Treesearch

Retention of visible implant (VI) tags by westslope cutthroat trout Oncorhynchus clarki lewisi inhabiting 20 reaches of 13 isolated headwater tributary drainages in Montana was evaluated during 1993 and 1994. In 1993, 2,071 VI tags were implanted in westslope cutthroat trout (100-324 mm fork length) and adipose tins were removed as a secondary mark to evaluate tag retention. Of 348 westslope cutthroat trout recaptured during the year they were tagged, 201 (58%) had retained their tags. Of 616 westslope cutthroat trout recaptured the year after tagging, 355 (58%) had retained their tags....

Fire dependent lodgepole pine communities are an important component of upper elevation forests of the Bitterroot Mountains and the Northern Rockies in generaL A study of 1937 aerial photos from the Bitterroot National Forest is describing the pre- 1900 disturbances that shaped lodgepole pine mosaics, The 1937 photos will be compared with stand history information provided by Mike Hartwell and Paul Alaback of the University of Montana to describe shifts in species dominance and age-class structure during the past half century, This information will be used to design management that...

The Tenderfoot Creek Experimental Forest, established in 1961, is representative of the vast expanses of lodgepole pine (Pinus contorta) found east of the Continental Divide in Montana, southwest Alberta, and Wyoming. Discrete generations of even-age lodgepole stands form a mosaic typical of the fireprone forests at moderate to high altitudes in the Northern Rocky Mountains. Spruce (Picea engelmannii) grows in the area's sparse but species-rich wetlands, while whitebark pine (Pinus albicaulis) and subalpine fir (Abies lasiocarpa) grace the higher ridgetops. Native cutthroat trout (Oncorhync...

High rural concentrations of ozone (O3) are thought to be either stratospheric in origin, advected from upwind urban sources, or photochemically generated locally as a result of natural trace gas emissions. Ozone is known to be transported vertically downward from the above-canopy atmospheric surface layer and destroyed within stomata or on other biological and mineral surfaces. However, here we report winter-time eddy correlation measurements of vertical O3 flux above a subalpine canopy of Picea engelmannii and Abies lasiocarpa in the Snowy Range Mountains of Wyoming that indicate...

Nitrogen saturation is occurring throughout high-elevation catchments of the Colorado Front Range. Annual inorganic N loading in wet deposition to the Front Range of ~4 kg ha-1 yr-1 is about twice that of the Pacific States and similar to many sites in the northeastern United States. In the last ten years at Niwot Ridge/Green Lakes Valley and Glacier Lakes, annual minimum concentrations of NO3- in surface waters during the growing season have increased from below detection limits to ¡­10 ¥ìequiv L-1, indicating that these two catchments are at the threshold of N saturation. The Loch Vale...

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...