Changes in carbon balance after insect disturbance in Western U.S. forests
Abstract
Mountain pine beetle outbreaks have infested more than 86 million hectares of forest in the U.S.A. since 2000. Using 8-year records of gross primary productivity (GPP) and respiration fluxes, and parallel disturbance chronosequences in two lodgepole pine forests in Colorado, we show that soil respiration sharply declines with GPP after tree mortality, reflecting the loss of autotrophic respiration and rhizodeposition. Three years post-disturbance, soil respiration rates recover before declining again, co-incident with a pulse of increased soil organic carbon, de-coupling respiration from concurrent GPP. We find systematic decreases in ecosystem respiration after mountain pine beetle outbreaks in western U.S. forests using valley CO2 monitoring and chronosequences of natural and induced tree mortality spanning an eight-year period following disturbance. The impacts of beetle outbreaks on the carbon cycle are likely more complex than previous estimates, and consideration of the dynamics of autotrophic and heterotropic substrate supply suggests that beetle-killed forests lose less carbon to the atmosphere than previously estimated.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.B31I..01M
- Keywords:
-
- 0414 BIOGEOSCIENCES / Biogeochemical cycles;
- processes;
- and modeling;
- 0426 BIOGEOSCIENCES / Biosphere/atmosphere interactions;
- 0480 BIOGEOSCIENCES / Remote sensing