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

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, 8 orders, 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 cp1 and cp2 compared with elsewhere. B. chungii had the lowest nematode density of cp1 and cp2,possibly because limited food availability limits the reproduction of cp1 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.