CO2 Soil Flux in Temperate Forests Located in Southern Ontario

Abstract

Forests sequester large amounts of CO2 from the atmosphere, playing a significant role in the global carbon cycle and contributing significantly to building carbon sinks. Some of the sequestered carbon is released back into the atmosphere through autotrophic and heterotrophic respiration. The release of carbon, known as soil respiration (Rs), is regulated by environmental factors, primarily soil temperature (Ts) and soil moisture (SM). This study examines the difference in Rs at two forests sites in Southern Ontario for the 2021 growing season using automated CO2 flux measurement systems. The first site is a mature coniferous forest (TP74), and the second is a mature deciduous forest (TPD). There was no clear relationship between Rs and Ts or SM at both sites, primarily due to limited observed data available in 2021. However, it was found that an increase in SM could cause a different Rs response between the sites. When both sites experienced an increase in SM, on the same day, Rs increased at TPD, but Rs decreased at TP74. The difference in the response may be due to differences in organic material between sites, with TPD having a higher amount of organic material. A Rs Ts SM model was fitted to the data, but the correlation was poor at both sites. Model parameters from a past study at TPD were used to simulate Rs at TPD for whole year. These findings contribute to the understanding of Rs in different forest types and how environmental factors may alter rates of Rs.