Chalk river

Petawawa National Forestry Institute (PNFI)

Atomic Energy of Canada Limited (AECL)

Research in the Chalk River area was conducted over a period of 10 years from 1981 to 1991 at two very different sites located ~12 km apart.  The site located at the Petawawa National Forestry Institute (PNFI) is a mixed coniferous-deciduous forest stand on shallow podzolic soil typical of forests on the Canadian shield in this area. The soil is rocky, approximately one metre deep, and overlies bedrock. The AECL site, located on the property of Atomic Energy of Canada Limited, is a birch-aspen stand underlain by a thick sandy soil, several metres deep. The close proximity of the sites, combined with their different soils and ecophysiological controls, make them ideally suited for climatological study. As well, the sites are exposed to the same basic regional climatology so differences in flux behaviour can be examined. The close proximity of the sites minimizes both logistical and infrastructure costs. 

A special thanks is offered to Dr. J. Harrington of PNFI who facilitated the establishment of the experiments in 1981. The incorporation of the site at AECL in 1989 was fostered by the support of Dr. P. Barry of AECL. Peter Lafleur, Trent University, was a collaborator in the experiments from 1989 to 1991 when both sites were worked simultaneously. 

The initial experiments that started in 1981 examined the nature of the water and energy exchange from the PNFI site. This involved installing instruments on a 39-m tall research tower for temperature, wind, and humidity profiles, and the components of the surface radiation balance. The Bowen ratio method was used to find the convective fluxes, and the methodology involved the use of reversing psychrometry using the Reversing Temperature Difference Measurement System (RTDMS), which was developed at Queen's University. The picture above shows a view of the tower and the tee-shaped instrument in the centre of the tower is the RTDMS. As well, in 1981 we examined the effects of logging the mixed forest. This involved the establishment of a companion site, designated the ‘cleared site’, that had been logged and was in the process of regenerating. When the measurements were taken, the site was vegetated by a mixture of bracken fern and shrub growth. Dave Brintnell used the results of these experiments for his M.Sc. 

Following the successful establishments of the two sites Peggy Hauschildt, Dave Mullins and Wendy Saxton completed their M.Sc. degrees. Peggy examined the nature of the surface radiation balances on the sites. Dave documented the energy balance and did the first analysis of the Penman-Monteith model for the PNFI forest and the cleared sites. Wendy focused on the minor energy balance terms of the PNFI forest and did extensive sampling of bole temperatures to find the heat storage in the biomass. 

Between 1983 and 1986 we attempted a long-term data collection effort on the radiation balance of the PNFI site. This was only partially successful given the state of the recording capacity at the time and the extreme winter temperatures typical of the area. However, the data series of surface albedo in particular proved invaluable in elaborating the seasonal phenological controls as well as the role of snow in winter.  

A major experiment was conducted at PNFI in 1987 in which two students, David Joiner and Tim Papakyriakou, completed M.Sc. theses. David worked on energy balance relations of the mixed canopy using both the RTDMS and eddy covariance to find the convective fluxes. Tim conducted a water balance of the site using the neutron probe to measure soil moisture content and soil psychrometers to measure soil tension. 

Tony Iacobelli completed his M.Sc. using the results of the 1989 experiment when the first comparative study was made of the energy exchanges of the two sites at the leaf and stand levels. He collected the first systematic series of stomatal conductance data at the aspen-birch forest at AECL. This was possible because the scaffold instrument tower allowed access to the canopy. He also did pioneering work sampling the spatial variation of conductance using a "cherry-picker" on loan from AECL. Paul Bartlett and Ian Strachan continued the comparative work in 1990 and 1991, respectively, for their M.Sc. theses. Paul extended the sampling of soil moisture and soil tension at AECL as well as incorporating improved bole temperature sampling. Ian included sampling of leaf area index of the AECL site using the LI-COR LAI-2000 plant canopy analyzer. 

The data generated from these sites has been used in the development and testing of the Canadian Land Surface Scheme (CLASS), a SVAT being tested and developed within the Canadian Research Network.

Further studies at the AECL site are planned, and in particular we are interested in measuring the carbon dioxide flux from this forest. The site at PNFI is no longer active following the closure of PNFI.