| In order to improve the plantation productivity of poplar plantations and study thecultivation pattern of big-diameter wood, six-year-old poplar plantations located in Chenweiforest farm of Sihong County were selected as experimental materials. Experimental treatmentsapplied in a split-plot design included four planting densities or spacings (6m×6m,5m×5m,4.5m×8m, and3m×8m) and three poplar clones (Populus×euramericana cv “Nanlin-95”,Populus×euramericana cv “Nanlin-895”, and Populus×euramericana cv “Nanlin-797”).However, four planting densities for clone Nanlin-95and three clones under spacing of6m×6m were selected to study the effect of the growth of poplar,density distribution and clone onplantation canopy density, LAI(leaf area index), litter, soil nutrient, and productivity of poplarin this paper. The main results are as follows:(1). There was no significant difference in poplar height growth among four plantingdensities as well as among the three poplar clones. However, a significant difference in DBHgrowth was observed, and the highest growth (18.81cm) was reached in the spacing of6m×6m, and the density of spacing was the lowest (1.72cm) was detected in the spacing of3m×8m. In term of the three clones, Populus×euramericana cv “Nanlin-895” wsa the highest(19.51cm) and Populus×euramericana cv “Nanlin-797” was the lowest (18.02cm).(2). There was no significant difference of the stand canopy density and the LAI amongthe6treatments. Both canopy density and LAI were the greatest in summer, and was the lowestin antumn. The highest canopy density and LAI were found in the spacing of5m×5m and thevalue were64.3％and1.77respectively for different planting density treatments, while for thevarious poplar clones, Populus×euramericana cv “Nanlin-895” was the highest, and Populus×euramericana cv “Nanlin-797” was the lowest.(3). Biomass per hectare and the single plant biomass of Populus×euramericana cv“Nanlin-895” was the highest among the3clones, and the value of biomass per hectare was37.68T/hm~2. In four planting densities, biomass per hectare in the spacing of5m×5m wasthe highest and the value was44.16T/hm~2, while the highest single plant biomass was observedin the spacing of6m×6m.(4). Among the four density configurations, the weight of of spacing of5m×5m was thehighest，the value was263.91g/m~2;while the value of spacing of4.5m×8m was the lowest.Among the three clones treatments，the weight of litter of various treatments of Populus×euramericana cv “Nanlin-797” was the highest，and the value was199.48g/m~2，while thevalue of Populus×euramericana cv “Nanlin-797” was the lowest. Among every treatments， the weight of litter was the highest in October，while the lowest in August.(5). Undergrowth biomass of spacing of5m×5m and Populus×euramericana cv“Nanlin-797” were the highest in the two processings. In spring and summer，diversities ofundergrowth vegetation of spacing5m×5m and Populus×euramericana cv “Nanlin-797”were the highest，the value was795.12kg/hm~2; in autumn，spacing4.5m×8m andPopulus×euramericana cv “Nanlin-895” were the highest.(6) Shannon-Wiener Index of understory vegetation in the spacing of5m×5m was thehighest among the four configuration mode during spring and summer，the values were1.732and2.030; spacing of4.5m×8m was the highest (2.313)，while spacing of5m×5m wasthe lowest. Among the3clone treatments, it was highest in Populus×euramericana cv“Nanlin-797” in spring and summer; it was highest in Populus×euramericana cv “Nanlin-895”in autumn.(7). There was no significant difference in the nutrient of understory vegetation for6treatments, and was basicly determined by the dominant understorey species. The soilnutrient of6treatments were decreaseing from0-5cm to10-20cm, and it were different forsoil nutrient in each level of soil. |
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