Effects of the Application of Nutrients on Soil Bacterial Community Composition and Diversity in a Larix olgensis Plantation, Northeast China

Bacteria are among the most critical components in soil. The application of nutrients as an important management measure to maintain soil fertility can affect the structure of soil bacterial communities. The objective of this study was to explore the influence of the application of nutrients on the soil bacterial community composition and diversity in a Larix olgensis Henry plantation after thinning using Illumina high-throughput sequencing technology. In July 2015, a middle-aged (27 years old) Larix olgensis forest, afforested in the spring of 1988 (thinning was conducted in the winter of 2012), in MengJiagang National Forest Farm, Jiamusi City, China, was assessed. Four fertilizer treatments were applied, each replicated three times: nitrogen (N, 250 kg/ha); nitrogen + phosphorus (NP, nitrogen 250 kg/ha + phosphorus 50 kg/ha); nitrogen + phosphorus + potassium (NPK, nitrogen 250 kg/ha + phosphorus 50 kg/ha + potassium 30 kg/ha); and a control (CK, no fertilizer). In mid-August 2018, soil samples of a 0–10 cm soil layer were collected; the diversity and composition of soil bacteria under different the application of nutrients conditions were determined by Illumina high-throughput sequencing technology on the MiSeq platform. Our results found that: (1) compared with the CK treatment, long-term the application of nutrients significantly reduced the soil pH and soil total potassium content (p < 0.05); and (2) the continued application of nutrients increased the Chao1 richness index of the soil bacteria in the Larix olgensis plantation (p < 0.05); (3) soil organic carbon and soil total nitrogen were key drivers of the soil bacterial community structure. Therefore, the different long-term the application of nutrients regimes did not affect the stability of the soil ecosystem in the Larix olgensis plantation.