Publication Date:
2013-05-09
Description:
The Western Boreal Plain (WBP) of North Central Alberta comprises a mosaic of wetlands and aspen ( Populus tremuloides ) dominated uplands where precipitation (P) is normally exceeded by evapotranspiration (ET). As such these systems are highly susceptible to the climatic variability that may upset the balance between P and ET. Above canopy evapotranspiration (ET C ) and understory evapotranspiration (ET B ) were examined using the eddy covariance technique situated at 25.5 m (7.5 m above tree crown) and 4.0 m above the ground surface respectively. During the peak period of the growing seasons (green periods) ET C averaged 3.08 mm d -1 and 3.45 mm d -1 in 2005 and 2006 respectively while ET B averaged 1.56 mm d -1 and 1.95 mm d -1 . Early in the growing season, ET B was equal to or greater than ET C once understory development had occurred. However, upon tree crown growth ET B was lessened due to a reduction in available energy. ET B ranged from 42 to 56% of ET C over the remainder of the snow-free seasons. Vapor pressure deficit (VPD) and soil moisture (θ) displayed strong controls on both ET C and ET B . ET C responded to precipitation events as the developed tree crown intercepted and held available water which contributed to peak ET C following precipitation events 〉10 mm. While both ET C and ET B were shown to respond to VPD, soil moisture in the rooting zone is shown to be the strongest control regardless of atmospheric demand. Further, soil moisture and tension data suggest that rooting zone soil moisture is controlled by the redistribution of soil water by the aspen root system. This article is protected by copyright. All rights reserved.
Print ISSN:
0885-6087
Electronic ISSN:
1099-1085
Topics:
Architecture, Civil Engineering, Surveying
,
Geography
Permalink
