不同林龄尾巨桉人工林生态系统生物量的研究

Ecosystem biomass in a chronosequence of Eucalptus urophylla×E.grandis plantation forests

对闽南山区不同林龄(2、3、4、5、6年生)尾巨桉人工林生态系统的生物量进行了研究,其中林木生物量采用标准木法,林下植被和地被物生物量采用样方收获法。结果表明:乔木层生物量随着林龄的增加而逐渐增加,分别为45.14、69.22、92.20、111.82、175.09t/hm2,其中树干占的比例最大(44.5%～60.4%),细根最小(0.2%～0.6%);各林龄尾巨桉生产力依次为22.86、26.07、32.63、32.70、46.69t/(hm2·a),叶的生产力随林龄增长呈现先增加后减少的趋势;林下植被生物量依次为5308.83、7201.62、5676.47、4033.42、9183.13kg/hm2,其中灌木生物量在3年生时最大,为2121.89kg/hm2,而草本生物量在6年生时最大,达到1062.19kg/hm2;不同年龄尾巨桉地被物现存量大小表现为6年生>3年生>5年生>2年生>4年生,2～5年生时未分解层现存量小于分解层,6年生时则是分解层现存量小于未分解层。

We investigated ecosystem biomass in a chronosequence of Eucalptus urophylla x E. grandis plantation forests （2-, 3-, 4-,5- and 6-year-old） in the mountain region of southern Fujian Province. The biomass of trees was determined by average tree sampling method, that of understory vegetation by harvesting grass and shrubs, and that of forest floor by collecting litter from subplots. The results showed that tree biomass was estimated to be 45. 14, 69.22, 92.20, 111.82 and 175.09 t/hm2, respectively, in the 2-, 3-, 4-, 5- and 6-year-old plantations, with stem wood making up the largest proportion （44.5% - 60.4% ） and fine roots the smallest （0.2% -0.65% ）. The net primary productivity was 22.86, 26.07, 32.63, 32.70 and 46.69 t/（hrn2 ~ year） in the 2-, 3-, 4-, 5- and 6-year-old stands, respectively, with leaf productivity increasing from 2- to 4-year-old stage but decreasing during the later growth phase. The understory biomass was 5 308.83, 7 201.62, 5 676.47, 4 033.42 and 9 183. 13 kg/ hm-＇ in the age sequences, among which shrub biomass reached the peak at the age of 3 （2 121.89 kg/ hm2） and grass biomass topped at the age of 6 （ 1 062. 19 kg/hm2）. The standing crop of the fi）rest floor decreased in the age order of 6 years 〉 3 years 〉 5 years 〉 2 years 〉 4 years, with the undeeomposed litter occupying greater proportion than the partially decomposed in the early ages （2- to 5-year-old）.