Biology subjects

Burcham, D. C.

Publications and source records attributed to Burcham, D. C..

3 recordsLinked to original sources

bioRxiv2026

Weak evidence for change in wind-induced bending moments on raised and thinned Colorado spruce (Picea pungens)

Trees are routinely pruned to mitigate the risk of wind damage, but there are few studies examining changes in wind loads after pruning, especially for large conifers. In this study, ten Colorado spruces (Picea pungens) were monitored before and after a series of pruning treatments. Trees were pruned to raise or thin crowns over a range of severities between 0% and 40%. Wind-induced bending moments were measured using two calibrated displacement probes installed orthogonally on the lower stem of each tree. Using a hierarchical Bayesian model, the relationship between maximum wind speeds and bending moments was quantified, consistent with theoretical and empirical expectations, as a non-linear power law. Random intercepts for model coefficients were used to account for individual variability in aerodynamic behavior among experimental trees, and predictions were made using the median response marginalized over the observed trees. The modeled relationship between wind speeds and bending moments was physically reasonable and like existing measurements with scaling exponents below two. Despite considerable variation among experimental trees, the aerodynamic behavior of trees, as indicated by model coefficients, was not clearly altered by pruning treatments, and, correspondingly, model predictions of bending moments over the range of observed wind speeds remained similar for all pruning treatments. Ultimately, the study yielded weak evidence for a change in bending moments following conventional pruning treatments for Colorado spruce, and the practical value of pruning to mitigate risk appeared limited for the studied conditions. Highlights- Wind loads were monitored on large Colorado spruce after crown raising and thinning - A hierarchical Bayesian model quantified wind speed and bending moment power laws - Negligible change in bending moments was found for all pruning types and severities - Conventional pruning methods may not mitigate risk for Colorado spruce

biophysics↗

bioRxiv2025

Tracking seasonal variation in modal properties of an open-grown green ash (Fraxinus pennsylvanica)

Despite longstanding interest and varied applications, the vibration behavior of trees remains poorly understood, largely due to methodological limitations. To more effectively identify and partition sources of natural variation in the modal properties of trees, there is a need for more reliable estimates derived from long-term observations. Using improved Bayesian methods, the modal properties of one green ash tree were identified over an entire growing season with simultaneous measurements of nearby weather conditions and phenological observations. The analysis confirmed many features of tree vibration observed in an earlier related study, including two prevalent close, nearly orthogonal modes and amplitude dependence for modal properties, but the more extensive and detailed measurements also revealed new characteristics, including changes in the arrangement of partial mode shapes and sizeable variation in modal properties over multiple time scales. For the leafless tree, the two modes were consistently oriented in directions aligned with the planting layout of surrounding trees, but their orientation varied erratically over time, while remaining roughly perpendicular to one another, during periods with leaves. Though some of the modal property variation closely paralleled other measurements, including weather conditions and vegetative phenophases, in physically reasonable ways, the reasons for other changes were not clear. Using a detailed assessment of the governing factors for estimate uncertainty, the cause of low-quality estimates was attributed to very close or nearly identical modes, and the causes and implications of close modes for tree vibration monitoring should be a main priority for future studies.

biophysics↗

bioRxiv2017

In vitro evaluation of antagonism by Trichoderma spp. towards Phellinus noxius associated with rain tree (Samanea saman) and Senegal mahogany (Khaya senegalensis)

A series of laboratory tests was conducted to screen and identify Tnchoderma spp. for the biological control of P. noxius on pruning wounds. In total, 7 Trichoderma isolates were evaluated for their biological fitness and antagonism towards 2 different P. noxius isolates associated with Senegal mahogany and rain tree in Singapore. The competitive ability of various Trichoderma isolates was assessed by their germination rates, growth rates, and chlamydospore production; and the antagonism of P. noxius by Trichoderma was assessed by the interaction of these fungi in dual culture and on wood blocks. In this study, the Trichoderma isolates showed greater competitiveness and antagonism towards P. noxius compared to similar reports in the literature. A majority of the Trichoderma isolates germinated and grew at consistently high rates, but there was considerable variability in the production of chlamydospores among isolates. All Trichoderma isolates routinely antagonized P. noxius in the different bioassays, but there was significant variability in the antagonistic capacity of various isolates and in the susceptibility of the P. noxius isolates to confrontation with Trichoderma. Relative to the controls, P. noxius cultures grew significantly slower in the presence of volatile organic compounds emitted by most Trichoderma isolates, and a large majority of Trichoderma isolates caused a significant reduction to the dry weight loss of wood blocks inoculated with P. noxius. Although no single Trichoderma isolate consistently antagonized P. noxius better than all others in every test, T. harzianum 9132 and T. virens W23 notably did so more regularly than others.

ecology↗