Effect of Mountain Bark Beetle Infestation On Soil CO2 Efflux In Lodgepole Forest Soils In Southeast Wyoming.

Effect of mountain bark beetle infestation on soil CO2 efflux in lodgepole forest soils in Southeast Wyoming. Bujidmaa Borkhuu1, Elise Pendall1, Urszula Norton2 and Brent E. Ewers1 1 Department of Botany, College of Arts and Sciences 2 Department of Renewable Resources, College of Agriculture Abstract Bark beetle outbreaks currently occurring across North American coniferous forests are triggering dramatic consequences to ecosystems. Increasing annual rates of tree mortality require active research on quantifying mountain bark beetle (Dendroctonus ponderosae) effects on the ecosystem. We hypothesize that the increased mortality rates are expected in logged stands (thinned) due to dominant tree sizes that susceptible to the beetle attack. This will result in overall reduction of the total soil CO2 efflux from infested stands than uninfested. The objective of this presentation is to determine the effect of bark-beetle induced mortality rates on soil CO2 efflux and its drivers, soil moisture and temperature. Our study site in southeastern Wyoming is home to one of the major types of effected trees - lodgepole pine ( Pinus contorta var. latifolia). The lodgepole stands are even-aged, approximately 110 years old, located at 2775m elevation.We utilized five research sites, including stands that have been thinned and unthinned and attacked by beetle in summers 2007 and 2008. Tree inventory and soil CO2 efflux and environmental measurements were taken biweekly during May to October of 2008-2010. For two thinned stands,tree mortality increased by 50% of within one year after infestation. The soil CO2 efflux mean values in infested stand was twice higher than uninfested stands. Mean soil water content for the 2009 summer was 0.4g g-1 which is twice higher than 2008. We suggest that higher soil moisture was caused by lower transpiration rates, and that autotrophic respiration rates decreased, resulting to lower soil CO2 efflux rates.