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SummaryLong-term changes of soil nematode diversity and distribution patterns in replant peach orchard (RPO) and continuous-planting peach orchard (CPPO) were assessed to evaluate different effects on nematode community and function by RPO and CPPO, in relation to peach replant problem from the point of soil fauna. Observations were conducted on a silt loam soil, and soil sampling was performed four times through the growing season of peach trees in the period from 2006 to 2008 in Pinggu, Beijing. The result showed that RPO differed from CPPO by its higher abundance of plant feeding nematodes but lower abundance of bacterivore nematodes, as well as signifi cantly higher values of plant parasite index but lower nematode biodiversity. Obviously, the absolute abundance of Paratylenchus in RPO was higher than that in CPPO, which could be a key factor for the peach replant problems from the part of soil nematode. Nematode function indices and weighted nematode fauna profi le analysis were no signifi cantly different in the two peach ecosystems, but they represented an indication of high disturbance, N-enriched, bacterial decomposition pathway.

SummaryNematode communities in the soils of wheat (Triticum aestivum Linn.) rhizosphere grown alone and grown in jujube (Ziziphus jujuba Mill.) orchard were investigated for three years in Hetian arid area, Xingjiang Uygur Autonomous Region, northwest of China. The results showed that eu-dominant families were Rhabditidae, Cephalobidae and Aphelenchidae among 15 families and 19 genera. Nematode abundance in wheat rhizosphere soil was smaller in wheat/jujube intercropping system, mainly because of lower numbers of bacterial feeders and fungal feeders. Besides, the nematode numbers of cp-1 and cp-2 (cp, colonizer-persister) guilds were signifi cantly lower in wheat/jujube intercropping system than that in monoculture wheat system, due to the markedly lower numbers of Rhabditidae and Cephalobidae, although those of cp-3 and cp-4 guilds had no signifi cant differences between monoculture and intercropping systems. Shannon-Weaver index (H'), genus dominance index (Ig) and structural index (SI), represented soil food web diversity and structure, had no differences between monoculture and intercropping systems. Signifi cantly lower values of Wasilewska index (WI) and PPI/MI in monoculture wheat than in intercropping system. It was concluded that the soil status in monoculture wheat system exhibited better soil ecosystem in compared with wheat/ jujube intercropping system.