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Biotic Responses to shifting Ecological Drivers in a Desert Community

Biotic Responses to shifting Ecological Drivers in a Desert Community. S.K. Morgan Ernest Dept of Biology & Ecology Center, Utah State University @ skmorgane. Static Mentality. Dynamic Reality. Shifting Ecosystems: Regime Shifts e.g. Scheffer et al. (2001) Nature. Shifting Drivers.

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Biotic Responses to shifting Ecological Drivers in a Desert Community

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  1. Biotic Responses to shifting Ecological Drivers in a Desert Community S.K. Morgan Ernest Dept of Biology & Ecology Center, Utah State University @skmorgane

  2. Static Mentality

  3. Dynamic Reality

  4. Shifting Ecosystems: Regime Shiftse.g. Scheffer et al. (2001) Nature

  5. Shifting Drivers • Driver: Controls the state of an ecosystem Ecosystem Driver Time

  6. Shifting Climate Driver

  7. Biotic Responses

  8. Shifting drivers, biotic responses • Two case studies: • Short-term driver shifts • Eruption of an exotic species • Long-term driver shift • Increasing shrub cover

  9. LTREB Portal Project - Background • Initiated 1977 by Jim Brown and associates • Monitor rodent and plant dynamics • Diverse rodent & winter and summer annual communities Portal

  10. Portal Project - Background • Control plots, kangaroo rat exclosures, rodent exclosures • Responses to climate and plant responses to granivory

  11. Case Study 1: Short-term Driver ShiftsGinger Allington, David Koons, Morgan Ernest, Michelle Schutzenhofer, Thomas Valone State Change: Exotic species increase Population increase Exotic species: Erodiumcicutarium Allington et al (2013) Ecology Letters

  12. Short-term Driver Shifts • Biotic Driver: • When kangaroo rats or all rodents experimentally reduced, Erodium increases. Population increase Allington et al (2013) Ecology Letters

  13. Short-term Driver Shifts • Biotic Driver: • Considerable variation in kangaroo rats and other rodents through time Population increase Allington et al (2013) Ecology Letters

  14. Short-term Driver Shifts • Abiotic Driver: • No variation across site, but considerable temporal variation in precipitation. Population increase Allington et al (2013) Ecology Letters

  15. Short-term Driver Shifts • Biotic Driver: • Extended drop in kangaroo rat consumption before eruption Population increase Allington et al (2013) Ecology Letters

  16. Short-term Driver Shifts • Abiotic Driver: • Preferred levels of precipitation before kangaroo rats could recover Allington et al (2013) Ecology Letters

  17. Best explanation: perfect storm Allington et al (2013) Ecology Letters

  18. Niche Opportunities • Driver shifts create niche opportunities (Shea & Chesson 2002) • How many drivers and what magnitude to create niche opportunity? Driver Shift Magnitude Number of shifting drivers

  19. Case Study 2: Long-term Driver Shifts The State Change: Arid Grassland to Shrubland Number of shrubs Year 1977 1995 Brown et al (1997) PNAS

  20. The Driver: Precipitation • Long-term increase in winter precipitation • Winter precipitation and shrub growth Brown et al (1997) PNAS

  21. PDO and Southwest Precipitation • Pacific Decadal Oscillation: 20-30 year cycle • Warm Phase: • La Nina – average winter precipitation • El Nino – higher than average precipitation • Cool Phase: • La Nina – drought • El Nino – average winter precipitation Gutzler et al. (2002); Flagstaff NWS Office: http://www.wrh.noaa.gov

  22. PDO Rain Shrubs Rodents Ernest et al 2008 Am Nat

  23. What will tomorrow look like? end Cool cycle end Warm cycle end Cool cycle? ?

  24. Long-term Driver Shifts & Reversals • Multiple drivers and the problem of ‘reversing’ state changes Driver Condition 1 Driver Condition 2 Driver Condition 1 Ecosystem State: Single Driver Ecosystem State: Multiple Drivers fire

  25. Regime Shift Theory • Focused on non-linear state-driver relationships • Multiple driver shifts • Natural shifts & anthropogenic shifts Ecosystem State Ecosystem Driver

  26. What will tomorrow look like? ?

  27. Acknowledgments • Portal Project: Hundred of volunteers, postdocs, graduate and undergraduate students • Alan Ernest • Funded by NSF for almost 35 years • Most recently by NSF LTREB & Utah State University

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