Landscapes all over the world are becoming increasingly urbanized. As a result, more attention is being focused on the functional role of carbon in these ecologically dynamic urban ecosystems. Organic carbon is an important component in all soil processes, such as microbial decomposition and nutrient cycling, all of which can be altered in urban areas. Riparian zones in undisturbed landscapes have the potential to store large amounts of soil organic carbon and could have a significant impact on the global carbon pool. As urban areas continue to grow, an understanding of how anthropogenic disturbance can affect soil organic carbon in both riparian zones and high urbanized areas is needed. This study is located in the Gwynns Falls watershed in Baltimore, MD as part of the Baltimore Ecosystem Study, one of two urban sites that are part of the National Science Foundation’s Long Term Ecology Research network. In order to determine organic carbon concentrations along an urbanizing gradient, the watershed was divided into an upper, middle, and lower section. An average of 7 transects were sampled in each section and soil cores were taken down to 1 meter and divided up by horizon. Replicate samples from each horizon were analyzed for loss-on-ignition (LOI). Carbon content measurements of each horizon were converted from LOI results. Sample replications from each horizon were averaged, then weighted and converted to percent carbon. A percent carbon value for each core was determined by averaging its horizons.
Results/Conclusions
Mean percent carbon values in the upper, middle, and lower sections of the watershed were 82%, 54%, and 44%, respectively. These data suggest a decrease in surface soil organic carbon as land use becomes increasingly urbanized. Coefficient of variance among transects in each section of the watershed ranged from 49% to 71%, indicating high spatial variability of carbon. To gain a better understanding of this high spatial variability, future investigations will focus on fine-scale analysis of carbon concentrations as they relate to localized factors such as vegetation, soil texture, and land use. In addition to analyzing organic carbon, attention will also be given to the black carbon pool, specifically soot carbon, as it has potential to be a sink for the unaccounted carbon in urban ecosystems. Soil organic carbon and black carbon may have a significant impact on the global carbon cycle with potential impact on global climate change
