Studies On Selection Of Clones And Management Of Intensive Short Rotation Pulpwood Of Triploid Hybrids Of Populus Tomentosa

Experiments on container seedling-raising and selection of clones were firstly conducted to determine feasibility for intensive short-rotation of Populus tomentosa with clones B301,B302,B305,B306,B307,B330 and B331 as material based on the objective of increasing timber yield and shortening rotation period.Research results as follows:(1) Technology on hardwood cuttings container seedling-raising of triploid hybrids of Populus tomentosa was achieved:research results indicated that survival rates of container seedlings could be obtained with cleft-grafting cuttings,budding cuttings,hardwood cuttings and softwood cuttings as material.Hardwood cuttings were the simplest method of propagation which was from root suckers,and cost of container seedling was less than 0.20yuan RMB per tree.Sources of cuttings,media and treatment of cuttings had significant effect on hardwood cuttings container seedling.Optimum combinatorial technology was to treat hardwood cuttings whose thickness was above 1.0cm,length was from 12 to 14cm with 50ppm NAA+100ppm VB₁ after dipped in water for 24 hours with sandy soil as medium.And high Survival rates of hardwood cuttings could be above 75.0%.(2) Method of forestation for container seedlings was brought forward.Site type and time of planting had significant effect on growth of stands of container seedling of triploid hybrids.Sandy soil is a kind of site type for planting container seedling of Populus tomentosa.Time of planting container seedlings was from end of March to beginning of June.Forestation of container seedlings had many advantages,such as without the stage of slowly growing,avoid sharp time of labor force,prolonging time of forestation and simple procedure of forestation,which was particularly suitable to culture intensive short-rotation pulpwood.(3) optimum spacing for intensive short-rotation of Populus tomentosa was determined.Triploid clones of Populus tomentosa had significant effect on tree height,size of tree crown,length of tree crown,diameter of tree crown,volume of tree crown and natural spurning,great effect on stem volume of stands,no effect diameter at breast height and fresh weight of single tree,Spacing had significant effect on diameter at breast height,stem volume of stands,fresh weight of single tree,size of tree crown,diameter of tree crown and volume of tree crown,great effect on length of tree crown,no effect on tree height.Diameter at breast height of clones increased with spacing decreasing,stem volume of stands increased with spacing increasing.Stands planted with 9990 trees/ha brought about the largest stem volume when final cut in 3 years.9990 trees/ha was the appropriate spacing of intensive short-rotation of Populus tomentosa.Clones B307s B331 and B302 planted with 9990 trees/ha brought about the largest stem volume.(4)Characteristics of fiber and chemical components of intensive short-rotation pulpwood of triploid hybrids of Populus tomentosa were proved to be suitable for pulping.Results indicated that triploid clones had significant effect on length of fiber,width of fiber,content of lignin,content of holocellulose,content of a-cellulose and basic density,great effect on content of pentosan,no effect on phenol-alcohol extraction.Spacing had only great effect on basic density.Features of 3-year-old triploid hybrids that Length of fiber from 0.71mm to 0.92mm and mean ratio to length and width from 23.00 to 31.36 was to meet need of pulp & paper industry.Wood properties which basic density from 0.247 g/cm³ to 0.282 g/cm³,mean phenol-alcohol extraction from 3.68%to 4.39%,mean content of pentosan from 12.86%to 13.47%,mean content of lignin from 18.16%to 19.77%,mean content of holocellulose from 74.91%to 77.61%and mean content ofα-cellulose from 40.28%to 43.49%was little worse than short rotation pulpwood(5 years).So craft yield would be little lower because of lower basic density and lower content of cellulose.Experimental results showed that wood property of intensive short-rotation pulpwood of clone B302 and B331 planted with 9990 trees/ha was the best.(5)Clones of intensive short-rotation of Populus tomentosa was screened to meet supply of raw material and need of economic development.A synthetical evalutation was conducted to determine wood quality and growth of intensive short-rotation pulpwood with stem volumes length of fiber,ratio to length and width of fiber,content of holocellulose and basic density as index,and clones B302 and B331 were selected out for intensive short-rotation management.Annual profit of intensive short -rotation pulpwood of clones B302 and B331 was 32.5yuan/mu.RMB Compared with short-rotation pulpwood(6 years),annual profit was less than 70.9 yuan/mu.RMB 11.0m³/mu would be obtained for intensive short-rotation pulpwood.more than 3.9m³ stem volume or 0.32t/mu craft yield per year for short rotation pulpwood(6 years) planted with 4m×1.5m spacing when final cut was carried out in 6years.So intensive short-rotation management was of great potential to pulp & paper industry which was short of raw material.