HR: 1340h
AN: GC33A-1251    [Abstracts]
TI: Limber Pine Forest Mortality Event in Response to 1990s Persistent Low Precipitation and High Minimum Temperatures
AU: * Millar, C I
EM: cmillar@fs.fed.us
AF: USDA Forest Service, Sierra Nevada Research Center, 800 Buchanan St, Albany, CA 94710 United States
AU: Westfall, R D
EM: bwestfall@fs.fed.us
AF: USDA Forest Service, Sierra Nevada Research Center, 800 Buchanan St, Albany, CA 94710 United States
AU: Delany, D L
EM: ddelany@fs.fed.us
AF: USDA Forest Service, Sierra Nevada Research Center, 800 Buchanan St, Albany, CA 94710 United States
AB: Limber pine (Pinus flexilis) is a long-lived, precipitation- and temperature-sensitive conifer of dry high-elevation habitats in western North America. Our previous dendrochronological analyses of live trees and deadwood in the eastern Sierra Nevada and western Great Basin revealed major colonization and extirpation events occurring at centennial scale and related to extensive dry periods over the last 3700 years. To better understand limber pine response to variation in precipitation and temperature, we analyzed climate relations of a recent short-term but extreme forest mortality event in the northeastern edge of the species range in the central Sierra Nevada, California. We collected increment cores from 135 dead trees and 30 live trees from three stands (mean elevation, 2740 m) in which mortality exceeded 50%. Two stands were infected with limber pine dwarf mistletoe (Arceuthobium cayanocarpum), and bark beetle signs were evident on dead trees in all stands. Tree ages were relatively young for limber pine, less than 200 years old. Mortality occurred from 1993-1998. Using individual and composite instrumental records from nearby mid-elevation weather stations, we evaluated precipitation and minimum temperatures from 1957-present based on K-means partitioning of principal component composite time series of three eastern Sierran weather records. Although other severe short droughts occurred in this period, the years 1985-1997 were unique in the combination of low winter and total precipitation (1987-1997), high winter, spring, and annual minimum temperatures (1985-1996), and low interannual variability in precipitation (1987-1997). The limber pine mortality event appears to have been a response to multiple stressors, triggered by extreme climate years and exacerbated subsequently by mistletoe and bark beetle infestations.
DE: 0429 Climate dynamics (1620)
DE: 0439 Ecosystems, structure and dynamics (4815)
DE: 0476 Plant ecology (1851)
DE: 1605 Abrupt/rapid climate change (4901, 8408)
SC: Global Climate Change [GC]
MN: Fall Meeting 2005