HR: 0800h
AN: PP51C-0660    [Abstracts]
TI: Interspecific Variation in Tree Growth Response to 20th Century Climate Variability in the Circumpolar Boreal Forest
AU: * Lloyd, A H
EM: lloyd@middlebury.edu
AF: Middlebury College, Biology Dept 372 Bicentennial Hall, Middlebury, VT 05753, United States
AU: Bunn, A
EM: andy.bunn@wwu.edu
AF: Western Washington University, Environmental Sciences, Huxley School, Bellinghma, WA 98225, United States
AB: We examined relationships between tree ring-width and climate at 232 existing tree-ring sites around the circumpolar boreal forest (north of 55° N). The data set included ten common boreal species: Larix gmelinii, Larix sibirica, Picea abies, Picea glauca, Picea mariana, Picea obovata, Picea sitchensis, Pinus banksiana, Pinus sylvestris, Tsuga mertensiana. We used moving-window correlation analysis for eight 30-year time windows, lagged by 10 years, to characterize the climate response at each site from 1902-2002. We identified two categories of response to temperature: a browning response characterized by inverse correlations between growth and temperature, and a greening response characterized by positive correlations between growth and temperature. Inverse growth responses to temperature were widespread, occurring to some extent in all species, during all time periods, and in nearly all geographic areas. Although the browning response did occur during all time periods, its frequency increased after 1942, during which time the frequency of the greening response declined. Although the trend in the frequency of browning paralleled the rise in Northern Hemisphere temperature in recent decades, the two were not significantly correlated. Browning was concentrated in five species ( Picea abies, Picea glauca, Picea mariana, Picea obovata and Pinus banksiana), and occurred infrequently in the remaining five species. The genus Picea thus appeared to be particularly prone to experience inverse responses to temperature: the only Picea species included in the analysis in which browning did not commonly occur was Picea sitchensis, which is restricted to the coastal temperate rainforests of southeastern and south-central Alaska. Our analyses identified two possible causes of inverse growth responses. First, browning occurred significantly more frequently in the warmer parts of species" sampled ranges, supporting the hypothesis that direct temperature stress might be a cause of inverse growth responses to temperature. Second, in some species, dry sites were also more likely to experience browning; moisture stress might thus be an additional explanation in some cases.
DE: 0473 Paleoclimatology and paleoceanography (3344, 4900)
DE: 0476 Plant ecology (1851)
DE: 1600 GLOBAL CHANGE
DE: 4920 Dendrochronology
DE: 9315 Arctic region (0718, 4207)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting