|B.S., Biological Sciences/Ecology, Cornell University (1980)
Ph.D., Botany/Plant Ecology, Oregon State University (1987)
My research explores the successional dynamics of forest and meadow communities of the Pacific Northwest. I am interested in the roles of natural and human-caused disturbance, climate change, speciesí life histories, and biotic interactions in shaping the spatial and temporal distributions of plant communities. My students and I study both natural successional processes and community patterns shaped by human disturbance and forest management. Research in this latter area spans the broad spectrum of management intensities characteristic of private, state, and federal lands in the Pacific Northwest.
The cornerstone of this research is a long-term (50-year) study of succession after clearcut logging and broadcast burning of old-growth Douglas-fir forests in western Oregon. We have explored the compositional and structural changes that characterize early stages of secondary succession and the degree to which these patterns are shaped by initial composition, disturbance intensity, and the life history traits of species (click here). The results of these long-term observations have led to a series of species-removal experiments that address the role of plant species interactions in shaping early successional changes, including patterns of species turnover, community development, and invasibility (click here). Our research also explores (i) the development of young, closed-canopy forest with an emphasis on the dynamics of tree growth and mortality (click here), (ii) the extent to which understory dynamics during canopy closure are driven by changes in overstory structure (click here), and (iii) the mechanisms by which ground-layer communities reinitiate during subsequent stages of stand development (click here).
A second, core area of research explores the effects forest management on plant species diversity and community structure. Large-scale field experiments form the basis of this work. The Demonstration of Ecosystem Management Options (DEMO) study, replicated at six locations in western Oregon and Washington, is among the first in the region to experimentally examine forest ecosystem responses to variable retention harvests (click here). Our vegetation studies encompass observations of ground-layer bryophytes, understory herbs, regenerating trees, and the residual forest overstory (click here). Studies in dense, second-growth stands in the Cedar River Watershed, in western Watershed explore the potential to enhance the abundance and diversity of forest understory species through thinning and creation of canopy gaps. We are focusing on the dynamics of vascular and non-vascular plants (mosses and liverworts) and their responses to changes in forest structure, light availability, and soil resources (click here).
A third general area of research addresses the ecology, dynamics, and restoration of mountain meadow communities. This work has evolved from traditional phytosociological studies of montane and subalpine meadows in the Oregon Cascades (click here), to historical reconstructions of tree invasion patterns and how these have been shaped by local environment, grazing history, and climate change (click here). We have also explored the potential for positive interactions among trees to facilitate invasions once tree establishment is triggered by other factors (click here). Conversely, we have studied the consequences of conifer encroachment for the biological diversity of these systems both at local scales (click here) and for larger, more diverse landscapes (click here). Finally, in systems in which recent conifer encroachment has reduced the quality or extent of montane meadows, we are using large-scale field experiments to test the potential for restoration through tree removal and prescribed burning (click here).