构树苗木切根和截顶对造林后土壤理化性质的影响

Effects of cutting top and/or root of Broussonetia papyrifera seedlings on soil physicochemical properties after afforestation

以3年生构树幼树为研究对象,研究构树实生苗造林,分别2个径级,即0.5 cm~1.0 cm、1.0 cm~1.5 cm,3种处理:即留顶+留根、截顶+留根(留顶30 cm)、截顶+切根(留顶30 cm+留主根5 cm)。通过对构树苗木不同处理造林后土壤理化性质指标测定,分析不同处理幼林地土壤理化性质的改良,为贵州喀斯特石漠化区构树造林苗木径级标准和处理方式提供依据。结论:(1)土壤物理性质:土壤容重垂直层表现为上层<下层,同一处理上层土壤容重大径级略小于小径级,下层大径级大于小径级。含水量表现为上层>下层,同一处理上层土壤含水量大径级大于小径级,下层大径级小于小径级。总孔隙度表现为上层>下层,同一处理上层土壤总孔隙度大径级、小径级相差不大,下层小径级大于大径级(C处理除外)。总体上两种径级均为C处理土壤容重最小,含水量和总孔隙度最大,土壤结构好。(2)土壤化学性质:有机质含量垂直分布为上层>下层,幼林地>无林地,同一处理上层土壤有机质含量大径级小于小径级,下层大径级大于小径级(C处理除外);两种径级C处理土壤有机质含量最大。试验区土壤属于碱性,pH值均在8.00左右。pH值是幼林地为上层>下层,无林地为上层<下层。

The study is carried out in Yintan Village of Zhenfeng County,Guizhou Province.The three-year seedlings of Broussonetia papyrifera were taken as the research objects.The seedlings were divided into two groups according to their diameters(small-diameter group:0.5 cm to 1.0 cm,large-diameter group:1.0 cm to 1.5 cm),and three different treatments were performed:(A)keeping top and root,(B)cutting top(30 cm left)while keeping root,and(C)cutting top(30 cm left)and root(5 cm left).The soil physicochemical properties after afforestation with different Broussonetia papyrifera seedlings were measured,so as to provide theoretical basis for the afforestation work in karst rocky desertification areas of Guizhou Province.The conclusions are as follows.Soil physical properties:the soil volume weight in the upper layer is smaller than that in the lower layer;for the same treatment,in the upper layer the soil volume weight of the large-diameter group is smaller than that of the small-diameter group,while in the lower layer the situation is the opposite;the soil water content in the upper layer is higher than that in the lower layer;for the same treatment,in the upper layer the soil water content of the large-diameter group is higher than that of the small-diameter group,while in the lower layer the situation is the opposite;the soil total porosity in the upper layer is higher than that in the lower layer;for the same treatment,in the upper layer the soil total porosity is almost the same,while in the lower layer the soil total porosity of the large-diameter group is lower than that of the small-diameter group(except for treatment C);for both diameter groups,treatment C shows the least volume weight,the highest water content and the highest total porosity.Soil chemical properties:the organic matter content in the upper layer is higher than that in the lower layer,and that in the afforested land is higher than that in the non-forested land;for the same treatment,in the upper layer the organic matter content of the large-diameter group is lower than that of the small-diameter group,while in the lower layer the situation is the opposite(except for treatment C);for both diameter groups,treatment C shows the highest organic matter content.The soil in the research area is alkaline and the pH value is about 8.0.In the afforested land,the pH value in the upper layer is higher than that in the lower layer,while in the non-forested land the situation is the opposite.