Treesearch

This report is the result of a workshop held in Denver, Colorado on April 9-11, 1991. It summarizes the current literature and techniques for using lichens to monitor air quality. Experts in lichenology and ecology contributed information on lichen floristics, characterization of monitoring sites, lichen species and communities, identifying lichen species sensitive to pollutants, active monitoring with transplants, chemical analysis of lichens, and case studies as examples of lichen biomonitoring scenarios.

Movements and habitat-use patterns were evaluated for a small population (n = 6 pairs) of Prairie Falcons (Falco mexicanus) nesting near Gillette, Wyoming. A total of 2462 falcon relocations was documented through telemetry. The average (n = 6) harmonic-mean 95%-contour home-range was 69 km2, whereas the average 75% contour was 26.6 km2. The convex polygon average home-range size was 29.4 km2. The average 95% and 75% foraging-area contours, where points less than 500 m from the eyrie were excluded, were 111.8 km2 and 57.4 km2, respectively. The convex polygon foraging area was 74.7 km2. It...

Lodgepole pine (Pinus contorta Dougl. var. latifolia) forests in the northern Rocky Mountains have experienced substantial variation in presettlement fire patterns (Arno 1976, Sneck 1977, Arno 1980, Romme 1982, Romme and Despain 1989, Barrett and Arno 1991, Barrett et a1. 1991, Barrett [in prep]). On relatively productive habitat types at lower elevations, short- to moderately long interval (25-150 yr) fires have occurred in a mixed severity pattern ranging from non-lethal underburns to total stand replacement (Arno 1976, Barrett and Arno 1991, Barrett et. al. 1991). Markedly different...

These lakes are moderately sensitive to acid deposition; acidification would require precipitation at least as acidic as that presently found in the more heavily impacted areas of eastern North America. Because most snowpack contaminants are released early in the melting process, seasonal acidification pulses would probably occur at much lower levels of acidic inputs.

The fairy shrimp Branchinecta paludosa is a persistent resident of aestival ponds at high elevation in the Medicine Bow Mountains of southern Wyoming. These populations are far removed from the Arctic tundra habitat that typifies the distribution of the species, and appear to represent the southern margin of the range in North America. All of the records for the northern United States and southern Canada appear to lie along the Central Flyway that is a major migration route for waterfowl and shorebirds that nest in the Arctic. Passive dispersal probably provides for frequent colonization...

Increasing atmospheric concentrations of the three main greenhouse gases-carbon dioxide, methane, and nitrous oxide account for about 70% of anticipated global warming, but the production-consumption budgets are not balanced for any of these gases2. Snow can cover between 44 and 53% of the land area of the Northern Hemisphere3 and may be several metres deep in alpine and sub-alpine regions for more than half the year. Most trace-gas budgets assume that trace-gas exchange stops when soil is snow covered or soil temperatures drop to ~0 °C (refs 4, 5). Thus alpine and sub-alpine soils are...

During the month of February, between 46 and 53% of the land area of the northern hemisphere is snow covered. Continental snowpacks act as chemical reservoirs; pollutants can accumulate in the pack over the entire winter and are released during a relatively short spring melt period. Interactions between the snow and the atmosphere can change the quantities of different chemical species stored in the snow. In addition, snow can retain chemical species to be incorporated into major ice sheets and large glaciers. The record of atmospheric chemistry preserved in this way is important in...

Snowpacks in both Colorado and Wyoming were sampled on 15 dates for total microbial biomass, ratio of bacteria to fungi, and major inorganic ions. Levels of viable microbial biomass remained low throughout the period, peaking at 0.05 micrograms carbon/mi. Microscopic analyses indicated this biomass was composed primarily of bacteria. Fungi were not detected in samples taken at or above treeline. With the exception of one date in early May at the Colorado site, bacteria were confined to a band within the snowpack approximately 20 em above the snow/soil interface. Laboratory incubations...

Controlled exposure of ice to a reactive gas, SO2, demonstrated the importance of the chemical composition of the ice surface on the accumulation of acidity in snow. In a series of bench-scale continuous-flow column experiments run at four temperatures (-1, -8, -30 and -60°C), SO2 was shown to dissolve and to react with other species in the ice-air interfacial region at temperatures approaching the melting point of ice. Experiments consisted of passing air containing SO2 through glass columns packed with 100-ìm ice spheres of varying bulk composition (0-5 ìM H2O2, and 0-1 mM NaCl), and...

The alpine timberline in much of western North America is characterized by a structurally complex transition from subalpine forest to alpine tundra, the forest-tundra ecotone. Trees within the ecotone are typically arrayed across the landscape within clumps or "ribbon forests," elongated strips oriented perpendicular to the prevailing winds. This study describes the structure and reconstructs the development of two study plots, one containing ribbon forest and the other, tree clumps. These data are used to develop a theory of ribbon forest origin and development. The plots are located...