滇西地区西南桦无性系早期测定与生长节律研究

目的]开展西南桦无性系早期生长变异及生长节律研究,揭示其生长规律及适应性,为西南桦无性系选育及速生丰产林营建提供参考。方法]以滇西地区20个无性系参试的3年生西南桦无性系测定林为研究对象,每月定期测定其树高、胸径,探讨各无性系的生长变异,应用聚类分析划分生长类型,运用有序聚类分析进一步揭示各类型无性系的生长节律特征,通过相关性分析探明影响生长节律的主要气象因子。结果]20个西南桦无性系间树高和胸径差异极显著(P0.01),根据生长表现,可将其划分为速生、中等和慢生3种类型,其中,B3、A10、Q3、Q4、Q2无性系属于速生型,其树高、胸径年均生长量大多超过2 m和2 cm;与中等和慢生型无性系相比,速生型无性系的生长优势并非完全表现在速生期,其在缓生期和滞生期的生长优势更大;各类型西南桦无性系的生长节律基本一致,其树高生长高峰在7—9月,低谷为4月和12月;其胸径生长高峰为5、10月,8月和12月为低谷,尤以8月生长最慢,这与该月的日照时数低有关。结论]在滇西地区,B3、A10、Q3、Q4、Q2等5个无性系生长最迅速,颇具发展潜力。从经营措施看,宜在树高、胸径生长高峰之前,即5月和9月加强幼林抚育施肥,促进林木生长。

Early Selection of Betula alnoides Clones and Their Growth Rhythm in Western Yunnan, China

Objective] To Study the early growth variation and rhythm of Betula alnoides clones so as to further understand their growth properties and adaptability, and provide scientific evidences for clone selection and establishment of fast-growing and high-yielding B. alnoides plantations. Method] The height and diameter at breast height (DBH) were investigated monthly in a three-year-old clone test plantation with 20 clones involved in western Yunnan, and the growth variance among clones was assessed. These clones were then divided into several types using clustering analysis, the growth rhythm was further demonstrated for each type of clones by sequence clustering analysis. The main meteorological factors influencing growth rhythm were discussed by correlation analysis. Result] Significant differences were observed in height and DBH among the 20 clones (P<0.01), these clones could be divided into three types as fast-, moderate-and slow-growing clones. Clones B3, A10, Q3, Q4 and Q2 belong to the fast-growing type, with the height and DBH increment over 2 m and 2 cm per year, respectively. These 5 clones showed their growth advantages not only in fast growing stage, and but also better performed in slow-growing stages. They kept higher growth speed longer than the clones of moderate-and slow-growthing types. The growth rhythm was almost the same for all the three types of clone. The peak of height growth occurred from July to September, and the nadirs occurred in April and December. For DBH growth, there were two peaks in May and October, and two nadirs in August and December, respectively, while the DBH grew the slowest in August due to the least sunshine hours in this month. Conclusion] Clones B3, A10, Q3, Q4 and Q2 grow fast in western Yunnan, and are of high potential for plantation. It is also recommended that management measures such as tending and fertilization should be taken before the peak of height and DBH growth, for example, May and September, so as to facilitate the tree growth.