Soil microbial response to increasing temperatures: influence of elevated temperatures on enzymatic activities, bacterial and fungal abundance and diversity

Abstract

Elevated temperatures, a defining characteristic of climate change, profoundly affect soil ecosystems by reshaping microbial communities The specific objectives of the present study were to 1) examine the effects of increasing temperatures on soil enzymatic activities in an environmental controlled setting and 2) assess the effects of elevated temperatures on bacterial and fungal abundance, diversity, and structure using temperature-controlled growth chamber. Soil samples were subjected to three temperature treatments (23°C, 30°C, and 37°C). Fresh soil samples were used as references. Activities of β-glucosidase (BG), β-N-acetylglucosaminidase (NAGase), aryl sulfatase (AS), acid phosphatase (AP), alkaline phosphatase (ALP), and peroxidase (PER) exhibited strong responses to temperature variations with activities peaking at 30°C and declining at higher temperatures (37°C). Candidatus Koribacter dominates the bacterial community in fresh samples and soils incubated at 23°C, 30°C. Overall, the abundance of the top five bacterial genera (except for Bradyrhizobium) revealed an inverse relationship between temperature and relative abundance that decreases as the temperatures increase. For Fungi, Trichomas was the most dominant genus in fresh soil with 40% of relative abundance while Umbelopsis was dominant in soils incubated at 23°C, 30°C, and 37°C with values ranging from 20% to 34 %). The relative abundance decreases as the temperature increases for Tricholoma and Russula and increases as the temperature increases for Umbeopsis and Holtermanniella. Shannon diversity entropy for samples treated at 23°C and 30°C were identical with value of 5.1 in fungal communities. This closeness between 23°C and 30°C was confirmed by Principal Coordinate Analysis plot, based on the weighted UniFrac distances for bacterial and fungal communities.