Update on Next-Generation Ecosystem Experiments

1. Update on Next-Generation Ecosystem Experiments Jeffrey S. Amthor, Ph.D.Biological and Environmental Research Climate and Environmental Sciences Division Meeting of the Biological and Environmental Research Advisory Committee February 23, 2010

2. Advancing the frontier of climatic change research in terrestrial ecosystems In the past few decades, BER developed and implemented leading technologies and approaches used for large-scale, long-term experimental study of potential effects of climatic change on terrestrial ecosystems. This includes successful implementation of ecosystem-scale free-air CO2 enrichment (FACE) and precipitation manipulations. Going forward, we now ask “What and where are the critical ecosystem research needs?” “What is the next-generation ecosystem experiment?” DOE/BER Wisconsin FACE experiment

3. Building on BERAC and community input To answer this question — “where do we go now?” — we are using a range of inputs, including: ► An ongoing series of discussions with BERAC, notably with Jim Ehleringer and Jim Tiedje ► “Workshop on Exploring Science Needs for the Next Generation of Climate Change and Elevated CO2 Experiments in Terrestrial Ecosystems” (2008; 50 scientists) ► Report on the BERAC workshop “Identifying Outstanding Grand Challenges in Climate Change Research: Guiding DOE's Strategic Planning” (2008; 57 scientists) ► “Report of the BERAC Subcommittee Reviewing the FACE and OTC Elevated CO2 Projects in DOE” (2006)

4. High-level criteria were developed The next-generation ecosystem–climatic change experiment should be: ► In ecosystems that are globally important with respect to potential feedbacks to climatic change, including the potential for significant effects on: • Carbon cycle • Surface albedo or sensible energy exchange • Hydrologic cycle ► In ecosystems that are expected to be sensitive to climatic change: • Temperature or precipitation are critical constraints • Near environmental thresholds

5. High-level criteria were developed (continued) The next-generation ecosystem–climatic change experiment should be: ► With ecosystem–climatic change combinations that have been relatively understudied, in order to fill larger knowledge gaps. These include, for example: • Tropical systems • High-latitude systems • Complicated/complex systems ► In locations and using technology that makes the experiments feasible with resources (including funds) expected to be available.

6. National lab “infrastructure expert” meeting We then hosted a focused one-day meeting (Feb 2009) of seven National lab scientists with unique expertise in long-term, large-scale ecosystem–climatic change field experiments. The discussion, based on the four criteria, concluded that: ► DOE priorities include multi-factor experiments (warming in combination withelevated CO2) in intact ecosystems. ► Ecosystem priorities were: • Tropical forest • Tropical savanna (grassland) • Boreal forest • Arctic tundra ◄ this one looks feasible in the near term

7. Some carbon stocks of importance Carbon pool Carbon content (Pg) Preindustrial atmosphere (280 ppm CO2) 594 Present atmosphere (387 ppm CO2) 820 Global soil (0-3.0 m depth) 2050 (excluding tundra and boreal forest) Northern permafrostregion (0-0.3 m depth) 191 (≈ tundra and boreal forest) (0-1.0 m depth) 496 (0-3.0 m depth) 1024 * (below 3 m depth) 648 (total) 1672 * This is more than the amount of CO2 now in the atmosphere. Sources: Barnola et al. (1995), Jobbagy & Jackson (2000), Tarnocai et al. (2009).

8. Arctic tundra as a next-generation target The structure (short vegetation) of arctic tundra may make it amenable to the next-generation experiment, but the arctic environment would pose challenges. Scientifically: ► High-latitude permafrost contains large stocks of carbon (under both tundra and boreal forest). ► Past, present, and future warming is greatest at high latitude. ► Warming increases the active layer depth (depth of summer soil thawing) and melts permafrost, which could cause a LARGE net release of CO2 and/or CH4 to the atmosphere — a strong positive feedback to warming. ► Warming might reduce albedo (another positive feedback).

9. Surface soil in northern Alaska is warming BP is monitoring active layer depth at Prudhoe Bay. The record is short, but for the period 2005–2008, active layer thickness increased. Could this be normal interannual variability?

10. Deep soil warmed for at least 12 years At Prudhoe Bay, from 1993 through 2008 there was a clear increase in temperature at depths from 20 to 55 meters (and below). While soil at those depths is still solidly frozen, the warming trend is rapid: +1.3°C in “only” 12 years at 20 m depth!

11. Ongoing warming may be regional in extent Deep soil (20-m) warming is greatest at the northern most sites (coldest soils), but may be occurring generally across Northern Alaska.

12. A simulation for a future northern Alaska An improved, deeper soil profile was added to the Community Land Model (CLM). In simulations based on the A1B IPCC emissions scenario, within about 50 years permafrost at 1 m depth becomes summer water. By year 2100 about 80% of “near-surface permafrost” is lost. Data courtesy of Dr. Dave Lawrence [see Journal of Geophysical Research 113, F02011, 2008]

13. “High-latitude” community workshop We hosted a focused one-day meeting (July 2009) of 17 scientists and engineers (university and laboratory) with 200+ person-years of experience conducting ecological research in arctic tundra. The purpose was to discuss a potential arctic tundra warming/elevated CO2 experiment (in Alaska for logistical reasons). Highlights of the discussion included: ► An experiment could be built around the high-level question: What is the overall climatic change feedback potential of the arctic? ► A wide range of temperature and [CO2] should be used to understand nonlinear and potential “threshold” responses to climatic change

14. “High-latitude” community workshop (continued) Other discussion highlights were: ► Good replication is needed, and question of where in Alaska to do the experiment (or experiments) is important. ► Active layer thickness would be a key variable, and possibly the best measure/integrator of the temperature treatment. ► Modeling would be critical before, during, and after the experiment. ► A full range of ecosystem processes should be studied ► Novel techniques will be needed for measurements, access to experimental plots (tundra is “sensitive”), and modeling. ► Wide community participation should be facilitated.

15. A Science magazine “Perspective” was blunt “Permafrost is a globally significant carbon reservoir that responds to climate change in a unique and very simple way: with warming, its spatial extent declines, causing rapid carbon loss….” —Zimov, Schuur, and Chapin (2006) Science 312:1612-1613 [positive carbon feedback] At the same time, ongoing warming is significantly increasing arctic plant productivity— the arctic has been “greening” with longer growing seasons and increased woody biomass. —Hudson and Henry (2009) Ecology 90:2657-2663 [negative carbon feedback; positive albedo feedback] Do we really know what to expect in the future arctic?

16. Proposed questions for the research community ► What are the most critical science questions about effects of climatic change in arctic ecosystems? ►How can the next-generation arctic climate change experiment best answer those questions? ►What critical lessons can be learned from ongoing (and past) studies in designing the next-generation experiments? ►What are the key technological requirements for future research? ►How can the next-generation experiment best complement other arctic research, both experimental and observational?

17. Experimental approaches — possibilities There are (at least) three general approaches to a controlled warming and elevated-CO2 experiment in a short-statured terrestrial ecosystem. (1) An open-air approach (FACE + infrared-emitting lamps). (2) Controlled-environment field chambers(open or closed). (3) In situ or “off-site” mesocosm arrangement. The field chamber approach to controlled warming differs from the “passive heating” approach now used in high-latitude research. Present systems are based on the “real” greenhouse effect, and lack fine temperature control. ► Both (1) and (2) would require new approaches to deep soil warming — soil must be warmed to at least a few meters depth to understand the permafrost issues.

18. Infrared lamps are nonintrusive (mostly) Combining infrared lamps for surface (vegetation) warming with FACE for CO2 enrichment can provide a completely open-air experiment. The stature of arctic tundra would be amenable to such a combination. Study of the critical belowground environment would, however, require independent soil warming technology not yet proven in the field. Lamps above a spring wheat crop (southern Arizona). Treatments were about +1.5°C daytime / +3.0°C nighttime. Plant development was accelerated. (courtesy of Dr. Bruce Kimball, USDA-ARS)

19. Field chambers are well-tested In this configuration (left; 3 m diameter, 2.4 m tall) a single fan blows air into the chamber with about four air exchanges per minute (the charcoal filter removes O3). Temperature control involves a heater (or chiller) inside the "fan box". CO2 control involves injection into the ingoing air stream. “Open-top chamber” designed by NCSU under contract from U.S. EPA (Heagle et al., 1973). Myriad implementations of this basic design are used to control CO2 and temperature. Many involve straightforward modifications to suit specific plants, ecosystems, and environment variables. On the right are highly transparent chambers used to increase CO2 and temperature in prairie (near Cheyenne, WY). Photo: Scott Bauer, USDA-ARS Information Staff

20. Mesocosms are effective for short vegetation Both “indoors” and “out-of-doors” mesocosms are successfully used for above- and below-ground environmental control. The U.S. Army Cold Regions Research and Engineering Laboratory has the technology needed to control (frozen) soil temperature at this scale very well (at their Frost Effects Research Facility). Courtesy of Dr. John Arnone DOE/BER warming experiment in Oregon

21. Each approach has “pros” and “cons” Present arctic experiments (i) use relatively small plots, (ii) have limited temperature “control,” (iii) do not warm the soil to depth, and (iv) rarely include CO2 control. Questions for the research community are: Which approach should be used going forward, and which question(s) will it be able to answer? Significant infrastructural support will be needed for any large-scale warming and elevated-CO2 experiment, including: • Large amounts of reliable power (electricity, gas). • Reliable clean CO2 (maybe large amounts). • Site access (for scientists) and protection.

22. We briefly toured Prudhoe Bay and Barrow to explore potential access and support infrastructure

23. Belowground warming technology Warming permafrost in situ — without causing a physical “mess” — will be a technological challenge. We have begun: ► Preliminary design of potential approaches for warming several meters of soil. We hope to begin prototype development and testing soon. ► Application of detailed 3-D heat transfer modeling in permafrost to understand where, and how much, heat should be added to an arctic soil. This is where in “mess” enters. ► Fluid dynamics modeling of aboveground heat and CO2 transport to evaluate various open-air or chambered systems in northern Alaska.

24. Beyond the next-generation experiments While working aggressively toward the immediate needs of the next-generation experiment, BER will continue to explore technological needs for research in other ecosystems. We appreciate the need for full-scale warming and elevated CO2 experiments in tropical forests — the next-next-generation experiments, but that is for another day.

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