| Poplar is an important afforestation tree species for timber and shelterbelt forest,widely cultivated in China.With further increases of market demand for large-diameter timber,the cultivation of large-diameter Poplar timber forest is becoming one of the research hotspots in Poplar management research.Xinguanzhou Forest Farm in Anqing City was selected as research site in thesis,based on the Poplar tree wood samples felled,Poplar trunk taper equation was established,and its merchantable volume yield rate table was compiled.According to the data of sample plots of different Poplar agro-forestry intercropping models and thinning treatmentes,volume of timber assortment of Poplar stand and crop yield at different age stages were compared and analyzed for different Poplar agro-forestry models,and net present value and internal rate of return calculated.The optimal Poplar agro-forestry model was put forward.At the same time,by comparing and analyzing the effects of different thinning treatments on tree growth and large-diameter timber yield,a tree growth model was constructed,and the impact of different thinning treatments on large-diameter timber yield was revealed,and the optimal thinning treatment and intensity were put forward for Poplar large-diameter timber cultivation.The results as follows:(1)The Poplar tree height equation is H=25.015/(1+10.969×e-0.174×D)(R2=0.956,SSE=10.133);DBH equation with(without)bark is D1=0.144+0.96 × D2(R2=0.999,SSE=2.218);the taper equation is d2/D2=1.055-1.106 ×(h/H)+0.047 ×(h/H)2(R2=0.952,SSE=0.577).(2)Among the different intercropping models,the Poplar-rape intercropping model has the highest input-output ratio,with a ratio of 4.51:1 and the highest capital profit margin.In terms of output-to-input ratio,the order from high to low is Poplar-rape>Poplar-wheat>Poplar-wheat-soybean>Poplar-rape-soybean.The net present value was found to be highest in the Poplar-rapeseed-soybean intercropping mode,the order of net present value is Poplar-rapeseed-soybean>Poplar-wheat-soybean>Poplar-rapeseed>Poplar-wheat>Poplar pure forest.Additionally,the internal income of the Poplar-rape intercropping model was the highest,and the internal rate of return ranked as follows:Poplar-rape>Poplar-wheat>Poplar-wheat-soybean>Poplar-rape-soybean.(3)When only considering total profit and net present value,the Poplar-rape-soybean is undoubtedly the optimal model.However,taking into account two factors:planting techniques and cost-effectiveness,the Poplar-rape intercropping model with the highest net present value is the optimal choice.(4)The average DBH,tree height and total volume growth of the 9-year-old of control group were 28.1 cm,23.1 m and 0.59 m3/667 m2,respectively.According to the thinning intensities of 50%,33%,and 20%,the average DBH,tree height and total volume growth of the 9-year-old Poplar stand were 32.1 cm,24.1 m and 0.82 m3/667 m2;31.6 cm,24 m and 0.79 m3/667 m2 and 29 cm,23.3 m and 0.64 m3/667 m2,respectively.The growth effect of trees is higher than that of the control group for different thinning intensities.The average DBH,tree height,and total volume growth of the stand at the 50%intensity were 1.14,1.04,and 1.39 times that of the control group,respectively.The yield of large-diameter timber with the different thinning intensities was as follows:50%intensity>33%intensity>20%intensity>control group.The research results of this paper are of great significance for the cultivation of Poplar large-diameter timber in the beaches of the Wanjiang River Basin. |
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