[Soil nematode community structure in the rhizosphere of Lycium barbarum.]

Lycium barbarum (Solanaceae) is an important Chinese herbal medicine and tonic species, having great contribution to local economic growth in Ningxia. It is important to study the rhizosphere nematode community structure at different conditions to prevent soil degradation of L. barbarum. The objective of this study was to determine the effect of seasonal changes, planting age and soil layers on soil nematodes community structure. The research was based on Zhongning County, where L. barbarum originated. The results showed that the abundance of soil nematode in summer was the highest and Rhabditidae and Acrobeloides were the dominant genera; the abundance of nematode in spring was significantly less than that in summer and in autumn; Rhabditidae, Pararotylenchus and Rotylenchus were the dominant genera in spring. The type and quantity of rare genera decreased gradually from spring to autumn. The abundance of nematode was increased then decreased in spring and autumn. The abundance of nematode gradually decreased with the planting age in summer. The proportion of bacterivores was the highest, and fungivorous nematodes and predators-omnivores had the lowest abundance. Plant parasites nematode was relatively higher at young and over 9-year stages. The abundance of nematode in 20-40 cm soil layer was 49.4% higher than that in 0-20 cm soil layer in summer. With the increase of planting age, Shannon diversity index (H), evenness index and richness index of nematode were in a decreased-increased-decreased pattern of change, and dominance index decreased then increased. There was significant positive correlation between soil pH and dominance index in summer. Organic matter was significantly positively correlated while available P was negatively correlated with plant parasites nematodes. Alkali-hydrolyzable N was significantly positively correlated with abundance of nematode, while available K and many nematode indexes were significantly negatively correlated. On the whole, the abundance of nematode had an increased-decreased tendency with the increasing of planting age in spring and autumn, while the abundance of nematode decreased in summer and diversity of nematode community decreased, gradually. In addition, the reproduction of plant parasites nematodes should be inhibited at young and over 9-years to ensure the L. barbarum live through the following periods.