三峡库区不同垂直带森林土壤大孔隙染色实验

Forest Soil Macropore of Different Altitudinal Zones with Dye Tracing Method in Three Gorges Reservoir Area

降雨过程中森林土壤大孔隙内优先流的发生,是森林植被调蓄径流和保持水土的主要方式。利用染色示踪法,对三峡库区宜昌大老岭-邓村地区不同垂直带内森林土壤大孔隙特征进行了实验研究。结果表明,山地植被-土壤类型的梯度变化使不同垂直带内土壤大孔隙数量差异显著,在土壤垂直剖面内呈现不同分布模式。亚高山阔叶林覆盖的山地棕壤下,土壤剖面染色面积比达62.3%,染色区域主要集中在根系发达的腐殖质层,染料下渗深度较浅。低山针叶林黄壤剖面染色比例低于亚高山阔叶林棕壤,但染料下渗深度较深可达69.5 cm,腐殖质层、淋溶淀积层和母质层间染色比例无显著差异。中山灌丛幼林黄棕壤剖面染色比例和染料下渗深度较小,腐殖质层染色比例显著高于淋溶淀积层,母质层几乎无染色现象。与森林土壤相比,低山弃耕坡地的染料下渗深度和染色面积比显著减小,染色区域集中在耕作表层。植物根孔、母质裂隙、土壤发育程度和土地耕作是造成山地不同垂直带间土壤大孔隙结构差异的主要因素。

Preferential flow in soil macropore was principle formation of forest function in runoff adjustment and soil and water conservation.Through dye tracing and image analysis,we studied soil macropore characteristics of different altitudinal zones in Three Gorges Reservoir area from Dalaoling to Dengcun of Yichang City.The results indicated that the number of soil macropore varied greatly at different altitudinal zones,and the distribution of dyed area in soil profile also show different modes,which were caused by the vertical gradient changes of forest vegetation and soil type.Under the mountain brown earth covered with subalpine broad-leaf forest,the ratio between dyeing area and total soil profile is 62.3%,but dyed zone concentrate on the Humus layer with more roots,and the dyed depth is shallow.The dyeing area of yellow earth covered with low-mountain conophorium was smaller than that of broad-leaf forest,but the dyed depth is deeper,even reached 69.5 cm.Macropores exsited not only in the Humus layer,but also in the leaching illuvial layer and the parent material layer,and no significant difference of dyeing area proportion between different layers.Dyeing area and depth of yellow brown earth covered with young thickets forest in mid-mountain were even smaller,and dyeing area of Humus layer was significantly larger than that of leaching illuvial layer,even no dyeing apperence in parent material layer.Compared with three kinds of forest soil,the dyeing depth and dyeing area of the abandoned farmland in low-mountain were significantly lower,and dyed zone concentrate in the surface plowing layer.Root channels,parent material fissures,development degree of soil and agricultural cultivation are the main reasons which caused the difference of soil macropore characterist between different forest soils under distinct altitudinal zones.