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

Soc

ieta

l val

ue /

bro

ader

impa

cts

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 CO2

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

Methodological gap

Upscaling

Downscaling

Airborne flux

Chamber flux or exp plot Tower

flux

Forest inventory Atmospheric budget

year

month

hour

day

Time Scale

Spatial Scale

(1m)2 = 10-4ha

(1000km)2 = 108ha

(100 km)2 = 10 6ha

(10k m)2 = 10 4ha

(1km)2 = 10 2ha

Rear th

1 ppm yr-1

~ 2 PgC yr-1.

Fossil fuel emissions are~ 6 PgC yr-1.

Sink is implied!

Interannualvariability!

Fate of emitted COFate of emitted CO22

• ~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: http://www.aip.org/pt/vol-55/iss-8/captions/p30cap2.htmlSarmiento and Gruber, Physics Today, 2003

Chequamegon Ecosystem-Atmosphere Study (ChEAS) region

Pho

to c

redi

t:

UN

D C

itatio

n cr

ew,

CO

BR

A

WLEF tall tower (447m)CO2 flux measurements at: 30, 122 and 396 mCO2 mixing ratio measurements at: 11, 30, 76, 122, 244 and 396 m

WLEF CO2 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 predictionState of carbon cycle prediction

• Terrestrial system is very relevant - human management is changing atmospheric CO2 rapidly at a time scale (~100 years) where terrestrial ecosystems will respond in a very dynamic (and unpredictable) fashion.

Friedlingstein et al. (2006)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

timeN 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:Model performance:Interannual variabilityInterannual variability

Ricciuto, 2006. 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, or2) 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.