Effects of aspen canopy removal and root trenching on understory microenvironment and soil moisture
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Effects of three aspen (Populus tremuloides Michx.) canopy removal treatments and root trenching on understory microenvironment and moisture were tested at Parkland and Boreal sites in Alberta, Canada. Aspen canopies moderated air temperature by reducing maximums and increasing minimums, and increased the frost-free period in the understory by reducing radiative frosts. When daily differences were found among canopy treatments, maximum absolute humidity was greater with complete canopy removal. Maximum daily relative humidity was greater in openings at night than with either full or partial canopy cover. Predictably, increasing aspen cover reduced PAR reaching the understory. Soil moisture response was highly variable, changing with site, aspen density and precipitation patterns, but there were only marginal differences due to root trenching. In the Parkland site, soil moisture conservation from aspen canopy and leaf litter effects were masked by tree uptake in most periods, but a net increase in soil water (+5.2%) was observed during drought. Soil and microclimatic conditions in thinned aspen stands suggest potentially favourable production benefits from developing and adopting agroforestry systems in these northern ecosystems.
KeywordsBoreal Humidity Parkland PAR Root trenching Soil water
Our gratitude is extended to James Cahill, Jane King, Vic Lieffers, John Hoddinott, Dale Bartos and 2 anonymous reviewers, for their feedback on earlier versions of this manuscript. Funding was provided by the Alberta Agriculture Research Institute, the Agriculture and Food Council of Alberta, the Alberta Crop Industry Development Fund, the Biodiversity Challenge Grants Program supported by the Alberta Conservation Association, the Natural Sciences and Engineering Research Council of Canada, and the Killam Trusts. Thanks to Sarah Green for her technical assistance, as well as Dr. Barry Irving and staff at the University of Alberta Kinsella Research Station and the Lakeland Agricultural Research Association.
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