TE-10 BOREAS Operations 1994

Objectives:
In this study we will correlate physiological processes at the leaf/needle level with and optical measurements amenable to remote sensing. Specifically, in situ measurements

Approach:
For gas exchange fluxes for CO₂ and water, plant stress as indicated by chlorophyll-a fluorescence, and other supporting measurements will be acquired for dominant species of the boreal forest overstory at the BOREAS Southern sites (mature aspen, mature jack pine, young jack pine, black spruce, and mixed aspen/white spruce). In the laboratory, further measurements of photosynthetic capacity will be made in conjunction with continuous visible/near-infrared spectral optical properties and pigment analyses. Nitrogen will be determined from dry foliar material. This data set will be utilized to estimate the vertical gradients of carbon assimilation, nitrogen use efficiency, and photosynthetic efficiency for different species as a function of phenology and environmental conditions, especially available water, nitrogen, and PAR. These data will be used to examine the relationships between the physiological parameters, especially photosynthetic and conductance rates, and the optical parameters (Fapar and spectral vegetation indices, or SVIs). Ultimately, these data will be used to test hypotheses relating leaf physiology to canopy physiology and remotely acquired SVIs. They will also be used to parameterize the canopy level radiative transfer and physiological models utilized in landscape analyses by other investigators.

Study Objectives:

• Examine the vertical and seasonal dynamics for net photosynthesis and transpiration, PAR, (absorbed, reflected, transmitted), spectral vegetation indices, and leaf characters for the primary overstory species of the major boreal forests (aspen, jack pine, and black spruce) of north-central Canada.
• Evaluate the relationships among net photosynthesis and vegetation indices and fAPAR.
• Evaluate "PAR Canopy Use Efficiency Parameter" Hypothesis (Sellers et al).
• Input to Canopy Models
  • Radiative Transfer Model (BRDF, R. Myneni);
  • Middleton is also Co-I on BOREAS RSS-1 (Deering et al.)
  • Canopy Physiological Processes
  • Canopy Carbon Uptake and Dynamics (Sib)

Measurements Acquired During 1994 IFC's:

1. I. Gas Exchange
   • In Situ (light-saturated): Photosynthesis, Conductance, Transpiration etc.
   • Lab: Photosynthetic Capacity (25°C < T < 29°C), with light curves

2. II. Leaf/Shoot Characters

   Broadleaf	Conifers
   (Aspen, Hazelnut, Misc.)	(Jack Pine, Black spruce, White Spruce)
   Fresh Weight	Fresh Wt., needles + stem
   Dry Weight	Dry Weight/ needles, stem separately
   Projected Area	Projected Area (by age class)
   L, W	L, W, H (needle sample) # needles per age class
   Munsell Color (both sides)	Munsell Color (both sides)
   Pigments: Chl a, Chl b, Total Carotenoids	Pigments: Chl a, Chl b, Total Carotenoids

3. Spectral Optical Properties (By Age Class)
   • Reflectance and Transmittance of abaxial and adaxial surfaces at 5 nm sampling rate (400-1000 nm). Spectral Absorbance (400-1000 nm) determined.

4. Fluorescence (By Age Class):
   • Spectra (360-800 nm), with excitation at 340 nm (IFCs 2-3).

5. Chemistry (By Age Class) from Dried Material: Nitrogen, Carbon (TBD).
   • Terrestrial Ecology Group 10 (TE-10)
   • CO₂ and Water Fluxes in the Boreal Forest Overstory:

   
   1994 Sites Studies (SSA):
   Old Aspen (aspen, hazelnut), Young Aspen (aspen, hazelnut), Old Jack Pine (jack pine, understory), Young Jack Pine (jack pine), Black Spruce, White spruce @ "Young Aspen".

   SSA Site	Species	1994 IFC	Field Dates
   Old Aspen (SSA-OA)	aspen	1	5/25 &29
   	poplar	1	6/10
   	hazelnut	2 2 3 3	7/21 8/03 9/02 9/15
   Young Aspen (SSA-YA)	aspen	1	5/24 & 26
   	hazelnut	1 2 3 3	6/04 7/28 9/02 9/12
   Old Jack Pine (SSA-OJP)	jack pine	1	5/31
   	understory	1 2 3	6/03 7/25 9/07
   Young Jack Pine (SSA-YJP)	jack pine	1 1 2 3	5/26 6/07 7/22 9/07
   Black Spruce (SSA-OBS)	black spruce	1 1 2 3	6/01 6/05 7/28 9/09
   Young Aspen [Snow Castle]	white spruce	2 3	7/30 9/08

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   Last Updated: October 2, 1998