Treesearch

Bolted/pinned joints in orthotropic composite materials have received considerable attention over the years. Bolt fastening is one of the most commonly used methods to connect wood to wood and/or wood to steel, etc. Stresses at such connections can be the “Achilles’ heel”, causing structural failures. Notwithstanding the challenges in stress analyzing bolted joints, their advantages and widespread use motivate developing ability to optimize their design. Acknowledging the above, a finite element code is combined here with a screening optimization algorithm to optimize a bolt-hole pattern...

The frequently observed forest decline in water-limited regions may be associated with impaired tree hydraulics, but the precise physiological mechanisms remain poorly understood. We compared hydraulic architecture of Mongolian pine (Pinus sylvestris var. mongolica) trees of different size classes from a plantation and a natural forest site to test whether greater hydraulic limitation with increasing size plays an important role in tree decline observed in the more water-limited plantation site. We found that trees from plantations overall showed significantly lower stem hydraulic efficienc...

Native bees are declining worldwide, but conserving or restoring their habitat requires a better understanding of bee-flower associations. High quality bee habitat includes flowers that provide pollen and nectar preferred by bees. However, little data exist about which plants are commonly used by bees in the Pacific Northwest, or whether bees prefer certain plant characteristics over others. We examined bee and plant communities in an Oregon riparian ecosystem. Our purpose was to describe bee-plant associations, determine which plants are most frequently visited by bees, identify plants...

Common walnut (Juglans regia L.) is an economically important hardwood tree species cultivated worldwide for its high quality wood and edible nuts. It is generally accepted that after the last glaciation J. regia survived and grew in almost completely isolated stands in Asia, and that ancient humans dispersed walnuts across Asia and into new habitats via trade and cultural expansion. The history of common walnut in China is a matter of debate, however. We estimated the genetic diversity and spatial genetic structure of 31 walnut populations sampled across its Chinese range using 22...

While research of Cross-Laminated Timber (CLT) structures prioritizes force-based design for earthquake hazards, this project navigates a complementary displacement-based route—charted by United States building code provisions for seismic isolation. Curvilinear cuts to the load-bearing edges of stock CLT panels enable walls to roll through pendulum motion. Elliptical geometry provides the mechanism to lift supported storeys, passively self-centre through oscillatory damping, and avert damage to the panel corners. Wider elliptical profiles reliably negate residual displacements, as a...

In subalpine forests where snowpacks can persist for 50% of the year or longer, wintertime subnivean soil respiration constitutes a significant, but poorly understood, portion of the carbon (C) cycle. The temporal and seasonal dynamics of this flux are difficult to measure compared to snow-free respiration. This makes it challenging to fully address key knowledge gaps in high-elevation forests, including effects of tree mortality on ecosystem C fluxes. Our paper attempts to overcome these challenges by developing a new method for estimating wintertime CO2 flux from soil underneath winter...

Urban ecosystems are widely hypothesized to be more ecologically homogeneous than natural ecosystems. We argue that urban plant communities assemble from a complex mix of horticultural and regional species pools, and evaluate the homogenization hypothesis by comparing cultivated and spontaneously occurring urban vegetation to natural area vegetation across seven major U.S. cities. There was limited support for homogenization of urban diversity, as the cultivated and spontaneous yard flora had greater numbers of species than natural areas, and cultivated phylogenetic diversity was also...

The prediction of snowmelt in mountainous forests strongly depends on the accurate description of sensible and latent heat turbulent fluxes. Uncertainty about the within‐ canopy wind conditions especially poses a challenge, with relatively few studies examining both above‐ and below‐canopy turbulent fluxes. In this study, turbulent flux predictions from a state‐of‐the‐art watershed model GEOtop were verified against eddy covariance data from one above‐canopy tower and two below‐canopy towers in a snow‐dominated coniferous forest in south‐eastern Wyoming. The model was applied in one‐dimensi...

Many species of wildlife require cavities in trees as locations for refuge or reproduction. In forests where the availability of cavities has been reduced, artificial cavities may provide surrogate locations. Artificial cavities are typically created using boxes and artificial cavity research has traditionally focused primarily on birds. However, there are numerous cavity‐dependent species of mammals that are of regional and global conservation concern, such as the Humboldt marten (Martes caurina humboldtensis). Martens (Martesspp.) are small mustelids that often use cavities for daily...

Fungi are the second largest group of eukaryotic organisms on Earth, providing essential ecosystem services throughout the world. Although early attempts were made in the 20th century to document various components of the mycota of North America, no extensive list of taxonomic names has ever been compiled for this region. This paper represents the first comprehensive checklist for nonlichenized Fungi from North America, which is defined here as Canada, Mexico, and the United States (and its territories), and is based on the efforts of 75 fungaria that deposited their data online in the...