Biotic Responses to shifting Ecological Drivers in a Desert Community

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

3. Static Mentality

4. Dynamic Reality

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

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

7. Shifting Climate Driver

8. Biotic Responses

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

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

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

12. 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

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

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

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

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

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

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

19. 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

20. 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

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

22. 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

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

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

25. 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

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

27. What will tomorrow look like? ?

28. 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