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造林密度对水曲柳人工林地上生长和细根生物量的影响

谷加存*,肖立娟,马振东,夏秀雪,高国强   

  1. (东北林业大学林学院, 哈尔滨 150040)
  • 出版日期:2017-11-10 发布日期:2017-11-10

Effect of planting density on the aboveground growth and fine root biomass in Fraxinus mandschurica Rupr. plantation.

GU Jia-cun*, XIAO Li-juan, MA Zhen-dong, XIA Xiu-xue, GAO Guo-qiang   

  1. (School of Forestry, Northeast Forestry University, Harbin 150040, China).
  • Online:2017-11-10 Published:2017-11-10

摘要: 密度对林木个体生长和林分蓄积量增长均有重要的影响,但是林分密度与树木根系之间的相互作用并不明确。为此,本研究以黑龙江省帽儿山4种造林密度(处理Ⅰ:株行距:1.0 m×1.0 m,Ⅱ:1.5 m×1.5 m,Ⅲ:2.0 m×2.0 m和Ⅳ:1.5 m×3.0 m)水曲柳(Fraxinus mandschurica Rupr.)人工林为研究对象,在2012—2016年连续测定了林木的胸径和叶生产量(2013、2014和2016年)以及每年的林木枯死状况,并在2013年采用根钻法和内生长法分别对细根(直径≤2.0 mm)和吸收根(直径≤0.5 mm)的现存量和生产量进行了估计。结果表明:密度最低的处理IV中树木分杈率最高(31.55%),平均树高最低;密度次低的处理III中,胸径和树高均高于其他处理。叶生产量随着林龄增加而增大,以处理II中最高。总的林木自然枯死率以密度处理I最高。样地水平上,近5年林木株数保存率与叶生产量、胸径年生长量均为负相关(前者统计上显著)。细根和吸收根的现存量与生产量均以处理IV最高,处理I~IV中吸收根现存量分别为(184.62±17.73)、(146.45±5.59)、(150.32±5.39)和(242.81±19.07) g·m-2。样地水平上,吸收根现存量和生产量均与林分密度负相关(后者统计上显著)。吸收根与叶生产量和胸径年生长量的比值以处理IV中最高,而其他处理间差异则相对较小。综合来看,造林密度2500株·hm-2林分具有最大的平均胸径和树高,最高的株数保存率,以及较为合理的吸收根和叶生产量比例,是本地区最适宜的密度。

关键词: 可加性模型, 刀切法, 生物量, 异速生长方程, 椴树

Abstract: Stand density has an important influence on the growth of individual trees and the accumulation of stand volume; however, the relationship between stand density and tree’s fine roots is still not well understood. We conducted an experiment in Fraxinus mandschurica Rupr. plantations with four planting densities (Treatment I: 1.0 m×1.0 m, II: 1.5 m×1.5 m, III: 2.0 m×2.0 m, and IV: 1.5 m×3.0 m) in Maoershan, Heilongjiang, China, and measured the diameter at breast height (DBH), selfthinning proportion from 2012 to 2016, leaf biomass production in 2013, 2014 and 2016, and used soil core and ingrowth core methods to estimate the standing biomass and biomass production of fine roots (diameter ≤2.0 mm ) and absorptive roots (diameter ≤0.5 mm). Results showed that the Treatment I had the highest branching intensity (31.55%) and the lowest tree height, while Treatment III had the largest mean DBH and tree height. Leaf biomass production increased with increasing stand age across all treatments, with the maximum occurring in Treatment II. Treatment I had the highest total selfthinning proportion. During the study period, the survivorship of living trees at the plot level was negatively correlated with annual leaf biomass production and increment of DBH (the former was statistically significant). Both fine roots and absorptive roots showed the largest standing biomass and production in Treatment IV, in which standing biomasses of absorptive roots were (184.62±17.73), (146.45±5.59), (150.32±5.39) and (242.81±19.07) g·m-2 in Treatment I to IV, respectively. At the plot level, both standing biomass and production of absorptive roots were negatively correlated with stand density (the latter was statistically significant). Ratios of annual production of absorptive roots to leaf production and to annual increment of DBH were the highest in Treatment IV, but were similar among the other three treatments. In summary, the initial planting density of 2500 ind·hm-2 was the optimal choice as manifested by the largest mean DBH and tree height, higher survivorship of living trees as well as the balanced biomass allocation between absorptive roots and leaves.

Key words: Tilia Linn., allometric equation, Jackknifing technique, biomass, additive system