1. Large carbon release legacy from bark beetle outbreaks across Western United States
- Author
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Christopher B. Williams, Bardan Ghimire, Melanie K. Vanderhoof, Dominik Kulakowski, Jeffrey G. Masek, G. James Collatz, and John Rogan
- Subjects
Bark beetle ,Ecology and Evolutionary Biology ,Climate change ,Forests ,Carbon cycle ,Carbon Cycle ,Trees ,Environmental Chemistry ,Animals ,Ecosystem ,Forest Biology ,Forest Sciences ,General Environmental Science ,Global and Planetary Change ,Biomass (ecology) ,Wood Science and Pulp, Paper Technology ,Forest inventory ,Ecology ,biology ,Biogeochemistry ,Models, Theoretical ,biology.organism_classification ,Forest Management ,Carbon ,United States ,Coleoptera ,Geography ,Productivity (ecology) ,Entomology - Abstract
Warmer conditions over the past two decades have contributed to rapid expansion of bark beetle outbreaks killing millions of trees over a large fraction of western United States (US) forests. These outbreaks reduce plant productivity by killing trees and transfer carbon from live to dead pools where carbon is slowly emitted to the atmosphere via heterotrophic respiration which subsequently feeds back to climate change. Recent studies have begun to examine the local impacts of bark beetle outbreaks in individual stands, but the full regional carbon consequences remain undocumented for the western US. In this study, we quantify the regional carbon impacts of the bark beetle outbreaks taking place in western US forests. The work relies on a combination of postdisturbance forest regrowth trajectories derived from forest inventory data and a process-based carbon cycle model tracking decomposition, as well as aerial detection survey (ADS) data documenting the regional extent and severity of recent outbreaks. We find that biomass killed by bark beetle attacks across beetle-affected areas in western US forests from 2000 to 2009 ranges from 5 to 15 Tg C yr(-1) and caused a reduction of net ecosystem productivity (NEP) of about 6.1-9.3 Tg C y(-1) by 2009. Uncertainties result largely from a lack of detailed surveys of the extent and severity of outbreaks, calling out a need for improved characterization across western US forests. The carbon flux legacy of 2000-2009 outbreaks will continue decades into the future (e.g., 2040-2060) as committed emissions from heterotrophic respiration of beetle-killed biomass are balanced by forest regrowth and accumulation.
- Published
- 2013