Impacts of leaf phenology and water table on interannual variability of carbon fluxes in subboreal u...
This presentation is the property of its rightful owner.
Sponsored Links
1 / 25

Impacts of leaf phenology and water table on interannual variability of carbon fluxes in subboreal uplands and wetlands PowerPoint PPT Presentation


  • 108 Views
  • Uploaded on
  • Presentation posted in: General

Impacts of leaf phenology and water table on interannual variability of carbon fluxes in subboreal uplands and wetlands. Implications for regional fluxes in the upper Midwest USA. Ankur R Desai, Benjamin N Sulman University of Wisconsin-Madison D. Scott Mackay

Download Presentation

Impacts of leaf phenology and water table on interannual variability of carbon fluxes in subboreal uplands and wetlands

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Impacts of leaf phenology and water table on interannual variability of carbon fluxes in subboreal uplands and wetlands

Implications for regional fluxes in the upper Midwest USA

Ankur R Desai, Benjamin N Sulman

University of Wisconsin-Madison

D. Scott Mackay

State University of New York-Buffalo

Ameriflux/ChEAS PIs

Ameriflux Meeting 2008


Motivation

  • Interannual variation (IAV) in carbon fluxes from land to atmosphere is significant at most flux sites

  • Key to understanding how climate affects ecosystems comes from modeling IAV

  • IAV (years-decade) is currently poorly modeled, while hourly, seasonal, and even successional (century) are better


Predicting NEE (Ricciuto et al)


Climate Drivers of Carbon Flux

  • Temperature

  • Precipitation

  • Radiation

  • [CO2]


Interannual

^

Climate Drivers of Carbon Flux

  • Temperature-> Phenology

  • Precipitation-> Drought

  • Radiation -> Light Quality

  • [CO2] -> Acclimation


Interannual NEE at ChEAS


Questions

  • What controls IAV of NEE in subboreal uplands?

    • Hypothesis: Phenology -> Growing season start, end, or length affects GPP

    • Piao et al (2008) -> Autumn warming and Rh

  • What controls IAV of NEE in subboreal wetlands?

    • Hypothesis: Phenology + Water table affects ER

    • Ise et al (2008) -> Decomposition and moisture

  • What controls IAV of regional NEE in subboreal North America?

  • Can a very simple model be constructed to explain IAV?

    • Can we make do a parameter opimization more attuned to IAV?

    • Hypothesis: MCMC overfits to hourly data


Optimization

HOURLY

IAV


Phenology

  • Five sites with 5-8 years of data

    • 1 regional (LEF), 1 wetland (LCR), 3 uplands (SYL, UMB, WCR)

    • Assimilate 1st 4 years of data


Phenology Model

  • Twice daily model, annually resetting pools

  • Driven by PAR, Air and Soil T, VPD

  • LUE based GPP model f(PAR,T,VPD)

  • Three respiration pools f(Air T, Soil T, GPP)

  • Model 1. NOLEAF

    • Constant leaf on and leaf off days

  • Model 2. LEAF (Phenology)

    • Sigmoidal Threshold GDD (base 10) function for leaf on

    • Sigmoidal Threshold Daily Mean Soil Temp function for leaf off

  • 17 parameters, 3 are fixed

    • Output: NEE, ER, GPP, LAI


Hourly

HOURLY NOLEAF

HOURLY LEAF

IAV NOLEAF

IAV LEAF


Interannual

HOURLY NOLEAF

HOURLY LEAF

IAV NOLEAF

IAV LEAF


NEE-Leaf


GPP ER Leaf


Precipitation and Water Table

  • Sulman et al (in prep) Biogeosciences - see Ameriflux poster


Shrub Wetland Flux Response


Three Wetlands


Three Wetlands


Regional NEE

  • See NACP poster in Feb.


Conclusions

  • Autumn soil temperature appears to be a major control on interannual variability in subboreal upper Midwest USA flux tower site annual NEE

    • Due mainly to effect of growing season length for GPP

    • Only detectable using a modified MCMC cost function that penalizes for poor fit to cumulative annual NEE

  • Additionally, growing season average water table strongly affects ER in wetlands

    • GPP effect in both uplands and wetlands -> related to precipitation deficits?

  • Regional NEE is messy

  • Thanks: DOE NICCR, DOE TCP, NASA CC, NOAA CPO, USDA/USFS NRS, NSF, UW Foundation, ChEAS


  • Login