Daniel W. Gilmore

Alternative measures of stem growth efficiency applied to Abies balsamea from four canopy positions in central Maine, USA

Abstract Stem analysis data collected from 39 Abies balsamea (L.) Miller from four distinct canopy positions (open-grown, codominant, intermediate, suppressed) were used to construct a model to predict stem volume increment (VINC) from projected leaf area (PLA), and test the hypotheses that the physiological-based measure for growth efficiency ( GE , stem volume increment per leaf area) and the empirical surrogates for GE (e.g. surrogates substituting other measures of stem volume increment or PLA into the GE equation) were equal among canopy positions. VINC was best predicted from PLA with an asymptotic model which suggests that once individual trees reach a critical leaf area, very little stem growth occurs relative to leaf area. Analyses of variance revealed that the suppressed crown class was the least efficient (in terms of GE or any of its surrogates) relative to the superior canopy positions. Observed and predicted patterns of growth efficiency were found to depend on the manner in which it was calculated or predicted. Suppressed trees, however, were consistently observed, and predicted to be the least efficient in terms of stem volume increment relative to the intermediate, codominant, and open-grown crown classes.

An evaluation of the uniform stress hypothesis based on stem geometry in selected North American conifers

Abstract. The uniform stress hypothesis of stem formation was evaluated by comparing stem taper of Abies balsamea, Abies lasiocarpa, Picea rubens, Pinus contorta, Pinus elliottii, Pinus palustris, Pinus ponderosa, Pinus taeda, and Pseudotsuga menziesii to the taper expected if stems develop to uniformly distribute bending stress. The comparison was conducted by regressing stem diameter at height h (Dh) against bending moment at h (Mh) using the model Dh=φ (Mh)δ where φ and δ are fitted coefficients, and testing for δ=0.333, the hypothesized value. Twelve curves were fitted with the model. Seven of the fitted values of δ were significantly different from 0.333, but eight of the values were within ±10% of 0.333 and eleven values were within ±15% of 0.333. Where the fitted value of δ was >15% of 0.333, residuals were biased with height. Fit by relative height, values of δ were within ±10% of 0.333 for large portions of these stems. While most of the fitted values of δ support the uniform-stress hypothesis, the values of δ for Pseudotsuga menziesii trees clearly did not. Many of the fitted values of φ were inversely related to the modulus of elasticity (E) of green wood reported for these species. With the exception of Pseudotsuga menziesii, growing conditions appeared to account for extraordinary values of φ. Increases in φ with stem height corresponded with reported decreases in E with height. The covariance between φ and E suggests some regulation of bending curvature by adjustments in cross-sectional area. These results suggest that stems taper to maintain a uniform bending curvature and that when E is relatively constant within and among stems, diameter along the stem or across stems can be predicted from bending moment using a simple power function.

Physical effects of weather events on the abundance and diversity of insects in North American forests

We summarize the effects of major weather events such as ice storms, wind storms, and flooding on the abundance and diversity of terrestrial forest insects and their allies. This synthesis indicates that weather events influence both spatial and temporal patterns of forests and insect communities in North American landscapes. The Atlantic and Pacific oceanic sides of the continent are relatively more susceptible to ice and wind storms, respectively. There have been more studies and reports on the responses of forest insects to wind storms, and on economically important subcortical insects than on gall-forming, foliage-feeding, fungal-feeding, litter-dwelling, pollinating, parasitizing, predaceous, root-feeding, and sap-feeding insects. Weather events positively affect populations of subcortical insect species, and impact their colonization patterns and dynamics. Species belonging to genera such as Dendroctonus (Scolytidae) and Monochamus (Cerambycidae) may sometimes cause economic damage by colonizing res...

Equations to describe crown allometry of Larix require local validation

Abstract Allometric equations were developed to describe crown attributes of three species of open-grown Larix in Minnesota and compared with similar data from Maine and published works from Austria. No differences were detected in allometric relationships to predict crown length, projected crown radius, and crown radius at different depths within the crown among tamarack, European larch, and hybrid European×Japanese larch grown in Minnesota. Small (

Assessing the Threat Posed by Indigenous Exotics: a Case Study of Two North American Bark Beetle Species

ABSTRACT The Douglas-fir beetle, Dendroctonus pseudotsugae Hopkins, was detected in 2001 in northern Minnesota outside its natural range and the range of its native hosts, Douglas-fir, Pseudotsuga menziesii (Mirbel) Franco, and western larch, Larix occidentalis Nutt. Consecutive years of detection indicated that D. pseudotsugae may have been established in a new environment and provided a possible example of an indigenous exotic species in North America. Pheromone-baited logs of P. menziesii and tamarack, Larix laricina (Du Roi) K. Koch, were placed at four sites in northern Minnesota in an attempt to detect this indigenous exotic. Bark was removed from one half of logs and checked for D. pseudotsugae galleries. The remaining logs were left intact and reared to collect adult beetles the following spring. No D. pseudotsugae galleries were identified and no adults of the indigenous exotic were located. Along with the eastern larch beetle, Dendroctonus simplex LeConte, native Minnesota populations of Polygraphus rufipennis (Kirby) and Dryocoetes autographus (Ratzeburg) colonized P. menziesii logs. The reciprocal study was conducted in Montana, primarily to determine whether D. pseudotsugae would attack pheromone-baited logs of L. laricina. Logs from the Minnesota and Montana experiments were used to estimate the success of D. simplex and D. pseudotsugae in the non-native hosts P. menziesii and L. laricina, respectively. Both D. simplex and D. pseudotsugae successfully colonized and reproduced in non-native logs in the field, albeit at low numbers. The potential threat of indigenous exotic species to North American forests also is discussed.

Alternative Fuel Reduction Treatments in the Gunflint Corridor of the Superior National Forest: Second year results and sampling recommendations

Fuel loadings need to be considered in two ways: 1) the total fuel loadings of various size classes and 2) their distribution across a site. Fuel treatments in this study affected both. We conclude that 1) mechanical treatments of machine piling and salvage logging reduced fine and heavy fuel loadings and 2) prescribed fire was successful in reducing fine fuel loadings (fuels less than 3 inches in diameter) but less successful than salvage logging and mechanical piling in reducing heavy fuel loadings (fuels greater than 3 inches diameter).

Integrating grouse habitat and forestry: An example using the ruffed grouse Bonasa umbellus in Minnesota

Abstract We quantified forest stand attributes at ruffed grouse Bonasa umbellus drumming display sites to develop tree stocking guides as a tool for guiding ruffed grouse management. We estimated tree density and basal area surrounding grouse drumming sites and compared these with unused sites. We used model selection to assess predictions about whether tree density and basal area surrounding drumming sites varied by site classification (primary drumming site, alternate site, unused site) or forest type. We plotted the predicted values from the best model on tree stocking guides, which are tools commonly used by forest managers. Tree density and basal area varied by site classification and by forest type. Our results show that stem density was higher and basal area lower at both primary and alternate drumming sites compared to unused sites in all forest types. We also found that grouse sites in aspen stands had a greater stem density and lower basal area than grouse sites in pine and spruce/fir stands. Incorporating these results into a tree stocking guide suggested that management for grouse in aspen stands should attempt to maintain stands with average stem density and basal area for this species. In contrast, foresters who are managing for conifers and also wish to maintain some grouse habitat should favour wider spacing of trees in stands. Wider spacing will encourage the development of dense understory vegetation favoured by grouse as well as enhance the growth of quality saw-logs. Our study describes a method for incorporating habitat data on ruffed grouse and other wildlife into tree stocking charts, which are commonly used to facilitate management of forest stands.

Commercial thinning in small-diameter aspen stands in Northern Minnesota: study establishment report.

In the spring of 1999, a long-term study was established to examine the physical and biological aspects of thinning young aspen stands in Minnesota. Three aspen stands ranging in age from 25 to 35 years were selected on lands owned by the State of Minnesota and UPM Kymmene. Two thinning treatments (low and high density) and an unthinned control were installed at each of the three locations. Permanent plots were installed to measure tree, shrub, and herb growth, and to monitor harvesting damage, insect and disease damage, soil strength, and fuel loadings. After 4 years, tree mortality was greater in the unthinned controls. Thinning treatment had no significant effect on the incidence of white trunk rot (Phellinus tremulae), Hypoxylon canker, or Saperda calcarata. No differences in post-harvest fuel loadings were detected among locations and treatments. Thinning increased the amount of light reaching the forest floor that resulted in greater herb and shrub biomass in the year immediately following thinning.