ASSESSING SEASONAL DYNAMICS OF SOIL CO2 EFFLUX USING CONTINUOUS MEASUREMENTS IN A TEMPERATE PINE FOREST

Abstract

<p>This study explores the seasonal dynamics of soil CO₂ efflux (Rs) in a temperate pine plantation forest located in Southern Ontario, Canada. Rs was continuously measured from June 15, 2008 to December 31, 2010 at this site using an automated soil CO₂ chamber system. Component analysis of Rs conducted by making continuous measurements in a trenched plot where live roots were excised indicated that heterotrophic respiration (Rh) contributed approximately 72 and 80% (895 and 920 g C m^-2 year^-1) of annual Rs in 2009 and 2010, respectively. Similarly, continuous Rs measurement in a litterless plot where the surface litter layer was removed contributed 65 and 57% (800 and 655 g C m^-2 year^-1) of annual Rs in 2009 and 2010, respectively. Results of this study suggested that overall soil temperature was the dominant control on Rs in this forest, except during the severe dry conditions.</p> <p>In order to explore the impact of soil water limitations on Rs a through-fall exclusion experiment conducted from April 1 to July 3, 2009 - the spring and early summer season. Through-fall exclusion caused a large reduction in daily Rs. This experiment further suggested that Rs became less sensitive to temperature and increasingly more sensitive to water as soil water content depleted due to the through-fall exclusion. This study helps to better understand the seasonal dynamics of Rs, and its components and controls in temperate conifer forests in Eastern North America. These forests are considered a large sink of carbon, and changes in Rs dynamics in this region may have implications for the global carbon cycle.</p>