Silvicultural Regimes Of Eucalypt Plantation For Sawlog Production

This research based on the silvicultural theory and regimes of eucalypt plantation for sawn log production has filled up the gaps with some technology innovation and it makes possible for improving wood product structure, speed upping the production of sawn logs, reducing the import and increasing wood security for the country.In silvicultural theory, on the target of sawn log production it was analyzed on factors of sociality, nature and management, and the structural models of factors was established. Meanwhile the contribution rates of all factors were calculated depending on the structural models and the application of error square theory. The results showed that (1) The two targets of economics and sociality were on the top layer of the models; the factors of social requirement, climate and land sites were on the bottom layer; the second layer were the factors of tree species selection and spacing; the third layer were fertiliser application and pruning.(2) In the silvicultural process of eucalypt sawn log, the contribution rates of all factors were calculated following as:density control has the largest contribution rates on DBH, site control has the largest contribution rates on H, site control, species, fertiliser, spacing have not significant difference on volume; it shows that spacing is the most factor for sawn log production. (3) Rainfall was the most important factor among the climatic factors, it significantly affect the growth of DBH and H, but the effect was negative on DBH and positive on H.In silvicutural regime research, based on the 7-year tree species trial and thining trial at Guangdong Zhangmutou Forest Farm, the tree species priority had been ranked and thining effect researched, based on the trials of 16-year spacing at Guangxi Dongmen Forest Farm, the results showed that:(1) The minimum site index for eucalypt sawn log production at normal spacing is 26, it needs 16 years. (2) It reaches the target of sawn log production when the mean DBH is 18.4 cm. (3)The timber amount and quality was significantly affected by DBH, H, volume, first branch stem and trunk form, which were the suitable factors for tree species selection.(4)The 7 tree species priority ranked as E. urophylla clone>E.urograndis>E. cloeziana> Corymbia Torelliana>E. grandis>E. saligna>E. pellita. (5)DBH distribution narrowed from 4-7 to 3-4 one year after thining, DBH growth was significantly improved by thining, it increased 12.46% and 41.87% by thining 40%,37.5% and 52.33% by thining 60% at the first and second year after thining.(6)The time to meet the target of eucalypt sawn log is different:when initial spacing is 3m×5m,84 months for site index 26,24 and 22;when initial spacing is 3m×4m,108 months for site index 26;when initial spacing is 2m×4m, only site index 26 was available to meet the target and the time was 192 months.(7)Volume was significantly affected by initial spacing from 27-88 months, it was no significant from 99 months; High-density stand have the characteristics of early rapid growth on volume, but it is different to the late, starting from 144 months old, the volume is highest of 3m×4m; the smaller the initial spacing, site index higher, the volume ratio of sawn log is much higher, the amount of material is greater.(8)Only 3 initial spacing treatments reached the sawn log target, m5 (3m×5m) had the highest wood recovery, it was 75.51% at age of 192 months when site index is 26; m4 (3mx4m) had the highest wood amount, it was 291.43m3.hm"2 at age of 192 months when site index is 28; m3 (2m×4m) just reached the target for sawn log production, it was 41.44% at age of 192 months when site index is 26.In silvicutural regime research, based on the trials of fertiliser with 6 treatments each at Guangxi Dongmen Forest Farm, The results showed that:(1)Mean DBH, H, basal area, volume growth were significantly affected by 6 fertiliser treatments, but effect decreased by time. (2)Spacing m5 (3m×5m) with fertiliser 525 g/tree was good for the growth of DBH, it reaches the sawn log target at the age of 86 months; Spacing m4 (3m×4m) with fertiliser 540 g/tree was good for the growth of DBH, it reaches the sawn log target at the age of 107 months. (3)mean DBH. P was better then K for improving DBH growth, P was slightly better than K for improving H growth before 50 months, but K1 was better from 62 months and keep the superiority till last measurement of 192 months, P was better then K for improving volume growth from the beginning to the end. (4)Soil nutrient status and fertilization results show that: there were no relationship between the content of soil nutrient N,P,K and 6 fertiliser treatments; the more P applied and the higher content of soil P level, but it did not reach the significant level, soil K is between N and P.(5)The relationship between current soil nutrition status and plantation growth, the contents of N,P,K,Mg,Zn has significantly relationship with DBH growth at the age of 27 months; The contents of N,P,Zn has significantly relationship with H growth at the period of 27-144 months and K,Mg has significantly relationship with H growth at the period of 27-88 months; B has significantly relationship with H growth at the age of 88 months. N,P,Zn has significantly relationship with dominant H growth at the period of 27-192 months; K,Mg,B at the period of 27-50 months. Based on the pruning trial of Corymbia Torelliana at South China Experiment Nursery, the pruning effect on wood qualities were research. The results showed that:(1)The pruning wounds started to reduce on 3 month after pruning, it reduced significantly on 7 months; some of the wounds width had become to 0 on 9.5 months, especially the large wounds recovered from>25mm to 0-5.5mm; the small and large wounds recovered 84.71% 1 year later. (2)The occlusion and complete occlusion ratio of pruning treatments after 1 year later, middling wounds is 7cm and 6cm treatments; big wounds is 7cm and 5cm treatments; large wounds is 8cm and 6cm treatments.(3)The wound treatments with painting urushi more to promote healing than waxing.(4)The higher the wound position the quicker recovering. The fastest trunk of complete occlusion ratio is 2.5-4.0m for middling wounds; it is 2.5-5.35m for big wounds and large wounds.The trials of fertiliser affect on wood properties had been researched, the results showed that, the fertiliser amount of treatment 1 and 2 were 2 or 3 times more then treatment 5 as normal fertilser application, but the wood properties of bending strength, diametric hardness and basic density of sapwood were significantly decreased at the age of 198 months, but other wood properties such as hardness of other sides, elastic modulus, shrinking rate, drying shrinkage, basic density of heartwood were tested and no significant change found.