Analyses of Rhizosphere Soil Physicochemical Properties and Microbial Community Structure in Cerasus humilis Orchards with Different Planting Years

Cerasus humilis has been widely used as a key ecological improvement plant species in barren lands in Northern China; however, the soil improvement effects of long-term C. humilis planting have rarely been reported. Our study aimed to determine the effects of planting C. humilis after 3, 6, and 10 years on the physicochemical properties and microbial community structures of the rhizosphere soil. pH decreased significantly with increasing time. Organic matter (OM), total phosphorus (TP), available phosphorus (AP), total potassium (TK), and available potassium (AK) increased gradually from 3 to 10 years. Alkaline and total nitrogen increased significantly and peaked at 6 years. Alkaline phosphatase, urease, sucrase, and hydrogen peroxide activities peaked at 6 years and decreased. Significant differences occurred in C. humilis rhizosphere bacterial and fungal community diversity and richness. Ace, Chaol, Shannon, and Simpson indices indicated diversity and richness of bacterial and fungal communities peaked at 3 and 10 years, respectively. Soil physicochemical properties, except pH, were positively significantly correlated with microbial community structure. AK and TK were the main factors for bacteria and fungi, respectively, with time. Increases in C. humilis rhizosphere soil microbial community relative abundance may be attributed to beneficial bacteria (Acidobacteria, Proteobacteria, and Actinobacteria) and fungi (Ascomycota, Mortierellomycota, and Basidiomycota). Physicochemical and soil and microbial community structure properties gradually improved; however, with time, adequate nutritional supplementation was needed to prevent decreased microbial community richness and diversity.