Current Research
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Graduate Students

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, species’ 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 (40+ yr) 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 and community development (click here). Our research also explores the development of young, closed-canopy forest with an emphasis on the dynamics of tree growth and mortality (click here), declines in understory biomass and diversity, and the potential mechanisms by which ground-layer communities are "reinitiated" during subsequent stages of stand development (click here).

A second, core area of research explores the effects forest management activities¾ past and present¾ on plant species diversity and community structure. Large-scale field experiments, chronosequence studies, and retrospective analyses form the basis of this work. For example, 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 (http://www.cfr.washington.edu/research.demo/). Our vegetation studies encompass observations of ground-layer bryophytes, understory herbs, regenerating trees, and the residual forest overstory (click here). A second study, also of regional scope, explores the long-term consequences of broadcast burning for forest understory composition and structure (click here). A third investigation, conducted on private timberlands in western Washington, explores patterns of plant diversity and understory development in intensively managed plantation forests. Here, we seek to document changes in understory vegetation through stand development; to quantify effects of silvicultural practices (e.g., thinning, N-fertilization, multiple rotation harvests); and to develop predictive models of understory development as a function of stand age, management history, and environmental controls (click here). We have recently initiated research in fire-prone ecosystems of eastern Washington ¾ here we are studying the response of forest understories to restoration activities (silvicultural thinning and prescribed burning) and to recent wildfires (click here).

A third general area of research addresses the ecology and dynamics of non-forested communities in the western and high Cascades. This work has evolved from traditional phytosociological studies of montane and subalpine meadow communities (click here), to historical reconstructions of tree invasion into meadows and how temporal and spatial patterns of invasion are shaped by local environment, grazing history, and climate change (click here). More recently we have begun to initiate field experiments that evaluate the effectiveness of thinning and prescribed burning for meadow restoration where fire exclusion has led to significant conifer encroachment and degradation or loss of these biologically diverse systems (click here).