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At least 991 records · Page 55Linked to original sources
USGS2008

Wildland fire in ecosystems: Fire and nonnative invasive plants

This state-of-knowledge review of information on relationships between wildland fire and nonnative invasive plants can assist fire managers and other land managers concerned with prevention, detection, and eradication or control of nonnative invasive plants. The 16 chapters in this volume synthesize ecological and botanical principles regarding relationships between wildland fire and nonnative invasive plants, identify the nonnative invasive species currently of greatest concern in major bioregions of the United States, and describe emerging fire-invasive issues in each bioregion and throughout the nation. This volume can help increase understanding of plant invasions and fire and can be used in fire management and ecosystem-based management planning. The volume’s first part summarizes fundamental concepts regarding fire effects on invasions by nonnative plants, effects of plant invasions on fuels and fire regimes, and use of fire to control plant invasions. The second part identifies the nonnative invasive species of greatest concern and synthesizes information on the three topics covered in part one for nonnative invasives in seven major bioregions of the United States: Northeast, Southeast, Central, Interior West, Southwest Coastal, Northwest Coastal (including Alaska), and Hawaiian Islands. The third part analyzes knowledge gaps regarding fire and nonnative invasive plants, synthesizes information on management questions (nonfire fuel treatments, postfire rehabilitation, and postfire monitoring), summarizes key concepts described throughout the volume, and discusses urgent management issues and research questions.

General Technical Report↗
USGS2016

Ecosystem development on terraces along the Kugururok River, northwest Alaska

Riverside terraces along the Kugururok River in the Noatak National Preserve provided an opportunity to study primary succession, considering general trends that apply across all terraces, and unique events that influence individual terraces. The 30-year-old willow/poplar (Salix spp., Populus balsamifera L.) terrace had no trees taller than 1.5 m; the abundant spruce trees were not tall enough to emerge from the canopy height of the willows and poplars, and moose (Alces alces [Clinton]) browsing limited the canopy height of these plants. The 75-year-old poplar/spruce (Picea glauca [Moench] Voss) terrace had a high density of poplars (> 1000/ha) and low density of spruce (125/ha); heavy browsing by moose reduced the density of poplar by about one-half. The removal of the poplar by moose in this stand resulted in sustained increases in growth of individual spruce trees. The 100-year-old younger spruce/poplar terrace had about twice as many spruce trees (1250/ha) as poplar trees (500/ha), and the spruce trees were larger on average than the poplar trees. In the 220+ year-old older spruce/poplar type, only a few poplars remained (about 25/ha), and the number of spruce trees (600/ha) was only half that of the younger stage, either from lower initial spruce density on this terrace, or increased mortality of spruce. The 240+ year-old spruce type was a second-generation forest, characterized by a high density (1950/ha) of small spruce trees, some of which were tilted, indicating discontinuous permafrost. Plant litterfall mass showed no strong trend with terrace age, although N content of litterfall appeared to decline by about 1/3 in the spruce-dominated stages. Fungal biomass increased with ecosystem age, whereas bacterial biomass and microfauna declined. We found no evidence of declining soil N supply in older stages, but fertilization experiments would be needed to determine if N limitation of productivity changed with ecosystem development. We conclude that the general successional trend of increased spruce dominance is robust for this location, but that unique events play important roles in determining tree densities and the timing of the shift in dominance from poplar to spruce. The arrival of moose in the 1970s accelerated dominance by spruce on young terraces.

Écoscience↗
USGS1997

Imperiled mammalian fauna of aquatic ecosystems in the Southeast: A management perspective

Management of imperiled mammals associated with aquatic ecosystems in the southeastern United States ranges from almost no management for some species to intensive, high-profile programs for others. Aquatic mammals are notoriously difficult to census because they are often secretive, trap-wary, relatively rare, or have extensive movement patterns. As a result, conservation efforts aimed at these animals often have been greatly hampered by a general lack of comprehensive population data. Historically, certain high-profile, "flagship" species have been the primary beneficiaries of management efforts. One of the earliest examples involves beaver, Castor canadensis , which had been reduced to a low ebb due to unregulated harvest and were subsequently live-trapped by state game officials in the 1940s and repatriated throughout the southeastern states. The success of this restocking program has exceeded expectations, and today beaver numbers have reached what many consider to be nuisance proportions in most states. Similar restocking stories can be told for muskrats ( Ondatra zibethicus ) and, to a limited extent, for river otters ( Lutra canadensis ). Unfortunately, other imperiled species of lesser economic or recreational value have not been as fortunate. Efforts to conserve these lower-profile species have been minimal or conservation problems so immense that their complete recovery has been unsuccessful. Wilson (1992) suggested that 20 percent of all species on earth may be lost to extinction in the next four decades. If this disaster should occur, it would rival the greatest geological extinction episodes. Certainly, conservationists need to explore new methods for preserving mammalian diversity. In this chapter we will discuss the resource management history of aquatic mammals which are imperiled in the Southeast. In doing so we define an aquatic mammal as any mammal that is directly or indirectly associated with aquatic ecosystems. Imperiled mammals are any mammalian species, subspecies, or population listed as endangered, threatened, or of special concern on any state or federal list, and also includes mammals experiencing long-term population declines or significant range contractions.

Book chapter↗
USGS2018

Mapping cropland waterway buffers for switchgrass development in the eastern Great Plains, USA

Switchgrass ( Panicum virgatum L.), a highly productive perennial grass, has been recommended as one potential source for cellulosic biofuel feedstocks. Previous studies indicate that planting perennial grasses (e.g., switchgrass) in high‐topographic‐relief cropland waterway buffers can improve local environmental conditions and sustainability. The main advantages of this land management practice include (i) reducing soil erosion and improving water quality because switchgrass requires less tillage, fertilizers, and pesticides; and (ii) improving regional ecosystem services (e.g., improving water infiltration, minimizing drought and flood impacts on production, and serving as carbon sinks). In this study, we mapped high‐topographic‐relief cropland waterway buffers with high switchgrass productivity potential that may be suitable for switchgrass development in the eastern Great Plains (EGP). The US Geological Survey (USGS) Compound Topographic Index map, National Land Cover Database 2011, USGS irrigation map, and a switchgrass biomass productivity map derived from a previous study were used to identify the switchgrass potential areas. Results show that about 16 342 km 2 ( c . 1.3% of the total study area) of cropland waterway buffers in the EGP are potentially suitable for switchgrass development. The total annual estimated switchgrass biomass production for these suitable areas is approximately 15 million metric tons. Results from this study provide useful information on EGP areas with good cellulosic switchgrass biomass production potential and synergistic substantial potential for improvement of ecosystem services.

Great Plains↗
USGS1996

Indicators of red squirrel (Tamiasciurus hudonicus) abundance in the whitebark pine zone

We investigated occupied squirrel middens and squirrel sightings and vocalizations as indicators of red squirrel (Tamiasciurus hudsonicus) abundance in the high-elevation whitebark pine (Pinus albicaulis) zone. Data were collected 1984-1989 from line transects located on 2 study sites in the Yellowstone ecosystem. We evaluated the performance of each measure on the basis of precision and biological considerations. We concluded that, of the 3 measures, active middens were the best indicator of red squirrel abundance. We also observed that the density of active middens dropped by 48%-66% between 1987 and 1989, following a severe drought and extensive wildfires that burned one of the study sites during 1988.

Great Basin Naturalist↗
USGS2021

Fire refugia in old-growth forests: Predicting habitat persistence to support land management in an era of rapid global change

Recent stand-replacing wildfires in late-successional and old-growth (LSOG) forests have increased land manager interest in fire refugia, which could provide vital habitat for threatened and endangered species during a time of rapid change. The overall goal of this project was to model, map, and share information essential for the conservation of LSOG forest ecosystems in the U.S. Pacific Northwest, within a diverse co-production team of state and federal land managers. We developed statistical models of contemporary (2002-2017) fire refugia, non-stand-replacing fire (NSR), and high-severity fire based on topography, fuels, fire weather, fire behavior and climate. Independent models were built for two ecoregions (Figure 1), one encompassing the Douglas-fir/western hemlock forests of the northwestern portion of our study area and the other encompassing dry-mixed conifer forests of the eastern Cascades and Klamath-Siskiyou region. We used these models to produce probability surface maps for fire refugia, NSR, and high-severity fire under low, moderate, and extreme fire weather and fire growth scenarios. These maps and associated products provide timely information about the likely persistence, change, and loss of LSOG forests under current and future climate conditions.

California, Oregon, Washington↗
USGS2012

Fire-driven alien invasion in a fire-adapted ecosystem

Disturbance plays a key role in many alien plant invasions. However, often the main driver of invasion is not disturbance per se but alterations in the disturbance regime. In some fire-adapted shrublands, the community is highly resilient to infrequent, high-intensity fires, but changes in the fire regime that result in shorter fire intervals may make these communities more susceptible to alien plant invasions. This study examines several wildfire events that resulted in short fire intervals in California chaparral shrublands. In one study, we compared postfire recovery patterns in sites with different prefire stand ages (3 and 24 years), and in another study we compared sites that had burned once in four years with sites that had burned twice in this period. The population size of the dominant native shrub Adenostoma fasciculatum was drastically reduced following fire in the 3-year sites relative to the 24-year sites. The 3-year sites had much greater alien plant cover and significantly lower plant diversity than the 24-year sites. In a separate study, repeat fires four years apart on the same sites showed that annual species increased significantly after the second fire, and alien annuals far outnumbered native annuals. Aliens included both annual grasses and annual forbs and were negatively correlated with woody plant cover. Native woody species regenerated well after the first fire but declined after the second fire, and one obligate seeding shrub was extirpated from two sites by the repeat fires. It is concluded that some fire-adapted shrublands are vulnerable to changes in fire regime, and this can lead to a loss of native diversity and put the community on a trajectory towards type conversion from a woody to an herbaceous system. Such changes result in alterations in the proportion of natives to non-natives, changes in functional types from deeply rooted shrubs to shallow rooted grasses and forbs, increased fire frequency due to the increase in fine fuels, and changes in carbon storage.

California↗
USGS2023

A restructured Bayesian approach to estimate the abundance of a rare and invasive fish

Quantifying invasive species abundance informs management and control strategies. However, estimating abundance can be challenging, particularly when dealing with rare species early in the invasion process. Data generated from control strategies, such as removing invasive species, are usually not suited to conventional statistical modelling approaches. Hence, we developed a Bayesian model using data generated by a grass carp ( Ctenopharyngodon idella ) control program in the Sandusky River, Ohio (USA) for estimating the abundance of rare, invasive species. The model is a restructured N-mixture model modified to incorporate the data generating process (i.e., setting a trammel net to isolate a sampling area followed by boat-mounted electrofishing). Allowing the estimation of grass carp abundance from the species removal data, which had very few detections relative to the sampling effort. Our results indicated that the average number of grass carp present in the river at any one time did not change substantially from 2018 to 2020. The highest abundance estimates were in the lower and upper-middle segments of the river, suggesting possible recolonization from Lake Erie, and possibly other tributaries. Ultimately, the ability to use species-control data to estimate abundance provides important information for management, particularly for invasive ‘sleeper’ species in freshwater ecosystems.

Ohio↗
USGS2006

Scaling uncertainties in estimating canopy foliar maintenance respiration for black spruce ecosystems in Alaska

A major challenge confronting the scientific community is to understand both patterns of and controls over spatial and temporal variability of carbon exchange between boreal forest ecosystems and the atmosphere. An understanding of the sources of variability of carbon processes at fine scales and how these contribute to uncertainties in estimating carbon fluxes is relevant to representing these processes at coarse scales. To explore some of the challenges and uncertainties in estimating carbon fluxes at fine to coarse scales, we conducted a modeling analysis of canopy foliar maintenance respiration for black spruce ecosystems of Alaska by scaling empirical hourly models of foliar maintenance respiration (Rm) to estimate canopy foliar Rm for individual stands. We used variation in foliar N concentration among stands to develop hourly stand-specific models and then developed an hourly pooled model. An uncertainty analysis identified that the most important parameter affecting estimates of canopy foliar Rm was one that describes R m at 0??C per g N, which explained more than 55% of variance in annual estimates of canopy foliar Rm. The comparison of simulated annual canopy foliar Rm identified significant differences between stand-specific and pooled models for each stand. This result indicates that control over foliar N concentration should be considered in models that estimate canopy foliar Rm of black spruce stands across the landscape. In this study, we also temporally scaled the hourly stand-level models to estimate canopy foliar Rm of black spruce stands using mean monthly temperature data. Comparisons of monthly Rm between the hourly and monthly versions of the models indicated that there was very little difference between the estimates of hourly and monthly models, suggesting that hourly models can be aggregated to use monthly input data with little loss of precision. We conclude that uncertainties in the use of a coarse-scale model for estimating canopy foliar Rm at regional scales depend on uncertainties in representing needle-level respiration and on uncertainties in representing the spatial variability of canopy foliar N across a region. The development of spatial data sets of canopy foliar N represents a major challenge in estimating canopy foliar maintenance respiration at regional scales. ?? Springer 2006.

Mitigation and Adaptation Strategies for Global Ch↗
USGS1997

Geology and hydrogeology of the Florida Keys

This chapter discusses the geology and hydrogeology of the Florida Keys, and focuses on the islands formed of Pleistocene limestone. These islands, which are crossed when driving from Miami to Key West, are typically regarded as "the Florida Keys." The outstanding and fragile character of ecosystems on and around the Florida Keys has prompted State and Federal efforts to protect and preserve the remaining public portions of the region. The Florida Keys were largely ignored during the sixteenth, seventeenth, and eighteenth centuries, although the waters just offshore provided a major shipping thoroughfare to and from the New World. The Florida Keys are now recognized as one of the great recreational and environmental resources of the United States. The islands are outposts of a laid-back, tropical resort culture that has as its foundation warmth and clear water. A significant part of the attraction is fishing, diving, and boating around the area's coral reefs, which the islands protect. But the reefs were not always so highly valued. The Florida Keys that have protected the reefs for millennia, may now be the source of the agents that may accomplish what Agassiz thought was beyond man's power a century ago.

Florida↗
USGS2002

Growth responses of subalpine fir to climatic variability in the Pacific Northwest

We studied regional variation in growth-limiting factors and responses to climatic variability in subalpine forests by analyzing growth patterns for 28 tree-ring growth chronologies from subalpine fir ( Abies lasiocarpa (Hook.) Nutt.) stands in the Cascade and Olympic Mountains (Washington and Oregon, U.S.A.). Factor analysis identified four distinct time series of common growth patterns; the dominant growth pattern at any site varied with annual precipitation and temperature (elevation). Throughout much of the region, growth is negatively correlated with winter precipitation and spring snowpack depth, indicating that growth is limited primarily by short growing seasons. On the driest and warmest sites, growth is negatively correlated with previous summer temperature, suggesting that low summer soil moisture limits growth. Growth patterns in two regions were sensitive to climatic variability associated with the Pacific Decadal Oscillation, apparently responding to low-frequency variation in spring snowpack and summer soil moisture (one negatively, one positively). This regional-scale analysis shows that subalpine fir growth in the Cascades and Olympics is limited by different climatic factors in different subregional climates. Climate–growth relationships are similar to those for a co-occurring species, mountain hemlock ( Tsuga mertensiana (Bong.) Carrière), suggesting broad biogeographic patterns of response to climatic variability and change by subalpine forest ecosystems in the Pacific Northwest.

Oregon, Washington↗
USGS2013

It's time for bold new approaches to link delta science and policymaking

California’s Sacramento–San Joaquin Delta is widely recognized as a highly damaged ecosystem. The Delta is also emblematic of a growing sense worldwide that society needs to do a better job of using scientific knowledge to guide conservation and resource management policies. Fortunately, we now have an unprecedented opportunity to get it right in building structures that support effective science–policy linkages in the Delta. By adopting bold steps to implement a “one Delta, one science” approach for a new Delta Science Plan, California can become a leading example of how to tackle the global problem of rapid ecological change and biodiversity loss. In this essay, we first describe the current paradox—continued environmental declines despite considerable investments in science and policy actions—and the high stakes of gambling with failure. Next, we explore why it is so hard to use scientific knowledge to design and implement policies that meet society’s sustainability goals. We then outline promising ways to overcome these obstacles, drawing on recent experiences. We conclude with thoughts on how to leverage this experience to develop a bold new approach to Delta science.

California↗
USGS2012

A circumpolar monitoring framework for polar bears

Polar bears ( Ursus maritimus ) occupy remote regions that are characterized by harsh weather and limited access. Polar bear populations can only persist where temporal and spatial availability of sea ice provides adequate access to their marine mammal prey. Observed declines in sea ice availability will continue as long as greenhouse gas concentrations rise. At the same time, human intrusion and pollution levels in the Arctic are expected to increase. A circumpolar understanding of the cumulative impacts of current and future stressors is lacking, long-term trends are known from only a few subpopulations, and there is no globally coordinated effort to monitor effects of stressors. Here, we describe a framework for an integrated circumpolar monitoring plan to detect ongoing patterns, predict future trends, and identify the most vulnerable polar bear subpopulations. We recommend strategies for monitoring subpopulation abundance and trends, reproduction, survival, ecosystem change, human-caused mortality, human–bear conflict, prey availability, health, stature, distribution, behavioral change, and the effects that monitoring itself may have on polar bears. We assign monitoring intensity for each subpopulation through adaptive assessment of the quality of existing baseline data and research accessibility. A global perspective is achieved by recommending high intensity monitoring for at least one subpopulation in each of four major polar bear ecoregions. Collection of data on harvest, where it occurs, and remote sensing of habitat, should occur with the same intensity for all subpopulations. We outline how local traditional knowledge may most effectively be combined with the best scientific methods to provide comparable and complementary lines of evidence. We also outline how previously collected intensive monitoring data may be sub-sampled to guide future sampling frequencies and develop indirect estimates or indices of subpopulation status. Adoption of this framework will inform management and policy responses to changing worldwide polar bear status and trends.

Ursus↗
USGS2013

A compilation of U.S. Geological Survey pesticide concentration data for water and sediment in the Sacramento–San Joaquin Delta region: 1990–2010

Beginning around 2000, abundance indices of four pelagic fishes (delta smelt, striped bass, longfin smelt, and threadfin shad) within the San Francisco Bay and Sacramento–San Joaquin Delta began to decline sharply (Sommer and others, 2007). These declines collectively became known as the pelagic organism decline (POD). No single cause has been linked to this decline, and current theories suggest that combinations of multiple stressors are likely to blame. Contaminants (including current-use pesticides) are one potential stressor being investigated for its role in the POD (Anderson, 2007). Pesticide concentration data collected by the U.S. Geological Survey (USGS) at multiple sites in the delta region over the past two decades are critical to understanding the potential effects of current-use pesticides on species of concern as well as the overall health of the delta ecosystem. In April 2010, a compilation of contaminant data for the delta region was published by the State Water Resources Control Board (Johnson and others, 2010). Pesticide occurrence was the major focus of this report, which concluded that “there was insufficient high quality data available to make conclusions about the potential role of specific contaminants in the POD.” The report cited multiple sources; however, data collected by the USGS were not included in the publication even though these data met all criteria listed for inclusion in the report. What follows is a summary of publicly available USGS data for pesticide concentrations in surface water and sediments within the Sacramento–San Joaquin Delta region from the years 1990 through 2010. Data were retrieved though the USGS National Water Information System (NWIS) database, a publicly available online-data repository (U.S. Geological Survey, 1998), and from published USGS reports (also available online at http://pubs.er.usgs.gov/). The majority of the data were collected in support of two long term USGS monitoring programs—National Water Quality Assessment Program (NAWQA; http://water.usgs.gov/ nawqa/) and National Stream Quality Accounting Network (NASQAN; http://water.usgs.gov/nasqan/)—and through projects associated with the USGS Toxics Substances Hydrology Program (http://toxics.usgs.gov/). In addition, data were collected during multiple research projects that were supported by various federal, state, and local agencies. Although these data have been previously published in some form, it is hoped that by focusing on samples collected within the delta region and presenting these data in a concise format, they will be a valuable resource for scientists, resource managers, and members of the public working to understand the role of pesticides in the POD and their potential effects on the overall health of the delta ecosystem.

California↗
USGS2010

Climate change and wildlife health: direct and indirect effects

Climate change will have significant effects on the health of wildlife, domestic animals, and humans, according to scientists. The Intergovernmental Panel on Climate Change projects that unprecedented rates of climate change will result in increasing average global temperatures; rising sea levels; changing global precipitation patterns, including increasing amounts and variability; and increasing midcontinental summer drought (Intergovernmental Panel on Climate Change, 2007). Increasing temperatures, combined with changes in rainfall and humidity, may have significant impacts on wildlife, domestic animal, and human health and diseases. When combined with expanding human populations, these changes could increase demand on limited water resources, lead to more habitat destruction, and provide yet more opportunities for infectious diseases to cross from one species to another. Awareness has been growing in recent years about zoonotic diseases— that is, diseases that are transmissible between animals and humans, such as Lyme disease and West Nile virus. The rise of such diseases results from closer relationships among wildlife, domestic animals, and people, allowing more contact with diseased animals, organisms that carry and transmit a disease from one animal to another (vectors), and people. Disease vectors include insects, such as mosquitoes, and arachnids, such as ticks. Thus, it is impossible to separate the effects of global warming on wildlife from its effects on the health of domestic animals or people. Climate change, habitat destruction and urbanization, the introduction of exotic and invasive species, and pollution—all affect ecosystem and human health. Climate change can also be viewed within the context of other physical and climate cycles, such as the El Niño Southern Oscillation (El Niño), the North Atlantic Oscillation, and cycles in solar radiation that have profound effects on the Earth’s climate. The effects of climate change on wildlife disease are summarized in several areas of scientific study discussed briefly below: geographic range and distribution of wildlife diseases, plant and animal phenology (Walther and others, 2002), and patterns of wildlife disease, community and ecosystem composition, and habitat degradation.

Fact Sheet↗
USGS2013

Summary of science, activities, programs, and policies that influence the rangewide conservation of Greater Sage-Grouse (Centrocercus urophasianus)

The Greater Sage-Grouse, has been observed, hunted, and counted for decades. The sagebrush biome, home to the Greater Sage-Grouse, includes sagebrush-steppe and Great Basin sagebrush communities, interspersed with grasslands, salt flats, badlands, mountain ranges, springs, intermittent creeks and washes, and major river systems, and is one of the most widespread and enigmatic components of Western U.S. landscapes. Over time, habitat conversion, degradation, and fragmentation have accumulated across the entire range such that local conditions as well as habitat distributions at local and regional scales are negatively affecting the long-term persistence of this species. Historic patterns of human use and settlement of the sagebrush ecosystem have contributed to the current condition and status of sage-grouse populations. The accumulation of habitat loss, persistent habitat degradation, and fragmentation by industry and urban infrastructure, as indicated by U.S. Fish and Wildlife Service (USFWS) findings, presents a significant challenge for conservation of this species and sustainable management of the sagebrush ecosystem. Because of the wide variations in natural and human history across these landscapes, no single prescription for management of sagebrush ecosystems (including sage-grouse habitats) will suffice to guide the collective efforts of public and private entities to conserve the species and its habitat. This report documents and summarizes several decades of work on sage-grouse populations, sagebrush as habitat, and sagebrush community and ecosystem functions based on the recent assessment and findings of the USFWS under consideration of the Endangered Species Act. As reflected here, some of these topics receive a greater depth of discussion because of the perceived importance of the issue for sagebrush ecosystems and sage-grouse populations. Drawing connections between the direct effects on sagebrush ecosystems and the effect of ecosystem condition on habitat condition, and finally the connection between habitat quality and sage-grouse population dynamics remains an important goal for science, management, and conservation. This effort is necessary, despite the perception that these complicated, indirect relations are difficult to characterize and manage, and the many advances in understanding and application developed toward this end have been documented here to help inform regional planning and policy decisions.

Arizona;California;Colorado;Montana;Nebraska;Nevad↗
USGS2011

Pathogens and diseases of freshwater mussels in the United States: Studies on bacterial transmission and depuration

Unionid mussels are recognized as important contributors to healthy aquatic ecosystems, as well as bioindicators of environmental perturbations. Because they are sedentary, filter feeding animals and require hosts (i.e., fishes) to transform embryonic glochidia, mussels are susceptible to direct adverse environmental parameters, and indirect parameters that restrict the timely presence of the host(s). Their numbers have declined in recent decades to a point that this fauna is regarded as one of the most imperiled in North America. The most significant threat to populations of native unionids in recent years has been the introduction and spread of zebra mussels Dreissena polymorpha. Many federal and state agencies, and private interests are now engaged in mussel conservation efforts, including collecting selected imperiled species from impacted rivers and lakes and propagating them at refuges for future population augmentations. One essential consideration with mussel propagation and their intensive culture at refugia is the prevention of pathogen introductions and control of diseases. Currently, there are few reports of etiological agents causing diseases among freshwater mussels; however, because of increased observations of mussel die-offs in conjunction with transfers of live animals between natural waters and refugia, disease problems can be anticipated to emerge. This review summarizes research to develop bacterial isolation techniques, study pathogen transmission between fish and mussels, identify causes of seasonal mussel die-offs, and develop non-destructive methods for pathogen detection. These efforts were done to develop disease preventative techniques for use by resource managers to avoid potential large-scale disease problems in restoration and population augmentation efforts among imperiled populations.

Conference Paper↗
USGS1994

Tamarisk control on public lands in the desert of southern California: two case studies

As a land manager, the Federal Government faces enormous challenges from exotic pest invasions and associated changes to the structure and stability of native ecosystems (Bureau of Land Management, 1988). On public lands administered by the Bureau of Land Management (BLM) alone, it is estimated that almost three million hectares are occupied by invasive exotic plant species (weeds). Assuming an annual rate of invasion of 14 percent, 930 hectares of BLM-administered land are infested everyday by weeds (Jerry Asher, personal communication). When one considers the fact that BLM administers only about one-third of the public land in the United States (The Keystone Center, 1991), the magnitude of the problem assumes staggering proportions. The scenario described in the quote above portrays only some of the problems associated with the spread of the exotic plant tamarisk, a species on the California Exotic Pest Plant Council’s list of exotic pest plants of greatest concern (California Exotic Pest Plant Council, 1993). In this paper we review the threats posed by tamarisk invasion and proliferation and examine the traits that make the plant such a successful competitor. In addition, we highlight two tamarisk control efforts conducted by the Bureau of Land Management in the southern California desert.

California↗