Influence of Decreasing Temperature on Soil Microbial Activity in a Boreal Shield Ecozone

Although the focus on warming is imperative to address climate change, addressing the effects of cooling is arguably just as relevant in characterizing the enzyme response to temperature fluctuations. In this study, the response of enzyme activity to diminishing temperatures in the field was evaluated. The targeted sites were located in the City of Greater Sudbury in Northern Ontario, Canada. Microbial activity variations during the summer and fall seasons were measured using freshly collected soil samples. The soil was acidic with an average pH of 4.8 and the level of soil organic matter was 11.3%. The local atmospheric temperatures recorded during the sampling period in Sudbury were 21.3°C (August), 2.3°C (October), and -6.3°C (November), respectively. Overall, nine enzymes were targeted including β-Glucosidase (BG), Cellobiohydrolase (CBH), β-N-Acetylglucosaminidase (NAGase), Aryl Sulfatase (AS), Acid Phosphatase (AP), Alkaline Phosphatase (AlP), Glycine Aminopeptidase (GAP), Leucine Aminopeptidase (LAP) and Peroxidase (PER). Microbial activities in the field during summer and fall seasons varied significantly with different enzymes analyzed. BG, CBH, NA Gase, and AS remained unchanged despite the decreasing temperature. The activities of AP, AlP, and PER increased significantly from the first sampling in August to October 2020. AlP, LAP activity decreased whereas LAP activity increased from October to November. Considering the complexity of the forest ecosystem, some factors other than the temperature might affect microbial activities in field conditions. Data on enzymatic activities in soil samples from different ecological conditions should be interpreted with caution because of the various effects of environmental variations on soil functions.