Treesearch

The Bernalillo Watershed Protection Project was begun in 1953 following catastrophic erosion and flooding of small communities below. Although erosion control features and protection from grazing successfully increased grass cover and stabilized watershed soils, the expansion of juniper woodland (Juniperus monosperma) into the grassland watershed prompted concern that gains in watershed stability could be reversed. In 1995, fire was reintroduced into the grassland as a means of maintaining perennial grass cover and preventing further expansion of the juniper woodland community.

The generalist pathogen Pyrenophora semeniperda is abundant in seed banks of the exotic winter annual grass Bromus tectorum in semiarid western North America and is also found in the seed banks of co-occurring native grasses. In this study, we examined natural incidence of disease caused by this pathogen on undispersed host seeds, that is, seeds that were never directly exposed to inoculum in the seed bank. We determined experimentally that at least 90% of undispersed B. tectorum seeds exhibiting the disease were likely infected after maturity by conidia borne superficially on the seed-cove...

Black-tailed prairie dogs (Cynomys ludovicianus) once ranged from Canada to Mexico throughout the Great Plains and west to Arizona. During the last 100 years, public and private control programs, plague, and habitat loss have reduced the distribution of black-tailed prairie dog populations by 98 percent, causing localized extinctions. This species is now considered uncommon or extirpated in many areas of its former range. Black-tailed prairie dogs significantly alter grassland ecosystems and are considered a "keystone" species that require active conservation efforts (Kotliar and others...

Classical biological control of weeds is generally considered an effective, safe, and cost effective tool for controlling widespread weeds in natural areas. However, only 60% of releases have become established and, of those, only 50% have led to control. Therefore, understanding the impacts of agents on target weeds across spatial scales, at different insect densities, and over time can give biological control practitioners the knowledge necessary to improve establishment and success rates. My studies characterized the impacts the biological control agent, Mecinus janthinus, on the...

Bioaccumulation of persistent organic contaminants (OCs) is well documented in lentic and marine ecosystems, but few studies have addressed OC bioaccumulation in streams. The limited research in streams is surprising given the magnitude and extent of OC pollution. Approximately 9% of wadeable stream length in the U.S. is underlain by contaminated sediments including OCs; atmospheric deposition of OCs into streams is widespread, and OCs in stream fishes often exceed wildlife risk values, even in remote locations. Human health risks from consumption of lotic fishes are widespread, with 38%...

Relating local demographic processes to spatial structure (e.g. habitat heterogeneity) is essential for understanding population and species persistence (Hanski & Gilpin, 1997; Fagan, 2002). Yet few studies have tested general hypotheses about the importance of spatial patterns in determining population dynamics within river­stream networks (Lowe, Likens & Power, 2006). Metapopulation studies of stream biota such as freshwater fishes often relate site occupancy to the hierarchical structure of river­stream networks (Dunham & Rieman, 1999; Taylor & Warren, 2001), but rarely consider how...

As the United States population has grown, so has all-terrain-vehicle (ATV) use on national forests and grasslands and other public lands. Annual sales of ATVs have increased over 272 percent since 1994 to an estimated 876,000 units in 2005 (Specialty Vehicle Institute of America - Special Report Summer 2006). ATVs are a popular choice for outdoor recreation. According to a national survey on recreation and the environment, about 36.3 million people participate in off-highway driving or ATV or motorcycle use (Cordell et al. 2001). An estimated 11 million visits to national forests involve...

Freshwater availability is an increasing concern across the globe and it may be the most important natural resource issue of the century. Climate change and its effects on water are expected to intensify freshwater scarcity and conflict. A forthcoming Forest Service, U.S. Department of Agriculture report will highlight the importance of managing forests to provide clean, abundant water. The report will explore likely impacts of climate change on the Nation's forested watersheds and describe how natural resource managers can incorporate a climate change perspective into watershed stewardship.

Resource managers face many challenges in developing management recommendations for wildlife habitat under a changing climate. Our research results offer states a more consistent and holistic approach to analyzing potential threats of climate change to terrestrial wildlife habitat. This process integrates a review of the scientific literature, the State Wildlife Action Plans (SWAPs), and analyses based on the state-of-the-art climate and ecological modeling, as well as current information on stressors to wildlife conservation. Our review of 50 State Wildlife Actions Plans (SWAPs) indicated...

California and Israel are both characterized by Mediterranean climates, and the native oaks growing in these two locales occupy similar ecological niches. However, in California certain oak species are having difficulty regenerating adequately, while in Israel this is not a problem. From 2004 to 2006, a series of greenhouse studies were conducted in both Israel and California to sort out the role of evolutionary history in influencing species regeneration rates and strategies. These studies have evaluated survival and growth, as well as the response of the species to disturbance including...