The average ring-width index of two published chronologies from the eastern Tennessee climatic division was used as a single predictor variable in linear regression to reconstruct May June precipitation. Regression equations obtained using regionally averaged precipitation data from stations within the climatic division were compared with regressions obtained using single-station (Knoxville, Tennessee) data for comparable periods. The (regionally averaged) division data always provided the better calibration statistics for the regression equations. When the regressions calibrated using division data were verified with independent data for the climatic division and for Knoxville, the better results were always obtained for the division data. When regressions calibrated using single-station data were verified, the independent division data once again provided better results than the independent Knoxville data. Regionally averaged precipitation data also provided more satisfactory results than single- station data in a similar experiment for central Iowa, and probably provides better results in general for this type of dendroclimatic experiment.

A new approach to removing the non-climatic variance of forest interior tree-ring width series, using the smoothing spline, is described. This method is superior to orthogonal polynomials because it makes no assumptions about the shape of the curve to be used for standardization. Also, because the spline curve can range continuously from a linear least squares fit to cubic interpolation through the data, it is far more flexible than polynomials and provides a more "natural" fit. For computing the spline, we found that specifying the Lagrange multiplier p which appears in the calculus of variation solution rather than the residual variance as suggested by Reinsche was both practical and more efficient. In effect, the smoothing spline is a one-parameter family of low-pass filters defined by p. We describe the general characteristics of these filters in the time and frequency domains and compute the response functions for several of them. The smoothing spline is an excellent tree-ring standardization method because its filtering characteristics are well defined. Its utility for dendroclimatology should be considerable since, outside of semiarid environments, sites similar to forest interiors predominate.

Dendroecological methods play a critical role in developing our understanding of forest processes by contributing historical evidence of climate variability and the temporal characteristics of disturbance. We seek to contribute to these methods by developing a research protocol for decoupling radial-growth signatures related to climate, fire, and insect outbreaks in central Oregon. Our methods are based on three independent, crossdated tree-ring data sets: 1) a 545-year tree-ring climate reconstruction, 2) a 550-year fire history, and 3) a 250-year pandora moth outbreak history derived from host (Pinus ponderosa) and non-host (Abies grandis-Abies concolor) tree-ring chronologies. Based on these data, we use visual criteria (marker and signature rings), statistical comparisons, and Superposed Epoch Analysis (SEA) to identify the timing of growth anomalies and establish the temporal relationships between drought, climate variation (ENSO and PDO), fire events, and pandora moth (Coloradia pandora) outbreaks. Our results show pandora moth outbreaks generally coincide with periods of below-average moisture, whereas fire in central Oregon often follows a period of wetter than average conditions. Fire events in central Oregon appear to be related to shifts in hemispheric climate variability but the relationship between fire and pandora moth outbreaks remains unclear.

Our objective is to report mortality rates for ponderosa pine trees in Oregon ten to eleven years after removing a fire-scarred partial cross-section from them, and five years after an initial survey of post-sampling mortality. We surveyed 138 live trees from which we removed fire-scarred partial crosssections in 1994/95 and 387 similarly sized, unsampled neighbor trees of the same species. These trees were from 78 plots distributed over about 5,000 ha at two sites in northeastern Oregon. The annual mortality rate for sectioned trees from 1994/95 to 2005 was 3.6% compared to 2.1% for the neighbor trees. However, many of the trees that died between 2000 and 2005 were likely killed by two prescribed fires at one of the sites. Excluding all trees in the plots burned by these fires (regardless of whether they died or not), the annual mortality rate for sectioned trees was 1.4% (identical to the rate from 1994/95 to 2000) compared to 1.0% for neighbor trees. During these fires, a greater proportion of sectioned trees died than did catfaced neighbor trees (80% versus 64%) but the difference was not significant.