红河干旱河谷地区植物根系与砾石对土壤优先路径形成的影响

Effect of Plant Roots and Gravels on the Formation of Soil Preferential Flow Paths in Arid Valley of Honghe River

为探究红河干旱河谷林草地植物根系与砾石特征对土壤优先路径形成的影响,基于染色示踪法在确定研究区样地土壤优先路径的位置及数量的基础上,结合染色区的植物根系与砾石体积含量特征,定量分析二者与优先路径特征的关系。结果表明:(1)林地优先路径发育水平明显优于荒草地;不同染色影响半径范围下的优先路径连通性也有所不同,其中荒草地中优先路径连通性从大到小为1~2.5 mm,≤1 mm,2.5~5 mm,5~10 mm,>10 mm;林地为1~2.5 mm,2.5~5 mm,≤1 mm,5~10 mm,>10 mm;优先路径数量与土层深度和同一土层内染色半径均呈负相关关系,此外,在同一土层内,优先路径的数量与染色半径也呈负相关关系。(2)林地中染色区的砾石总体积含量与土层深度呈负相关,而荒草地中在20—30 cm土层中增多,其余径级下的则随土层深度增加而减少;(3)两种样地中的根长密度与根重密度都随土层的深度增加和根径增大而单调递减,林地中不同径级下的根长密度都明显高于荒草地;(4)林地中优先路径数量的主要影响因子是根径范围在≤1 mm的根重密度和径级为5~10 mm的砾石体积含量;而荒草地样地中的主要影响因子为根径在≤1 mm和1~3 mm范围下的根重密度、径级在2~5 mm间的砾石体积含量、根径在1~3 mm范围下的根长密度。因此,样地中砾石分布存在明显的空间异质性,细根更易促进优先路径的形成,二者共同影响着优先路径的形成。

The purpose of this study was to investigate the effect of the characteristics of plant roots and gravels on the formation of soil preferential flow paths in forest in arid river valley of Honghe River.Based on the staining tracer method,the location and quantity of the preferential flow paths of the soil in the study area were determined,and the relationship between the root system and gravel volume content in the stained area was analyzed quantitatively.The results show that:(1)the development degree of woodland preferential flow paths is obviously better than that of wasteland;the connectivity of the preferential flow paths is also different in different dyeing radius;In the wastrel,the connectivity of the preferential flow paths decreases in the order:1~2.5 mm,≤1 mm,2.5~5 mm,5~10 mm,>10 mm;in the forest land,the connectivity of the preferential flow paths decreases in the order:1~2.5 mm,2.5~5 mm,≤1 mm,5~10 mm,>10 mm;the number of preferential flow paths is negatively correlated with the depth of soil layer and the radius of staining in the same soil layer;(2)in the stained area of forestland,the total gravel volume content decreases with the increase of soil depth,while in the stained area of wasteland,the total gravel volume content increases in the 20—30 cm soil layer,and the volume contents of rest particle sizes decrease with the increase of soil depth;(3)the root length density and root weight density decrease monotonously with the increase of soil depth and root diameter;the root length densities of plants under different diameters are higher in woodland than those in wasteland;(4)the main influencing factors on the number of preferential flow paths in the forest land are the root weight density within the root diameter range≤1 mm and the gravel volume content with the diameter of 5~10 mm.The main influencing factors in wasteland plots are root weight densites of the roots with the diameter ranges of≤1 mm and 1~3 mm,volume contents of gravels with the diamter range of 2~5 mm,and root length densities of roots with the diamer range of 1~3 mm.Therefore,the gravel distribution in the sample plot has obvious spatial heterogeneity,and the fine roots are more likely to promote the formation of the preferential flow paths,and the root system and gravel together influence the formation of the preferential flow paths.