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在美国路易斯安纳州中、北部,按火炬松苗木的不同等级造了一片试验林,以测定其保存率、生长量和材积的区别。通过13年的观察,发现用Ⅰ级苗造的林每年每公顷平均可生产30立方米木材,比用Ⅱ级苗造林的林分高17.59%,是值得提倡的方法。一、试验内容和方法本试验采用6个天然火炬松种源,其中2个种源在一般林分中采集,4个种源从种子林中获得。1966年在路易斯安纳州霍奇大陆森林工业苗圃分别进行播种,1967年2月起苗,并按1954年Wakeley的标准进行苗木
In the northern and central Louisiana, USA, a pilot plantation was made at various grades of loblolly pine seedlings to determine the difference in their conservation, growth and volume. After 13 years of observation, it is found that the average annual production of timber of Grade I seedlings can produce 30 cubic meters of timber per hectare per year, which is 17.59% higher than that of the grade II seedling afforestation, which is an advocated method. First, the test content and methods In this experiment, six natural sources of Pinus densiflora were used, of which two were collected in the general stand, and four provenances were obtained from the seed forest. Seeds were planted separately in 1965 in the Forest Industrial Nursery in Hodge Ridge, Louisiana, starting in February 1967 and nursery stock according to Wakeley, 1954