" BES Project Abstracts 2005
Institute of Ecosystem Studies

2005 BES Annual Meeting Presentation and Poster Abstracts


The contribution of soil respiration to urban carbon dynamics at Cub Hill in response to global change
 
Q. HOLIFIELD, J. L. HOM and M. PATTERSON.
 
Abstract: Soil respiration is the second largest factor in the flux of carbon between the Earth’s ecosystems and the atmosphere and is one of the most frequently used indicators for measuring soil biological activity. To determine how much carbon is exchanged between an urban forest and the atmosphere, the microbial activity and carbon concentration (CO2) were measure in the forest floor of a suburban forest. CO2 data for 2004 suggest that the fraction of carbon that is being “lost” may be attributed to the reduction of soil microbial activity during the winter months. By comparison, the data indicated that CO2 concentrations increased by 50% in 2005 during the months of June and July, possibly due to increased vegetation in the area. In 2004, significant differences in soil temperature were observed. On average, soil temperature decreased from a high of 21oC to a low of 6oC. Soil moisture increased as a result of hurricane activity in August 2004. An inverse correlation (- 0.75, P < 0.0001) indicated that as soil moisture increased, soil temperature decreased. Similar results were also observed with the change in seasonal patterns in early autumn (-0.61, P< 0.001) as soil moisture increased, soil temperature decreased as a result of the loss of canopy cover. As the temperatures declined in October 2004, soil microbial activity was reduced by 36%. However, a completely different trend for soil temperature, soil moisture and CO2 flux was observed in 2005. Soil temperature remained fairly constant, with no significant differences at the varying depths (0.05 P>0.23). Soil moisture showed a less erratic trend in 2005, with increases occurring during the month of August, where significant rainfall did occur in the area. Soil respiration also increased by 60% in 2005. A positive correlation (0.62, P< 0.001) indicated that as soil moisture increased, soil respiration increased. Current data have not show what other factors may be related to below canopy soil respiration at Cub Hill. However, we are currently analyzing soil and root samples to determine what percentage of soil microbial biomass and root respiration is contributing to the total soil respiration at Cub Hill. We expect to improve our understanding of soil respiration that will lead to the development of better models of carbon dynamics in urban forest ecosystems, which may in turn, lead to more reliable predictions of how forest patches will respond to global change.