Community characteristics and functions of phosphate-solubilizing bacteria in rhizosphere soil of natural and planted Pinus tabuliformis forests on the Loess Plateau, Northwest China

Abstract

To investigate the interaction between Pinus tabuliformis and root microorganisms and its effects on the stability of P. tabuliformis forests, we collected rhizosphere and non-rhizosphere soil from natural and planted P. tabuliformis forests in Huanglong County of Shaanxi Province. The non-rhizosphere soil was used to analyze chemical properties, while the rhizosphere soil was used to isolate and purify phosphorus-solubilizing (organic and inorganic phosphorus) bacteria. We mea-sured the phosphate-solubilizing ability and identified those bacteria using DNA genes sequencing. The results showed that soil total carbon concentration (TC), total nitrogen concentration (TN), carbon:nitrogen (C/N), and nitrogen:phosphorus (N/P) were significantly higher in natural forest than those in the plantation. A total of 20 genera and 65 species of phosphate-solubilizing bacteria were identified in those two forests, with Bacillus, Streptomyces and Pseudomonas as the dominant group. The diversity, richness, and evenness of phosphate-solubilizing bacteria in the natural forest were higher than that in the planted forest, but dominance was lower. Streptomyces was positively correlated with soil TC, TN, C/N and N/P ratios, while Bacillus and Pseudomonas were positively correlated with soil nitrate (NO3-), ammonium (NH4+), available phosphorus (AP), and total phosphorus (TP). The solubilizing ability of phosphate-solubilizing bacteria was different between two forest types, indicating that Pseudomonas sp.34-5 shared in two forests had the strongest phosphate-solubilizing ability for calcium phosphate with 11.40 μg·mL-1 and Bacillus mycoides BF1-5 exclusive to natural forest had the strongest phosphate-solubilizing ability for lecithin with 4.58 μg·mL-1. The composition and structure of phosphorus-solubilizing bacterial community were different in two forest types, with higher diversity, richness and phosphate-solubilizing ability in natural forest than that in plantation.