A distinct seasonal pattern of the ratio of soil respiration to total ecosystem respiration in a spruce-dominated forest

Annual budgets and fitted temperature response curves for soil respiration and ecosystem respiration provide useful information for partitioning annual carbon budgets of ecosystems, but they may not adequately reveal seasonal variation in the ratios of these two fluxes. Soil respiration (Rs) typically contributes 30-80% of annual total ecosystem respiration (Reco) in forests, but the temporal variation of these ratios across seasons has not been investigated. The objective of this study was to investigate seasonal variation in the Rs/Reco ratio in a mature forest dominated by conifers at Howland, ME, USA.We used chamber measurements of Rs and tower-based eddy covariance measurements of Reco. The Rs/Reco ratio reached a minimum of about 0.45 in the early spring, gradually increased through the late spring and early summer, leveled off at about 0.65 for the summer, and then increased again to about 0.8 in the autumn.