Response of soil chemical properties and microbial community characteristics in <i>Lycium barbarum</i> orchard to planting years.

With the extension of <i>Lycium barbarum</i> planting years, there would be significant changes in the chemical properties and microbial community distribution of rhizosphere soil, which limits the sustainable management and production of <i>L. barbarum</i>. Using high-throughput sequencing technology, we analyzed the chemical properties, diversity indices and relative abundance of bacterial and fungal community in rhizosphere soil in <i>L. barbarum</i> orchards planted for 3, 5, and 10 years. The results showed that, with the increases of planting years, soil pH significantly increased, and soil total nitrogen, total organic carbon, available phosphorus, available potassium, mineral nitrogen, and electrical conductivity all showed a trend of first increasing and then decreasing. The highest levels occurred in the 5-year planting. The α-diversity of soil bacterial community did not vary among different planting years, but the diversity of fungal communities first decreased and then increased. Principal coordinate analysis revealed that the structure of bacterial and fungal communities in the rhizosphere soil of <i>L. barbarum</i> were significantly different in 5-year-old plants from that under 3-year-old and 10-year-old plants. However, the dominant bacterial phyla in the root zone at different planting years were Proteobacteria, Acidobacteria, Chloroflexi, Actinobacteria, and Gemmatimonadetes, accounting for 76.0% to 82.0% of the total abundance. The dominant fungal phylum was Ascomycota, accounting for 75.3% to 80.7% of the total abundance. Compared with the 3-year planting period, the relative abundance of Gemmatimonadetes decreased significantly by 40.6% and the relative abundance of Bacteroidetes increased significantly by 63.2% after 5 years of planting. Compared with the 5-year planting period, the relative abundance of Acidobacteria, Planctomycetes, Chloroflexi, <i>RB41</i>, <i>Roseiflexus</i> in bacteria, and the <i>Fusarium</i> in fungal increased significantly by 48.7%, 125.5%, 28.2%, 60.1%, 84.6%, and 260.9%, respectively, after 10 years of planting, while the relative abundance of Firmicutes and Bacteroidetes decreased significantly by 61.6% and 56.3%, respectively. The Mantel-test results indicated that available potassium was the most significant factor affecting both bacterial and fungal community structure in the root zone. In conclusion, after 5 years of planting, there were significant changes in the chemical properties of rhizosphere soils, with a decrease in the abundance of beneficial bacteria and an increase in the abundance of pathogenic fungi, leading to a deteriorated microecological environment and adverse effects on the sustainable management and production of <i>Lycium barbarum</i> orchards.