Treesearch

Historically, frequent, low-severity fires in dry western North American forests were a major driver of ecological patterns and processes, creating resilient ecosystems dominated by widely-spaced pine species. However, a century of fire-suppression has caused overcrowding, altering forest composition to shade-tolerant species, while increasing competition and leaving trees stressed and susceptible to pathogens, insects, and high-severity fire. Exacerbating the issue, fire incidence is expected to increase with changing climate, while fire season has been observed to begin earlier and last...

Hawai‘i’s most widespread native tree, ‘ōhi‘a lehua (Metrosideros polymorpha), has been dying across large areas of Hawai‘i Island mainly due to two fungal pathogens (Ceratocystis lukuohia and Ceratocystis huliohia) that cause a disease collectively known as Rapid ‘Ōhi‘a Death (ROD). Here we examine patterns of positive detections of C. lukuohia as it has been linked to the larger mortality events across Hawai‘i Island. Our analysis compares the environmental range of C. lukuohia and its spread over time through the known climatic range and distribution of ‘ōhi‘a. Analyses show this fungal...

Reactive extrusion was used for dicumyl peroxide (DCP)-initiated grafting of glycidyl methacrylate (GMA) to poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). The effects of GMA and DCP content and their weight ratio on the GMA grafting percentage (GP%), the polymer melt viscosity, and the PHBV molecular weight were investigated. FTIR spectroscopy determined that the DCP did indeed initiate GMA grafting. However, the changes in both the zero-shear viscosity (η0) and the molecular weight suggested the existence of crosslinking products in the extruded polymers. A negative correlation...

Forests are an important part natural ecosystems, by for example providing food, fiber, habitat, and biodiversity, all of which contribute to stable natural systems. Assessing and modeling the structure and characteristics of forests, e.g., Leaf Area Index (LAI), volume, biomass, etc., can lead to a better understanding and management of these resources. In recent years, Terrestrial Laser Scanning (TLS) has been recognized as a tool that addresses many of the limitations of manual and traditional forest data collection methods. In this study, we propose a density-based approach for...

Fraud and misrepresentation in forest products supply chains is often associated with illegal logging, but the extent of fraud in the U.S. forest products market, and the availability of forensic expertise to detect it, is unknown. We used forensic wood anatomy to test 183 specimens from 73 consumer products acquired from major U.S. retailers, surveyed U.S. experts regarding their forensic wood anatomy capacity, and conducted a proficiency-testing program of those experts. 62% of tested products (45 of 73) had one or more type of fraudulent or misrepresented claim. Survey respondents...

Cellulose nanomaterials have been demonstrated to improve the mechanical and barrier properties of various polymers, but numerous challenges, such as drying, remain to viably produce polymeric cellulose nanocomposites for packaging applications. In this paper we describe a method for drying and blending cellulose nanocrystals into polylactic acid (PLA) using a single process referred to as wet compounding. Aqueous suspensions of CNCs were directly compounded with PLA in a thermokinetic mixer in which viscous heating creates sufficient temperature to evaporate water and melt polymers during...

Most regions of the United States are projected to experience a higher frequency of severe droughts and longer dry periods as a result of a warming climate. Even if current drought regimes remain unchanged, higher temperatures will interact with drought to exacerbate moisture limitation and water stress. Observations of regional-scale drought impacts and expectations of more frequent and severe droughts prompted a recent state-of-science synthesis (Vose et al. 2016). The current volume builds on that synthesis and provides region-specific management options for increasing resilience to...

We examine the applicability of predicting the daily flow–duration curve (FDC) using mean monthly runoff represented in its stochastic form (MM_FDC) to aid in predictions in ungauged basins, using long-term hydroclimatic data at 73 catchments of humid climate, in the eastern USA. The analysis uses soil hydrological properties, soil moisture storage capacity and the predominant runoff generation mechanism. The results show that MM_FDC did not distinguish the shapes of the upper and lower thirds of the FDC. The upper third is where the precipitation pattern and the antecedent moisture...

To explore the history of California roach (Hesperoleucus symmetricus) in the Eel River, we compiled mitochondrial DNA data for the putatively introduced Eel River population and comparative collections from throughout the native range. Consistent with an introduction scenario, we found that: 1) one haplotype occurred at high frequency in the Eel River, Russian River and Clear Lake populations, making the Russian River and Clear Lake likely source areas, and 2) the introduced population exhibited reduced haplotype diversity in comparison to populations from the native range. However, we...

Liquid moisture evaporation and pyrolysis of a biomass fuel slab subject to heating were computationally investigated in a one-dimensional domain where the fuel shrinkage was accounted for. The evaporation dynamics was separately represented by equilibrium and Arrhenius models. The equilibrium model describes evaporation as a thermodynamic process whereas the Arrhenius model treats it as a chemical reaction. For calculations, Gpyro, a pyrolysis computational framework, was used after its source code was revised to include the equilibrium model. By default, Gpyro is only capable of operating...