Event Title

Streamwater Nitrogen Dynamics During a Bark Beetle Infestation of Subalpine Watersheds, Fraser Experimental Forest, CO

Event Website

http://www.nafew2009.org/

Start Date

22-6-2009 12:00 AM

End Date

26-6-2009 12:00 AM

Description

Forested watersheds of western North America are experiencing rapid and extensive canopy mortality caused by a variety of insect species. The mountain pine bark beetle (Dendroctonus ponderosae) began to attack lodgepole pine (Pinus contorta) at the U.S. Forest Service, Fraser Experimental Forest in 2002. By 2007, bark beetles had killed 50 to > 80% of the overstory pine in Fraser research watersheds. The hydrologic, climatic, biogeochemical and vegetation records available at the Fraser Experimental Forest provide a unique opportunity to quantify the impacts of this widespread, but poorly-understood disturbance in basins relative to a multi-decade, pre-disturbance period. Here we compare streamwater chemistry and nutrient export in the six years since the bark beetle outbreak began with the twenty years pre-attack record for Frasers’ four main research watersheds. During the years following the onset of bark beetle activity at Fraser, in basins dominated by old-growth forest spring and late fall streamwater nitrate was higher than pre-outbreak concentrations. In these basins, bark beetles had killed more than 75% of the pine and 40% of the total overstory basal area. Since few physical changes have altered forest structure at this point, the higher streamwater nitrate concentration and export are the likely result of decreased nutrient demand following mortality of overstory pine. The influence of the outbreak is an aggregate of short (i.e. halted overstory water and nutrient use) and longer-term (i.e. altered canopy interception, windthrow, and understory growth) processes, so the consequence of current beetle active will not be fully realized for decades.

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Jun 22nd, 12:00 AM Jun 26th, 12:00 AM

Streamwater Nitrogen Dynamics During a Bark Beetle Infestation of Subalpine Watersheds, Fraser Experimental Forest, CO

Forested watersheds of western North America are experiencing rapid and extensive canopy mortality caused by a variety of insect species. The mountain pine bark beetle (Dendroctonus ponderosae) began to attack lodgepole pine (Pinus contorta) at the U.S. Forest Service, Fraser Experimental Forest in 2002. By 2007, bark beetles had killed 50 to > 80% of the overstory pine in Fraser research watersheds. The hydrologic, climatic, biogeochemical and vegetation records available at the Fraser Experimental Forest provide a unique opportunity to quantify the impacts of this widespread, but poorly-understood disturbance in basins relative to a multi-decade, pre-disturbance period. Here we compare streamwater chemistry and nutrient export in the six years since the bark beetle outbreak began with the twenty years pre-attack record for Frasers’ four main research watersheds. During the years following the onset of bark beetle activity at Fraser, in basins dominated by old-growth forest spring and late fall streamwater nitrate was higher than pre-outbreak concentrations. In these basins, bark beetles had killed more than 75% of the pine and 40% of the total overstory basal area. Since few physical changes have altered forest structure at this point, the higher streamwater nitrate concentration and export are the likely result of decreased nutrient demand following mortality of overstory pine. The influence of the outbreak is an aggregate of short (i.e. halted overstory water and nutrient use) and longer-term (i.e. altered canopy interception, windthrow, and understory growth) processes, so the consequence of current beetle active will not be fully realized for decades.

http://digitalcommons.usu.edu/nafecology/sessions/posters/4