How Scientists Study Climate Change A Rangeland Perspective

1. How Scientists Study Climate Change A Rangeland Perspective Photo: Sam Cox

2. How Scientists Study Climate Change • Reviewing our present state of knowledge • What we know (accepted by scientists) • Predictions; implications; uncertainty • How we study the problem (techniques that scientist use, their strengths and limitations) • Observation • Manipulative experimentation • Modeling

3. WHAT WE KNOW: Atmospheric CO2 concentrations measured accurately for many decades; they are steadily increasing. Annual cycle due to photosynthesis and respiration of soils. Long term trend due to emission of fossil fuels Charles David Keeling 1928-2005 2002 Nat’l Medal of Science

4. WHAT WE KNOW: Ice core sampling & other techniques indicate rising CO2 in Earth’s atmosphere is a relatively new phenomenon. IPCC Working Group I Report, Chapter 2, 2007

5. WHAT WE KNOW: A direct effect of rising CO2: Stimulation of plant growth. CO2 Food, Glorious Food! Nutrients, H2O Any change in light, water, nutrients or carbon dioxide will alter plant growth.

6. WHAT WE KNOW: Global average surface temperature has increased 0.74 C (1.2 F) in the last hundred years. Rate of warming has doubled in the past 50 years. Predictions indicate future accelerated & extreme warming. IPCC 2007: WG1-AR4

7. IMPLICATIONS OF WHAT WE KNOW Warmer temperatures mean: Longer growing season Desiccation due to warming Altered hydrologic cycle atmosphere holds more water vapor intense rainfall events timing (altered seasonal precipitation; earlier loss of snow pack) some regions will experience more drought Photo: Sam Cox

8. Areas of Uncertainty weather, climate rangeland responses How will climate change be expressed at local and regional scales? How will climate change be expressed at regional and local levels? How will rangelands respond to increased occurrences of extreme events? How will rising CO2, warmer temperature and altered pre- cipitation affect rangelands? How will rangelands & rangeland managers adapt to a more variable environment? Photos: Cox, Derner & SGS LTER

9. OBSERVATIONAL INFORMATION: Historical records & correspondences of early explorers & settlers. Caption from Barker et al., 1934 speaks of “ Coronado and his Band …wandering across … burning sands”, but the expeditions journal of 1541 recorded not deserts but grasslands. (Hart and Hart. 1997. Rangelands 19:4-11)

10. OBSERVATIONAL INFORMATION: Photographs can provide additional qualitative information Mesquite encroachment in SW over past two centuries (photograph courtesy of ARS Jornada Experimental Range photo gallery). Honey locusttree islands in Kansas Tallgrass Prairie. Present-day encroachment? Fire removal, climate change, CO2? (photograph courtesy of Alan K. Knapp).

11. OBSERVATIONAL INFORMATION: Quantitative monitoring for management purposes may be especially useful for climate change Aerial photography & imaging software for quantifying range condition. High resolution infor- mation for assessing rangeland ecological services. Booth, Cox & Simonds

12. Observation Combined with Experimental Treatments Over Time Can Be Powerful Derner & Schuman. 2007. Jour. Soil & Water Cons. 62:77-85

13. Plants leave geochemical fingerprints in soils ! % C4 Vegetation Warmer/dry C4 grasses 0-10 ka Bignell Loess 10-13 ka Brady Soil 13-23 ka Peoria Loess Cooler/wet C3 shrubs & grasses Kelly and Busacca, in Prep

14. Observational Information • Information on ecosystem attributes, obtained in realistic environments, oftentimes of considerable time lengths • Information is often complicated by other factors, like management, which have changed over time • Interpretations often speculative • Limited information on future environments, including multiple changes

15. Manipulative Research for Assessing Ecosystem Responses to CC IR Warming on Tibetan Plateau Free Air CO2 Enrichment in Mojave Mostly single factor experiments Run for two to several years Photos: Nowak, Wang & Knapp Precipitation manipulation in Kansas tallgrass

16. Open Top Chamber CO2 Enrichment Work on the Colorado Shortgrass Steppe: 1996-2001 USDA-ARS & Shortgrass Steppe LTER • Doubling Ambient CO2: • Increased NPP 44% • Increased plant WUE • Favored some plant • spp. over others • Forage N and forage • quality declined • CO2-production responses • cool-season, C3 grasses • fringed sage, 40-fold

17. Prairie Heating and CO2 Enrichment (PHACE) Cheyenne, Wyoming, USA (summer, 2008)

18. PHACE EXPERIMENTAL TREATMENTS ACN AHN ECN EHN ACIs ACId Ambient CO2 Ambient temp No irrigation Ambient CO2 High temp No irrigation High CO2 Ambient temp No irrigation High CO2 High Temp No irrigation Ambient CO2 Ambient temp Shallow irrigation Ambient CO2 Ambient temp Deep irrigation 2 IRRIG Trts (5 reps each) 2 CO2 by 2 TEMP factorial (5 reps each) CO2A (present ambient, 380 ppm), E (elevated, 600 ppm) TEMP C (present temp), H (+ 1.5/3.0 C day/night) IRRIGIs (several seasonal water additions), N (non-irrigated) IRRIGId (one or two annual water additions)

19. PHACE EXPERIMENTAL TREATMENTS ACN AHN ECN EHN ACIs ACId Ambient CO2 Ambient temp Shallow irrigation High CO2 Ambient temp No irrigation Does water replacement give the same response as elevated CO2? CO2A (present ambient, 380 ppm), E (elevated, 600 ppm) TEMP C (present temp), H (+ 1.5/3.0 C day/night) IRRIGIs (several seasonal water additions), N (non-irrigated) IRRIGId (one or two annual water additions)

20. Prairie Heating and CO2 Enrichment (PHACE) Experiment (Cheyenne, WY, USA) CO2 ring Direct Responses to GC Factors Indirect Effects of Water Sentek SWC

21. Trace gas exchange Root dynamics Canopy photosynthesis Plant species abundances

22. Manipulative Experiments • Can expose plants and plant communities to altered environmental conditions • Can provide mechanistic information (NOT considered simulations of the future) • Manipulations artificial, often with known and unknown artifacts • Costly • Few multiple GC experiments

23. Modeling • Mathematical representations of reality • empirical (based on observation; practical) • theoretical (based on mechanisms) • Useful for understanding how systems function • Can fill in knowledge gaps • Predictive tools

24. Plant Community Modeling • Modeled Future Relative Abundances in Temperate Grasslands of North & South America. • Based on: • GCMs • Relative Abundance Equations Based on observations & measurements obtained in the real world. Empirical relationships may not capture CO2 response Epstein, Gill, Paruelo, Lauenroth, Jia and Burke. 2002. J. of Biogeography 29:875-888

25. Summary • Observation, manipulation, & modeling: useful tools for studying climate change and impacts on rangelands • The complexities and uncertainties of climate change argue strongly for • utilizing all of these in our predictions • accepting that policy and management decision will always rely on a certain amount of uncertainty

26. Summary • Science can help us understand & deal with that uncertainty • weather forecasting, monitoring and decision support systems can help us cope with an increasingly uncertain world • learning from other regions/countries where today we may find examples of our future climates (e.g., Australia in terms of variable weather)

27. THANKS FOR YOUR ATTENTION 2008 SUMMER BIOMASS FIELD CREW 2008 SUMMER HARVEST FIELD CREW