Doctoral Dissertation Research: Understanding and Managing Ecosystem Change at the Forest-Peatland Ecotone

Portland State University, Portland OR

Investigators

Abstract

This doctoral dissertation improvement project will investigate the impacts of changing environmental conditions on the patterns and mechanisms of forest loss and subsequent peatland expansion in temperate and other non-boreal regions. Using a variety of methods, the doctoral student will reconstruct and compare fire-climate-vegetation dynamics of the past century to those that have occurred over the past millennium. The results of this project will reveal whether once-forested but now peat-accumulating sites are novel ecosystems, or whether such transitions have occurred in the past in these regions, possible due to drought conditions and fire frequencies that are similar to those observed today. These results are of interest to land managers, who require tools to determine how best to manage altered ecosystems. By identifying whether (and which) ecological thresholds have been crossed, this project will provide crucial input for decision-making regarding best practices for land management. The doctoral student will work closely with regional land managers and other stakeholders, including land owners and educators, to ensure that project results are available to inform collaborative land use decisions. The PIs will also engage K-12 and college students in hands-on fieldwork, thus preparing future scientists to employ multiple lines of evidence in investigating the causes and consequences of environmental change. In addition, as a Doctoral Dissertation Research Improvement award, this award will provide support to enable a promising graduate student to establish a strong independent research career. The overarching objective of this doctoral dissertation improvement project is to contribute to the scientific literature on alternative stable states that result from changes in the fire regimes of forested ecosystems. Using methods from paleoecology, dendroecology, and community ecology, this research will examine fire-mediated effects on ecosystem structure at varying spatiotemporal scales at the peatland-forest ecotone, a transition zone that, like tree line, is particularly sensitive to changes in fire and climate. The project addresses the following questions: (1) How has fire activity during post-European settlement periods with distinct climate conditions differed quantitatively from that of pre-settlement conditions? (2) How has fire impacted the vegetation community of the forest-peatland ecotone during the most recent extreme warm/dry and cool/wet periods? (3) What are the mechanisms that favor a transition from forested to peat-accumulating lands in a site? Specifically, the doctoral student will use tree-ring fire scar dates, forest stand structure reconstructions, and sedimentary records to answer these questions. In addition, surveys of present-day vegetation composition/structure at control and burned sites will be paired with those of abiotic and biotic factors to uncover the mechanisms underlying the persistence of the peat-accumulating state. Although this project will focus on the forest-peatland ecotone of southwestern Patagonia, the research will provide new insights and approaches for dealing with the interactive effects of environmental change in many other regions, including some in the United States. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.