A Study On Effects Of Biological Mulching On Growth And Soil Properties Of Poplar Plantation In Southern Upland Area

Recent years lots of poplar plantations have been established in the upland area. However, poor soil conditions are the main factors to affect poplar growth. In order to improve the soil properties and increase the productivity of poplar plantations in this area, biological mulching treatments were designed in Guizhou province. Two treatments were arranged in this experiment, e.g. mulching weights(four levels:0.0, 2.5, 5.0 and 7.5kg/m~2 with mixed muching materials) and four mulching materials(Quercus fabri, Imperata cylindrical var. major and Pteridium aquilinum var.latiuscukum,Coriaria nepalensis with muching weights of 5.0kg/m~2). The two-year results are as follows:There are great differences in decomposition rate and nutrient release rate for various plants. Both decomposition rate and nutrient release rate of Quercus fabric are the largest among the mulching plants. With time passing, decomposition rate of mulching plants and release rate of plant nutrients are slowed down gradually, but its stability varies in different plant species.Biological mulching in poplar plantation not only affects the soil physical properties, such as soil temperature, soil water content, soil bulk density, but also influences the soil chemical properties(such as the contents of total nitrogen, available nitrogen, available phosphate, available potassium, pH value and organic matter) and nitrogen mineralization process(such as the amount of nitrobacteria, the amount of net nitrogen mineralization). Although some differences exist in changing trends of soil properties, the dynamics of the soil properties could be described by "S" shape curves or polynomial functions after biological mulching of 2-years. In mulching period of 2-years, the stability in soil temperature, water content, bulk density, total nitrogen, available nitrogen, the amount of nitrogen net mineralization, the amount of nitrobacteria in soil, available phosphate content, available potassium content, pH value and organic matter in soil are changed with the different mulching weights and mulching plants.Originally, the soil is divided into three layers based on the amount and stability of physical and chemical properties in soil, eg, changeable layer of 0-5cm, transforming layer of 5-20cm,and relatively steady layer of 20-40cm. The stability of physical and chemical property in soil varies according to different layers.Leaf water content, leaf area, nutrient and chlorophyll content of the leaf are affected by the biological mulching, furthermore, the tree height, diameter at breast height, root grow and total biomass are also influenced. Compared with the control (ck), poplar growth is significantly improved by biological mulching. However, the growth increments vary among the treatments, for example, compared with the control, the increment of tree height and...