Treesearch

1. Deformations of Engelmann spruce and subalpine fir trees were surveyed for the purpose of determining climatic wind speeds and directions and snow depths in the Glacier Lakes Ecosystem Experiments Site (GLEES) in the Snowy Range of southeastern Wyoming, USA. Tree deformations were recorded at 50- and 100-m grid intervals over areas of c. 30 ha and 300 ha, respectively, over the GLEES. 2. The climatic mean wind speed was estimated to be 7.4 m s-1; the mean air flow was predominantly westerly. The snow depths ranged from less than 0.2 m to 5.5 m, depending on topographic features and...

Three alpine and three subalpine sites were monitored for up to 4 years to acquire data on the temporal and spatial variability of CO2 flux through snowpacks. We conclude that the snow formed a passive cap which controlled the concentration of CO2 at the snow-soil interface, while the flux of CO2 into the atmosphere was controlled by CO2 production in the soil. Seasonal variability in the flux at all sites was characterized by early winter minima followed by a rise in flux that averaged 70% above the minima over about a 1-month period. The seasonal variability was not related to soil...

We define criteria for documenting episodic acidification of amphibian breeding habitats and examine whether episodic acidification is responsible for observed declines of amphibian populations in the Rocky Mountains. Anthropogenic episodic acidification, caused by atmospheric deposition of sulfate and nitrate, occurs when the concentration of acid anions increases relative to the concentration of base cations, resulting in a decrease in acid-neutralizing capacity (ANC). However, because several natural processes can also depress ANC, monitoring pH and ANC alone cannot provide evidence...

We examined distribution and habitat characteristics of spawning sites of cutthroat trout Oncorhynchus clarki at various spatial scales to assess effects of sedimentation within a large basin in Montana. Redd density varied widely across the basin; nearly all (99%) of the 362 redds observed occurred in two high-elevation headwater tributaries. Redd density at the reach scale was positively correlated (r2 = 0.72, P = 0.001) with abundance of spawning gravels. Other habitat variables, such as gradient, width, depth, embeddedness, bank stability, and percent riffle, were not significantly...

Biologists lack sufficient information to develop protocols for sampling the abundance and size structure of bull trout Salvelinus confluentus. We compared summer estimates of the abundance and size structure of bull trout in a second-order central Idaho stream, derived by day snorkeling, night snorkeling, and electrofishing. We also examined the influence of water temperature and habitat type on day and night counts of bull trout. Electrofishing yielded the largest estimates of abundance of age-1 and older bull trout. Day snorkeling counts accounted for a mean of 75% and night snorkeling...

Intragravel water exchange provides oxygenated water, removes metabolic waste, and is an essential factor in salmonid embryo survival. Measurements of intragravel flow velocity have been suggested as an index of gravel quality and also as a useful predictor of fry emergence; however, proposed methods for measuring velocity in gravel are problematic. We evaluate an ion adsorption technique that uses natural streamwater solute chemistry, which therefore does not require introduction of a dye or solute tracer. However, the method requires an access tube for placing an ion exchange resin bag...

A study of visitors to Oregon's Eagle Cap Wilderness in 1965 offered a baseline against which to evaluate how those who recreate in wilderness have changed their views of wilderness. A study of visitors to that same wilderness area in 1993 provided comparative data. Some characteristics of the visitors changed in ways that would suggest that the values visitors placed on wilderness and on the behaviors they would consider appropriate had changed as well. Specifically, visitors were better educated and were more likely to be members of conservation or outdoor recreation organizations. In...

Prescribed burning is an effective way of restoring the fire process to ponderosa pine (Pinus ponderosa Doug I. ex Laws.) ecosystems of the Southwest. If used judiciously, fire can provide valuable effects for hazard reduction, natural regeneration, thinning, vegetation revitalization, and in general, better forest health. Relatively short burning intervals are required to maintain the benefits of fire.

Recent underestimates of total volume for timber sales in the Black Hills National Forest prompted analysis of two felled ponderosa pine (Pinus ponderosa Laws.) data sets that were collected approximately 10 years apart. Though neither data set collected was a representative sample of the Black Hills, both were similar in terms of diameter at breast height and total height. We investigated several methods for assessing differences in tree form and applied them to these two data sets. Under the assumption that these two data sets were representative of harvested trees in the Black Hills...

This review of the disturbance ecology literature, and how it pertains to forest management, is a resource for forest managers and researchers interested in disturbance theory, specific disturbance agents, their interactions, and appropriate methods of inquiry for specific geographic regions. Implications for the future of disturbance ecology-based management are discussed.