西双版纳普文实验林场西南桦人工林的生长研究

对11~13年生西南桦纯林(初植密度包括2 m×2 m,2 m×3 m,2 m×4 m,2 m×5 m,2 m×6 m,3 m×3 m和2 m×3 m×7 m)、12年生西南桦与高阿丁枫(初植密度2 m×3m)和11年生西南桦(初植密度3 m×3 m)与山桂花(初植密度3 m×1.5 m)混交林的生长分析显示,西南桦造林后迅速进入速生期。7年生前尤为速生,速生期可延续至10年生林分,在速生期内,平均木的胸径、树高和木材年平均生长量分别为1.17~2.50 cm.yr-1、1.20~3.60 m.yr-1和0.000 11~0.018 04 m3.yr-1,其连年生长量分别为0.50~2.65 cm.yr-1、0.5~4.0 m.yr-1和0.000 11~0.018 68 m3.yr-1。西南桦纯林中,2 m×5 m和2 m×4 m的初植密度较为有利于林木生长和木材生产,其13年生林分生长量分别达:(1)年平均胸径1.42 cm.yr-1和1.72 cm.yr-1,年平均树高1.77 m.yr-1和1.72 m.yr-1;(2)单位面积材积为209.807 1 m3.hm-2和208.933 8 m3.hm-2,并且胸径>16 cm的林木分别占80.00%和60.00%。混交林的木材产量:(1)12年生西南桦与高阿丁枫混交林单位面积木材产量是同林龄西南桦纯林(初植密度2 m×3 m×7 m)的1.845倍(172.363 7 m3.hm-2比94.978 9 m3.hm-2);(2)11年生西南桦与山桂花混交林单位面积木材产量是同林龄西南桦纯林的2.774倍(158.742 0m3.hm-2比57.219 0 m3.hm-2)。在西南桦与高阿丁枫混交林中,1行西南桦与2行高阿丁枫混交模式能提高西南桦高生长和木材产量。高阿丁枫和山桂花是可以同西南桦相匹配营造混交林的两个云南热带乡土树种。

Growth and Timber Yield of Betula Alnoides within Juvenile Plantations in Puwen Tropical Forestry Experimental Farm,Xishuangbanna, Yunnan, China

The attention was focused on the growth and timber yield of 11 to 13 years old pure Betula alnoides plantations(including 2 m×2 m,2 m×3 m,2 m×4 m,2 m×5 m,2 m×6 m,3 m×3 m,2 m×3 m×7 m initial spacing), 12 years old mixed B.alnoides ×Altingia excelsa (2 m×3 m initial spacing), and 11 years old mixed B.alnoides (3 m×3 m initial spacing)×Paramichelia baillonii(3 m×1.5 m initial spacing) stand in this study.After transplanting seedlings, the B.alnoides began the fastest growing phase, which prolonged to 10th year, especially before the seventh year.In this stage, mean tree MAI ranges of DBH, height, and volume were 1.17～2.50 cm·yr-1, 1.20～3.60 m·yr-1, and 0.000 11～0.018 04 m3·yr-1, while the CAI of which were 0.50～2.65 cm·yr-1, 0.5～4.0 m·yr-1, and 0.000 11～0.018 68 m3·yr-1, respectively.In pure B.alnoides plantations, the 2 m×5 m and 2 m×4 m was optimal initial spacing for growth (1.42, 1.29 cm·yr-1 and 1.77, 1.72 m·yr-1 of stand DBH and height MAI), timber yield (209.807 1 and 208.933 8 m3·hm-2), and big diameter lumber (80.00 and 60.00 % of number of DBH>16 cm) in 13 years old stands.Mixed plantations increased timber yield in unit area, of which mixed B.alnoides×A.excelsa was 1.845 times of pure B.alnoides (2 m×3 m×7 m initial spacing) in 12 years old stands (172.363 7 vs.94.978 9 m3·hm-2), and mixed B.alnoides×P.baillonii was 2.774 times of pure B.alnoides in 11 years old plantations (158.742 0 vs.57.219 0 m3·hm-2).In mixed B.alnoides×A.excelsa stand,1-row B.a×2-row A.e mixing arrangement promoted B.alnoides height growth and increased timber yield.A.excelsa and P.baillonii are two native species which are compatible to establish mixed plantations with B.alnoides in Yunnan tropical area.