| 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/m2 with mixed mulching materials) and four mulching materials (Quercus fabri, Imperata cylindrical var. major, Pteridium aquilinum var. latiuscukum and Coriaria nepalensis with muching weights of 5.0kg/m2). The main results are as follows:1.Organic matter, N, P and K contents in Rhizospheric soil, especially available nutrient, obviously increased after mulching. Upmost nutrient contents were found in the treatment with 7.5kg/m2 mulching; for different mulching materials, organic matter content was highest in the treatment with mulching of Imperata cylindrical var. major; the contents of total N and available N in the treatment with mulching of Pteridium aquilinum var. latiuscukum and Coriaria nepalensis were higher than that of Quercus fabric and Imperata cylindrical var. major; there were few differences in the contents of total P and total K among mulching materials; the contents of available P and available K were comparatively higher in the treatment with mulching of Imperata cylindrical var. major and Coriaria nepalensis than that of other mulching materials.2. Mulching increased moisture and regulated pH value in rhizospheric soil. With the increasing of mulching weights, its ameliorative function was strengthened . Compared with the control, the moisture and pH value in the treatment with mulching 7.5kg/m2 were higher 22.29% and increased by 0.49 . Moisture mulching of Pteridium aquilinum var. latiuscukum was higher 8.56% than the control, and the effect of which on improving moisture was a little better than other vegetation in different mulching materials, and the regulative function of pH value is maximal in Pteridium aquilinum var. latiuscukum and Coriaria nepalensis, which increased by 0.39 and 0.25 respectively.3. After mulching, activity of microbe and enzyme was enriched in rhizosphere soil. As mulching weights increased, the numbers of bacterium and fungi swelled, and activity of urease and phosphatase was further intensified. The numbers of bacterium and fungi in the treatment with mulching 7.5kg/m2 were more 49.58% and 6.14 times than that of the control. Among different mulching materials, the amount of bacteria was most in Imperata cylindrical var. major , while the largest amount of fungi was observed in the treatment with mulching of Quercus fabri. Activity of urease and phosphatase was higher in the treatment with mulching of Coriaria nepalensis , which increased by 0.14mg/g compared with the control, and which was 6.14 times of the control , than that of other mulching plants.4. Biological mulching enriched nutrient contents of poplar in leaves, branches and roots. Upmost nutrient contents in different organs were found in mulching of the 7.5kg/m2 treatment, and nutrient contents varied with different mulching materials.5. The growth of poplar plantation was obviously improved after mulching. With the increasing of mulching weights, increment of tree height and DBH increased. The increments of three-year tree height and DBH in the treatment with 7.5kg/m2 mulching were 1.94 and 1.91 times of the control respectively. For different mulching material treatment, the increments of 3-year tree height and DBH in the treatment with Quercus fabric and Imperata cylindrical were 80.19% and 82.08%, 52.94% and 33.33% higher than that of control respectively.6. As mulching weights increased, biomass in leaves, branches and roots trended towards large. Upmost biomass in leaves, branches and roots were observed in the treatment with mulching of the Pteridium aquilinum var.latiuscukum, Imperata cylindrical var. major and Quercus fabric which were 1.98, 1.93 and 2.08 times of the contron respectively, and total biomass was larger in the treatment with mulching of the Quercus fabric and Imperata cylindrical var. major than that of other mulching materials.7. Based on the results from this study, we suggest that mulching weight of 7.5kg/m2, and Quercus fabri, Imperata cylindrical var. majoris, as mulching materials can be applied in poplar plantation in Guizhou upland areas.
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