Research on changes to C and N stocks due to urbanization has typically focused on comparisons of developed and undeveloped conditions, but comparatively little work has been done to quantify change over time. We used a chronosequence approach to examine how aboveground C stocks, and belowground C and N stocks, changed over time for different land use change trajectories in the Greater Boston area.
Results/Conclusions
Contrary to expectations, there was no significant correlation between development age and aboveground vegetation biomass, despite evidence of increased tree-level NPP following development. Among the four time periods over which we stratified our sampling (pre-1972, ‘72-‘85, ‘85-’99, ’99-‘12), we found that soil C and N increased over time following development, but variability was high, and differences between consecutive time periods were not always statistically significant. Soils in forest land use had higher C and N stocks than young developed land uses, but were not significantly different from older developed land uses. We compared our results to soil chronosequence data from three other cities and found that developed soils in all regions experienced initial C and N losses relative to pre-development conditions, followed by increases in C and N over time. Soil C and N accumulation rates were highest and most consistent in lawns on former agricultural sites. Our results suggest that urban C and N stocks are variable over space, dynamic over time, and that the processes driving these trends are influenced by land use history, management, and regional climactic and edaphic factors.