Treesearch

Experiments were conducted to determine speed of action and toxicities of extracts of Tagetes minuta L., a source of naturally occurring insecticidal compounds. LC50 values for male and female Mexican bean weevils, Zabrotes subfasciatus (Boheman), were determined for floral, foliar, and root extracts of T. minuta. The 24-h LC50 values ranged from 138 μ g/cm2 for males exposed to the root extract (most susceptible) to 803 μ g/cm2 for females exposed to the foliar extract (least susceptible). Increasing the duration of exposure to 48 h decreased all LC50 values 20-30 μ g/cm2. Males were more...

This conference brought together scientiests and managers from federal, state, and local agencies, along with private-sector interests, to examine key concepts involving sustainable ecological systems, and ways in which to apply these concepts to ecosystem management. Session topics were: ecological consequenses of land and water use changes, biology of rare and declining species and habitats, conservation biology and restoration ecology, developing and applying ecological theory to management of ecological systems, sustainable ecosystems and forest health, and sustainable ecosystems to...

The sustainability of aquatic and riparian ecological systems is strongly tied to the dynamics of the streamflow regime. Timber harvest can influence the flow regime by increasing total flow, altering peak discharge rate, and changing the duration of flows of differing frequency of occurrence. These changes in the energy and sediment transporting capability of the fluvial system can cause an alteration in both channel morphology and aquatic habitat. Depending on practices used, timber harvest can increase the rate of sediment introduction to the channel system, thus further confounding the...

Many species of songbirds have experienced population declines in the eastern U.S. in recent years, but conclusive data on population trends and factors affecting populations in the West are lacking. Few studies have evaluated the importance of surrounding land configuration to songbird abundances. In 1992, we initiated a study in mixed conifer forest in west-central Idaho to compare songbird composition and abundances among two untreated watersheds and three watersheds having clearcuts. Watersheds were selected on the basis of their la-rge size, accessibility, dominant tree type, and...

Recent concerns about the future for migratory birds, particularly those that migrate to the Tropics, have led to the development of a variety of new research and education initiatives addressing avian population ecology and conservation. Research that focuses on the relationships between migrant population trends, geographical patterns, and spatial and temporal scales is central to solving conservation problems for migrants. Understanding how and why avian populations are declining is difficult because population trends vary in relation to numerous factors, including species, habitat,...

The declining populations of North American landbirds that migrate to the neotropics has attracted widespread attention from resource specialists. Documented declines in populations of eastern neotropical migrants, as well as habitat fragmentation on breeding grounds and habitat loss on wintering grounds have led researchers and resource managers to increase efforts to understand and effectively manage for the long-term conservation of these bird populations. Despite this attention, little is known on the population ecology of neotropical migrants inhabiting the western United States. One...

This glossary provides standard definitions for many of the terms used in avian conservation biology. We compiled these definitions to assist communication among researchers, managers, and others involved in the Neotropical Migratory Bird Conservation Program, also known as Partners in Flight. We used existing glossaries and recent literature to prepare this glossary. The cited sources were not necessarily the first ones to use the terms. Many definitions were taken verbatim from the cited source material. Others were modified slightly to clarify the meaning. Definitions that were modified...

Natural regeneration of interior cedar-hemlock-white pine forests is usually prompt and abundant. These productive sites support up to 10 commercial timber species. Retrospective examination of cutover forest stands allowed determination of variables that are important predictors of regeneration. This report discusses variables such as habitat type, slope, aspect, elevation, residual overstory density and species composition, site preparation, and the number of years since disturbance. These variables can be used to predict stocking, density, and species composition of regeneration....

Advance conifer regeneration readily survives release from overstory competition in the Inland West, but foresters are concerned about the ability of released trees to attain normal growth rates. There are also concerns about forest health issues associated with managing advance regeneration. The best pre-release predictors of post-release growth response are pre-release vigor and crown ratio at release. The fastest growing trees before release grow the fastest following release. A general recommendation is that at least a 0.50 crown ratio at release is necessary for good response to...

Forest health is most appropriately based on the scientific paradigm of dynamic, constantly changing forest ecosystems. Many forests in the Inland West now support high levels of insect infestations, disease epidemics, fire susceptibilities, and imbalances in stand structures and habitats because of natural processes and past management practices. Impending, potentially catastrophic fires can be avoided or modified through proactive forest health management-protecting, creating, and maintaining stand structures, processes, and species populations at viable levels across substantial...