摘要
喀斯特坡地壤中流与地表径流并存,共同驱动了土壤关键生源物质的迁移,造成该区土壤生产力下降、地下水污染。为揭示喀斯特坡地土壤碳氮流失途径及其水文驱动机制,本研究以喀斯特坡地径流微区(2 m×1.2 m)为研究对象,分析了火烧、轻度砍伐、重度砍伐、人工林、耕地、牧草6种不同土地利用方式对土壤碳氮流失途径、形态及通量的影响。结果表明:降雨是土壤碳氮流失的主要驱动因子,降雨产流阈值为16 mm,55 mm时达到产流峰值。各土地利用方式仅在暴雨下有显著差异,其中,人工林的土壤碳氮流失量较大,而重度砍伐的流失量较小。土地利用方式不改变土壤碳氮的流失途径,各土地利用方式均以地表流失为主(51.29%~75.15%),壤中流为辅,其中壤中流主要通过A层流失(65.20%~89.12%)。氮素流失形态以NO_(3)^(-)-N为主(45.84%~56.49%)。研究结果可为揭示喀斯特坡地生源物质流失过程及其水文驱动机制、研发水土流失与面源污染阻控技术提供参考。
There is no direct contact between shallow soil and underlying carbonate rock in karst slope.Due to the unique karst processes in the karst hillslopes,in the process of secondary rainfall,overland flow and subsurface flow jointly drive the migration of key biogenic materials in the soil rock profile,resulting in the decrease of soil productivity and groundwater pollution in this area.However,the main migration pathways and driving mechanisms of soil carbon and nitrogen loss under different land use modes remain unclear.Based on a complete hydrological annual rainfall runoff-nutrient monitoring from 6 different land use experimental hillslopes(burned land,light felling land,heavy felling land,planted forest,farmland and grassland),we took the slope runoff micro-area(2 m×1.2 m)of Huanjiang Karst Ecosystem Observation and Research Station of Chinese Academy of Sciences as the research object.This study analyzed the loss path,loss form and average loss of soil TN and Toc driven by the near-surface multi-interface lateral hydrological processes(surface runoff,lateral flow from Layer A and lateral flow below the layer).Results show that the karst slope has a high soil infiltration coefficient,and the soil carbon and nitrogen loss per unit area is positively correlated with rainfall.Rainfall is the main driving factor of soil carbon and nitrogen loss.The threshold rainfall of nutrient loss driven by runoff is 16 mm,and the peak rainfall is 55 mm,indicating that the karst slope shows the characteristics of nutrient loss driven by full runoff.There are significant differences of soil carbon and nitrogen loss among different land use modes,but only under heavy rainfall.Compared with other land use mods,planted forest can improve canopy interception,increase transpiration and infiltration,and thus weaken the surface flow production.However,research results also show that the soil carbon and nitrogen loss of planted forest is relatively large,which on the one hand is related to the single vegetation type,high surface exposure,and fast soil surface saturation;on the other hand,the channels formed by the interpenetration of plant roots have natural continuity and are interconnected with other channels in the soil to form a huge water transport network and promote the occurrence of runoff.Therefore,species suitable for karst areas should be cultivated;the allocation of shrub and grass species at the bottom of canopy should be strengthened;and moderate human interference should be carried out to optimize plant community structure and reduce the risk of soil carbon and nitrogen loss.In this study,it is found that the soil carbon and nitrogen loss of heavy felling land is relatively small.During the process of heavy felling and root removal,the original pores of soil were destroyed,which had a negative impact on the occurrence of preferential flow and near-surface flow.The higher soil carbon and nitrogen loss in farmland and grassland is related to fertilization in tillage period,but the difference between them is not significant,indicating that conservation tillage is beneficial to soil microbial activities and thus improve soil fertility.Combined with the effect of fertilization,the difference in nutrient loss driven by hydrological processes may be concealed.Meanwhile,surface filling increase,thus reducing the near-surface loss.Land use modes do not change the path of soil carbon and nitrogen loss.The soil carbon and nitrogen in the slope of karst dolomite mainly loss through the surface(51.29%-75.15%),because the pores and joints in the dolomite area are evenly distributed and the water-barrier layer is easy to be generated and the permeability is good under the dual influence of physical weathering and tectonic forces.At the same time,the monitoring results of soil flow show that the flow loss in Layer A is much higher than that below Layer A,which is related to nutrient enrichment in Layer A on the one hand.On the other hand,the flow generation in karst areas follows the theory of interfacial flow generation,and the permeability of Layer A is much higher than that below Layer A.[Math Processing Error]-N is the main form of soil carbon and nitrogen loss under different land use experimental hillslopes(45.84%-56.49%).The results of this study can provide reference for revealing the process of biogenic material loss and its hydrologic driving mechanism in karst slope,and developing the prevention and control technology of soil loss and non-point source pollution.
作者
任惠敏
付智勇
王发
陈洪松
REN Huimin;FU Zhiyong;WANG Fa;CHEN Hongsong(Key Laboratory of Agro-ecological Processes in Subtropical Region,Institute of Subtropical Agriculture,Chinese Academy of Sciences,Changsha,Hunan 410125,China;Huanjiang Observation and Research Station for Karst Ecosystems,Chinese Academy of Sciences,Huanjiang,Guangxi 547100,China;University of Chinese Academy of Sciences,Beijing 100049,China)
出处
《中国岩溶》
CAS
CSCD
北大核心
2023年第1期84-93,共10页
Carsologica Sinica
基金
国家自然科学基金联合基金(U21A20189)
广西重点研发项目(桂科AB22035058)
国家自然科学基金面上项目(42077077)。
关键词
喀斯特生态系统
人为干扰
面源污染
碳氮流失
壤中流
karst ecosystem
human disturbance
non-point source polution
carbon and nitrogen loss
soil flow.
