Effects of Soil Microbes on Forest Recovery to Climax Community through the Regulation of Nitrogen Cycling

Abstract

Microbes, as important regulators of ecosystem processes, play essential roles in ecosystem recovery after disturbances. However, it is not clear how soil microbial communities and functions change and affect forest recovery after clear-cutting. Here, we used metagenome sequencing to systematically analyse the differences in soil microbial community composition, functions, and nitrogen (N) cycling pathways between primary Korean pine forests (PF) and secondary broad-leaved forests (SF) formed after clear-cutting. Our results showed that the dominant phyla of the two forest types were consistent, but the relative abundance of some phyla was significantly different. Meanwhile, at the genus level, the fold-changes of rare genera were larger than the dominant and common genera. The genes related to microbial core metabolic functions, virulence factors, stress response, and defence were significantly enriched in SF. Additionally, based on the relative abundance of functional genes, a schema was proposed to analyse the differences in the whole N cycling processes between the two forest types. In PF, the stronger ammoniation and dissimilatory nitrate reduction (DNRA) and the weaker nitrification provided a genetic explanation for PF dominated by ammonium (NH4+) rather than nitrate (NO3−). In SF, the weaker DNRA, the stronger nitrification and denitrification, the higher soil available phosphorus (AP), and the lower nitrogen to phosphorus ratio (N/P) comprehensively suggested that SF was faced with a greater degree of N limitation. These results offer insights into the potential relationship between soil microbes and forest recovery, and aid in implementing proper forestry management.