Abstract: This study aimed to explore the effects of cultivation years on the community structure of nematodes in agricultural soils of watermelon/melon. Soils from cropland planted with watermelon/melon for different cultivation years were collected in the main watermelon/melon production area of Jiangsu Province. We examined the populations, community structure and ecological index of soil nematodes. Results showed that 54 genera of soil nematodes were recorded, with an average abundance of 682 per 100 g dry soil. The dominant genera were Protorhabditis,Acrobeloides, andTylenchorhynchus. While nematode populations did not change with increasing cultivation years, the abundance of bacterivores and omnivorespredators significantly decreased and that of plant-parasites increased significantly. The populations of Tylenchorhynchus and Meloidogyne gradually increased. With increases of cultivation years, Shannon index (H), Wasilewska index (WI) and freeliving nematode maturity index (MI) decreased significantly, while the nematode channel ratio (NCR), plant parasitic index (PPI) and PPI/MI increased significantly. Results of correlation analysis showed that nematode populations were positively correlated with soil pH, available phosphorus, available zinc and available boron. The dominant genera of soil nematodes were largely affected by soil pH, organic matter, total nitrogen, available potassium, available boron and available zinc. The comprehensive analysis suggested that continuous planting of watermelon/melon can increase the abundance of plant-parasites in the soil, which may result in continuous cropping obstacle. Soils continuously planted with watermelon/melon for 6-10 years had a lowest diversity and a worst stability of nematodes, leading to soil deterioration.

Key words: truncation, Dendrocalamus latiflorus, living culm, biomass allocation.