巨桉人工林土壤动物群落结构特征

为深入了解巨桉人工林生物养分循环及土壤肥力变迁，客观全面地评价巨桉人工林的生态效益，对比研究了四川省洪雅县巨桉人工林和青冈次生林土壤动物群落结构特征。研究方法，大型土壤动物采用野外分层手捡计数，中小型土壤动物用取土器分层取土，带回室内分别用干湿漏斗分离并镜检。结果表明：（1）洪雅巨桉人工林共获1312头土壤动物，分属6门10纲21目，其优势类群分别为蜱螨目、弹尾目、线虫纲、膜翅目；（2）巨桉人工林土壤动物群落的类群数和个体数均低于青冈次生林．其Shannon—Wiener指数和密度一类群指数分别为1．818和4．002，低于青冈次生林的1．963和8．091；（3）巨桉人工林土壤动物群落中腐食性同功能种团比例为81．78％高于青冈次生林的64．18％；（4）巨桉人工林与青冈次生林土壤动物密度剖面分布具明显表聚性，二者经F-检验无显著差异；（5）巨桉人工林与青冈次生林土壤动物群落有比较高的Jaccard相似性系数和Gower，系数，表明两类林分在土壤动物类群和个体数量分布上有比较大的相似度。

The characteristics of soil animal community structure in Eucalyptus grandis plantation

Recently, much attention has been given to soil animal because they play an important role in nutrient cycling as well as a potential bioindicator of soil fertility in the forest ecosystem. However, there is lack of the information on soil animal under the eucalypt (Eucalyptus grandis) plantation in Hongya County, Sichuan, which is difficult to meet needs of man-made forest management. The groups and the densities of soil animal communities in the eucalypt plantation and oak (Quercus acutissima) secondary forest were investigated here to understand the nutrient cycling, provide the information on changes in soil fertility, and evaluate the ecological effects of conversion of secondary forest to eucalypt plantation. Soil macrofauna were picked up by hand in the fields. Nematodes and mesofauna were separated and collected from the soil samples by Baermann and Tullgren methods, respectively.By preliminary identification, there were 1311 specimens of soil animals, which belonged to 6 phyla, 10 classes and 20 orders in the eucalypt plantation. Acarina, Collembola, Nematoda and Hymenoptera were the dominant groups in the eucalypt plantation. Although Acarina, Nematoda and Hymenoptera were the dominant groups in the oak forest, there was lack of Collembola. The results here indicated that soil animal community structure has changed with plant species composition when oak secondary forest was converted to eucalypt plantation.The groups and individual number were lower in eucalypt plantation than in oak secondary forest. Moreover, the Shannon-Wiener index and DG (Density-groups) index of soil animals in the eucalypt plantation were 1.818 and 4.002, which were also lower than those of oak secondary forest. It implies that soil biodiversity might decline when oak secondary forest was converted to eucalypt plantation.The percentage of saprozoic animal, which was used as a potential bioindicator of soil fertility, was 81.78% in the eucalypt plantation, and was higher than that in oak secondary forest (65.00%), resulting from higher organic material returns via litterfall in the former in comparison with the latter.The groups and individual numbers decreased with the increase of soil depth in two forest ecosystems. However, there was no significant difference in soil animal density between eucalypt plantation and oak secondary forest.There were higher Jaccard and Gower coefficients between the two studied forests, implying that the group composition of soil animal community was similar to a certain extent in the two forest ecosystems. The results indicated that soil animal community structure had not changed significantly although the soil biodiversity declined slightly when oak secondary forest was converted to eucalypt plantation. To deeply understand the ecological processes in the eucalypt plantation, soil ecological processes related to soil animal need to be performed in the future.