Treesearch

Quantification of the mechanical properties of cellulose nanomaterials is key to the development of new cellulose nanomaterial based products. Using contact resonance atomic force microscopy we measured and mapped the transverse elastic modulus of three types of cellulosic nanoparticles: tunicate cellulose nanocrystals, wood cellulose nanocrystals, and wood cellulose nanofibrils. These modulus values were calculated with different contact mechanics models exploring the effects of cellulose geometry and thickness on the interpretation of the data. While intra-particle variations in modulus...

Invading species rarely spread homogeneously through a landscape and invasion patterns typically display irregular frontal boundaries as the invasion progresses through space. Those irregular patterns are generally produced by local environmental factors that may slow or accelerate movement of the frontal boundary. While there is an abundant literature on species distribution modelling methods that quantify local suitability for species establishment, comparatively few studies have examined methods for measuring the local velocity of invasions that can then be statistically analysed in...

Urban networks of air-quality monitors are often too widely spaced to identify sources of air pollutants, especially if they do not disperse far from emission sources. The objectives of this study were to test the use of moss bio-indicators to develop a fine-scale map of atmospherically-derived cadmium and to identify the sources of cadmium in a complex urban setting. We collected 346 samples of the moss Orthotrichum lyellii from deciduous trees in December, 2013 using a modified randomized grid-based sampling strategy across Portland, Oregon. We estimated a spatial linear model of moss...

There has been considerable interest in developing management techniques for creating mixed shortleaf pine (Pinus echinata)–hardwood forests in the Southern Appalachian Mountains. This interest has increased in recent years due to the need to manage for more diverse and resilient forests, and to reestablish shortleaf pine as a dominant species throughout its native range. The fell-and-burn regeneration technique was developed in the 1980s as a low-cost method to establish planted pines among hardwood sprouts for regenerating mixed species stands. This study documented the success of the...

In addition to selecting loblolly pine (Pinus taeda L.) genotypes for superior growth, the concept of customized genetic selection may apply where tree vigor is threatened by insects and disease. A study conducted with seedlings from 15 loblolly pine genotypes found significant correlation between phenolic production and foliage mass when dry mass allocation to the stem was relatively low. Validation of this relationship in trees was attempted among four genetic sources of juvenile loblolly pine. Tree biomass allocation information was collected from six individuals per genotype at age 5...

Factors affecting the density and distribution of yellow-poplar regeneration after a single growing season prescribed fire were studied in mature upland oak stands in the southern Appalachian Mountains. In burned and unburned stands, density of one and two year old yellow-poplar seedlings was inventoried within 50 m from isolated yellow-poplar canopy seed trees in response to distance from seed source, litter layer present and competition by other species. Yellow-poplar regeneration was absent on the forest floor in unburned stands, but averaged over 97 thousand seedlings/ha around seed...

This study reports growth and carbon storage of four bottomland hardwood forest sites in the Lower Mississippi Alluvial Valley (LMAV) of southern Louisiana. Forest growth and carbon sequestration rates at the four sites were highly variable because of differences in stand composition, age, structure, and site hydrology. Mean annual carbon assimilation rates ranged from 1.9 - 3.4 Mg/ha/yr during a seven year period. The highest sequestration rates occurred in trees on the drier, ridge site. Remnant mature trees accounted for a large proportion of total carbon assimilated and stored and at...

The Lower Mississippi Alluvial Valley (LMAV) once had the largest expanse of bottomland forest cover in the United States, but these diverse forests have been heavily cleared for agricultural purposes. In recent decades significant forest restoration efforts have been attempting to restore bottomland forest cover and the environmental services it provides (e.g. water quality, soil conservation, wildlife habitat). One of the most commonly planted groups of species in these afforestation efforts are different oak (Quercus spp.) species However, information about their growth and yield are...

Long-term productivity of loblolly pine (Pinus taeda L.) plantations can be increased by early suppression of herbaceous and woody competing vegetation (Zutter and others 1986, Haywood 1994, Miller and others 2003a). The USDA Forest Service’s Competition Omission Monitoring Project (COMP) was designed to isolate influences of two major competition groups (herbaceous and woody plants) at a range of sites in the Southeast U.S. A broad array of results from the COMP study improved understanding of loblolly pine growth (Miller and others 1991, 1995a, 1995b, 2003a), soil and foliage nutrients...

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