Flux Measurements and Systematic Terrestrial Measurements

1. discuss gaps and opportunitiesWhat are gaps?

2. brainstorm ideas about collaborative projects (synthesis activities, modeling approaches, data management)

3. prioritize these ideasWhat activities can help address gaps?

4. consider how to move forward (working groups, workshops, etc.)

• Treatment of uncertainty in measurements and models• Components of the N.Am. carbon budget: current status

and potential• AmeriFlux network synthesis: between-site coherence in

fluxes.• Integration of short-term and long-term measurements

(e.g. flux sites compared to biometrics)• Formal intercomparisons of inverse modeling methods.• Formal intercomparisons of forward modeling methods.• Comparison of forward and inverse modeling methods.• Carbon-nitrogen cycle interactions

SUGGESTED TOPICS:

Canadian Carbon Program / Fluxnet-Canada Perspective

Gaps in Data, Analysis, and Infrastructure: 1. Arctic sites – vulnerable, vast gradients, diversity of systems 2. Support for long-term data records. 3. Young and intermediate aged forests 4. Other trace gases – methane, VOC, N2O 5. Industry support

Suggestions for Integration: 1. Fluxnet-Canada DIS has 110 site-years of data currently 2. We are very open to NACP collaboration (conceptually). 3. There is a data policy protocol to follow.

Organizing Teams:1. The existing CCP framework and our Science Committee is definitely a good way to go2. But we are stretched quite thin right now due to lack of resources.

• Use available natural abundance and induced isotope additions to characterize and understand soil C cycle mechanisms for model improvement

– Enriched isotopic tracers• 14C - EBIS-AmeriFlux; 13C-FACE work; C3plant/C4soil or C4plant/C3soil studies

– Interpretation of 13C patterns along altitudinal and latitudinal gradients (Garten)• Establish measurement protocols and sampling schemes for uniform analyses of organic

and mineral soil C pools (labile vs. recalcitrant forms) across the AmeriFlux network. – A number of measurement approaches are summarized in posters at this meeting– Uniform multi-site measurements have been proposed (AmeriSoils - Jastrow et al.)

• Plan for extrapolations to the earth outside of N. America.• Conduct cross-project syntheses

Soil Carbon Issue: We shouldn’t assume fixed C pools in our analysis of intra- or inter-annual NEE patterns at the flux sites. Organic layer carbon and labile pools of mineral soil carbon may not be as stable as often assumed.

We need to conduct or continue experiments and observations to understand changing soil carbon dynamics and soil C pools, sensitivity of soil carbon pools to warming, and the net effect of warming plus CO2 fertilization on soil carbon pools.

•Answer the question: Will projected future carbon losses from warming be balanced by the potential for carbon replacement through CO2 fertilization?

Measurements• Spatial and temporal patterns of C stocks and fluxes• Mechanisms/processes (C sink)

– Growth enhancement (fertilization, climate change)– Ecosystem recovery (land use history, fire suppression)

• Underlying mechanisms/processes – Photosyn/respiration - Emissions– Fertilization/pollution - Land Use– Nutrient limitation - Land Management– Allocation - Fire Management– Competition - …– Natural disturbance– …

• All available in “real time” -Hurtt/NACP

We need a comprehensive understanding and reconciliation of uncertainties:

• In observations – for example…

• Flux measurements compared to site-specific biometrics

• Site-specific biometrics compared to inventory data

• Inventory data compared to remote sensing products

• In modeling – for example

• Diagnostic (inverse, top down) models compared to prognostic (forward, bottom up) models

• Site-specific parameterizations compared to regional (or global) parameterizations

• Comparisons across levels of complexity in process speciffication

• Observations compared to model results

Who/How?? NACP Synthesis Task Force is a potential point of coordination. But first we need to decide as a group on a short list of high priority needs that are not currently met.

J. Collatz - Needs

• biomass and biomass components • To help diagnose interannual and seasonal variability as well

as test remote sensing data flux tower sites should measure seasonal and interannual lai/fpar (e.g. licor or over-under canopy incident par). There are far too few of these types of measurements available, especially for forest systems.

• Interannual variability in biomass/detrital pools would be highly useful. In the case of herbaceous systems via harvesting, in the case of forests, periodic measurements using tree cores or dendrometers and measurements of litter fall.

• measurement of component fluxes such as, soil respiration, leaf photosynthesis etc would be great but are harder and more expensive to make. 

• Seasonal-interannual soil moisture measurements are also important but rare

Baldocchi, unpublished