Dr. Sybille Haeussler, University of British Columbia

Seminar Abstract: Conservation of ecosystem diversity -by comparison with species diversity- has suffered from lack of a strong body of theory that explains the evolution of ecosystems as emergent, self-organizing entities and predicts their biophysical isolation from their nearest neighbours. Dr. Haeussler will present a model of terrestrial ecosystem diversity and resilience that is based on complex systems theory and draws on empirical research in rapidly changing northern temperate and southern boreal forest and grassland ecosystems of northern British Columbia, Canada. The model is a simplification of Jenny's (1941) state factor model that describes the development of ecosystems as a function of three variables: e = f(r, o, t) where r = resource availability (temperature, water, nutrients), o = organisms (functional group richness), and t = time or disturbance. The three variables interact to generate higher orders of complexity through self-organizing plant-soil feedback switches. Highest complexity is hypothesized to occur in landscapes, such as northern British Columbia, that have moderate to low values of these variables, and are poised near the transition between order and disorder. Highest ecological resilience should occur in environments where negative feedbacks prevent any one of several ecosystem attractors (e.g., podzolization, paludification, melanization) from becoming dominant. Conversely, highest beta or ecosystem diversity should occur where each of the attractors is able to become dominant at various points in space and time. Field studies in forest and grassland ecosystem of northern B.C. exposed to gradients of anthropogenic and natural disturbance illustrate how the model was derived and how it can provide guidance on managing for ecosystem diversity and resilience in the face of global change.

Research Interests: Dr. Haeussler's research addresses the origins, maintenance and restoration of terrestrial ecosystem diversity with a focus on her home region of northern British Columbia, Canada. After many years studying the dynamics and diversity of plant communities in the context of sustainable forest management, she has recently shifted to using methods from complex systems science to model how self-organizing processes arising from positive feedbacks between forest soils and vegetation contribute to ecological resilience and to creating complex mosaics of ecosystems across landscapes. Her ongoing field research encompasses a range of highly resilient to critically endangered ecosystems including boreal coniferous, mixedwood and deciduous forests, grasslands, coastal floodplains and subalpine woodland ecosystems.

Host: Dr. Charles Canham