轮伐期前后不同密度巨桉(Eucalyptus grandis)人工林土壤动物群落结构特征

在前期巨桉(E.grandis)人工林土壤生物多样性在轮伐期前(4年左右)降低,此后随林龄显著升高的研究基础上,在四川省丹棱县选择轮伐期前即4年和轮伐期后即8年的不同密度(D1:2000, D2:1600, D3:1200株/hm~2)巨桉人工林,研究了其土壤动物群落结构特征。结果显示:1)共捕获土壤动物2904只,隶属于4门8纲22目70科,其中大型土壤动物541只,以蚁科和康叭科为优势类群;中小型土壤动物2363只,以大翼甲螨科、等节虫兆科和线虫为优势类群。2)土壤动物类群数、个体数和密度随林分密度和林龄具有显著差异,4年生林地大型土壤动物个体数随密度降低显著增加,8年生巨桉人工林中小型土壤动物个体数及类群数随密度降低均显著增加;土壤动物个体数及类群数除D1密度时4年高于8年,其余密度均表现为8年高于4年。3)林分密度对土壤动物多样性指数有显著影响,4年生林地大型土壤动物Margalef丰富度指数随密度降低显著增加,8年巨桉人工林中小型土壤动物Shannon-wiener指数及Margalef丰富度指数随密度降低显著升高。4)巨桉人工林大型土壤动物以杂食性为主,枯食性次之,中小型土壤动物以腐食性为主,杂食性次之。5)RDA分析显示,林分密度、土壤含水量和土壤pH为对土壤动物的主要作用环境因子,4年时对奥甲螨科、长角长虫兆科、寄螨科、隐翅甲科、丽甲螨科等类群影响较大;8年时对线虫、蜚蠊科、康叭科、厉螨科、棘虫兆科等类群影响较大。为此,延长轮伐期、降低林分密度可改善巨桉人工林土壤动物生境、增加土壤动物多样性、促进土壤动物群落结构稳定性。

Characteristics of soil faunal community structure before and after the rotation period of Eucalyptus grandis plantations with various densities

Our previous studies found that biodiversity in soil of Eucalyptus grandis plantations gradually decreased at the initial four years after afforestation, but then significantly increased. Therefore, in this study, we studied the community structure of soil fauna at the stand age of four and at the age of eight, which is usually considered to be a regular rotation period for E. grandis. Three densities (D1:2000, D2:1600, D3:1200 ind/hm²) were selected to compare community structure of soil fauna among above age groups. Picking up, Tullgren funnel and Baermann methods were used to collect the macro, meso and micro soil fauna in Danling County, Sichuan Province. The results showed that:1) in total, 2904 individuals of soil fauna were collected, which belonged to 4 phyla, 8 classes, 22 orders, and 70 families. There were 541 macro individuals dominated by Formicidae and Campodeidae, and 2636 individuals of meso-micro fauna dominated by Galumnidae, Isotomidae and Nemata. 2) There were differences in group numbers, individual numbers, and densities of soil fauna between forest ages and stand densities. The individual numbers of soil macro fauna in 4-year old E. grandis plantation increased significantly with the decrease of density. Both group and individual numbers of meso-micro fauna in 8-year old E. grandis plantation increased significantly with the decrease of density. Both group and individual numbers of soil fauna in D1 density were higher in 4-year old stand than those in 8-year old stand. The remaining density was the opposite. 3) The soil fauna diversity indexes were significantly affected by forest density. The Margalef richness index of soil macro fauna in 4-year old E. grandis plantation increased significantly as forest density decreased. While the shannon-wiener index and Margalef richness index of soil meso-micro fauna in 8-year old E. grandis plantation increased significantly with the decrease of density. 4) The soil macro fauna in the E. grandis plantation were mainly omnivores, followed by debris-feeder''s. The soil meso-micro fauna were mainly saprozoic, followed by omnivores. 5) RDA analysis indicated that the soil fanual communities were mainly affected by following environmental factors:forest density, soil moisture content, soil pH, and total nitrogen content. Soil fauna belonged to Oppiidae, Orchesellidae, Parasitidae, Staphylinidae, and Liacaridae were greatly affected by above factors at 4-year old of E. grandis plantation, while those belonged to Nemata, Blattidae, Campodeidae, Lacclapidae, and Onychiuridae were greatly affected by above factors at 8-year old of E. grandis plantation. Therefore, prolonging rotation period and reducing the forest density appropriately is necessary to improve the stability, increase biodiversity of soil fauna, and thus promote the stability of community structure of soil fauna in E. grandis plantation.