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    关于无性系林业若干问题的认识和建议——以杨树为例

    Cognition and suggestions on some issues related to clonal forestry:taking poplar as an example

    • 摘要: 随着林木育种和无性繁殖技术的进步以及森林工业的发展,无性系林业开始在世界人工林培育中发挥越来越重要的作用,并逐步进入无性系定向选育、定向栽培、定向利用的时代。该文针对我国无性系林业存在的问题提出了自己的认识和建议,并从无性系特性角度阐释了“三北”地区大规模发生的杨树“小老树”、严重病虫危害以及退化甚至死亡的原因。认为无性系林业不仅包括无性系选育和无性系造林,还应该涵盖无性系利用等内容。指出应充分利用无性系的基因型与环境互作效应,重视良种的适地适基因型栽培,为不同的生态环境条件选配适宜的主栽品种进行造林。同时加强重要树种无性繁殖技术标准的制定,以约束采取科学的无性繁殖技术和繁育制度进行良种生产,尽可能降低成熟效应与位置效应对无性系林业发展的影响。强调发展无性系林业要根据栽培环境条件和利用目标选择适宜品种,并突出良种和良法配合,重视林分数量成熟与工艺成熟最佳配合下的经济成熟,保证整个产业链条的综合效益最大化。尤其是提出了无性系人工林群体衰退的概念,即在同一无性系品种组成的人工林内,各植株的遗传组成和生活习性相同,随着林龄的增加,林分内各无性系对水分和营养的需求加大,当栽培环境不能满足林分生长需求时,如不能及时采取人工疏伐等措施进行密度调整,林分会因个体竞争能力相似而同时发生各无性系植株生长势衰退、病虫害加剧直至死亡等现象。建议国家应针对无性系人工林的特点,修订、完善相关的林业政策和法律法规,将杨树等无性系林业发展较好的用材或用材和生态兼用树种列入木本作物范畴,在无性系人工林达到经济成熟时及时通过间伐进行密度调控,或通过轮伐更新利用,避免在林分水肥等资源紧缺时,因个体竞争能力相似而引发无性系人工林群体衰退等问题,在有效发挥生态效益的同时,保证国家珍贵的宜林地资源的高效利用

       

      Abstract: With progress of tree breeding, vegetative propagation technique and forest industry, clonal forestry has already played a significant role in the world plantation cultivation, and gradually step into the orientational clonal selection, silviculture, and utilization era. In this paper, author's own cognition and suggestions on some issues related to clonal forestry were provided. Based on the characteristic clonal forestry, reasons for dwarf-old trees, serious forest diseases and insect pest damage, recession of plantation were also analyzed in the Three-North Region of China. Not only clonal breeding and clonal afforestation but also clonal utilization should be included in clonal forestry. When developing main cultivated varieties for different planting sites, genotype by environment interaction and matching planting sites with genotype should be fully considered. Moreover, ramet production of main cultivated varieties with high quality was formulated via scientific vegetative propagation techniques by reinforcing the formulation of vegetative propagation technique standard for important tree species. Therefore, there were some advantages in decreasing age and position effects in clonal forestry development. It was necessary to select suitable varieties for developing clonal forestry according to planting environment and aims of utilization. Combining good planting methods and varieties and economic maturity was also required to obtain maximum benefit from forestry industry. The concept of population recession of clonal plantation was brought about. Among the plantations, with age increasing, the ramets with the same genetic constitution need more water and nutrition. Negative competition would be observed among these ramets if forestland could not provide enough nutrition, resulting in uniformly weak growth potential, forest diseases and insect pest damage, unless pruning was conducted to decrease the spacing. Gradually, all the ramets in plantation will be dead. We suggested that related forestry policy and law should be revised according to the characteristics of clonal plantations. Tree species with timber or ecological function, such as poplar, could be considered as ligneous crop. Spacing control by pruning or reafforestation could be used to prevent population recession of clonal plantation owing to the shortage of fertilization and water after economic maturity of clonal plantation. In this condition, not only better ecological benefits could be obtained from clonal forestry, but also national valuable forestland resources were also effectively used.

       

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