Hom, John L. (USDA Forest Service, Northeastern Research Station, 11 Campus Blvd., Ste. 200, Newtown Square, PA, 19087; Phone: 610-557-4097; Fax: 610-557-4095; Email: jhom@fs.fed.us)

Studies on Carbon dioxide Concentration and Carbon Flux in a Forested Region in Suburban Baltimore

J. Hom *, Matt Patterson, Sue Grimmond, Ben Crawford, Quinn Holifield, Ian Yesilonis, Dan Golub, Brian Offerle , David Nowak, Gordon Heisler, Rich Pouyat, and Wayne Zipperer

The purpose of this study is to characterize carbon dioxide concentrations and the carbon fluxes from a highly vegetated residential area of Baltimore, and to provide annual estimates of carbon sequestration for this forested suburban ecosystem. The Cub Hill site is located 14 km from the Baltimore city center. It is the first permanent urban carbon flux tower to measure carbon flux in an urban/suburban environment. The site is in a yellow poplar-oak-hickory stand with a canopy height of 65-80 feet. Immediately south is a residential area, and large areas of forest and vegetation are to the north and west. The ten level profile system for CO₂ and H₂O concentration was initiated in 2001. An eddy correlation system for carbon, water, and energy fluxes was added later.

The average concentration in this Baltimore suburban environment is slightly higher than the global background, averaging 385ppm at the top of the Cub Hill tower. Monitoring stations in Baltimore city center, where there is less tree cover and more automobile traffic, is much higher - averaging 511ppm. The influence of the workweek showed a weekly cycle with lower overall CO₂ emissions for the weekends than that of the weekdays during the winter, possibly due to higher energy use for the workweek. However, this was less obvious in the spring and summer with the influence of the deciduous vegetation.

Metropolitan areas have an average tree cover of 33.4 percent (urban counties) and support 25 percent of the USA’s total tree canopy cover. Estimates of suburban forest area and the amount of carbon stored are not well known, as they fall between the inventories of rural and urban forests. This study will improve our understanding for carbon flux and carbon sequestration in areas traditionally classified as non-forest lands.