Implications of Galling Herbivory on Ground Thaw Through Shrub-Soil Heat Transfers Within Canada’s Northern Boreal Forest
Implications of Galling Herbivory on Ground Thaw Through Shrub-Soil Heat Transfers Within Canada’s Northern Boreal Forest
Previously Published Material: Poster presentation of preliminary findings at the 2nd Annual General Meeting of the Changing Cold Regions Network, October 19-22, 2014. Research is not currently under review or recently accepted by a scientific journal.
Abstract ID#: 34621
English Abstract:
The significant climate warming faced by Canada’s northern boreal forest has the potential to affect forest dynamics by altering the dispersion and abundance of resident natural enemies. Warmer air temperatures can impact the distribution and overwinter survival rate of these arthropods. Thus, the impacts of arthropod pests on their host plants require better understanding. Gall-inducing mites are a resident natural enemy in high latitude forests and have been shown to drive dramatic reductions in photosynthetic carbon uptake and transpiration rates of infested plants with the potential to alter shrub-energy balance. In this study we examine the impacts the gall-inducing eriophyoid mite, Vasates oldfieldi, has on Betula shrub energy inputs to the underlying ground surface. Two hypotheses will be tested: 1) a positive feedback to permafrost thaw through a reduction in evaporative cooling on the leaf surface increasing the canopy temperature of the Betula shrubs. The increase in the incident longwave radiation to the ground surface leads to an increase in the active layer thickness. 2) a negative feedback on permafrost thaw through a compensatory response in the shrub leading to an increase in leaf area index (LAI) to offset the loss of photosynthetic function. This reduces the amount of incident solar radiation at the ground surface resulting in a shallower active layer. To test these hypotheses, we measured soil moisture and surface temperature, leaf temperature, active layer thickness, shortwave radiation, transpiration and LAI. Our initial findings have shown an increase in active layer thickness and soil temperature under ungalled shrubs compared to galled shrubs of similar size for both the 2013 and 2014 field seasons. The results from this experiment are of great significance as the potential for a positive feedback of warming at a very local scale can potentially influence ground thaw in the northern boreal forest.