PARENT SESSION
Poster Session 19: Biodiversity
Wednesday, August 10, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal
Variable retention harvesting homogenizes arthropod biodiversity in western boreal mixedwood forests.
Work, Timothy *,1, Shorthouse, David2, Spence, John2, He, Fangliang2, 1 Université du Québec à Montréal, Montréal, QC, Canada2 University of Alberta, Edmonton, AB, Canada
ABSTRACT- Variable retention harvesting has been advocated to maintaining biodiversity in managed boreal mixedwood landscapes. One key concern is that the effects forest harvesting will effectively homogenize any cover-type differences observed among the mosaic of successional stand-types. We surveyed the arthropod fauna at the EMEND project (Ecosystem Management Emulating Natural Disturbance) in Western Alberta. At EMEND,100 whole-stand experimental units (10 ha or greater) are used in an ANOVA-like design to test the interaction between four successional forest cover-types (deciduous dominated, deciduous dominated with developing understory of white spruce, mixedwood, and spruce dominated) and six levels of variable retention (0-2% or clearcut, 10, 20, 50, 75 and 100% retention). We collected over 110,000 epigeaic beetles (Coleoptera:Carabidae and Staphylinidae) from 189 species. We tested the interaction between cover-type and harvest intensity on species composition using multivariate regression trees (MRT). Log-transformed MRT explained the most variance (49%) and showed harvesting effects were strong enough to effectively homogenize differences between deciduous and mixed and conifer cover types. When rare species were emphasized, effects of harvesting increased and effectively homogenized all cover-types at relatively high levels of retention (50% or less). This suggests that partial retention harvesting is largely ineffective for maintaining biodiversity even at relatively high levels of retention. We further evaluated harvesting effects on relative dispersal ability of epigeaic species by comparing species abundance distributions with fitted neutral models. Dispersal parameters derived from fitted neutral models suggest that stands are largely insular and that inter-stand dispersal is less important than within stand factors that maintain diversity through high birth rates.
Key words: biodiversity, variable retention harvesting, boreal mixedwood forests, arthropods