Treesearch

It is common practice to assume that a two-parameter Weibull probability distribution is suitable for modeling lumber properties. Verrill and co-workers demonstrated theoretically and empirically that the modulus of rupture (MOR) distribution of visually graded or machine stress rated (MSR) lumber is not distributed as a Weibull. Instead, the tails of the MOR distribution are thinned via “pseudo-truncation.” The theoretically portion of Verrill’s argument was based on the assumption of a bivariate normal—Weibull (Gaussian—Weibull) MOE—MOR distribution for the full population of lumber (as...

Droughts in the western United States are expected to intensify with climate change. Thus, an adequate representation of ecosystem response to water stress in land models is critical for predicting carbon dynamics. The goal of this study was to evaluate the performance of the Community Land Model (CLM) version 4.5 against observations at an old-growth coniferous forest site in the Pacific Northwest region of the United States (Wind River AmeriFlux site), characterized by a Mediterranean climate that subjects trees to water stress each summer. CLM was driven by site-observed meteorology and...

This package adds several classes, generics and associated methods as well as a few various functions to help with wavelet decomposition of sampling surfaces generated using sampSurf. As such, it can be thought of as an extension to sampSurf for wavelet analysis.

Predicting the effects of global climate change on species interactions has remained difficult because there is a spatiotemporal mismatch between regional climate models and microclimates experienced by organisms. We evaluated resource selection in a predominant ectothermic predator using a modeling approach that permitted us to assess the importance of habitat structure and local real-time air temperatures within the same modeling framework. We radio-tracked 53 western ratsnakes (Pantherophis obsoletus) from 2010 to 2013 in central Missouri, USA, at study sites where this species has...

Context. Ungulate browsers often alter plant composition and reduce diversity in forests worldwide, yet our ability to predict browse impact on vegetation remains equivocal. Theory suggests, however, that ungulate distribution and foraging impacts are shaped by scale-dependent decisions based on variation in habitat composition and structure encountered within their home range. Objective. Examine how variation in habitat composition at landscape (259 ha) scales modulates browse impact on vegetation at local scales. Methods. We measured vegetation richness and abundance in plots with and...

Reference charts have long been used in the medical field for quantitative clinical assessment of juvenile development by plotting distribution quantiles for a selected attribute (e.g., height) against age for specified peer populations.We propose that early stand dynamics is an area of study that could benefit from the descriptions and analyses offered by similar references for various tree measures. Reference charts provide a flexible quantitative framework that would complement traditional methods for assessing tree development. In young, mixed stands, competitive dynamics are, in part,...

The mountain pine beetle, Dendroctonus ponderosae Hopkins, is a significant agent of tree mortality in lodgepole pine (Pinus contorta Dougl. ex Loud.) forests throughout western North America. A large outbreak of mountain pine beetle caused extensive tree mortality in north-central Colorado beginning in the late 1990s. We use data from a network of plots established in 2006-2007 on the Sulphur Ranger District of the Arapaho and Roosevelt National Forests to develop simple probability of infestation and extent of mortality models using classification and regression trees, respectively. A...

This report gives early results, 18 years after treatment and 30 years after planting, from a trial of early thinning and gap creation intended to increase biodiversity in a very uniform extensive Douglas-fir plantation. Gap creation has introduced canopy irregularity and a substantial hemlock component into what was originally a very uniform pure Douglas-fir plantation, produced some natural regeneration of Douglas-fir, and considerably changed diameter distributions. Long-term effects will depend on whether additional stand density manipulation is carried out in coming years.

Many hectares of intensively managed Douglas-fir (Pseudotsuga menziesii Mirb. Franco) stands in western North America are fertilized with nitrogen (N) to increase growth rates, but only about ⅔ of all stands respond. Understanding the mechanisms of response facilitates prioritization of stands for treatment. The primary objective of this study was to test the hypothesis that the short-term basal area growth response to a single application of 224 kg N ha
-1 as urea was associated with reduced stable carbon isotope discrimination (Δ13C) and increased intrinsic water use efficiency (iWUE) in...

ssWavelets is an R package that is meant to be used in conjunction with the sampSurf package (Gove, 2012) to perform wavelet decomposition on the results of a sampling surface simulation. In general, the wavelet filter decomposes the sampSurf simulation results by scale (distance), with each scale corresponding to a different level of the decomposition. This results in a set of anisotropic wavelet coecients for each scale or level, one each for horizontal, vertical and diagonal components; the sum of these yields an isotropic decomposition for that scale.