Changes in Soil Bacterial and Nematode Communities during Long-term Continuous Cotton Cropping in an Arid Region.

larifying the effects of continuous cotton cropping (CC) on soil biological communities is essential for maintaining agricultural productivity. In this study, high-throughput sequencing was used to study the effects of different CC durations (0-yr, 5-yr, 10-yr, 15-yr, 20-yr, and 25-yr CC treatments) on soil microbial and nematode communities. The results showed that the dominant bacterial phyla were Actinobacteria and Proteobacteria, and the dominant nematode genus was Helicotylenchus in all CC treatments. The richness indexes (ACE and Chao1 index) and diversity index (Shannon index) of bacterial and nematode communities were the highest in the 15-yr and 10-yr CC treatments, respectively. Bacterial community was significantly correlated with soil pH and available potassium (AK), and nematode abundance was significantly correlated with microbial biomass carbon (MBC). Soil bacterial PICRUSt analysis results showed that carbon metabolism and amino acid metabolism were the main metabolic functions of bacteria in the CC treatments. The composition and diversity of soil nematode communities were significantly related to the structure of soil bacterial communities, and the niche breadth of soil bacteria was negatively correlated with that of nematodes. Panagrolaimus and Acrobeles were the main genera of bacterialfeeding nematodes affecting bacterial communities, and their relative abundances were significantly positively correlated with the relative abundance of bacterial communities. Overall, long-term (10-15 years) continuous cotton cropping negatively impacts soil biota and the microecological environment of cotton fields in arid regions.