Characteristics of Soil Nematode Community Structure in Tobacco Fields with Different Continuous Cropping Years

To clarify the relationship between tobacco continuous cropping duration and soil nematode community characteristics, 35 tobacco fields were sampled in the western Hubei tobacco-growing region, which were categorized into five continuous cropping duration groups: 2 years, 5-10 years, 11-20 years, 21-30 years, and >30 years. High-throughput sequencing was employed to investigate the effects of different continuous cropping durations on soil nematode community structure and trophic groups. The results showed that the increase in tobacco field continuous cropping duration enhanced soil nematode diversity and altered the nematode community structure. Among the 36 identified nematode genera, 11 showed significant differences among different continuous cropping durations. Specifically, the relative abundance of Caenorhabditis increased after 10 years of continuous cropping, while the opposite trend was observed for Aphelenchus, Mononchus and Panagrolaimus .With the extension of continuous cropping duration, the nematode maturity index first increased and then decreased; the relative abundance of bacterivorous nematodes (bacterivores) first decreased and then increased, while that of fungivorous nematodes (fungivores) significantly declined. Both the enrichment index and structural index were higher under long-term continuous cropping (over 10 years). Further nematode faunal analysis indicated that the nematode communities in short-term continuous cropping (under 10 years) and long-term continuous cropping (over 10 years) were significantly separated. Comprehensive analysis revealed that long-term continuous cropping (over 10 years) increases soil nematode community diversity, alters the structure of trophic groups, enriches soil nutrients, and reduces environmental disturbance intensity. Additionally, this study elucidates the dynamic process of the soil microhabitat from initial environmental stress to long-term stability.