Decomposition (carried out primarily by soil bacteria and fungi) is a major bottleneck in the recycling of nutrients within ecosystems. It is also the main way that C fixed during photosynthesis is ultimately returned to the atmosphere. Thus, understanding the factors that control rates of decomposition is crucial to understanding the global C budget. Human activities such as fertilizer production, cultivation of legume crops, and fossil fuel combustion have doubled natural rates of N fixation. Nitrogen from agricultural or industrial areas can be transported downwind or downstream and be deposited on terrestrial ecosystems, where its effects on ecosystem C storage are unknown. I have been conducting long-term experiments to better understand the effects of elevated N inputs on decomposition.
Human activities are causing widespread and diverse environmental changes on global scales. In an ongoing, long-term experiment at the CCNHA (the Biodiversity, CO2, and Nitrogen Experiment, BioCON), we are exploring the consequences of interactions among four such global changes: increased concentrations of atmospheric CO2, elevated inputs of N via deposition, alterations in both the composition and numbers of plant species in communities, and changes in precipitation regimes.
The landscape around Cedar Creek is rapidly developing. However, relatively little is known about the ecosystem consequences of residential development. We are determining the temporal dynamics of organic matter accumulation in soils and plant biomass in residential landscapes surrounding Cedar Creek by establishing a chronosequence of residential landscapes in Anoka County that complements the old field chronosequence (E014) that has already been the focus of work on C and N dynamics following agricultural abandonment.
This work is supported by DEB-0080302, DEB-0322057, and DEB-0347103 from the National Science Foundation. Any opinions, findings, conclusions, or recommendations expressed in the material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
We are quantifying total fluxes of C, N and P through households along an urban to rural gradient in the Twin Cities Metropolitan Area to understand factors that influence household choices regarding consumption and thus the macroelement fluxes through households. We are using survey data to link factors related to human choices (attitudes, norms, perceived control, demographic factors) to understand variation among households in element fluxes.
This work is supported by BCS-0709581 and DEB-0080302 from the National Science Foundation. Any opinions, findings, conclusions, or recommendations expressed in the material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
We are studying the likely impact of climate warming on the ecotone between the southern boreal forest and the north temperate forest. In manipulations near Cloquet and Ely, Minnesota, we are examining the effects of experimental warming on recruitment of both boreal and temperate tree species.
This work is funded by the Department of Energy.
We are assessing the potential for changes in land use (e.g., restoration of forests, prairies and wetlands) and agricultural management (e.g., conservation tillage and incorporation of cover crops) to offset Minnesota's fossil fuel emissions. To date, we conclude that, at best, Minnesota could offset about 3 to 6 percent of the its fossil fuel emissions through changes in land use. This limited potential mainly arises because of the lack of land available for conversion, as well as because of the limited potential of some land use practices (namely, conservation tillage) to sequester carbon.
