| In the background of give full play to the potential use of eucalyptus wood utilization for increasing the added value of eucalyptus wood products and improve the sustainable development of Eucalyptus plantation is of great significance, this paper focusing on comparativing Eucalyptus multiple traits at medium-term in the cultivation of large-diameter timber against its quality requirements, clones with the use of the wood utilization value were comprehensive selected, study on the impact of planting density and fertilizer to multiple traits of Eucalyptus at the same time, and initial search suitable cultivation mode of large-diameter timber of eucalyptus by growth characteristics as an indicator in broad mode, the main conclusion as follows:(1). Analyse data at age of 5.5-years from an experimental pulpwood forest of 20 eucalypt clones established at shankou in Guangxi. Results from the trial at Shankou showed that there were significantly differences in growth traits among the 20 clones tested. Optimal for growth was DH32-28 with an individual tree volume of 0.1262m3; this was 31.0% more than the average value. The clone with the largest forest standing volume was DH167-2 with 54.8% more than the average value. Analyse data at age of 4.5-years from an experimental pulpwood forest of 22 eucalypt clones established at changle in Guangxi. Results from the trial at changle showed that there were significantly differences in growth traits among the 22 clones tested. Optimal for growth was DH32-28 with an individual tree volume of 0.1548m3; this was 59.73% more than the average value. The clone with the largest forest standing volume was DH33-27 with 42.35% more than the average value. Indications are that selection based on growth traits will be valuable in producing large-diameter timber from eucalypt clones.(2). Analyse data at age of 5.5-years from an experimental pulpwood forest of 20 eucalypt clones established at shankou in Guangxi. Experiments show that:There were significantly differences in form traits among the 20 clones tested., Stem form of DH32-26, DH184-1, A33 (IV-13), DH167-2, DH33-9 achieved full marks; in branch traits TH9211-LH1, U6 and DH167-2 were the best scoring close to the maximum. Analyse data at age of 4.5-years from an experimental pulpwood forest of 22 eucalypt clones established at changle in Guangxi. Experiments show that:There were significantly differences in form traits among the 22 clones tested. Stem form of DH33-9, DH32-29, DH42-6, DH196, DH30-10, DH33-27 achieved full marks; in branch traits DH32-29, DH42-6, DH196, DH30-10, DH33-27 were achieved full marks too. Results from this trial indicate that there is sufficient variation in stem form and branching between eucalypt clones to provide a basis for selection for large-diameter timber.(3). Analyse data at age of 5.5-years from an experimental pulpwood forest of 20 eucalypt clones established at shankou in Guangxi. Results from this trial indicate that there were significant differences in wood property among the 20 clones tested. The clone with the highest wood basic density and modulus of elasticity at 5.5 years was TH9211-LH5 with 0.48g·cm-3 and 6.166GPa respectively, which were 16.7% and 30.6% more than the overall average values. Analyse data at age of 4.5-years from an experimental pulpwood forest of 22 eucalypt clones established at changle in Guangxi. Results from this trial indicate that there were significant differences in wood property among the 22 clones tested. The clone with the highest wood basic density and modulus of elasticity at 4.5 years was THD3 with 0.46g·cm-3 and 5.55GPa respectively, which were 12.19% and 32.19% more than the overall average values. Results indicate selection for these traits will be useful in producing large diameter timber from eucalypt clones.(4). That is, information on all valuable traits is integrated into a simple index value which in theory is an ideal method in selection at shankou in Guangxi. In this study, five eucalypt clones were selected as good for large diameter timber production. These selected clones were DH184-1, DH167-2, DH32-26, DH32-28 and DH33-9. These five clones with the highest integrated score, indicating that its growth, form, wood property was excellent and reaches to purpose of comprehensive selecting.(5). In this paper, two clones were selected with the multi-characters index selection method by independent culling method at changle in Guangxi, these selection clones were DH42-6, DH33-27, respectively. Selection rate was only 9.10%, has great selection intensity. Further compare the two clones:If you consider taper to have priority, the quality of DH42-6 is better than the quality of DH33-27; if you consider modulus of elasticity to have priority, the quality of DH33-27 is better than the quality of DH42-6.(6). Individual tree volume and forest standing volume have a larger Coefficient of variation from an experimental pulpwood forest at shankou and changle in Guangxi. The greater selection gain was expected to accumulate in Individual tree volume and forest standing volume through comprehensive selection of each indicators, also showed that better effect was generated by improvement on the growth traits especially individual tree volume and forest standing volume, while if you want to create a noticeable gain on the rest of the indicators, you must breeding by higher, more generations genetic improvement.(7). Analyse data at 18-months and 66-months from experimental for large-diametet timber of eucalyptus cultivation in Lei Zhou Peninsula. The results showed that growth traits in plant density differences between the various levels are extremely significant at 18-months and 66-months; modulus of elasticity in plant density differences between the various levels is to extremely significant at 66-months, wood property in plant density differences between the various levels is to extremely significant at 66-months. Bark rate has reduced the trend with planting density reduction, wood basic density, wood density, modulus of elasticity decrease are gradually increasing trend with planting density reduction.(8). Large-diametet timber of eucalyptus cultivation experiment in Lei Zhou Peninsula showed:Large-diameter timber of Eucalyptus cultivation should choose sparser planting density. Integrated analysis by plant density, fertilizer treatments and economic efficiency, the experiment showed that effect of large-diameter timber for eucalyptus cultivation under the conditions of density with 4m×3.5m coordinates fertilizing Leilinl# fertilizer with 800g is ideal.(9). Broad strip plantation was setted in the Leizhou Peninsula, try to find Eucalyptus-crops interplant model against large-diameter timber for Eucalyptus, according to growth characteristics traits in Eucalyptus-crops interplant model at 6 year-old, height, DBH, individual tree volume and forest standing volume were optimal under cultivation mode of bandwidth 14m coordinate spacing in the rows 0.8m, reach to 16.367m,11.7cm,0.075 m3, 110.09 m3·hm-2, respectively, which increased by 30.9%,17.4%,81.4%,87.0%compared with the control, respectively. There was significant to extremely significant difference by analysis of variance and multiple comparison analysis under each treatment. The final result witnessed that agro-forestry alternate planting modes improve the woodland nutrient cycle, increased eucalyptus efficiency in the use of natural resources as light, heat, water and gas, thus promoting the growth of eucalyptus. The potential of Large-diameter timber for Eucalyptus in agro-forestry alternate planting is favorable.
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