Soil microbial community is resilient to thinning disturbance

To engage sustainable forest management, understanding the impact of disturbances on the stability of soil microorganisms is important. This study reported the immediate effects of two-level thinning intensities on the soil microbial population, community composition and functions of a plantation forest over two years. Results showed that the thinning of Cryptomeria japonica forest significantly increased viable counts of soil bacteria from 7.7 × 10 6 to 1.4 × 10 7 or 1.6 × 10 7 in the 3rd month and the effect subsided in the 6th month post-thinning. The counts of actinobacteria, cellulolytic, nitrogen-fixing and phosphate-solubilizing bacteria groups maintained stable populations in the forest soils. Denaturing gradient gel electrophoresis profiles indicated that soil bacterial communities significantly differed among 25% thinning, 50% thinning and control treatment from the 12th to 18th month post-thinning, with no significant differences after 22 months. The community level physiological profiles were significantly different between control and thinning treatments in the 12th month post-thinning, the impacts of thinning then subsided by the 22nd month post-thinning as well. Soil bacteria were sensitive to thinning disturbances, but with resilience, their community and function approached to the control status in 2 years. This study demonstrates that the soil microbes of Taiwanese C. japonica forests are very sensitive to thinning disturbances, but recover stability after a relatively short period of time.