An Analysis of Soil CO2 Emissions in a Temperate Deciduous Forest Ecosystem

English Abstract:

The production and emission of carbon dioxide (CO₂) from soils, referred to as soil respiration (Rs), has a significant influence on the global carbon balance. Carbon is acquired by vegetation from the atmosphere through photosynthesis and stored on the surface and in soils as organic matter. This stored organic matter is returned to the atmosphere as CO₂ through belowground decomposition of organic matter by microbial communities (heterotrophic respiration) and metabolic activity of roots and mycorrhizae (autotrophic respiration). In this study, we explore temporal and spatial dynamics of Rs in a temperate deciduous forest located in Southern Ontario and how it is influenced by climatic controls. The site is a 90-year-old managed hardwood forest (Carolinian species). It is part of the Turkey Point Flux Station and global Fluxnet network. An automated soil CO₂ flux system (LI-8100A) was utilized for continuous monitoring of Rs since July 2014 at our site. To better capture the spatial variability of Rs, a portable soil CO₂ flux system (LI-6400) was also used along two 50-m transects. Comparing the two chamber systems, they both measured within one standard deviation of each other indicating that the long-term automatic chamber site is representative of the surrounding area. Monthly mean Rs varied from a maximum of 12.78µmol/m²/s in July to a low of 1.0µmol/m²/s in December. The seasonal trend of Rs followed closely that of soil temperature. Spatially variability in the soil water content had little effect on Rs values. This study will allow us to have a better understanding of the dynamics of Rs and how it responds to its main controlling variables, soil moisture and temperature. It will also help us to determine the impact of climate change and extreme weather events on Rs in temperate deciduous forests and help in developing vegetation ecosystem models.