Impact of land use change on biogeochemical cycling in the Florida Panhandle

Background/Question/Methods

The Gulf Coast of Florida has been considered a “hotspot” of population growth and very few studies exist that focus on the impact of land use change on biogeochemical cycling along coastlines.  Previous research in the Florida Panhandle has indicated that shifts in land use from pine flatwoods and maritime forests to urban forests increase carbon storage in the top 90 cm of the mineral soil.  As an example, urban forest pine dominated sites can have a forest floor mass of 97 Mg ha^-1, a significantly higher mass than that stored in the forest floor of pine plantations and naturally regenerating forest (33 to 38 Mg ha^-1, respectively).   The focus of this research is to investigate the impact of land use change on carbon and nutrient cycling by measuring foliar decomposition rates, nitrogen mineralization and microbial biomass over a two year period.   Plots representing five different land use types (pine plantation, urban pine forest, urban oak forest, natural pine forest, and natural oak forest) were blocked across  four soil drainage classifications (very poorly drained, poorly drained, somewhat poorly drained and moderately well drained). 

Results/Conclusions

Preliminary data suggests that urbanization is increasing nitrogen mineralization rates in the surface soil on average 85 g ha^-1 d^-1 for oak forests (p=0.04) and 114 g ha^-1 d^-1for pine forests (p=0.01).   Microbial biomass was on average 670 ug C g^-1 soil (p=0.003) higher in urban pine forests as compared to natural pine forests.  Microbial biomass did not differ between urban oak and natural oak forests.   As of week 42, the effect of urbanization on litter decomposition in oak and pine dominated forests is non-significant.  The effect of pine plantation development was also non-significant for pine plantation sites compared to natural forest pine sites.  This area of the Florida Panhandle has undergone a drought over the course of this study and it is likely that the dry soil conditions are restricting the foliar decomposition rates across all of the land use types.  Preliminary data suggests that urbanization increases nitrogen mineralization rates and microbial biomass in surface soils and these parameters appear to be more sensitive indicators of urbanization compared to foliar decomposition rates.