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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.
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.
Knowledge of the spatial heterogeneity of wood is useful for industrial applications and improving dendrogeomorphic sampling, because it allows a better understanding of 3-D wood density structure in tree stems damaged by geomorphic processes. X-ray computed tomography (XRCT) scanning as a means of non-destructive measurement has become an important technique in tree research as it allows the detection of internal variations in wood density. In this paper a new methodology for modelling spatial variations of relative wood density using variograms on XRCT images is developed. For each tree, XRCT images perpendicular to the stem axis were obtained with 1-mm spacing. In a first step, ImageJ software was used to process each image. Then, more than 30 one-dimensional variograms were studied for a selected number of cross-sections. The results show that there is a pattern in the diffusion of relative wood density linked to the attenuation of the geomorphic damage along the stem from the wounded area. Although the number of samples could be increased, these preliminary results demonstrate that variograms of XRCT are a useful tool to optimize dendrogeomorphic sampling, saving time and costs.
The goal of this research report is to describe annual precipitation reconstruction from Pinus sylvestris trees on three sites in the Abakan region, located in the Minusinsk Depression, at the confluence of the Yenisei and Abakan Rivers, Russia. The study was performed during the 4th annual international summer course “Tree Rings, Climate, Natural Resources and Human Interaction” held in Abakan, 5-19 August 2013. The reconstruction, for the 12-month total precipitation ending in July of the growth year, is based on a reliable and replicable statistical relationship between precipitation and tree-ring growth, and shows climate variability on both interannual and interdecadal time scales. The regional tree-ring chronology accounts for 56% of the variance of observed annual precipitation in a linear regression model, with the strongest monthly precipitation signal concentrated in May and June of the current growing season. Composite 500 mb height-anomaly maps suggest that the tree-ring data from this site, supplemented by other regional tree-ring data, could yield information on long-term atmospheric circulation variability over the study area and surrounding region.