Nonlinear models of height growth for Douglas-fir in southwestern Oregon

A review is made of methods which assess the bias and non-normality of parameter estimates and predictions obtained with nonlinear regression. Particular emphasis is placed upon curvature measures of nonlinearity, related measures of parameter and prediction bias, and the effects of reparameterizations. Alternate models of individual tree height growth are compared on the basis of mean square error, intrinsic nonlinearity, parameter effects nonlinearity, and estimated bias. While results are specific to the data examined, some general conclusions are made concerning appropriate models for individual tree height growth. Both the Richards and a Weibull-type growth model are found to adequately describe individual tree height growth, with low levels of intrinsic nonlinearity, and acceptable parameter effects nonlinearity following repararneterization. Some evidence is found for a modification of either the Richards or Weibull model to include an asymptotic linear growth rate when modeling the height growth of some western conifers past the age of 200. Stem analysis data on Douglas-fir height growth in mixed confier stands located in southwestern Oregon are used to develop a system of dominant height growth and site index prediction. The Weibull model is used successfully to develop a polymorphic height growth prediction equation. A linear model, estimated with site index as the dependent variable, is used to predict site index. A comparision is made of pooled least squares and random coefficient estimation methods. The random coefficient method is found to more closely model the shape of early height growth, but appears to result in more biased predictions and performs very poorly on older height growth, with both the estimation and validation data. Alternative error assumptions are examined with the pooled data method. The best performance in validation is obtained with assumption of independent errors, heteroscedastic across trees

Consequences of Shifts in Abundance and Distribution of American Chestnut for Restoration of a Foundation Forest Tree

Restoration of foundation species, such as the American chestnut (Castanea dentata) that was devastated by an introduced fungus, can restore ecosystem function. Understanding both the current distribution as well as biogeographic patterns is important for restoration planning. We used United States Department of Agriculture Forest Service Forest Inventory and Analysis data to quantify the current density and distribution of C. dentata. We then review the literature concerning biogeographic patterns in C. dentata. Currently, 431 +/- 30.2 million stems remain. The vast majority (360 +/- 22 million) are sprouts \u3c 2.5 cm dbh. Although this number is approximately 10% of the estimated pre-blight population, blight has caused a major shift in the size structure. The current-day population has a larger range, particularly west and north, likely due to human translocation. While climate change could facilitate northward expansion, limited seed reproduction makes this unlikely without assisted migration. Previous research demonstrates that the current, smaller population contains slightly higher genetic diversity than expected, although little information exists on biogeographic patterns in the genetics of adaptive traits. Our research provides a baseline characterization of the contemporary population of C. dentata, to enable monitoring stem densities and range limits to support restoration efforts

Consequences of Shifts in Abundance and Distribution of American Chestnut for Restoration of a Foundation Forest Tree

Restoration of foundation species, such as the American chestnut (Castanea dentata) that was devastated by an introduced fungus, can restore ecosystem function. Understanding both the current distribution as well as biogeographic patterns is important for restoration planning. We used United States Department of Agriculture Forest Service Forest Inventory and Analysis data to quantify the current density and distribution of C. dentata. We then review the literature concerning biogeographic patterns in C. dentata. Currently, 431 ± 30.2 million stems remain. The vast majority (360 ± 22 million) are sprouts \u3c 2.5 cm dbh. Although this number is approximately 10% of the estimated pre-blight population, blight has caused a major shift in the size structure. The current-day population has a larger range, particularly west and north, likely due to human translocation. While climate change could facilitate northward expansion, limited seed reproduction makes this unlikely without assisted migration. Previous research demonstrates that the current, smaller population contains slightly higher genetic diversity than expected, although little information exists on biogeographic patterns in the genetics of adaptive traits. Our research provides a baseline characterization of the contemporary population of C. dentata, to enable monitoring stem densities and range limits to support restoration efforts

Performance Effects of Outside Pollen on Seed Orchards In and Out of the Genetic Source Area

Contamination by outside pollen sources is recognized as a serious problem that reduces the genetic gain obtained from open-pollinated seed orchards. A mitigating tactic is to locate an orchard outside the source area into a region with higher performance, e.g. Virginia source clones established in the more southerly, and high performing, Atlantic Coastal source region. Previous studies have emphasized estimation of the degree of contamination. This study sought to quantify the impact on realized gain from two Virginia source orchards, one located in the Virginia source area, and another located in Georgia. Field performance of progeny from controlled crosses using an orchard pollen mix were compared to open-pollinated progeny. Contamination by outside pollen resulted in a significant increase in volume growth for the Georgia progeny, but no significant effect on the Virginia orchard progeny. Outside pollen resulted in decreased performance in straightness ratings for both orchards, with the negative effect more pronounced with the Georgia orchard progeny.Papers and abstracts from the 27th Southern Forest Tree Improvement Conference held at Oklahoma State University in Stillwater, Oklahoma on June 24-27, 2003

Comparison of evoked vs. spontaneous tics in a patient with trigeminal neuralgia (tic doloureux)

A 53-year old woman with tic doloureaux, affecting her right maxillary division of the trigeminal nerve (V2), could elicit shooting pains by slightly tapping her teeth when off medication. The pains, which she normally rated as > 6/10 on a visual analog scale (VAS), were electric shock-like in nature. She had no other spontaneous or ongoing background pain affecting the region. Based on her ability to elicit these tics, functional magnetic resonance imaging (fMRI) was performed while she produced brief shocks every 2 minutes on cue (evoked pain) over a 20 min period. In addition, she had 1–2 spontaneous shocks manifested between these evoked pains over the course of functional image acquisition. Increased fMRI activation for both evoked and spontaneous tics was observed throughout cortical and subcortical structures commonly observed in experimental pain studies with healthy subjects; including the primary somatosensory cortex, insula, anterior cingulate, and thalamus. Spontaneous tics produced more decrease in signals in a number of regions including the posterior cingulate cortex and amygdala, suggesting that regions known to be involved in expectation/anticipation may have been activated for the evoked, but not spontaneous, tics. In this patient there were large increases in activation observed in the frontal regions, including the anterior cingulate cortex and the basal ganglia. Spontaneous tics showed increased activation in classic aversion circuitry that may contribute to increased levels of anxiety. We believe that this is the first report of functional imaging of brain changes in tic-doloureaux