Studies on carbon dioxide concentrations and carbon flux in a forested region in suburban Baltimore
John Hom, Sue Grimmond, Dan Golub, Brian Offerle , David Nowak, Gordon Heisler, Rich Pouyat, and Wayne Zipperer
The purpose of this study is to characterize the carbon fluxes and carbon dioxide concentrations from a highly vegetated residential area of Baltimore. This will provide annual estimates of carbon sequestration in suburban ecosystems, areas traditionally called non-forest. The Cub Hill site is located 14 km from the Baltimore city center. It is the first permanent flux tower to measure carbon flux in an urban/suburban environment.
The ten level profile system for CO2 and H2O concentrations was initiated in February 2001. An eddy correlation system for carbon, water, and energy fluxes was started in late May 2001; however, data were not collected continuously until September 2001.
The average yearly carbon dioxide concentration in this Baltimore suburban environment is 385 ppm at the top of the 40 m Cub Hill tower, with peaks of more than 475 ppm. Additional CO2 monitoring stations in the Baltimore city center were much higher - averaging 511 ppm. A weekly anthropogenic cycle was observed with lower CO2 concentrations for the weekends than the weekdays during the winter, however this was less obvious during growing season.
This residential region of Baltimore had high seasonal carbon uptake, similar to that of a natural deciduous forest due to the high 36% tree cover. Uptake showed two dominate vegetation responses: seasonal deciduous canopy with “grasslands” understory.
This suburban flux tower showed C dynamics with land use change, human patterns and energy cycles. Urban conditions of elevated carbon dioxide, ozone, nitrogen deposition and elevated heat island effects represent future scenarios which forests may face. This study give us a “window” into the future, so that we can estimate future long-term growth response to these multiple stresses.
Keywords: carbon dioxide, carbon sequestration, urban and suburban forests

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