In this study, the inverse relationship between lifetime and secondary creep rate was verified suggesting that shorter duration tests can be used to evaluate lifetimes. Also, the variability in creep rate was significantly lower than previous studies suggesting that using enhanced testing facilities could reduce required number of repetitions. A novel finding was an observed transition point in applied loading level where cyclic humidity conditions had the highest creep rates at low loads and constant high humidity conditions had the highest creep rate at high loads. Finally, it was determined that a standard moisture cycling history for a standard test protocol will be difficult to determine and the moisture sorption behaviour of each box type must be accounted for.
Background: To understand the effects of silvicultural treatments on tree and product modulus of elasticity (MOE), an intensive study along the stand-tree-product value chain was conducted. Acoustic tests were performed on 460 Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) trees from two sites in the US Pacific Northwest. Methods: Trees on a site in Washington were 51 years old, while those situated in Oregon were 45 years old. Both sites comprised five plots: Plot A was the control, while Plots B, C, D, and E were prescribed with differing thinning treatments. Acoustic readings were stratified, and a sample of six trees per plot randomly selected from the stratified samples. Trees were harvested, cross-cut, and peeled into veneer. Veneer was acoustically tested, and density and MOE calculated for each sheet. Veneer sheets were grouped by parent bolt and tree, and MOE of the butt veneer bolt and the parent tree determined from the mean. Plot means were compared using one-way analysis of variance (ANOVA), and regression models developed with mean tree MOE as the response variable and non-destructive tree measures as explanatory variables. Further models were developed to demonstrate the relationship between tree diameter and the number of veneer sheets peeled, and between MOE of the parent tree and butt bolt.
Exposure to carbon monoxide (CO) emitted by chainsaws can negatively impact health in forestry workers. This exploratory study measures CO concentration within the breathing zone of chainsaw operators during motor-manual operations, and discusses the potential influences on CO exposure levels. A CO monitoring instrument was paired with a concurrent video recording of task activities to enable correlation of exact working operations to critical exposure levels. Multiple streams of meteorological data were also collected from sensors worn by the eight professional tree fellers/log makers. Time-weighted averages were applied to investigate levels of CO exposure during a nominal 1-hr monitoring period. The differing task demands and environment were found to influence worker exposure to CO, supporting previous research. Pending further investigation, a number of possible actions are recommended to reduce observed high exposure levels and/or emission concentration.
Shrubland biomass is important for fire management programmes and for carbon estimates. Aboveground biomass and the combustible portion of biomass, the fuel load, in the past have been measured using destructive techniques. These techniques are detailed, highly labour intensive, and costly; hence, an alternative approach was sought. The new approach used linear mixed-effects models to estimate biomass and fuel loads from easily measured field variables: shrub overstorey height and cover, and understorey height and cover. Site was regarded as a random effect. Sampling sites were located throughout New Zealand and included a range of shrubland vegetation types: manuka ( Leptospermum scoparium J.R. Forst. et G. Forst.) and kanuka ( Kunzea ericoides (A. Rich.) J. Thomps.) scrub and heath, pakihi (mixed low heath, fern, and rushes), and gorse ( Ulex europaeus L.). The approach was extended and confidence intervals were constructed for the regression models. Statistical analysis showed that understorey height and overstorey cover were significant (at the 5% level) in some cases. Overstorey height was highly significant in all cases (p < 0.0001), allowing development of models useful to the operational user. The models allow rapid estimation of average fuel loads or biomass on new sites, and double sampling theory can be applied to calculate the error in the resultant biomass estimate.
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