TITLE

Seasonal gas exchange of black spruce using an automatic branch bag system

AUTHOR(S)
Rayment, M. B.; Jarvis, P. G.
PUB. DATE
October 1999
SOURCE
Canadian Journal of Forest Research;Oct1999, Vol. 29 Issue 10, p1528
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
Four large cuvettes were used to measure whole-branch CO2and H2O vapour exchange at the Boreal Ecosystem-Atmosphere Study, Southern Study Area, Old Black Spruce site. Measurements started before the spring thaw and continued until after the winter freeze-up. Daytime photosynthesis, nighttime respiration, transpiration rate, and branch conductances were zero at the start and the end of the measurement period. Maximum photosynthetic uptake rates were ca. 6 Mumol7m-27s-1 (0.02 Mumol7g-17s-1). Maximum nighttime respiration was ca. 0.8 Mumol7g-17s-1. Maximum transpiration rates were ca. 2 mmol7m-27s-1 (7.1 Mumol7g-17s-1). Maximum branch conductance was ca. 35 mmol7m-27s-1 (0.123 mmol7g-17s-1). A simple model combining light and temperature responses accounted for 80-90% of the day-to-day variation in daytime carbon uptake. Total annual daytime carbonuptake ranged from 151 to 271 g7m-2 (530-868 mg7g-1). Total nighttime loss ranged from 12.7 to 15.5 g C7m-2 (22.4-27.3 mg C7g-1). Total transpiration ranged from 20.4 to 35.0 kg H2O7m-2 (70.2-112.2 g H2O7g-1).
ACCESSION #
8053100

 

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