Vertical gradients of ozone and carbon dioxide within a deciduous forest in central Pennsylvania

Ambient concentrations of ozone (O₃) and carbon dioxide (CO₂) were measured at locations from the forest floor to the top of the canopy in a deciduous forest at the Moshannon State Forest in northcentral Pennsylvania. O₃ concentrations were measured from May-September for three years (1993-1995) while CO₂ concentrations were measured only during July and August of 1994. O₃ concentrations increased steadily during the day at all locations, peaking during the middle to late afternoon hours. O₃ concentrations then steadily declined to their lowest point, just before dawn. Vertical O₃, concentration gradients varied seasonally and among years. However, O₃ concentrations were highest within the forest canopy and lowest at the forest floor, with an average difference of approximately 13%. Differences in O₃ concentrations between the canopy and forest floor were greatest at night. O₃ concentrations were slightly higher at locations within the canopy than above the canopy. CO₂ concentrations were consistently higher near the forest floor and were higher above the canopy than within the canopy. CO₂ concentrations were higher at night than during the day at all locations, especially near the forest floor.