广州长岗山森林土壤线虫群落的功能结构特征

Functional structure of soil nematode community in Changgangshan Nature Reserve of Guangzhou,southern China

为进一步认识植被类型通过影响土壤生物进而影响整个土壤生态系统过程，对城市森林不同林分类型下的土壤线虫群落功能结构特征进行了研究。2010年1-12月，对广州市长岗山自然保护区4种典型林分（木荷、青皮、尾叶桉和粉单竹）的凋落物层、0～10cm和10～20cm土层的土壤线虫群落进行逐月调查，采用Baermann漏斗法分离线虫；土壤含水量采用烘干法进行测定；应用营养类群组成、c-p类群结构及营养结构特征指数等特征值分析城市林地土壤线虫群落功能结构及其特征。4种林分样地共分离得到32879头土壤线虫，隶属于2纲8目39科93属，土壤线虫的平均个体密度为669头／100g干土；土壤线虫空间分布的表聚性明显。不同林分类型的土壤线虫群落营养类群组成及分布特征存在一定差异，植物寄生性线虫和食真菌性线虫是调查区域的主要营养类群。c-p类群组成结构特征结果表明：土壤线虫cp2类群为优势类群，所有类群的生活策略以r-对策为主；cp1和cp2类群在木荷林与青皮林中个体密度较高，木荷林与青皮林的线虫食物资源在4种林分中相对丰富；竹林中cpl和cp2类群的个体密度最低，但cp3-cp5类群个体密度最高。竹林PPI值最高，其受扰动的影响程度大于其他林型；通过竹林土壤线虫的MI值、PPI／MI值及cp3-cp5类群个体密度值的分析结果表明，竹林的稳定性相比其他林型高。4种林型的F／B及NCR值无显著差异，土壤有机质分解均主要依靠真菌分解途径。

To understand the functional structure of soil nematode community in urban forests of southern China, soil nematodes in four representative forest types （ Schima superba, Eucalyptus urophylla, Bambusa chungii and Vatica astrotricha） located in Changgangshan Nature Reserve of Guangzhou, southern China were sampled monthly from January to December 2010. Soil nematode communities in litterfall, 0 -10 cm and 10 - 20 cm layers of the upper soil were investigated. The soil nematodes were collected using the Baermann＇ s methods. The soil water content was tested by oven drying method. The trophic composition, c-p group structure and functional structure index, as well as the characteristic values between trophic groups, were analyzed to understand the effect of different types of urban forest on the functional diversity of soil nematodes. The results showed that a total of 32 879 nematodes, which belonged to 2 classes, 8orders, 39 families and 93 genera, were collected during the investigations. The average individual density was 669 nematodes per 100 g dry soil. The results demonstrated that soil nematodes obviously appeared to aggregate in the upper soil layers. The composition and spatial distribution of tropic groups varied among different forest types. Herbivorous and fungivorous nematodes were the dominant communities in the area. An analysis of the constitution of the c-p groups showed that all cp2 groups were predominant ones in all forest types, and all c-p groups were mainly r-strategists. S. superba and V. astrotricha were the more common food sources for nematodes than others, and they had the higher nematode density of cpl and cp2 compared with elsewhere. B. chungii had the lowest nematode density of cpl and cp2, possibly because limited food availability limits the reproduction of cpl and cp2 nematodes. However, soil nematode density of cp3 - cp5 was the highest in B. chungii than other forest types. The analysis of the plant parasite index （PPI） indicated that the B. chungii community was easier for nematodes to populate when compared with the other three forest types, whereas the data from the maturity index （MI）, PPI/MI and cp3-cp5 demonstrated that nematode stability in the B. chungii was highest among four forest types. The fungal to bacterial feeder ratio （F/B） and nematode channel ratio （NCR） showed that fungal decomposition was the major decomposition pathway in the soil organic substance decomposition system.