Barbara E. Kishchuk

Wood-feeding beetles and soil nutrient cycling in burned forests: implications of post-fire salvage logging.

1 Rising economic demands for boreal forest resources along with current and predicted increases in wildfire activity have increased salvage logging of burned forests. Currently, the ecological consequences of post‐fire salvage logging are insufficiently understood to develop effective management guidelines or to adequately inform policy decision‐makers. 2 We used both field and laboratory studies to examine the effects of post‐fire salvage logging on populations of the white‐spotted sawyer Monochamus scutellatus scutellatus (Say) (Coleoptera: Cerambycidae) and its ecological function in boreal forest. 3 Monochamus s. scutellatus adults were relatively abundant in both burned and clear‐cut logged sites but were absent from salvage logged sites. 4 An in situ mesocosm experiment showed that the abundance of M. s. scutellatus larvae in burned white spruce bolts was linked to changes in total organic nitrogen and carbon in mineral soil. 5 Organic nutrient inputs in the form of M. s. scutellatus frass increased mineral soil microbial respiration rates by more than three‐fold and altered the availability of nitrogen. Changes in nitrogen availability corresponded with decreased germination and growth of Epilobium angustifolium and Populus spp. but not Calamagrostis canadensis. 6 Although the present study focused on local scale effects, the reported findings suggest that continued economic emphasis on post‐fire salvage logging may have implications beyond the local scale for biodiversity conservation, nutrient cycling and plant community composition in forest ecosystems recovering from wildfire.

Long-term soil response to variable-retention harvesting in the EMEND (Ecosystem Management Emulating Natural Disturbance) experiment, northwestern Alberta

Kishchuk, B. E., Quideau, S., Wang, Y. and Prescott, C. 2014. Long-term soil response to variable-retention harvesting in the EMEND (Ecosystem Management Emulating Natural Disturbance) experiment, northwestern Alberta. Can. J. Soil Sci. 94: 263-279. We report on soil responses to variable-retention (VR) harvesting from a large-scale experiment (>1000 ha). Samples were taken prior to treatment, and 1 and 6 yr after treatment under cover types representing the successional trajectory for boreal mixedwood forests in northwestern Alberta, Canada. Variable-retention harvesting at six overstory-retention levels [100 (control), 75, 50, 20, 10, and 0% (clearcut)] were applied to 10-ha experimental units under four cover types: deciduous-dominated (80-95% trembling aspen); deciduous-dominated with coniferous understory (80-95% trembling aspen with white spruce understory at 60-80% of full stocking); mixed coniferous-deciduous (35-65% of each); and coniferous-dominated (80-95% white spruce). Only a few clear differences in soil properties attributable to VR harvesting were evident 6 yr post-harvest: (1) both extractable NH4-N in forest floor and 0-7 cm mineral-soil, and forest floor exchangeable K decreased with increasing canopy removal, and (2) forest floor exchangeable Ca increased with canopy removal. There was a decreasing trend in forest floor and mineral soil C (kg ha-1) in undisturbed stands between 1998 and 2005. Differences in soil properties among cover types included higher pH and N concentration in forest floors, and higher cation exchange capacity and exchangeable Ca and Mg in mineral soils in deciduous-dominated stands. Deciduous-dominated stands appear to have distinct soil properties that change under stand development.