Treesearch

Abstract. This paper reports on the response by amphibians, benthic macroinvertebrates, and zooplankton in naturally fishless alpine lakes to fish introductions and subsequent fish disappearance. We assessed resistance (the degree to which a system is altered when the environment changes) by comparing faunal distribution and abundance in lakes that have never been stocked with fish vs. the distribution and abundance in lakes that have been stocked and still contain fish. We assessed resilience (the degree and rate of a system’s return to its previous configuration once the perturbation is...

The density and development of snowbrush, greenleaf manzanita, goldenbush (rabbitbrush), and graminoids were evaluated in a young California white fir plantation in northern California from 1986 through 1995. Manual grubbing and an herbicide created treatment regimes that lasted for 3 to 6 years and vegetation recovery times of 4 to 10 years. The timing and duration of the grubbing and spraying operations constituted the treatments. In terms of foliar cover and height, snowbrush was the most vigorous shrub species. By the end of the study it had more foliar cover (16,350 ft2 per acre) in...

Ecological assessments and monitoring programs often rely on indicators to evaluate environmental conditions. Such indicators are frequently developed by scientists, expressed in technical language, and target aspects of the environment that scientists consider useful. Yet setting environmental policy priorities and making environmental decisions requires both effective communication of environmental information to decision makers and consideration of what members of the public value about ecosystems. However, the complexity of ecological issues, and the ways in which they are often...

Understanding habitat relationships; of forest dwelling bats has become a wildlife management priority during the past decade. We used radiotelemetry to examine the use of day roosts by fringed myotis (Myotis thysanodes) in a Douglas-fir (Pseudotsuga menziesii) forest in northern California. We located 52 roosts in 23 trees and com-pared the characteristics of roost sites and structures to random sites and structures. All roost trees were snags in early to medium stages of decay. Bats switched roosts often, and the number of bats exiting roosts varied from 1-88. The most important factor...

Abstract - Cumulative effects are the combined effects of multiple activities, and watershed effects are those which involve processes of water transport. Almost all impacts are influenced by multiple activities, so almost all impacts must be evaluated as cumulative impacts rather than as individual impacts. Existing definitions suggest that to be significant, an impact must be reasonably expected to have occurred or to occur in the future, and it must be of societally validated concern to someone or influence their activities or options. Past approaches to evaluating and managing cumulativ...

Abstract - Bed material waves are temporary zones of sediment accumulation created by large sediment inputs. Recent theoretical, experimental and field studies examine factors in fluencing dispersion and translation of bed material waves in quasi-uniform, gravel-bed channels. Exchanges of sediment between a channel and its floodplain are neglected. Within these constraints, two factors influence relative rates of dispersion and translation: (1) interactions between wave topography, flow and bed load transport; and (2) particle-size differences between wave material and original bed material....

Most of us have come to expect that the general public will ignore the primary message of Quaternary science that change happens. A flurry, however, of recent media attention to 20th-century global warming and its anomalies from climates of the last millennium has brought climate science at least momentarily into popular focus. Similarly, public land-managing agencies and conservation groups have begun, under the rubric of ecosystem management, to incorporate concepts of historic variability into landscape analysis, ecological monitoring, population-viability assessment, and ecological...