Effects of aspen canopy removal and root trenching on understory microenvironment and soil moisture

摘要

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.