Why study biogeochemistry(sciences?) at regional scales? Ken Davis Department of Meteorology The Pennsylvania State University

Hypotheses Most students of environmental sciences are in the field (primarily? secondarily?) because they are interested in helping society to protect/manage/improve the environment of the earth. Graduate programs that educate students about the societal application of their research and involve them in these applications will provide the best educational experiences for those students.

Pasteur’s quadrant Scientific merit low high Societal value / broader impacts low high don’t go here pure curiosity- driven science pure applied research Pasteur’s quadrant (Stokes, 1997)

Hypotheses Investigating the societal applications of one’s research causes one to pose new and different scientific questions. These scientific questions are often both good basic research and of high societal value. Regional biogeosciences research often falls within Pasteur’s quadrant.

Why are we focusing on regional scales? There is a methodological challenge

Example: Carbon cycle science We know the global budget very well from atmospheric measurements, but we don’t know the processes responsible. Flux towers - we have a decent chance of understanding the processes the yield observed fluxes, but it is very hard to extrapolate these to explain the global budget of atmospheric CO 2

Inherent spatial and temporal scales of methods of studying the (carbon) cycle

1 ppm yr -1 ~ 2 PgC yr -1. Fossil fuel emissions are ~ 6 PgC yr -1. Sink is implied! Interannual variability!

Fate of emitted CO 2 ~45% of fossil fuel emissions absorbed by something in the earth system Large interannual variability in sink strength Governed by climate variability (e.g. ENSO)? Anthropogenic land-use emissions ~ 2 GtC yr -1  implies even larger sink Source: Sarmiento and Gruber, Physics Today, 2003

Chequamegon Ecosystem- Atmosphere Study (ChEAS) region

Photo credit: UND Citation crew, COBRA WLEF tall tower (447m) CO 2 flux measurements at: 30, 122 and 396 m CO 2 mixing ratio measurements at: 11, 30, 76, 122, 244 and 396 m WLEF CO 2 flux and mixing ratio observatory

WLEF Lost Creek Willow Creek Sylvania

Example of the research direction hypothesis A motivation to manage the earth’s climate may alter our research direction. Example: If forest area is increasing (potential cause of the terrestrial sink of carbon), how will this alter the earth’s albedo, thus feed back to climate? (new Pasteur’s quadrant question emerges)

Potential (personal) motivations for pursuing regional biogeochemistry Methodological challenge. You’re curious. Accounting – reporting. Someone (government?) wants to know the numbers. See Kyoto protocol, etc. Personal pragmatism – you can do it, it advances your career. You want to be famous. You want to be rich. You want to help manage the future climate and ecological health of the planet. We need to develop the ability to predict the future. See SOCCR, IPCC.

My Motivation Maintain the environmental integrity of the earth, while protecting human quality of life. Requires that we develop the capacity to predict the future climate - immense scientific challenge. Underlying value – we believe it is valuable to maintain the earth as a good place for life. Advice: Examine your motivations and values. Guide your work appropriately.

We need to be able to validate our predictive models with observations and experiments. See the IPCC for a good example.

Science plan Via observations and experiments, gain a predictive understanding of the earth’s (carbon) cycle. Local-scale observations and experiments are best for developing process understanding required for predictive models (e.g. soil flux measurements, biomass inventories). Global-scale measurements make sure we get to the correct end-result when we up-scale. Regional methods are a key step in evaluating our ability to upscale our local process understanding to the globe. Method-hopping - see M. Goulden’s talk.

State of carbon cycle prediction Terrestrial system is very relevant - human management is changing atmospheric CO 2 rapidly at a time scale (~100 years) where terrestrial ecosystems will respond in a very dynamic (and unpredictable) fashion. Friedlingstein et al. (2006)

Wish: Detect climate-driven trends in local observations, hindcast these trends with process-models, match to experimental results, improve predictability. Long-term data that represents specific processes is most easily obtained at a local scale. Regional-scale methods are needed to evaluate our ability to upscale the local understanding. flux time N years of observations required(?) Flux tower time series Multi-decade terrestrial carbon cycle model prediction and uncertainty Manipulative experiment

Example of one potential long-term observation that we can use to develop process models - flux towers.

Flux tower time series - can we predict them? Do they represent regional processes? Gap-filled fluxes from the 5 sites used in TRIFFID analysis Harvard and Howland: Coherent between 1996 and 2000, then breaks down. UMBS and Morgan Monroe: coherent (similar PFT, climate) WLEF: 2002 missing, coherent with UMBS and Morgan Monroe

Model performance: Interannual variability Ricciuto, Penn State Ph.D. - paper in preparation.

Observed interannual variability: Only local processes? Probably not. Gap-filled fluxes from the 6 midwestern flux tower sites. Interannual variability of similar plant functional types appears to be coherent. Similar processes, linked to climate, influencing sites as far as several hundred kilometers apart in a similar way? Work in preparation. LC = wetland; WC, MMSF, UMBS = mature hardwood; Syl = mixed old growth; WLEF = mixed

Why (eco?)regions? Ecoregions have similar ecological processes, human management and climate, and often correspond to governmental boundaries (reporting). Regions are big enough to test process understanding over large scales, but not so large as to easily get the right answer (agreement between “top-down” and “bottom- up” methods) for the wrong reason (aggregated errors and the errors cancel) (?)

What is the value to society of improving carbon cycle/climate prediction? If we endeavor to manage the climate of the planet, uncertainty leads us to either: 1) not do a good enough job and suffer the consequences of environmental harm, or 2) devote too many resources to management, resulting in unnecessary damage to the quality of human life. Thus developing predictive skill for the earth’s climate has very practical and significant benefits to society, while also addressing a very challenging scientific question. Pasteur’s quadrant. Motivation for regional biogeosciences.