Event Title

Compensatory Mechanisms and Recovery Following Disturbance in Forest Ecosystems

Event Website

http://www.nafew2009.org/

Start Date

24-6-2009 10:50 AM

End Date

24-6-2009 11:10 AM

Description

Quantifying and predicting rates of recovery following disturbance are central to our understanding of forest carbon dynamics. We studied recovery of carbon (C) and nitrogen (N) fluxes and pools following three major disturbances in pine and oak-dominated stands on the Atlantic Coastal Plain; clearcutting, complete insect defoliation, and prescribed fires. We used net ecosystem exchange of CO2 and annual ecosystem respiration (Reco) derived from eddy flux data to calculate gross primary production (GPP), and tracked understory and overstory biomass and N during and following disturbance events. At all stands, annual Reco varied by less than 16% pre- and post-disturbance, with the greatest increase associated with the most intense disturbance (+291 g C m-2 yr-1 following clearcutting). GPP closely tracked the recovery of leaf area of understory vegetation, which increased from an LAI of < 0.1 to 3.0 in 6 months following clearcutting. In stands defoliated by Gypsy moth, understory LAI increased from < 0.2 to 0.8 within 6 months, and accounted for > 25% of overall LAI one year following defoliation. Disturbance also impacted internal N cycling. For example, N in annual litterfall in defoliated stands increased by ca. 50%, yet N pools and N mineralization in mineral soil were nearly unaffected, apparently because of storage in detrital and microbial pools. Model simulations using PnET, BiomBGC, and CENTURY predicted pre-disturbance C fluxes well, but large changes in leaf area during the growing season were difficult to model correctly, leading to large overestimates of GPP in all cases. Our results indicate the importance of rapid increases in LAI of understory vegetation and the stability of detrital pools in the recovery of C and N cycles in disturbed forests.

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Jun 24th, 10:50 AM Jun 24th, 11:10 AM

Compensatory Mechanisms and Recovery Following Disturbance in Forest Ecosystems

Quantifying and predicting rates of recovery following disturbance are central to our understanding of forest carbon dynamics. We studied recovery of carbon (C) and nitrogen (N) fluxes and pools following three major disturbances in pine and oak-dominated stands on the Atlantic Coastal Plain; clearcutting, complete insect defoliation, and prescribed fires. We used net ecosystem exchange of CO2 and annual ecosystem respiration (Reco) derived from eddy flux data to calculate gross primary production (GPP), and tracked understory and overstory biomass and N during and following disturbance events. At all stands, annual Reco varied by less than 16% pre- and post-disturbance, with the greatest increase associated with the most intense disturbance (+291 g C m-2 yr-1 following clearcutting). GPP closely tracked the recovery of leaf area of understory vegetation, which increased from an LAI of < 0.1 to 3.0 in 6 months following clearcutting. In stands defoliated by Gypsy moth, understory LAI increased from < 0.2 to 0.8 within 6 months, and accounted for > 25% of overall LAI one year following defoliation. Disturbance also impacted internal N cycling. For example, N in annual litterfall in defoliated stands increased by ca. 50%, yet N pools and N mineralization in mineral soil were nearly unaffected, apparently because of storage in detrital and microbial pools. Model simulations using PnET, BiomBGC, and CENTURY predicted pre-disturbance C fluxes well, but large changes in leaf area during the growing season were difficult to model correctly, leading to large overestimates of GPP in all cases. Our results indicate the importance of rapid increases in LAI of understory vegetation and the stability of detrital pools in the recovery of C and N cycles in disturbed forests.

http://digitalcommons.usu.edu/nafecology/sessions/recovery/1