures on Soil and Water Loss Progress in Karst Areas

Through simulated rainfall experiments, the experimental micro-plots were used to simulate different soil macropore structures (exposed type, shallow-buried type, and deep-buried type), and the totally soil filled micro-plots were used as a control to discuss the effects of soil macropore structure on karst soil and water loss processes. The results showed that: Compared with the totally soil filled micro-plots, the presence of soil macropore significantly accelerated the vertical water leakage, and different soil macropore structures had distinction runoff peaks (exposed > shallow-buried > deep-buried > totally soil filled). The soil macropores also exacerbated soil loss risk, and there were significant differences in soil loss between different soil macropore structure treatments (exposed > shallow-buried > deep-buried > totally soil filled). The soil loss amounts were relatively small (less than 10 g), and larger soil loss amounts only occurred under extreme conditions (exposed soil micropores with a rain intensity of 120 mm/h). Small-sized sediments less than 2 mm were dominated during soil loss processes for all treatments, and the sediments larger than 5 mm mostly occurred in the exposed soil macropore treatments. There were significant correlations between soil loss factors (soil loss amount and fine sediment content) and water leakage factors (water leakage initiation time and water leakage amount).The water leakage process was mainly affected by rainfall intensity, and the soil loss process was mainly affected by the soil macropore structures. The results of this study can provide scientific and technological support for the prevention and control of rocky desertification and groundwater pollution in karst areas.