.|  Baltimore Ecosystem Study
Soil CO2 efflux measurements in suburban landscapes

Figure 1. Installation of the soil gas sensor system at Cub Hill, Baltimore. Sensors were placed at the surface, and at 2, 4, 10, 20, and 30 cm depth.
Carbon dioxide is an important greenhouse gas, and its atmospheric concentration has been predicted to increase in the future. It is widely known that soil respiration is one of the largest CO2 fluxes to the atmosphere. In urban ecosystems land cover change and management practices are two major human activities that alter the local and regional carbon cycle. The objective of this study is to quantify the soil CO2 efflux in a suburban area by continuously monitoring CO2 concentrations in the soil profile and by numerically modeling the CO2 transport through the soil profile. Three stations per land cover (forest and grass) were selected at the Cub Hill urban flux tower site. Six VAISALA CO2 sensors (Vaisala Inc., Finland) per monitoring station were horizontally installed at 6 different depths (soil surface, 0.02, 0.05, 0.1, 0.2, and 0.3 m from the soil surface). To evaluate the continuous method CO2 efflux using the standard chamber method was measured once a week. We detected clear daily cycles as well as "pulse effects", i.e., rapid increases of CO2 concentrations right after rainfall events. The "pulse effect" was more apparent in grass, where changes in soil moisture were higher, than in the forest (Fig. 2). This study will provide a better understanding of the contribution of the soil ecosystem to the carbon cycle in urban environments. The study is a collaborative effort between the Johns Hopkins University and the US Forest Service.

Figure 2. "Pulse effect" of precipitation at Cub Hill lawn (left side) and forest (right side). Line D0 corresponds to soil surface, while d30 to a depth of 30 cm.
References:
Chun JA, KA Szlavecz, D Ferrer, M Bernard, SL Pitz, JL Hom, BF Zaitchik 2011, M. Estimation of Soil CO2 Effluxes from Suburban Forest and Lawn Using Continuous Measurements of CO2 Profiles in Soils and a Process-based Model. Abstract B11A-0462 2011 AGU Fall Meeting, San Francisco, CA, Dec 5-9.
 
Chun, J., Szlavecz, K., Ferrer, D. Hom, J, Saliendra, N., Bernard, M. Estimation of soil CO2 effluxes from suburban forest and lawn using a process-based model. Submitted to Agriculture and Meterorology
 
Collaborators:
Katalin Szlavecz, JHU Dept. of Earth and Planetary Sciences
 
Jong Ahn Chun, APEC Climate Center, South Korea
 
John Hom, US Forest Service
 
Andreas Terzis, JHU Dept of Computer Sciences
 
Contact: Katalin Szlavecz: szlavecz@jhu.edu
 
Students:
Darci Ferrer, Loyola University, Baltimore
 
Doug Carlson, JHU Dept. of Computer Sciences