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Coloradia pandora (Blake) is a phytophagous insect that defoliates Pinus ponderosa (Dougl. ex Laws.) in south-central Oregon. Little is known about the extent of damage this insect inflicts upon its host trees during an outbreak. In this paper, we present stem analyses on four dominant Pinus ponderosa trees that enable us to determine the amount of volume lost during each Coloradia pandora outbreak on this site for the past 450 years. We found that on average an outbreak inhibits radial growth so that an individual tree produces 0.057 m3 less wood volume than the potential growth for the duration of an individual outbreak. A total of 0.549 m3 of growth per tree was inhibited by 10 outbreaks during the lifetime of the trees, which, in this stand, equates to 9.912 m3/ha (1,700 board feet/acre) of wood suppressed over the last 450 years throughout the stand. Our results do not support previous findings of a lag in suppression onset between the canopy of the tree versus the base. Crossdating of stem analysis samples is paramount to definitively examine the potential for a lagged response throughout the tree, which has bearing on the mechanisms of growth initiation and as well as the tree's stored reserves.
We use a simulation model to generate tree-ring like data with systematic growth forcings and subject it to two methods of standardization: Regional Curve Standardization (RCS) and Negative Exponential Curve Standardization (NECS). The coherency between very low frequency forcings (hundreds of years) and the chronologies was higher when RCS was used to detrend the component series. There was no difference between standardization methods at decadal or annual time scales. We found that the detectability of systematic forcings was heavily dependent on amplitude and wavelength of the input signal as well as the number of trees simulated. These results imply that for very long tree-ring chronologies where the analyst is interested in low-frequency variability, RCS is a better method for detrending series if the requirements for that method can be met. However, in the majority of situations NECS is an acceptable detrending method. Most critically, we found that multi-centennial signals can be recovered using both methods.
We examined tree rings from cross-sections of shortleaf pine (Pinus echinata Mill.) timbers extracted from a house in Forsyth County, Georgia, that was reportedly built in the mid-19th Century during the Antebellum Period (pre-1860). Our goals were to (1) determine the probable construction year for the house to help assess its possible historical significance, and (2) create a new long-term reference chronology for the northern Georgia area where such chronologies are lacking. Sections of shortleaf pine were removed from the structure during a renovation project in 2001. Sixteen sections were used to build a floating tree-ring chronology 217 years in length from series that crossdated conclusively with other series both graphically via skeleton plots and statistically via COFECHA. We then statistically evaluated the probable absolute temporal placement of this chronology using several regional tree-ring chronologies from the southeastern U.S. A statistically significant (p < 0.0001) correlation between our chronology and a shortleaf pine chronology from Clemson, South Carolina, anchors our chronology between 1652–1868. Two missing rings are probable in the early portion of our chronology, but we currently do not have a sufficient number of samples to conclusively identify their exact placement. No cluster of outermost rings was found to support the reported construction date of 1851, although the outermost rings on 13 of 16 samples dated before 1851. This new chronology could aid further dating of wood from archaeological sites and historical structures, and establish an initial data set that could eventually provide important new insights about the climate of northern Georgia during the 17th–19th Centuries.
Two new online products are available to the international tree-ring community. The Bibliography of Dendrochronology (published online in February 2003) currently has 10,000 references and is the world's largest online bibliography specializing in tree-ring research. In March 2004, the Glossary of Dendrochronology was made available and is a searchable database of 351 terms and definitions in English, German, French, Spanish, Italian and Portuguese. Both databases result from the collaboration of numerous tree-ring scientists worldwide.