• Morphological and Physiological Phenology of Pinus longaeva in the White Mountains of California

      Hallman, C.; Arnott, H. (Tree Ring Society, 2015-01)
      Natural variations and responses to climate change can be identified within climatically sensitive ecosystems by monitoring growing season events. In 1962-1964, Fritts conducted a phenologic study on Pinus longaeva in the White Mountains of California. He monitored growing season events, environmental data, and dendrometer readings. In this study morphological and physiological phenophases, dendrometer traces, and environmental data were collected throughout the summers of 2007 and 2008 in the White Mountains of California to better understand variability in Pinus longaeva phenology and identify any shifts in the growing season since the 1962-1964 study (Fritts 1969). As a result of a late-season snow storm, observable phenophases in 2008 were 12 days later than in 2007. Pollination onset was slightly earlier than in the 1962-1964, which may indicate that accumulated heat or a combination of environmental factors influence these phenophases. Duration and timing of cambial activity in the present study was similar to that recorded in the Fritts (1969) investigation despite a median summer temperature increase of at least 2°C. © 2015 The Tree-Ring Society.
    • The Dendroclimatological Potential of Willamette Valley Quercus garryana

      Gildehaus, S.; Arabas, K.; Larson, E.; Copes-Gerbitz, K. (Tree Ring Society, 2015-01)
      We develop a 341-year Oregon white oak (Quercus garryana Dougl.) tree-ring chronology in Oregon's Willamette Valley to evaluate climate-growth relationships and determine the species' dendroclimatological potential at our site and in the surrounding region. The standardized and residual chronologies exhibit significant positive correlations with previous-year April and May temperatures, inverse correlations with previous-year spring precipitation and summer PDSI, a positive correlation with current-year July precipitation and summer PDSI, and inverse correlations with current-year June temperatures. The strength of these relationships varies over time. Significant shifts in the chronologies' mean and variance align with phase changes in the Pacific Decadal Oscillation (PDO), with lower and more variable growth during the warmer, drier positive phase of the PDO over the instrumental record. The absence of similar shifts prior to the 1900s, suggests a lack of temporal consistency in the expression of PDO variability at our site. The strong crossdating at our site reflects a cohesive climate signal, and the climate analysis illustrates the potential to develop proxy data over multiple centuries. Together, these results indicate a potential to expand the network of currently available climate proxy data by utilizing Q. garryana in dendroclimatological research. © 2015 The Tree-Ring Society.