| Slash pine is one of the forestation tree species in South China which is a fast growing timber and a short rotation industrial raw material. As the major tapping tree species, favored by forestry farmers.Slash pine artificial resin tapping mainly started at 10A after birth. The study of early using is still blank. How to carry out the early using of Slash pine, so that obtain and improve economic benefit is very important. Through the evaluation of the early growth observation, thinning tending, four different tapping age performance, resin yield and economic benefit to the Slash pine plantation of Huashan forest farm in Huanjiang Maonan Autonomous, investigated the feasibility of Slash pine’s early resin tapping. The results showed that:(1)The growth peak of DBH appeared in the third year, mean annual growth was 2.31cm. First six years was the rapid growth period, the growth rate was more than 10.6%. The 7-9 years was the rapid decline period of DBH growth. At the tenth year, DBH growth tends to grow slowly, the annual growth in only 0.36cm. Average DBH of 10 year old slash pine was 13.4cm. The first seven years of the tree height was rapid growth period.The overall annual growth volume decreased slightly with the increase of age, mean value was 0.67m. Tree height growth rate has rebound in the tenth year. The total amount of individual volume growth increased with aging. Successive growth have annual differences, in the range of 0.0074-0.0094m3/a. The average growth was rapid before six years, and the growth rate decreased rapidly with the increase of age. The growth rate reached the lowest value at 9th year, but until ten years the growth rate was greater than 10%, still in the fast-growing period. Forest stock volume in first ten years had a trend of rapid growth. At tenth year can up to 165.17m3/hm2. The preservation rate of stand began to decline from eighth year. Stand natural thinning gradually appeared and started to strengthen. Appropriate thinning time was in sixth to seventh year.(2) The thinning intensity of 5-25% to forest stand at sixth year can promote the height, DBH and volume. When the thinning intensity was more than 20%, the effect was more obvious and can sustain 3-4 years, Thinning can cause short term reduction of stand volume. But after the four years’ growth, the stand volume start to be consistent. In the natural growth situation, the stand volume at ninth year can reach 152.85m3/hm2. The stand volume of the different thinning treatments at tenth year tend to be 150m3/hm2. Starting resin tapping at sixth year in the 25% thinning intensity, can obtain the maximum stand volume at tenth year. Considering the effect of stand growth and gaining more stand volume, initial planting density of 2924 trees/hm2 was more suitable to 25% intensity of thinning at seventh year.(3) Tapping on the young Slash pine forest has little effect to height growth, but has a great influence on the DBH, individual volume, forest preservation and stand volume. The difference of stand total height growth of resin tapping and no resin tapping did not reach significant level. Each annual height growth of fifth, sixth, seventh and eighth year resin tapping and no resin tapping was 2.03m,1.98m; 2.11m,2.14m; 2.05m,1.90m;1.34m,1.34m, which means tapping has little influence to the young Slash pine forest. Influence of resin tapping to the DBH growth was decreased with increasing of initial resin tapping age. Resin tapping at fifth year stimulates the late growth, other ages’levels have inhibitory effect. The resin tapping effects to individual stand volume growth was similar to the resin tapping effects to DBH, Resin tapping has inhibitory effect to stand volume growth of six year old Slash pine forest, seventh year resin tapping showed most inhibitory effect. In the forest preservation rate and stand volume,the seventh and eighth year resin tapping was more easily cause the plants die than the fifth and sixth year resin tapping. Slash pine’resin tapping was more suitable at the fast growth stage not at the slow growth stage. Influence of resin tapping on stand volume of the young Slash pine forest was mainly on the inhibition of stand growth and plants dying. Among them, inhibition of stand growth through out the whole resin tapping process. And the plants dying gradually increased with the resin tapping process. Resin tapping and no resin tapping stand volume differences aggravated gradually with the resin tapping process. Effect of resin tapping on the stand volume was related to the initial tapping age, resin tapping at the slow growth stage can be more easily lead to decline of stand volume growth.(4) The individual resin yield has downward trend with the increasing of resin tapping ages. At the first two years, resin yield remained at the same level. The differentiation of resin yield appeared at the third year. After six years, the differentiation becomes small. Slash pine individual resin yield increased with the increase of the DBH. Except the second year’s resin yield was higher than the first year’s, the overall resin yield declined with the tapping ages. Resin yield on the same level of DBH decreased with the increase of initial resin tapping age, and with the increasing of the DBH the decreasing range becomes small. Correlation between the individual resin yield and plant dominance in the stand was positive. In the same resin tapping age, with the increasing of resin tapping ages, DBH larger, the plant survival rate was higher; DBH smaller, the plant mortality caused by resin tapping was more serious. The weak plants can be easily dead in the resin tapping process, while the dominant tree’s mortality rate was low. For the point of resin yield of unit area, the young Slash pine forest can be started resin tapping at fifth year, also can obtain high yield. For the point of stable yield, sixth year can be the suitable resin tapping time.(5) Developing early resin tapping of Slash pine can recover the investment, shorten the production cycle and get early profit. Starting resin tapping at fifth year for five years and lumbering at tenth year, can get 32338.49yuan/hm2 of net present value. The internal rate of return was 39.5%, much higher than the 12% which was issued by the Ministry of construction and State planning commission at 1994. The net present value of no resin tapping forest was negative, the internal rate of return was 7.8%, less than 12%. It means in the same conditions and the same management level, developing resin tapping at early age, can timely recover the investment, shorten the production cycle, and has good economic benefit. |
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