Estimated biomass and carbon committed to decomposition in a north Georgia 2011 tornado swath

1. Estimated biomass and carbon committed to decomposition in a north Georgia 2011 tornado swath Chris J. Peterson1, Jeffery B. Cannon2, and Luke J. Snyder1 1University of Georgia, Dept. of Plant Biology CARBON CONSEQUENCES OF DISTURBANCE A common consequence of natural disturbance is tree mortality; across large areas, many Mg of C may be transferred from living to decomposing carbon pools. Hurricanes and large derechos may impact > 400,000 ha. Large tornadoes may damage > 20,000 ha, and there are many tornadoes each year in North America. Photo in upper left corner shows an aerial color infrared photo of an F4 tornado swath through old-growth forest of Pennsylvania in 1985. Chambers et al. (2007) estimated ~ 100 Tg of C transferred from living to dead by Hurricane Katrina. Zeng et al (2009) estimated that in 20th century, hurricanes on average transferred ~ 20 Tg of C yr-1 from living to dead, for eastern U.S. RESULTS Image below shows classification of severity (proportion of basal area down) for a 5 km section at western end of tornado track. FIELD METHODS • We established 37 damage survey plots haphazardly across the wind disturbed areas of the Boggs Creek site (western portion of the north Georgia tornado). • In each plot, we surveyed damage by recording for each tree its size, species, and type of damage, among other data. • Pre-disturbance basal area calculated retrospectively by totaling damaged and undamaged trees. • Mean pre-disturbance biomass = 266.3 Mg ha-1. • After scaling up, damage ranged from 1.3 to 345.4 Mg carbon ha-1. AIR PHOTO ANALYSIS We have acquired air photos of the entire length of two tornado tracks, including the north Georgia tornado. The north Georgia tornado was ~66 km long and damaged ~3320 ha. Ground survey plots were used for validation of a supervised classification of the remainder of the tornado track. CONCLUSIONS We binned all pixels in above image into 10% damage categories, and then multiplied this severity distribution across the total damage path area of 3320 ha. Total ha in each damage category was then summed for entire tornado path, and multiplied by pre-disturbance mean biomass of 266.3 Mg ha-1. Total of 0.115 Tg of biomass, or 0.076 Tg of C transferred from living to dead by this one tornado. Considering the > 300 tornadoes in the April 2011 outbreak, this outbreak may have cumulatively transferred 3-4 Tg of C from living to dead carbon pools. Annual average of nearly 1200 tornadoes suggest that these types of storms may play a substantial role in forest carbon dynamics. THE LATE APRIL 2011 TORNADO OUTBREAK One of the worst natural disasters in U.S. history. 359 tornadoes across 21 states; $11 billion in damages; 322 deaths; 3251 miles of total path length. What is the carbon impact of tornadoes? ACKNOWLEDGMENTS This work was conducted with funding from NSF RAPID grants DEB-1143511 from the Population & Community Ecology program, and AGS-1141926 from the Physical & Dynamic Meteorology Program. We thank Chattahoochee National Forest for permission to work at Boggs Creek. 0% 1-25% 26-50% 51-75% >75%