美国东南部5年生桉树能源林生长规律及耐寒性分析

Growth and Cold Tolerance of Five- year- old Eucalyptus benthamii Plantation for Bioenergy in the Southeastern United States

为应对美国南部生物新能源市场的兴起,评估边沁桉(Eucalyptus benthamii)供应市场的能力,对边沁桉人工林生长参数及其抗寒性能进行了试验研究。试验种植了两种不同密度(1 650棵/hm2和1237棵/hm2)的桉树林并连续5 a进行观测分析。结果表明:幼年期的边沁桉个体生长具有显著差异性。5年生桉树最大胸径和最小胸径分别为27.9 cm和1.27cm;最大高度和最小高度分别为22.86 m和2.44 m;桉树胸径和树高的年增长也具有显著差异性。两种不同密度年存活率也存在差异性,同时影响着树高和胸径的生长。密度为1 650棵/hm2人工林平均胸径和树高分别为11.18 cm和15.03 m。密度为1 237棵/hm^2平均胸径和树高分别为13.46 cm和16.28 m。密度为1 650棵/hm^2和1 237棵hm^2平均每公倾公顷材积分别为111.45 m3和101.15 m^3;平均每年的直径和树高生长分别为2.54 cm和3 m。边沁桉人工林的生长随着生长环境的不同也呈现差异。本次试验人工林中的第1行和第7行就是一个很好的例证。边沁桉的生长受年平均气温的影响不大,但受最低温的限制,一般认为边沁桉能耐受的温度为-7.4℃。

The growth parameters and cold tolerance Eucalyptus benthamii plantation were tested in order to evaluate the market supply ability for the emerging bioenergy markets that are developing in the southern U. S. The Eucalyptus benthamii were planted in two different densities and the stands were measured annually through five growing seasons. The results indicated that the growth difference among the young E. benthamii was noticeable. For example,the maximum and minimum diameters at breast height（ DBH） of five- year old trees were 27. 9 cm and 1. 27 cm,respectively; and the maximum and minimum tree height were 22. 86 m and 2. 44 m,respectively. The yearly change in DBH and height of E. benthamii had significant differences. The average annual survival rates of E. benthamii had differences under the two planting densities（ 1 650 trees hm^2 and 1 237 trees hm^2）. The densities also had effects on the height and DBH growth of E. benthamii. The average DBH and height with planting density of 1 650 trees hm^2were11. 18 cm and 15. 03 m,and the average DBH and height with planting density of 1 237 trees hm^2 were 13. 46 cm and 16. 28 m. The volume per hectare for the density of 1 650 trees / hm^2 and 1 237 trees hm^2 plantations were 111. 45 cm^3 and 101. 15 cm^3,respectively.Average diameter growth was almost 2. 54 cm per year and average height growth was over 3 m. The growth of E. benthamii also varied depending on the surrounding conditions. The growth difference in row seven versus row one was a good example. The growth of E.benthamii plantation was lightly affected by temperatures, but was restricted by the lowest temperature. It is believed that E.benthamii plantations can afford the temperature as low as- 7. 4℃.