Contrasting effects of different organic amendments on the microbial responses to extreme temperature changes

Abstract

Soil organic amendments can change microbial communities, potentially impacting their resilience to environmental stresses and, consequently, their transformation of soil carbon and nitrogen. While several studies have investigated the impact of a few organic amendments on microbial resilience to stresses in the form of absolute change in environmental conditions, the potential stress effects of different rates of change have received much less attention. The rate of change in environmental properties such as temperature may induce different microbial stress responses, given the reliance of microbial defensive mechanisms on time-dependent signalling and activation processes. In this research, we explored the relevance of the rate of temperature change as a microbial stressor and evaluated the potential use of organic amendments in steering soil ecological response. We monitored the changes in microbial properties and concentrations of different carbon and nitrogen fractions to temperature change treatments of 2.5 and 30 °C/d after the application of three commonly available rural organic amendments to a podzol soil in a laboratory incubation study. Results showed significant effects of the temperature treatments on bacterial and total microbial DNA concentrations, as well as on dissolvable and insoluble carbon and nitrogen ratios regardless of the organic amendment treatment. Temperature impacts on respiration rates, priming rates and the concentration of soil hot water extractable carbon and nitrogen differed depending on the organic amendment treatment. Results demonstrated that compost-amended soils were least sensitive to the temperature treatments, while grasses and fermented grasses treatments were generally more sensitive while showing opposite responses. Our findings indicate that organic amendments might be utilized to manipulate the impact of environmental stresses on soil carbon and nitrogen concentrations, and highlight the need for future research to investigate the relevant ecological properties and mechanisms.