Scaling to Regional Controls Over Prairie Plant Range Distributions under Future Climate Change

Principal Investigators:

Scott Bridgham, Bart Johnson, Laurel Pfeifer-Meister, and Bitty Roy–University of Oregon

Mitchell Cruzan–Portland State University

Daniel Doak–University of Colorado, Boulder

William Morris–Duke University

 

Paul Reed, University of Oregon Ph.D. Student

Graham Bailes and Aaron Neson, University of Oregon Technicians:

Funded by National Science Foundation MacroSystems Biology Program, 7/2014 – 7/2019

Site Collaborators: The Nature Conservancy (OR), Siskiyou Field Institute (OR), Capitol Land Trust (WA)

This is a renewal of the Department of Energy Office of Biological and Environmental Research grant titled “Climate Effects on Plant Range Distributions and Community Structure of Pacific Northwest Prairies” from 1/2009 – 12/2013.

A key challenge in global change ecology is to understand how climate change will interact with other perturbations, such as land use and invasive species, to impact biodiversity through changes in species range distributions. There is overwhelming evidence that many species have shifted their ranges in the past 30 years concurrent with recent climate change. However, previous empirical studies of observed range shifts and bioclimatic envelope modeling studies have lacked a strong theoretical foundation for their predictions of future change. Thus, a mechanistic approach that fuses theory with experimentation will be necessary to understand controls of geographic range distributions. Moreover, dispersal has not been incorporated in models of species range shifts to date except in very rudimentary ways, but dispersal may limit many species from responding to climate change, especially in today’s fragmented landscapes.

Pacific Northwest (PNW) prairies are imperiled ecosystems that contain a large number of plant species with high fidelity to this habitat, many of which have northern and/or southern range limits from southwestern Oregon/northern California to Washington. The few remaining high-quality prairies harbor a number of sensitive, rare, and endangered plant species that may be lost with climate change. This situation is also typical of many other habitats that contain rare and/or endemic species. We are experimentally manipulating temperature and precipitation in three upland prairie sites along a natural climate gradient from southwestern Oregon to central-western Washington to determine (1) how future climate change will affect the range distribution of native plant species, and (2) how viable current restoration practices are under future climate change.

The goal of this research is to advance the understanding of how climate change will affect species range distributions from the local to regional scale by coupling four tasks:

  • We are experimentally manipulating temperature and precipitation in three upland prairie sites embedded within a natural climate gradient from southwestern Oregon to central-western Washington. We are using this unique experimental design to examine the role of climate vs. local factors in controlling the demography of a broad suite of 12 native grass and forb species that currently reach range limits in the Pacific Northwest (PNW). Demographic models will be used to quantitatively determine the relative effect sizes of local factors (e.g., plant community composition and soil variables), regional-scale climate differences, and interannual climate variability on the vital rates of the focal species.
  • We are also these same questions in natural populations of the six perennial plant species along this climate gradient in the PNW. Besides allowing a comparison of the results from the manipulative experimental populations to natural populations, this also gives us a much larger dataset for the regional demographic modeling described below.
  • Landscape genetics will be used to determine dispersal probabilities of eight of the focal species in landscapes with different ‘resistances’ to dispersal due to both historical and contemporary land use/land cover, geographic dispersal barriers, and distance between prairie habitat patches.
  • The first three components will be synthesized in a regional landscape simulation under three climate change scenarios within interior-valley prairies in the PNW. We will then use the simulation to determine whether the focal species are likely to go extinct in all or parts of their current ranges, where they are capable of surviving outside of their current ranges under future climatic conditions, and the probability of reaching these new favorable habitats, if they exist. The effects of increased or decreased landscape resistance to dispersal through loss (e.g., increased development pressure) or gain (e.g., increased prairie restoration) of prairie habitat in the future will also be examined.
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