Landscape variation in canopy nitrogen and carbon assimilation in a temperate mixed forest.

Academic Article


  • Canopy nitrogen (N) is a key factor regulating carbon cycling in forest ecosystems through linkages among foliar N and photosynthesis, decomposition, and N cycling. This analysis examined landscape variation in canopy nitrogen and carbon assimilation in a temperate mixed forest surrounding Harvard Forest in central Massachusetts, USA by integration of canopy nitrogen mapping with ecosystem modeling, and spatial data from soils, stand characteristics and disturbance history. Canopy %N was mapped using high spectral resolution remote sensing from NASA's AVIRIS (Airborne Visible/Infrared Imaging Spectrometer) instrument and linked to an ecosystem model, PnET-II, to estimate gross primary productivity (GPP). Predicted GPP was validated with estimates derived from eddy covariance towers. Estimated canopy %N ranged from 0.5 to 2.9% with a mean of 1.75% across the study region. Predicted GPP ranged from 797 to 1622 g C m-2 year-1 with a mean of 1324 g C m-2 year-1. The prediction that spatial patterns in forest growth are associated with spatial patterns in estimated canopy %N was supported by a strong, positive relationship between field-measured canopy %N and aboveground net primary production. Estimated canopy %N and GPP were related to forest composition, land-use history, and soil drainage. At the landscape scale, PnET-II GPP was compared with predicted GPP from the BigFoot project and from NASA's MODIS (Moderate Resolution Imaging Spectroradiometer) data products. Estimated canopy %N explained much of the difference between MODIS GPP and PnET-II GPP, suggesting that global MODIS GPP estimates may be improved if broad-scale estimates of foliar N were available.
  • Status

    Publication Date

  • October 2018
  • Published In

  • Oecologia  Journal
  • Keywords

  • Carbon
  • Ecosystem
  • Foliar nitrogen
  • Forests
  • GPP
  • Land use
  • Landscape
  • Mixed forest
  • Nitrogen
  • Photosynthesis
  • Trees
  • Digital Object Identifier (doi)

    Pubmed Id

  • 30003370
  • Start Page

  • 595
  • End Page

  • 606
  • Volume

  • 188
  • Issue

  • 2