Land reclamation and short-term cultivation change soil microbial communities and bacterial metabolic profiles.

Background: Soil microbes play an important role in many critical ecosystem processes, but little is known about the effects of land reclamation and short-term cultivation on microbial communities in red soil. In this study, soil microbial communities under five land use patterns-artificial pine forest (Fp), tussock and shrub (TS), shrubbery (Sh), sugarcane (Su) and maize and cassava rotation (Ma)-were characterised by DNA fingerprinting and metabolic profiling to reveal how land reclamation and cultivation affect the underlying diversity and function of soil microbial communities in southwestern China.

Results: Eight years of reclamation and cultivation significantly affected population size, composition and structure, bacterial metabolic profiles and diversity values (Shannon-Wiener index) of soil microbial communities. Soil organic carbon and pH were the most important factors shaping the underlying microbial communities; however, with significant correlations between soil carbon/nitrogen ratio and bacterial taxonomic and metabolic diversities, soil total nitrogen was a potentially important factor for soil microbial composition and function, as well as soil moisture, cation exchange capacity and physical structure to a lesser extent. In addition, the lowest pH, lower nutrient availability and the most compact soil in pine forest resulted in the lowest microbial taxonomic and metabolic diversities among the five land use patterns studied.

Conclusion: Soil organic carbon, nitrogen and pH appeared to be the most important factors influencing microbial biomass, composition and function in red soil of southwestern China. The study suggests that measures to lessen the impact of changes in this edaphic environment should be taken to avoid an imbalance of microbial function and improve ecological sustainability in southwestern China.