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瑞典能源林建设的目的之一是选择能在短轮伐期内生产最多干物质的落叶树种速生无性系。已在瑞典各种天然林和人工林里初选了许多无性系。1978年把柳树当年枝条生长量超过2.5米的190个无性系选入良种收集圃,并都列入速生柳树测验计划,以期选出更适于大面积栽培的优良无性系。 要评价用作能源林及制浆造纸等工业用材的性能,把木材容重作为一项指标来考虑选择高产的无性系是很重要的。一般认为容重主要受遗传因素所控制,并具无性系间的变异,这表明对柳树的材质进行选择,正象对杨树一样,具有很大的可能性。 从1978年收集的柳树无性系中选择了20个生长最快的无性系进行专门的研究,目的是确定一些重要性状,如木材容重、含水量和树皮率等的稳定性和变异性。
One of the goals of Sweden’s energy forest construction is to select fast-growing deciduous tree species that produce the most dry matter in short rotations. Many clones have been primaries in various natural forests and plantations in Sweden. In 1978, 190 clones of elm trees that had more than 2.5 meters of branch growth were planted in the elite collection and were all included in the fast-growing willow tree test program to select elite clones more suitable for large-scale cultivation. It is important to consider the use of wood bulk density as an indicator to consider the selection of high-yielding clones in order to evaluate the performance of wood for energy forest and pulp and paper industry. It is generally accepted that bulk density is dominated by genetic factors and has clonal variation, indicating that the choice of willow material is just as probable as for poplar, with great potential. Twenty of the fastest growing clones were selected from the willow clones collected in 1978 for specialized studies aimed at identifying important traits such as the stability and variability of wood bulk density, water content and bark rates.