Field Note: Attributes of Windthrown Trees in a Sierra Nevada Mixed-Conifer Forest

Abstract

On Nov. 30 to Dec. 1, 2011, an extreme wind event affected the central Sierra Nevada mountain region of California, causing extensive windthrow of trees. The wind event was caused by an extreme pressure gradient from north to south over Nevada and the Sierra that was unusual for the region in its duration, atypical wind direction, and high-intensity wind. Within Devils Postpile National Monument, there were approximately 118.5 windthrown trees km-1. The average diameter at 1.37 m of windthrown trees was 55.36 cm, 2.2 times greater than that for pre-windstorm standing trees. Trees differed in damage type; 86% of trees were uprooted, whereas 14% were snapped, and dead trees were more likely to snap than uproot relative to live trees. Tree species was not a factor in likelihood of windthrow because species composition and relative abundance of windthrown trees were representative of the preexisting forest composition. This wind event is the most extensive on record for California's Sierra Nevada range and may have long-lasting effects on forest composition and function.