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Research
 My research within the field of ecosystem ecology and plant physiological ecology focuses on the relationship between forest carbon cycling and global change. Forests are an important component of the global carbon cycle, storing carbon in biomass, detritus, and soils. Plants remove carbon dioxide from the atmosphere, thereby absorbing anthropogenic greenhouse gas emissions and potentially slowing climate change. The rate of forest carbon uptake (i.e., photosynthesis) and release (i.e., respiration) is affected by multiple variables, including land-use history, disturbance, succession, climate, soil fertility, and management. Exploration of these controls on carbon cycling processes at the leaf, whole-plant, and ecosystem scales is the focus of my research.
I am co-principal investigator of a project entitled “Forecasting Carbon Storage as Eastern Forests Age: Joining Experimental and Modeling Approaches at The UMBS Ameriflux Site”, which beginning in August will be supported by the Department of Energy's Terrestrial Ecosystem Science program and operates within the Ameriflux Network of long-term carbon cycle research. Our ecosystem-scale experiment, which was initiated in Spring 2008, is  hastening the successional transition from an even-aged aspen-dominated forest to an uneven-aged mixed deciduous-conifer forest, and resulting in major changes in plant species composition, forest age distribution, canopy structure, detritus production, and other variables that affect a broad array of ecological processes at all trophic levels, including the carbon cycle. More information on the Forest Accelerated Succession Experiment (FASET) is found on the University of Michigan Biological Station website.
For more, check out the latest FluxLetter, which offers an overview of recent project progress: http://www.fluxnet.ornl.gov/fluxnet/FluxLetter_Vol4_No2.pdf.
Ongoing research includes:
1) Carbon fluxes and storage in forests of the upper Midwest (DOE supported). This component of my research explores forest carbon cycling in response to a climate, disturbance, and ecological succession. We use multiple techniques to quantify forest carbon fluxes and storage, measuring processes such as photosynthesis and respiration at the leaf level, and also the growth and production of forests at the ecosystem scale. Forest carbon flux and storage estimates derived from physiological and ecological data are validated against independently calculated estimates, including those derived from meteorological and modeling methods.
2) Mechanisms sustaining high rates of forest productivity in old forests (DOE supported).
Growing evidence indicates that many old forests, contrary to early ecological theory, are capable of storing carbon for centuries; however, the mechanisms responsible for sustained high rates of forest productivity are largely unknown. At the University of Michigan Biological Station, we are examining how forest structural changes that occur over time intervals relevant to ecological succession (i.e., decades) are linked to sustained high rates of carbon storage. Recent work at our site has demonstrated that increases in forest canopy structural and biological diversit y play integral roles in maintaining productivity as forests age. This work has important implications for how old forests, once thought to be largely carbon neutral, are managed for carbon storage.
3) Controls on carbon storage in urban ecosystems.
The goal of this research program is to identify the physical and human constraints on carbon cycling in urban ecosystems. Rates of terrestrial carbon storage are sensitive to human disturbance, and consequently vary as the footprint and intensity of human dominance shifts. Several studies have quantified spatial variation in urban carbon storage. However, few have directly examined the importance of human intervention in shaping trajectories of carbon storage across complex, heterogeneous landscapes that comprise urban areas. Recent work conducted locally in Richmond and now published (see "Publications") with undergraduate collaborators at VCU indicates that soil carbon storage in urban ecosystems is strongly correlated with human demography (e.g., neighborhood affluence). We also found that partially restored ecosystems in urban areas exhibit striking functional resilience following human abandonment, with rates of carbon storage potentially increasing following vacancy.
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