丹江口库区不同植被类型地表根系对土壤渗透性的影响

Effects of surface root system on soil infiltration at different vegetation types in Danjiangkou Reservoir area

为研究地表根系结构特征及其对土壤渗透性的影响,通过对丹江口库区针阔混交林、灌木林、针叶林和阔叶林35块样地进行地表土壤（0～10和10～20 cm土层）和根系采集和室内实验,分析4种植被类型根系结构特征、土壤渗透特性及其相互作用关系,并建立回归方程。结果表明：4种植被类型土壤0～10土层的土壤初渗率和稳渗率均高于10～20 cm土层;土壤0～10和10～20 cm土层土壤初渗率和稳渗率在不同植被类型间均表现相同趋势,即阔叶林〉针阔混交林〉灌木林〉针叶林;不同植被类型土壤初渗率、稳渗率等指标均与根长密度和根表面积密度存在显著的线性相关性（P〈0.05）;根系直径在0.5～5 mm范围内的根系结构特征参数与土壤入渗特征指标之间存在显著的线性相关性（P〈0.05）;在Kostiakov入渗模型中,直径介于0.5～5 mm不同径级的根长密度和根表面积密度与b值正相关,与a值负相关。丹江口库区阔叶林和针阔混交林土壤渗透性能优于灌木林和针叶林,4种不同的植被类型土壤入渗特征值均随根系结构参数值增大而增大,且直径在0.5～5 mm径级范围内的根系对土壤渗透能力的增强作用最明显。

[ Background] Forest vegetation plays a key role in soil erosion in Danjiangkou Reservoir area, and different vegetation has different ability on soil infiltration. Soil hydraulic properties drive water distribution and availability in soil. There exists limited knowledge of how plant growth especially surface root might influence soil hydraulic properties. Roots growing near the soil surface may influence soil detachment, and modify the properties of soil in their immediate vicinity. [ Methods] To investigate the effects of root on soil infiltration capacity, the soil and root （two layers of 0 -10 cm and 10-20 cm） of 35 samples representing the main vegetation types in Danjiangkou Reservoir area were surveyed and analyzed. The root structure characteristics and its influence on soil infiltration were studied, and the methods of modeling, correlation analysis and regression were introduced. [ Results] The soil infiltration capacity of 0 - 10 cm soil layer of different vegetation types were higher than that of 10 - 20 cm. Soil initial infiltration rate and soil steady infiltration rate of 0 - 10 cm and 10 - 20 cm soil layer showed the same trend of the broadleaf forest 〉 coniferous and broadleaf mixed forest 〉 shrub 〉 coniferous forest. Soil infiltration rate and soil steady infiltration rate had significant linear correlation with root length density and root surface area density among different vegetation types. The index of soil infiltration had significant correlation with root structure parameters of different root diameter ranged from 0.5 to 5 mm （P 〈 0.05 ）. Kostiakov infiltration model, Philip infiltration model and Horton infiltration model stimulated the soil infiltration processing, and in Kostiakov infiltration model, root length density and root surface area density of different root diameter ranged from 0.5 to 5 mm presented the positive correlation with b values and negative correlation with a value. Root length density, root volume density and root biomass had significant correlation relation with the indexes of soil infiltration, which could be used to study the relation of root distribution and soil infiltration. The results indicated that vegetation types significantly affected soil infiltration, and coniferous and broadleaf mixed forest as well as broadleaf forest were better in soil infiltration and root structure. Root at diameter of 0.5 - 5 mm played the key role in the root system on soil infiltration capacity. [ Conclusions] The study promotes better understanding of surface root in different vegetation types and its influence on the soil infiltration, and suggests that coniferous and broadleaf mixed forest, and broadleaf forest should be protected, and shrub and coniferous forest should be transformed to promote the soil and water conservation capacity in Danjiangkou Reservoir area.