The BOREAS Information System
Terrestrial Ecology (TE)


TE-9: Relationship Between Measures of Absorbed and Reflected Radiation and the Photosynthetic Capacity of Boreal Forest Canopies and Understories


P.I.(s): Hank A. Margolis -- Universit`eacute Laval
Collaborators: Geoffrey Edwards, Keith Thomson, Alain Viau -- Universit`eacute Laval

Objectives: This project will examine the relationship between net photosynthetic (net Ps) capacity, N concentration and percent photosynthetically active radiation (%PAR) of three major boreal forest cover types (jack pine, black spruce and aspen) as well as their link to remotely-sensed and land-based measures of reflected and absorbed radiation. We will attempt to establish general relationships which can be used to predict the vertical distribution of the net Ps capacity for these cover types, including their understories, when neither water nor temperature is greatly limiting. We will also determine how these relationships will vary over the growing season and among six different stand conditions at the Northern Study Area (NSA). Furthermore, the photosynthetic response surface of foliage from the three main cover types with respect to light, temperature, vapor pressure deficit and internal CO2 will be determined during each IFC using a laboratory-based photosynthetic system with cut branches. The effects of in situ frost exposures on the photosynthetic characteristics of the three main cover types as well as their patterns of recovery will be determined in order to introduce more realistic algorithms of the effects of frost on carbon flux. PAR measurements taken within the the canopy will be supplemented with geometry measurements of the different canopy constituents and the spatial variability of these measurements within the stand will be examined. Additionally, the BRDF of soil and understory components, the spatial variability of the spectral signatures of soil and understory components, and the spectral distribution of hemispherical downwelling radiation will be characterized in order to drive and validate a forest canopy reflectance model (TRELITE). This model will be used to estimate PAR levels within the various forest canopies and these estimates will then be used as input to the photosynthetic model. Depending on the availability of additional resources, canopy biochemistry (lignin, cellulose, starch, sugars, chlorophyll and terpenes) will be followed over the growing season for six stands.

TE-9 Data Sets

  • Photosythetic Response to CO2
  • Photosythetic Response to Temperature
  • Photosynthetic Response to Light
  • Photosynthetic Response to VPD
  • Photosynthetic Response to Water Potiential
  • Leaf Biochemistry
  • Understory Reflectance
  • N versus PAR Profile
  • N versus Photosynthesis
  • Diurnal Gas Exchange

  • Get some TE-9 data using FTP (BOREAS Investigators only, password required). [FTP Help]

    TE-9 BOREAS Operations 1994


    Objectives:
    There are five main components to this study:

    1. Measure the response of branches, for all foliage age-classes, to light, CO2 concentration, temperature and vapor pressure deficit for jack pine, black spruce and trembling aspen.
    2. Determine diurnal photosynthesis of intact branches.
    3. Produce profiles of %PAR versus nitrogen concentration for each IFC.
    4. Measure concentrations of chlorophyll, nitrogen, starch, lignin, cellulose, and sugars.
    5. Make measurements of angular and nadir reflectance of the understory.


    Data Collection and Equipment:

    1. Response of branches to light, CO2 concentration, temperature and vapor pressure deficit. All foliage age-classes combined for jack pine, black spruce and trembling aspen in the Northern Study Area were measured. A cut branch technique was used. A laboratory-based open photosynthetic system was used.
    2. Diurnal photosynthesis of intact branches was measured with LiCor-6200 from canopy access towers in the Northern Study Area.
    3. Profiles of %PAR versus nitrogen concentration used PAR data taken with LiCor quantum sensors from the canopy access towers on overcast days. Nitrogen measured in the lab using kjeldahl procedure.
    4. Concentrations of chlorophyll, nitrogen, starch, lignin, cellulose, and sugars were measured using branches harvested in the field and analyzed using standard laboratory procedures (refer to Data Documentation for details).
    5. Measurements of angular and nadir reflectance of the understory in the NSA. An Analytical Spectral Devices Personal Spectrometer II, a 35 mm photographic camera and a LiCor Integrating Sphere were used.


    Measurement Sites and Periods:

    1. Response of branches to light, CO2 concentration, temperature and vapor pressure deficit for jack pine, black spruce and trembling aspen. Data were collected for each of the three IFC's.
    2. Diurnal photosynthesis of intact branch branches was collected for selected days for each IFC for NSA -OJP, -YJP, -OBS, -TE-BS, and -OA.
    3. Profiles of %PAR versus nitrogen concentration were collected for each IFC for NSA -YJP, -OJP, -OBS, -TE-BS, -OA and -YA.
    4. Concentrations of chlorophyll, nitrogen, starch, lignin, cellulose, and sugars were collected for NSA -OBS, -OJP and -OA for all three IFC's and the two FFC's.
    5. Measurements of angular and nadir reflectance of the understory . Measurements were made in the NSA -YJP, -OJP, -YA and -OA sites. Measurements were taken on 23 different days between May 27 and July 31, 1994.


    Known Problems and Caveats:
    Measurements of angular and nadir reflectance of the understory, the solar plane orientation was generally random in respect to the angular plane but was known in most cases. Some of the data were normalized to the white reference panel when the panel was in shade.

    Click on a team designation to go to that page.

    TE Overview || TE-1 | TE-2 | TE-4 | TE-5 | TE-6 | TE-7 | TE-8 | TE-9 | TE-10 | TE-11 | TE-12
    TE-13 | TE-14 | TE-15 | TE-16 | TE-17 | TE-18 | TE-19 | TE-20 | TE-21 | TE-22 | TE-23

    Send a data request to the BOREAS Data Manager (BOREAS Investigators only)
    E-Mail a comment on this page to the curator
    Send e-mail to Shelaine Curd, the BORIS representative for the TE group

    Return to the TE Overview
    Return to the BOREAS Science Groups Overview
    Return to the BOREAS Home Page
    Last Updated: October 29, 1997