洞庭湖区不同土地利用方式下的土壤动物群落结构

Soil animal communities of variously utilized in the Dongting Lake region

2004年4月和7月,对洞庭湖区5种不同土地利用方式下土壤动物群落结构进行调查,以了解洞庭湖区湿地土壤动物多样性的基本情况,以及不同土地利用方式对土壤动物群落结构的影响。实验采得土壤样本270个,经分离后获土壤动物6282头,分属于5门、10纲、29类。通过对物种丰富度(S)、多样性指数(H)、均匀度指数(j)、相似度指数(q)和密度-类群指数(DG)几个多样性指标进行分析,结果表明农林间作的黑杨-苔草-菜地的物种丰富度、均匀度和密度-类群指数均显著高于其它生境,土壤动物多样性随土地利用方式和人为干扰程度的不同而存在很大差异。不同类型区的大、中、小型土壤动物的数量和组成有季节性变化,大型动物的类群组成在每个样地4、7月间均有很大差别,黑杨-苔草-菜地、黑杨-苔草地和稻田3个样地4月份蜱螨目数量均显著高于7月份;而弹尾目的数量仅在稻田4月份显著高于7月份,油菜-棉花+水稻地却是7月份显著高于4月份,其它样地无显著性差异;线虫数量仅在黑杨-苔草地和油菜-棉花+水稻地7月份的数量显著高于4月份。人类的农业生产活动导致土壤动物物种多样性降低,优势集中度提高,优势种突出,均匀性降低,形成了只利于少数几个种群栖息和生存的环境,土壤动物生物多样性受到影响,但适度干扰能提高土壤动物生物多样性。

The Dongting Lake region, which is an important region for agricultural production in the Yangtze Valley, is located in the north of Hu＇nan Province in China. In this subtropical region, the weather is warm and humid with a mean annual temperature of 16- 17℃ and rainfall of 1200 to 1550 mm. In order to protect biodiversity, the Hu＇nan Provincial Government carried out a project of restoring farmlands to the lake. There are two main kinds of ways to restore the farmlands： ① DRP （double restoration polder） which removed human habitation from the polder and gave up associated agricultural activity, and ② SRP （single restoration polder）, which only removed human habitation from the polder but retained agricultural activity. In the DRP, the polder is flooded annually during the flood season, but there is no flooding in the SRP. In April and July 2004, soil animals were investigated in five kinds of variously utilized land, and five typical plots were selected for investigation in the Dongting Lake region. They were the DRP （Populus. L-Carex spp. Plot Ⅰ ）, SRP （Populus. L- Carex spp. -vegetable,Plot Ⅱ ）, SRP （Brassica-Gossypiμm herbaceμm＋Oryza satire,Plot Ⅲ ）, paddy field （Oryza satire,Plot Ⅳ ） and the beach of the lake （Plot Ⅴ ）. Three replicates were taken from each plot to collect the mesofauna and the microfauna. Soil specimen were sliced horizontally into four 5 cm layers to a depth of 20 cm , and 2 samples （100 cm^3 and 25 cm^3） of each layer were each placed separately in a cotton bag and transported to the laboratory. The mesofauna and microfauna were separated from the samples using Tullgren＇s and Bearmann＇s methods, respectively. Three replicates were taken from each plot to collect the macrofauna. The soil specimens were sliced horizontally into two 5 cm layers to a depth of 10 cm and a sample （50cm× 50cm× 5cm） of each layer. The macrofauna was collected by hand and the mesofauna and the microfauna were collected through microscopic investigation. Twenty-nine groups of soil animals and belonging to 5 phyla and 10 classes were collected. Nematodes were the dominant animal group, accounting for 64.15% of the total. Acarina, Gastropoda, Araneae, Coleoptera, Oligochaeta, Collembola, Lepidoptera, Coleoptera, Hymenoptera and Diptera represented 31.02% of collected taxa. The other 18 animal groups were infrequent, representing 4.83% of the total individuals. Total soil animal numbers were statistically analyzed through use of diversity indexes （S, H, DG, j, and C）. The Population-density quantity （DG） was more suitable for evaluating soil animal biodiversity than was the biodiversity quantity （H）. Because of the complexity of the habitat and the temperate interference, soil animal abundance （24） and biodiversity （DG =15. 3009） were highest in the SRP （Populus. L-Carex spp. -vegetable,Plot Ⅱ ）. DRP （Populus. L-Carex spp. , ,Plot Ⅰ ） had the second highest values （S=22, DG=8. 8242）; paddy field （Oryza satire,Plot Ⅳ ） had the third highest values （S=21, DG = 8. 4070）, and the beach of the lake, （Plot Ⅴ ） （S = 15, DG = 2. 8729） and SRP （Brassica-Gossypiμm herbaceμm ＋ Oryza satire, Plot Ⅲ ） （S= 14, DG= 1. 8738） followed. We also analysed seasonal change of different kinds of soil animals in each plot. Macrofauna and meso- and micro-arthropods were affected significant by seasonal change, whereas nematodes were not. Biodiversity is one of the most important factors with which to evaluate quality of the ecological environment. Soil animal communities are strongly influenced by land utilization. SRP with intercropping is the best way to protect the biodiversity of soil animal. Restoring farmlands to the Dongting Lake area protects the biodiversity of soil animals.