Carbon flux and biological monitoring at the Baltimore Cub Hill flux tower: Partitioning the role of land use, carbon emissions and respiration

Background/Question/Methods

Carbon flux measurements and carbon dioxide concentrations were taken along an urban to rural gradient from Cub Hill in Baltimore, Maryland (CH), Elk Neck, Maryland (EN) to the Silas Little Experimental Forest (SLEF) in the New Jersey Pine Barrens. These sites incorporate heavily vegetated urban and rural forests. We obtained net ecosystem exchange (NEE) values stratified according to wind direction from areas of different vegetation cover and land use composition.  Urban forest benefits and ecological services, primarily carbon sequestration are discussed.  

Results/Conclusions

Carbon flux estimates were closely correlated with the percent vegetation cover estimated from remote sensing. Annual net CO₂ exchange at the Baltimore flux site indicated that this site was a net source from, due to high CO₂ emissions from fossil fuel energy use as well as leaf off from the deciduous trees during the domant seasons. We estimated the anthropogenic CO₂ emissions in suburban Baltimore by comparing the eddy fluxes in rural forest in New Jersey (SLEF) and with a mobile tower at Elk Neck (EN) for the background biogenic CO₂ flux.   Despite the large emissions around this urban tower, CH showed higher C uptake during the growing season than SLEF due to the high vegetation cover surrounding the tower. Soil respiration studies in maintained lawns compared to forest floor plots indicated that there was considerable night time respiration from lawns that coincided with the seasonality and magnitude observed in the growing season NEE.  This study supports management and policy use of urban forest for ecological benefits, such as urban canopy tree cover initiatives to offset carbon dioxide, reduce emissions , and lower land surface temperatures.