Tom Wessels, MA
Department of Environmental Studies
At the Harvard Forest in Petersham, MA, the Environmental Measurement Station (EMS) on the Prospect Hill Tract has measured the net ecosystem exchanged (NEE) of carbon ( C) by the eddy correlation method for three consecutive years. This method accounts for above and belowground C storage. Carbon flux varies by wind direction from the tower. Mean annual C storage is 4-6 metric tons (MT) Carbon/hectare/year (C/ha/yr) to the southwest and 1-2 MT C/ha/yr to the northwest. These directions differ in drainage, land-use history and topography. Weather associated with these two wind directions differs as well. The IDRISI Geographic Information System (GIS) was used to compare drainage patterns and land-use history with field-based soil respiration measurements to the southwest (SW) and northwest (NW) of the EMS. Data analysis was based on three paradigms guiding today's understanding of C storage rates. Higher uptake of C may be a result of, 1) different land-use history (tilled rather than pasture or woodlot; pasture rather than woodlot); 2) poorer drainage (higher soil moisture); and 3) lower soil respiration rates. Though land-use appears to confirm the EMS data at 200m to 500m, soil respiration and land-use agree only at 200m. Drainage agrees with the EMS data only at 100m but is in agreement with soil respiration at 100m, 300m, 400m, and 500m. Overall the NW/SW C flux pattern is consistent with low soil respiration and poor soil drainage within 100m of the tower and land-use and soil respiration at 200m from the tower.