PARENT SESSION
Oral Session #62: Forest Carbon Dynamics.
Presiding: R. Norby
Wednesday, August 7. 1:00 PM to 4:45 PM. Greenlee Meeting Room, TCC.

Carbon fluxes at a naturally regenerated Jack pine stand in northern Michigan.

Euskirchen, Eugénie^*,1, Chen, Jiquan², Pregitzer, Kurt¹, ¹ Michigan Technological University, Houghton, MI² University of Toledo, Toledo, OH

ABSTRACT- An understanding of the terrestrial carbon cycle at the landscape and regional scales requires knowledge of how the individual ecosystems within a larger mosaic function as a net source or sink of atmospheric carbon dioxide. Jack pine stands are the focus of management practices in the upper Great Lakes region, and the CO₂ budgets of this type of stand may differ significantly from those in other forested ecosystems. In May 2001, we initiated carbon flux measurements using the eddy covariance technique within a young (10-12 years old) naturally regenerated Jack pine stand in northern Michigan. Results from our study show that from mid-May to mid-November 2001, the stand acted as weak carbon sink, gaining roughly 1.26 Mg/ha. Half-hourly C fluxes commonly fell between -3 to 3 mol m^-2 s^-1, with some values ranging from -10 to 8 mol m^-2 s^-1. Diurnal carbon fluxes exhibited a clear pattern, with highest carbon uptake occurring during the noon-time hour and losses taking place at night. There were about 20 days when the stand acted as a net source of CO₂, and many of these days corresponded with warm temperatures (25-32°C) and hence higher rates of soil respiration. It is likely that this young stand has just passed its negative stage of net ecosystem productivity, but still exhibits respiration losses that are only slightly less than gross C uptake. Future measurements can help us to assess more accurately the seasonal and interannual variability in net ecosystem exchange at this site, and aid in estimates of regional carbon fluxes.

KEY WORDS: carbon flux, Great Lakes Region, Jack pine