By Dr. Ross Hinkle, Professor and Chair, and Dr. Jiahong Li, Adjunct Research Associate, Department of Biology, University of Central Florida; Dr. David Sumner, Hydrologist, US Geological Survey; Dr. Francisco Escobedo, Assistant Professor, School of Forest Resources and Conservation, University of Florida; & Dr. Wayne C. Zipperer, Research Scientist, Southern Research Station-USDA Forest Service

As of 2008, 94% of Florida’s popula-tion lived in urban areas and ap-proximately 7 million acres of rural land will be converted for urban uses by 2060. Urban areas are also one of the main sources for carbon dioxide (CO2) emissions and substantial energy and water use. From 1990 to 2007, Florida’s CO2 emissions increased 36% - double the national average- and 32 million equivalent tons CO2 were emitted in Miami-Dade County in 2005.

The key to understanding the role of forests and urban vegetation in CO2 cy-cles is to collect information from vari-ous land use and cover types in urbaniz-ing ecosystems. What little information exists is from the temperate northern forests, desert southwest, and mid-Atlantic forested areas of the United States. To fill this gap, we quantified changes in ecosystem structure and function by collecting site-specific data on fluxes in carbon stocks and analyzing the carbon cycle of human influenced urban vegetation. Preliminary research results from the University of Florida (UF) indicate that urban trees offset 1.6% and 3.8% of annual CO2 emissions in Miami-Dade County and Gainesville, respectively.

Researchers from University of Central Florida (UCF) are carrying out a long-term study that will describe and quan-tify urban carbon flux and drivers in central Florida. The work represents a continuing collaboration between UCF, the US Geological Survey (USGS) - \Florida Integrated Science Center, and St. Johns River Water Manage-ment District, to evaluate urban car-bon, water, and energy fluxes in metro-politan Orlando. In October 2008, that partnership installed an eddy covari-ance tower system on the UCF campus that measures carbon flux in east Or-lando. The tower footprint spans an area that is representative of existing land uses that encompass urbanized eastern Orlando and more open agricultural/forest lands of eastern Orange County.

Already, the data from the flux meas-urements is detecting the human con-tribution within the tower’s 200 km2 carbon footprint. By measuring, the average net ecosystem CO2 exchange (NEE) over a one month sample pe-riod (Oct. 4 – Nov. 6, 2008), UCF/USGS were able to detect a daily pattern from the urban (west) and rural (east) segments of the urban to rural gradi-ent (Figure 1). Results indicate that in the more urban western areas the CO2 concentrations are higher and the daily net CO2 emissions are double those in the less urbanized eastern areas, and net carbon sequestration is occurring on the rural/less urbanized eastern segment of the footprint at midday.

In the summer of 2009, UCF/USGS collaborated with UF and the US For-est Service (USFS) in measuring ran-dom field sites around the CO2 flux tower footprint to quantify urban eco-system structure and function. Data from these permanent UF/USFS plots show that there is 25% tree cover and approximately 560,000 trees in the study area. Trees in urban and natural areas are estimated to annually seques-ter 430tC/ha (tons of carbon per hec-tare) and 1,500tC/ha, respectively, and most carbon was sequestered in forests and low density residential areas. How-ever, trees located in medium density residential areas were more effective in reducing the amount of energy used by residential buildings. Furthermore, for-ested areas and medium density resi-dential areas removed the most air pollution.

This collaboration among UCF, UF, USFS and USGS hopes to develop a multidisci-plinary, multi-institutional project for accurately measuring, comparing, and predicting CO2 flux in an area undergoing rapid land use change in Orlando.

Results from this effort will be used to better understand similar field measurements obtained elsewhere in Florida.

For more information about this project contact Ross at rhinkle@mail.ucf.edu