Treesearch

Although climate warming is generally expected to facilitate upward advance of forests, conifer seedling regeneration and survival may be hindered by low substrate moisture, high radiation, and both low and high snow accumulation. To better understand substrate-related factors promoting regeneration in the alpine treeline ecotone, this study compared 2 substrates supporting conifer seedlings: rotten downed wood and adjacent soil. Study locations, each with 3 levels of incoming radiation, were randomly selected at forest line–alpine meadow borders in Pacific Northwest wilderness areas...

La historia de las truchas del Pacífico, pertenecientes al género Oncorhynchus, es una historia muy interesante que se basa en la persistencia y diversificación de sus especies debido, en gran parte, al dinamismo propio que existe en su medio ambiente. Desde el oeste de Norteamérica, extendiéndose hasta el este de Asia, las truchas del Pacífico han experimentado la influencia de los avances y retrocesos de glaciares, vulcanismo, condiciones extremas en el caudal de los ríos, al igual que eventos geotectónicos, que han permitido la formación de cordilleras y mesetas. Dichos eventos son los...

Forest pathogens have strong potential to shape ecosystem function by altering litterfall, microclimate, and changing community structure. We quantified changes in litter decomposition from a set of distinct diseases caused by Phytophthora ramorum, an exotic generalist pathogen. Phytophthora ramorum causes leaf blight and increased litterfall %N, but no mortality on California bay laurel (Umbellularia californica), a common overstory tree that accumulates high levels of infection. Lethal twig and bole cankers on tanoak (Notholithocarpus densiflorus) lead to the disease sudden oak death...

The USDA Forest Service is required to appraise timber prior to it being offered for sale. Currently the Forest Service uses a transaction evidence based approach, but concerns have been raised about availability—both in number and applicability—of timber sales used as the basis of this approach. In addition to the problem of few sales, in certain situations a notable fraction of the sales may be made at the minimum rate. This transaction evidence system and the application of a rollback factor in setting a minimum bid can result in appraised prices declining over time in areas with low...

The availabilty of information on wood energy continues to improve, particularly for commoditized woodfuels. Wood energy consumption and production vary in the UNECE region because demand is strngly affected by weather and the prices of competing energy sources. There has been an increase in wood energy in the power-and-heat sector in the EU28 and North American subregions in the last en year, with prospects for a similar trend in the CIS. The implementation of renewable energy targets and financial incentive programmes, and improvements in energy conversion efficiency, has helped drive...

Two sets of paired watersheds on north and South facing slopes were utilized to simulate the effects of temperature differences that are on the scale of those expected with near-term climatic warming on decomposition. Two watersheds were pine plantations (Pinus strobus L.) and two were mature deciduous forests established at similar elevation ranges and precipitation at the Coweeta Hydrologic Laboratory, but they differed in slope aspect (north vs. South facing), solar radiation, and litter temperature by about 2.0 °C. Nylon netting was placed on plots each year for 13 years and litterfall...

Earthworms were collected and identified in different ecological habitats of the Stephen F. Austin Experimental Forest (SFAEF) in the Piney Woods Ecoregion (PWE) of Texas. Earthworm spatial distribution data were collected over four distinct ecological habitats with a range of soil conditions and vegetative cover. A total of 128 sampling plots were surveyed in two different, broadly defined locations (mesic slope = 68 plots, dry-mesic upland = 60 plots). Using multivariate classification/ordination (TWINSPAN) and detrended correspondence analysis (DCA) of overstory vegetation data, these...

Hynes (1970) observed that living organisms in streams may significantly affect nutrient concentrations, but our understanding of these effects remains elusive and subject to debate (Cardinale, 2011a,b; Baulch et al., 2011). The possible role of biotic, in-stream processes for affecting nutrients is important to understanding how upstream processes are linked to downstream responses (Vannote et al., 1980; Mulholland et al., 1995), to the biogeochemical interpretation of watershed exports (eg, Bernhardt et al., 2005), and to delivery of nutrients to coastal waters (Doney, 2010).

Packera franciscana (Greene) W.A. Weber and Á. Löve (Asteraceae) (San Francisco Peaks ragwort) is an alpine-zone endemic of the San Francisco Peaks in northern Arizona. Previous studies have shown that P. franciscana is patchily distributed in alpine-zone talus habitats. The purpose of this study was to describe the relationship between snow duration and P. franciscana abundance. We established trailside transects through P. franciscana habitat along the Weatherford Trail to estimate the abundance of P. franciscana ramets. Snow-free and snowbed sample segments were chosen based on a 17 May...

Sonic anemometers are the principal instruments in micrometeorological studies of turbulence and ecosystem fluxes. Common designs underestimate vertical wind measurements because they lack a correction for transducer shadowing, with no consensus on a suitable correction. We reanalyze a subset of data collected during field experiments in 2011 and 2013 featuring two or four CSAT3 sonic anemometers. We introduce a Bayesian analysis to resolve the three-dimensional correction by optimizing differences between anemometers mounted both vertically and horizontally. A grid of 512 points ( ~ +/-...