Nitrogen Limitation and Terrestrial C StorageNitrogen Limitation and Terrestrial C StorageAdrien C. FinziAdrien C. Finzi

Boston UniversityBoston Universityafinzi@bu.eduafinzi@bu.edu

Christine L. GoodaleChristine L. GoodaleCornell UniversityCornell Universityclg33@cornell.educlg33@cornell.edu

NACP MeetingNACP MeetingSan Diego CASan Diego CAFebruary 17-20 2009February 17-20 2009

30 Participants30 Participants

Cramer et al. (2001) DGVMCramer et al. (2001) DGVM Hungate et al. (2003)Hungate et al. (2003)

C x N InteractionsC x N InteractionsA Missing Component of the Predicted Terrestrial-C SinkA Missing Component of the Predicted Terrestrial-C Sink

N limitation constrain ecosystem responses to elevated CON limitation constrain ecosystem responses to elevated CO22??a continuum of responsesa continuum of responses

POP-POP-EUROFACEEUROFACE

RhinelanderRhinelander

ORNLORNL

DukeDuke

SETRES, SCSETRES, SCCostal PlainCostal Plain

slow or no loss

of stimulation

rapid loss or no rapid loss or no stimulationstimulation

Texas TunnelTexas Tunnel

Minnesota BioCONMinnesota BioCON

Florida Scrub OakFlorida Scrub Oak

Flakaliden, Flakaliden, Boreal Boreal SwedenSweden

Can the current generation ofecosystem models accuratelyrepresent the variation in responsefor the right reasons?

atmospheric N deposition may reduce N limitation to terrestrial C uptakeatmospheric N deposition may reduce N limitation to terrestrial C uptakeeffects are disputedeffects are disputed

holland et al., 2005, ecol. appl.holland et al., 2005, ecol. appl.

what is the relationship between atmospheric N deposition and primary what is the relationship between atmospheric N deposition and primary production?production?

magnani et al., 2007, naturemagnani et al., 2007, nature nadelhoffer et al. 1996, naturenadelhoffer et al. 1996, nature

Science Challenges:Science Challenges:

1.1. Limited (but growing) engagement of the C cycle science community Limited (but growing) engagement of the C cycle science community A. stoichiometric constraintsA. stoichiometric constraintsB. developing models of belowground dynamicsB. developing models of belowground dynamics

i. N supply not solely a function of climatei. N supply not solely a function of climateii. belowground C allocation drives N cyclingii. belowground C allocation drives N cycling

2.2. No real time or automated measurements of N cycling variables (except No real time or automated measurements of N cycling variables (except remotely sensed foliar [N])remotely sensed foliar [N])

3.3. Resource intensive measurements (time & money) limit spatial and Resource intensive measurements (time & money) limit spatial and temporal extent of available datatemporal extent of available data

4.4. Significant uncertainties in the effects of N deposition on NEPSignificant uncertainties in the effects of N deposition on NEP

Agenda Item for NACP CommunityAgenda Item for NACP Community

Explicitly incorporate the biogeochemical cycle of N into discussions and Explicitly incorporate the biogeochemical cycle of N into discussions and measurements of the terrestrial C cyclemeasurements of the terrestrial C cycle

1.1. Development of databases for model development and calibrationDevelopment of databases for model development and calibration

2.2. Model-data intercomparison activities Model-data intercomparison activities use existing, detailed experiments to test model C-N interactionsuse existing, detailed experiments to test model C-N interactions

- 15N tracer experiments to model dynamics of N dep. correctly- 15N tracer experiments to model dynamics of N dep. correctly

- - LIDET studies to assess model N mineralization dynamicsLIDET studies to assess model N mineralization dynamics

3.3. Develop standard measurements of N pools at carbon observation sitesDevelop standard measurements of N pools at carbon observation sites

A. Foliar N at existing sitesA. Foliar N at existing sites

-spectral methods for high frequency measurements on time scales -spectral methods for high frequency measurements on time scales comparable with C flux measurementscomparable with C flux measurements

B. Leverage existing biometric measurements by sending samples for C & N B. Leverage existing biometric measurements by sending samples for C & N analysisanalysis

4.4. Develop next-generation C-N experiments to aid model developmentDevelop next-generation C-N experiments to aid model development