Conversion of rural lands to urban and other built-up uses could have important impacts on the carbon balance of terrestrial ecosystems in the Southern United States (US), a region experienced dramatic land-use changes in the last 100 years. We generated a spatially explicit historical land-use change dataset of this region from 1865 to 2002 based on high resolution land cover maps derived from remote sensing imagery, historical urban coverage, and long-term population census records. We then applied the process-based Dynamic Land Ecosystem Model (DLEM) over the Southern US to investigate the impacts of urbanization on terrestrial ecosystem carbon balance for the time period from 1865 to 2002.

Results/Conclusions

Our analysis showed that after the 1940s, the urban/developed area in Southern US increased rapidly. The mean annual urbanization rate after 1940 was 11 times the rate before 1940. In the last 30 years of the 20^th century, urbanization accelerated in the Southern US. The mean annual urbanization rate after 1970 was about 130% higher than the urbanization rate before 1970. Our simulation results indicate that due to the rapid urbanization, the carbon stored in urban/developed ecosystems become more and more important to the regional total carbon storage in the Southern US since the mid of 20^th century. Most of urban carbon is stored belowground. In Southern US, Large amount of carbon has been released due to urbanization. In some arid lands in the Southwest, however, urban/developed area has higher carbon storage than the natural shrubland, mainly due to the lawn management. More field studies, especially regarding impervious surface in the urban land area, are necessary to provide parameters and a calibration dataset to improve the accuracy of model assessment.