Research projects in the Hobbie Lab

My research is almost exclusively part of two different Long-Term Ecological Research (LTER) programs, the Minneapolis-St. Paul Urban LTER (MSP), which I lead, and the Cedar Creek LTER (CDR).

Minneapolis-St. Paul Urban LTER

The MSP LTER got underway in March, 2021. We are exploring interactions between people and nature in the Twin Cities metro, towards understanding how environmental outcomes can be improved for all residents. In addition to leading the MSP LTER, I am part of research teams exploring the resilience of urban forests, the functioning of urban watersheds, and the impacts of various urban stressors on lakes and streams. This research is done with several large, collaborative research teams.

Cedar Creek LTER

Decomposition Studies

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. Most recently, we have begun examining N effects on decomposition on fungal necromass, exploring interactions between fungal necromass chemistry and response to N enrichment; long-term fungal necromass dynamics; and interactive effects of saprotrophs and mycorrhizal fungi on decomposition. This work is done in collaboration with Peter Kennedy.

Biodiversity, nitrogen enrichment, elevated CO2, water, and temperature effects on ecosystems

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 for plant communities and ecosystems: increased concentrations of atmospheric CO2, elevated inputs of N via deposition, alterations in both the composition and numbers of plant species in communities, warming, and changes in precipitation regimes. this work is done in collaboration with Peter Reich and Forest Isbell.

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.