石漠化山区露石岩面流对岩-土界面土壤氮磷淋溶与输入作用的研究

Leaching and Input Effects of Exposed Rock Surface Flow on Soil Nitrogen and Phosphorus at Rock-soil Interface in Rocky Desertification Mountainous Area

基岩出露的石漠化区露石岩面在承接降水(含穿透雨)后易形成岩面流,并携带岩面有机或无机物质输送至岩周土壤中,对岩-土界面土壤养分变化具有重要影响。为探明岩面流对岩-土界面土壤氮磷的淋溶与输入影响,选取基岩明显出露的休耕地(1年岩面流作用)、退耕灌草地(5年岩面流作用)和坡耕地(无/少岩面流作用)3种样地,并分别选择外凸、平直和内凹3种特殊的岩面形状,研究了距岩面不同水平距离及土层的岩-土界面及非岩-土界面土壤的全氮和全磷变化特征。结果表明:岩面流对0~10 cm表层岩-土界面土壤氮磷产生输入或淋溶作用,对10~20 cm层岩-土界面土壤氮磷作用不明显。不同岩面形状形成的岩面流对岩-土界面土壤氮磷的淋溶与输入作用强度依次为:内凹型>平直型>外凸型。其中,在1年岩面流作用的休耕地中,内凹型岩面形成的岩面流对岩-土界面土壤氮素的影响主要表现为淋溶,而平直型和外凸型岩面表现为输入作用;不同形状岩面流对岩-土界面土壤磷素的影响均表现为淋溶。然而,在植被生长较好的退耕灌草地中,5年岩面流作用下不同形状岩面流对岩-土界面土壤氮磷的影响主要表现为输入。研究结果可为深入认识出露岩石对喀斯特生态系统土壤特性的影响提供科学依据。

【Objective】After receiving precipitation,exposed rock surface in a rocky desertification area exposed to bedrock is easy to form rock surface flow,which carries organic and inorganic substances on the rock surface to the surrounding soil.This has a significant impact on the change of soil nutrients at the rock-soil interface.【Method】This study was designed to investigate the effect of rock surface flow on the leaching and input of nitrogen and phosphorus in the soil at the rock-soil interface.Three plots:fallow land(one-year rock surface flow),abandoned irrigated grassland(five-year rock surface flow),and sloping farmland(no/little rock surface flow)with obvious bedrock exposure,were chosen.We chose three special shapes of the rock surface,namely convex,straight,and concave,at different horizontal distances from the rock surface and soil layer to study the variation characteristics of total nitrogen and total phosphorus in the soil at rock-soil interfaces and non-rock-soil interfaces.【Result】The results indicated that rock surface flow contributed either to the input or leaching of nitrogen and phosphorus in the 0-10 cm surface of the rock-soil interface soil.However,it had a minimal effect on nitrogen and phosphorus in the 10-20 cm deep rock-soil interface soil.The intensity of the leaching and input of nitrogen and phosphorus in the surface soil of the rock-soil interface formed by different rock surface shapes followed concave>straight>convex.In the 1-year fallow land,under the action of rock surface flow,the influence of rock surface flow formed by concave rock surface on soil nitrogen at the rock-soil interface was mainly manifested as leaching,while flat and convex rock surfaces exhibited input effects.Also,the effects of rock surface flow with different shapes on soil phosphorus at the rock-soil interface showed leaching.For the 5-year rock surface flow,the result depicted mainly an input phenomenon.【Conclusion】These results can provide a scientific basis for further understanding the influence of exposed rock on soil characteristics of the karst ecosystem.