THE EFFECT OF PRIMING ON SOIL CARBON DYNAMICS: DEVELOPMENT AND INVESTIGATION WITH CLM4-BETR

JINYUN TANG, W. J. RILEY, C. D. KOVEN, Z. SUBIN AND M. TORN

Funded through CSSEF by DOE-BER

THE MICROBE MODULATED CN SYSTEM

Plants

MicrobesSoil

organic matter

NutrientN,P

Priming

CLM4-BETR: BIOGEOCHEMICAL TRANSPORT & REACTION

CLM4-BETR IMPLEMENTATION

Multi-time stepping Process adaptive 1D generic tracer transport Two-layer surface-plant-atmosphere coupling Multiphase chemistry, fast equilibrium assumption Explicit tracking of fluxes due to: run-off/on, ice/water

phase change, precipitation, dry deposition, ebullition, diffusion

s: solid phaseg: gas phasew: aqueous phase

PRELIMINARY MODEL RESULTS

Single point simulation at Harvard forest

THE MICROBIAL-CN MODEL

PLTR SOM

PSOM

DOM microbes

IMPLEMENT THE GENERIC MICROBIAL-CN MODEL Microbial groups with different

specialties/competitions Different electron acceptors, e.g. aerobic or

anaerobic pathway Dual status, active or dormant (microbial

activity) Multi-substrate feeding, DOC, DOM With colonization capability Step adaptive temporal integration Fully coupled with plants and atmosphere

TEST THE PRIMING EFFECT

Hypothesis: More carbon respired than input under favorable conditions

Model dynamics: Two microbial communities, compete for DOC and inorganic N (NI), coupled with plants and full CN chemistry

DOC/NI PUNCTUATED DOC EXPERIMENT

The input was done on Apr.1st, Jun. 1st, Aug. 1st and Oct. 1st in the first model year. All simulations start with identical initial conditions.

Input DOC Input NH4Exp1 0.05 mol C 0

Exp2 5 mol C 0

Exp3 0.05 mol C 0.01 mol N

Exp4 5 mol C 1 mol N

CHANGE OF CUMULATIVE HETEROTROPHIC RESPIRATION

Exp 2Exp 1

Exp 3 Exp 4

Unit: mol CO2

PUNCTUATED DOC/NI EXPERIMENT

Exp 3 Exp 3

Exp 4 Exp 4

Changes in Microbial biomassUnit: mol C m-3 soil

Changes in litter degradationUnit: mol C m-3 soil s-1

0

0

DOC MOVEMENT EXPERIMENT

Microbial activity: fraction of active microbesImmobile: no vertical movement of DOC allowedMobile: DOC is free to move vertically

SUMMARY CLM4-BeTR is successfully developed for vertically

resolved biogeochemistry modeling Microbial dynamics is critical to improving the CN

modeling The priming effect depends on the dose of

substrate/nutrient input The vertical movement of DOC may provide a subtle

way to increase the carbon sequestration Measurements are need for serious model

evaluations (let me know if someone has measurements, we are open for collaborations!)

THE END?