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At least 1,333 records · Page 74Linked to original sources
USGS2015

An empirical evaluation of landscape energetic models: Mallard and American black duck space use during the non-breeding period

Bird conservation Joint Ventures are collaborative partnerships between public agencies and private organizations that facilitate habitat management to support waterfowl and other bird populations. A subset of Joint Ventures has developed energetic carrying capacity models (ECCs) to translate regional waterfowl population goals into habitat objectives during the non-breeding period. Energetic carrying capacity models consider food biomass, metabolism, and available habitat to estimate waterfowl carrying capacity within an area. To evaluate Joint Venture ECCs in the context of waterfowl space use, we monitored 33 female mallards ( Anas platyrhynchos ) and 55 female American black ducks ( A. rubripes ) using global positioning system satellite telemetry in the central and eastern United States. To quantify space use, we measured first-passage time (FPT: time required for an individual to transit across a circle of a given radius) at biologically relevant spatial scales for mallards (3.46 km) and American black ducks (2.30 km) during the non-breeding period, which included autumn migration, winter, and spring migration. We developed a series of models to predict FPT using Joint Venture ECCs and compared them to a biological null model that quantified habitat composition and a statistical null model, which included intercept and random terms. Energetic carrying capacity models predicted mallard space use more efficiently during autumn and spring migrations, but the statistical null was the top model for winter. For American black ducks, ECCs did not improve predictions of space use; the biological null was top ranked for winter and the statistical null was top ranked for spring migration. Thus, ECCs provided limited insight into predicting waterfowl space use during the non-breeding season. Refined estimates of spatial and temporal variation in food abundance, habitat conditions, and anthropogenic disturbance will likely improve ECCs and benefit conservation planners in linking non-breeding waterfowl habitat objectives with distribution and population parameters. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

Arkansas, Delaware, Louisiana, Michigan, New Jerse↗
USGS2025

Cultivating reciprocity and supporting Indigenous lifeways through the cultural transformation of natural resource management in North America

Recent decades have seen increasing calls for implementing Indigenous Knowledges (IK) in natural resource management (NRM). However, efforts have been limited by the cultural incommensurabilities between (1) NRM institutions, which are rooted in worldviews that prioritize extraction for dominant cultures and assume dominance over nature and (2) Indigenous worldviews that prioritize kincentric reciprocity with the environment. This manuscript addresses how transforming NRM institutions enables management to better support Indigenous Knowledges and lifeways. This manuscript examines incommensurabilities between NRM institutional cultures and Indigenous cultures, with the value and lifeway of reciprocity as the focal point. Through synthesizing interdisciplinary scholarship and examples from author experiences, we explore how NRM institutions in North America can transform to honour and facilitate reciprocity, especially within efforts to implement IK and support Indigenous lifeways. NRM institutions are cultural products, and in North America were born of colonial histories and cultural roots connected to modern governance and power dynamics. These cultural foundations led to NRM approaches that prioritize maximizing economic growth while guarding against overexploitation. Kincentric reciprocal relations with the environment often emphasize interdependency with more-than-human kin, place-based holistic Knowledges grounded in cultural practices and communal responsibility to cultivate social-ecological abundance for present and future generations. Incommensurabilities between NRM institutional cultures and Indigenous cultures impede efforts to implement IK and support Indigenous lifeways as: (1) rigid institutional structures do not account for Indigenous worldviews and values but instead attempt to fit IK within dominant paradigms; (2) the siloing of NRM leads to the piecemealing and invalidation of IK at the expense of Knowledge Holders and (3) ineffective public engagement strategies limit the possibility of reciprocal relations between NRM institutions and communities throughout management processes. Incommensurabilities between NRM institutional cultures and Indigenous cultures impede efforts to implement IK and support Indigenous lifeways as: (1) rigid institutional structures do not account for Indigenous worldviews and values but instead attempt to fit IK within dominant paradigms; (2) the siloing of NRM leads to the piecemealing and invalidation of IK at the expense of Knowledge Holders and (3) ineffective public engagement strategies limit the possibility of reciprocal relations between NRM institutions and communities throughout management processes. Transforming NRM institutional cultures to better implement IK and support Indigenous lifeways is key for redressing long-standing issues and ensuring social-ecological resilience and abundance. Heavy investments of time, personnel and resources are necessary for transforming NRM institutions to appropriately cultivate reciprocal relations with Indigenous communities and lands. Strategies towards transformation include decentralization through decolonial frameworks, knowledge co-production and using place-based cultural evaluation processes to improve cultural alignment.

People and Nature↗
USGS2017

Crustal structure interpreted from magnetic anomalies

In this review, we discuss publications during the last quadrennium (1987–1990) that used aeromagnetic data, marine magnetic data, satellite magnetic data, and rock magnetic and petrologic data to provide information on the sources of magnetic anomalies. Abstracts and papers by non‐U.S. authors are not described. The publications reviewed reflect increased integration of rock magnetic property and petrologic studies with magnetic anomaly interpretation studies, particularly in deep crustal magnetization, exploration for hydrocarbons, and inversion of marine magnetic anomalies. Interpretations of aeromagnetic data featuring image display techniques and using the horizontal gradient method for locating magnetization boundaries became standard. The magnetic anomaly map of North America appeared, the first such map of an entire continent. MAGSAT data contributed to the development of a new model for the magnetization of the oceanic crust. Forward modeling of sources of magnetic anomalies contributed to a wide range of geologic investigations on land, and inverse magnetic modeling techniques became popular for marine geologic investigations.

Reviews of Geophysics↗
USGS2026

A tool for prioritizing gravel augmentation reaches for sediment starved rivers

Gravel augmentation is a widely used restoration technique used to improve habitat below dams, including salmonids spawning habitat. However, gravel augmentation can be cost-prohibitive, and it is often unclear which stream segments have the highest potential to benefit spawning salmonids. A tool to help prioritize reaches for gravel restoration could aid managers in making good decisions. To address this need, we convened a group of fishery managers to create Intrinsic Potential (IP) habitat models. We used stream attributes related to salmonid spawning habitat: elevation, width, and gradient from the synthetic stream channel dataset NetMap. We then used the IP models to develop an easy-to-use and flexible tool for identifying high spring-run Chinook Salmon ( Oncorhynchus tshawytscha ) IP along ~100 m reaches based on a conceptual model developed by the fishery managers. The tool allows for the inclusion of winter steelhead ( O. mykiss ) IP spawning habitat and allows users to incorporate mean August stream temperature maxima under recent conditions and projected under future climate change, land ownership (public or private or both), reach access distance, distance to and type of gravel sources, and relative gravel movement potential. We explore the prioritization tool with three demonstration strategies for the Upper Rogue River basin, Oregon, USA: (1) Spring Chinook Salmon Strategy, (2) Co-occurrence with winter steelhead Strategy, and (3) Climate Change Strategy. Our analysis demonstrates that altering management priorities directly influences which stream reaches are identified for gravel augmentation. In the three strategies we compared, a small number of current conservation reaches located downstream of spring Chinook Salmon spawning were identified using the tool. In addition, we identified a small number of reaches with no conservation strategy for winter steelhead spawning that meet prioritization criteria. Furthermore, under a climate change scenario, we highlight how new gravel source permitting could expand the set of viable augmentation reaches. The tool is publicly available on GitHub.

Oregon↗
USGS2022

Applied citizen science in freshwater research

Worldwide, scientists are increasingly collaborating with the general public. Citizen science methods are readily applicable to freshwater research, monitoring, and education. In addition to providing cost-effective data on spatial and temporal scales that are otherwise unattainable, citizen science provides unique opportunities for engagement with local communities and stakeholders in resource management and decision-making. However, these methods are not infallible. Citizen science projects require deliberate planning in order to collect high data quality and sustain meaningful community partnerships. Citizen science practitioners also have an ethical responsibility to ensure that projects are not putting the safety of participants at stake. We discuss here how citizen science is being applied in freshwater research, emerging challenges in project planning and implementation, as well as how citizen science is shaping public understanding, policy, and management of freshwaters.

WIREs Water↗
USGS2022

Examining landowners’ preferences for a chronic wasting disease management program

Private landowners are key partners in chronic wasting disease (CWD) management, especially in landscapes where there is limited public ownership. In this study, we evaluated landowners' preferences for alternative hypothetical CWD management programs using a stated choice experiment. We were particularly interested in understanding preferences for the use of financial incentives to motivate white-tailed deer harvest and facilitate hunter access to private lands as potential CWD management tools. We used latent class analysis to characterize preference heterogeneity among landowners stemming from patterns of choice. We compared means and distributions of auxiliary variables related to landowners' perceived risks, trust, attitudes toward management, and sociodemographics across latent classes stemming from choice model results. The pooled model demonstrated that reducing deer population density, providing payments to landowners for CWD-positive deer taken from their property, the form of incentives for public access, and banning recreational deer feeding had a small positive effect on respondents' choice of CWD management program. However, providing financial payments to hunters for harvesting CWD-positive deer and the use of targeted culling had the opposite effect on choice. Latent class models revealed that a majority of respondents exhibited a pattern of preference where all forms of incentives exerted a negative effect on choice, but smaller subsets of landowners positively evaluate the use of some incentives. Post-hoc contrasts revealed relationships between patterns of preferences and trust, risk, and attitudes toward CWD management with small to medium effects. Results demonstrated limited support for the use of financial incentives as a tool to manage access and harvest in the southeast Minnesota CWD management zone

Minnesota↗
USGS2016

The North American model and captive cervid facilities—What is the threat?

The North American Model of Wildlife Conservation represents the key principles that in combination resulted in a distinct form of wildlife conservation in the United States and Canada. How and to what extent captive cervid facilities comport with or conflict with these principles has implications for wildlife conservation. Greatest threats appear to be toward principles of public ownership of wildlife, allocation of wildlife by law, and in policy decisions based on science. Captive cervid facilities have potential to contribute to erosion of the underlying principles of the Model and could undermine public support for conservation initiatives.

Wildlife Society Bulletin↗
USGS2016

Light Goose Conservation Order effects on nontarget waterfowl behavior and energy expenditure

When the Light Goose Conservation Order (LGCO) was established during 1999 in the Rainwater Basin of Nebraska, USA, LGCO activities were limited to 4 days/week and 16 public wetlands were closed to the LGCO to limit disturbance to nontarget waterfowl during this energetically important time period. However, the effects of LGCO activities on waterfowl behavior and energy expenditure are relatively unknown in this critical waterfowl staging area. To evaluate LGCO effects on target and nontarget species, we paired wetlands open and closed to LGCO and recorded waterfowl behavior and hunter encounters during springs 2011 and 2012. We constructed hourly energy expenditure models based on behavior data collected for mallards ( Anas platyrhynchos ) and northern pintails ( A. acuta ). In 2011, dabbling ducks ( Anas spp.) spent more time feeding and less time resting in wetlands closed to hunting during early season when the majority of hunting encounters occurred; behaviors did not differ between hunt categories during late season when hunting activities subsided. However, in 2012, dabbling ducks spent more time feeding and less time resting in wetlands open to hunting during early and late seasons. We detected no differences in behaviors of lesser snow geese ( Chen caerulescens ) or greater white-fronted geese ( Anser albifrons ) between hunting categories in early season. Mallards had slightly greater energy expenditure on wetlands closed to hunting ( = 38.94 ± 0.31 kJ/bird/hr), compared with wetlands open to hunting ( = 37.87 ± 0.32 kJ/bird/hr); therefore, greater energy spent by mallards cannot be attributed to hunting disturbance. We also detected no differences in dabbling duck behavior or energy expenditure between days open or closed to hunting in the region. A refuge system of wetlands closed to LGCO activities in the Rainwater Basin may be an important management strategy in providing reduced disturbance for nontarget waterfowl species in some years. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.

Nebraska↗
USGS2011

White-tailed deer age ratios as herd management and predator impact measures in Pennsylvania

A review of the Pennsylvania Game Commission's (PGC) deer management program and public concern about predator impacts on deer ( Odocoileus virginianus ) populations compelled the PGC to investigate the role of age ratios in developing management recommendations. Age ratios, such as proportion of juveniles in the antlerless harvest, may provide an index to population productivity and predator impacts. We estimated proportion of juveniles in the antlerless harvest from hunter-killed deer, population trends using the Pennsylvania (USA) sex–age–kill model, and reproduction from road-killed females. Using these estimates and a simulation model, we concluded that no single age-ratio value would serve as a reliable measure of population status. Wildlife Management Unit-specific trends in proportion of juveniles in the antlerless harvest and population trends provided the most relevant management information. We also provide an example decision chart to guide management actions in response to declining age ratios in the harvest. Although predator management activities and juvenile survival studies are often desired by the public, our decision-chart example indicated a number of deer management options exist before investing resources in predator management activities and juvenile survival studies.

Pennsylvannia↗
USGS1979

Manganese nodule resources in the northeastern equatorial Pacific

Recent publication of maps at scale 1:1,000,000 of the northeastern equatorial Pacific region showing publicly available information on the nickel plus copper content of manganese nodules has made it possible to outline the prime area between the Clarion and Clipperton fracture zones which has been the focus of several recent scientific and commercial studies. The area, defined as that in which the nodules contain more than 1.8 percent nickel plus copper, is about 2o5 million km 2 . The available evidence suggests that about half of it contains nodules in concentration (reported in wet weight units) greater than 5 kg/m 2 and averaging 11.9 kg/m 2 . If we assume that 20 percent of the nodules in this area of 1.25 million km 2 are recoverable, its potential recoverable resources are about 2.1 billion dry metric tons of nodules averaging about 25 percent Mn, 1.3 percent Ni, 1.0 percent Cu, 0.22 percent Co, and 0.05 percent Mo—enough to support about 27 mining operations each producing an average of 75 million metric tons of nodules over their lifetimes. Estimates based on other plausible assumptions would be higher or lower, but of the same order of magnitude. Thus it seems probable that the magnitude of the potentially recoverable nodule resources of the Clarion-Clipperton prime area—the most promising now known—is at most in the range of several tens of the average-size operations postulated.

Book chapter↗
USGS2019

Wildlife mortality at wind facilities: How we know what we know how we might mislead ourselves, and how we set our future course

To accurately estimate per turbine – or per megawatt – annual wildlife mortality at wind facilities, the raw counts of carcasses found must be adjusted for four major sources of imperfect detection: (1) fatalities that occur outside the monitoring period; (2) carcasses that land outside the monitored area; (3) carcasses that are removed by scavengers or deteriorate beyond recognition prior to detection; and (4) carcasses that remain undiscovered by searchers even when present. To accurately estimate regional or national annual wildlife mortality, data must come from a representative (or appropriately weighted) sample of facilities for which estimates of mortality account for all sources of imperfect detection. I argue that the currently available data in the United States and much of the world do not represent the impacts of wind power on wildlife because not all facilities conduct monitoring studies, not all study results are publicly available, and few studies adequately account for imperfect detection. I present examples illustrating the limitations of our current data and pitfalls of interpreting data without accurately adjusting for detection bias. I close by proposing a solution through a simplified monitoring process that can be applied at every facility as part of normal operations. Application of an unbiased estimator that accounts for all sources of imperfect detection would assure comparability of mortality estimates. Public access to reported estimates would achieve representation. With these data we could develop a clearer understanding of how wind power is affecting wildlife throughout the world and inform our efforts to address it.

Book chapter↗
USGS2020

“Good” and “bad”: Human perceptions of and interactions with urban wildlife

Urban environments offer habitat for many species of animals. Although some of those are ubiquitous and/or undesirable, others are native and in some cases, of conservation value. In many cases, urban wildlife populations are a source of enjoyment for human residents, who sometimes invest considerable amounts in attracting them to yards and public spaces. Their presence there can serve an important educational role that helps protect non-urban habitats and species. Nonetheless, urban wildlife must survive what has been termed a “landscape of fear.” Although some of the urban wildlife that do well in this environment are benign, other populations – sometimes of a species that, in other locations, is iconic and desirable – can become problematic. Some species can serve as vectors that carry important zoonosis, such as the plague or diseases that affect other wildlife. Others can create noise or olfactory nuisances and degrade structures or usability of public spaces. Some pose hazards at busy airports, whereas still others may present an envenomation or predation risk on unwary humans. Here, we review the role that reptiles, birds, and mammals play in urban environments and discuss how urban wildlife rehabilitation centers help address some related issues. We close by looking ahead and trying to predict how global patterns such as increased urbanization and population growth may affect urban wildlife and its value for conservation.

Book chapter↗
USGS2021

History of Great Salt Lake, Utah, USA: Since the termination of Lake Bonneville

During the past half century or so diverse histories of Great Salt Lake have been written from differing perspectives and all of them have contributed ideas and essential data. The published literature, however, can be confusing and misleading. In this chapter, we review and provide context for a number of those publications. This chapter is intended as a summary of what is known, what is not known, and what cannot be known with precision about the history of the lake. Great Salt Lake is the largest hydrographically closed lake in the Bonneville basin of northwestern Utah. It responds to both short-term weather and long-term climate. In the Lake Bonneville/Great Salt Lake lacustrine system, the end of Lake Bonneville at 13,000 yr BP marks the beginning of Great Salt Lake. The much larger and deeper lakes of the Bonneville lake cycle responded to the pluvial climate of oxygen isotope stage 2, but the warmer, drier climate of oxygen isotope stage 1 led to rapid fluctuations within a relatively narrow, well-documented elevation range, 5 m above and 9 m below the historical mean elevation of ~1280 m. Two exceptional but short-lived rises of Great Salt Lake to elevations higher than 5 m above ~1280 m have been documented —one during the Gilbert episode, which peaked about 11,600 yr BP near an elevation of 1295 m, and one to about 1289 m sometime after about 11,000 yr BP. The historical Great Salt Lake hydrograph (the past 150 years) shows its labile behavior. Smooth-curve hydrographs based on estimates of lake level at time scales of decades, centuries, or millennia, such as those presented in previous publications, do not accurately portray the way lake level rises and falls, and a precise plot of post-Bonneville changes in level of Great Salt Lake would resemble the “jagged” historical record. The available sedimentary and geomorphic data are not conducive at this time to the production of a highly precise hydrograph, so we suggest that post-Bonneville lake-level history be portrayed, imprecisely but accurately, as confined generally between the elevation limits of 1285 and 1271 m, with an indication of the exceptional spikes in the lake level.

Utah↗
USGS2011

Inference for occupancy and occupancy dynamics

This chapter deals with the estimation of occupancy as a state variable to assess the status of, and track changes in, species distributions when sampling with camera traps. Much of the recent interest in occupancy estimation and modeling originated from the models developed by MacKenzie et al. (2002, 2003), although similar methods were developed independently (Azuma et al. 1990; Bayley and Petersen 2001; Nichols and Karanth, 2002; Tyre et al. 2003), all of which deal with species occurrence information and imperfect detection. Less than a decade after these publications, the modeling and estimation of species occurrence and occupancy dynamics have increased significantly. Special features of scientific journals have explored innovative uses of detection–nondetection data with occupancy models (Vojta 2005), and an entire volume has synthesized the use and application of occupancy estimation methods (MacKenzie et al. 2006). Reviews of the topical concepts, philosophical considerations, and various sampling designs that can be used for occupancy estimation are now readily available for a range of audiences (MacKenzie and Royle 2005; MacKenzie et al. 2006; Bailey et al. 2007; Royle and Dorazio 2008; Conroy and Carroll 2009; Kendall and White 2009; Hines et al. 2010; Link and Barker 2010). As a result, it would be pointless here to recast all that these publications have so eloquently articulated, but that said, a review of any scientific topic requires sufficient context and relevant background information, especially when relatively new methodologies and techniques such as occupancy estimation and camera traps are involved. This is especially critical in a digital age where new information is published at warp speed, making it increasingly difficult to stay abreast of theoretical advances and research developments.

Book chapter↗
USGS2013

Ecosystem services: developing sustainable management paradigms based on wetland functions and processes

In the late nineteenth century and twentieth century, there was considerable interest and activity to develop the United States for agricultural, mining, and many other purposes to improve the quality of human life standards and prosperity. Most of the work to support this development was focused along disciplinary lines with little attention focused on ecosystem service trade-offs or synergisms, especially those that transcended boundaries of scientific disciplines and specific interest groups. Concurrently, human population size has increased substantially and its use of ecosystem services has increased more than five-fold over just the past century. Consequently, the contemporary landscape has been highly modified for human use, leaving behind a fragmented landscape where basic ecosystem functions and processes have been broadly altered. Over this period, climate change also interacted with other anthropogenic effects, resulting in modern environmental problems having a complexity that is without historical precedent. The challenge before the scientific community is to develop new science paradigms that integrate relevant scientific disciplines to properly frame and evaluate modern environmental problems in a systems-type approach to better inform the decision-making process. Wetland science is a relatively new discipline that grew out of the conservation movement of the early twentieth century. In the United States, most of the conservation attention in the earlier days was on wildlife, but a growing human awareness of the importance of the environment led to the passage of the National Environmental Policy Act in 1969. Concurrently, there was a broadening interest in conservation science, and the scientific study of wetlands gradually gained acceptance as a scientific discipline. Pioneering wetland scientists became formally organized when they formed The Society of Wetland Scientists in 1980 and established a publication outlet to share wetland research findings. In comparison to older and more traditional scientific disciplines, the wetland sciences may be better equipped to tackle today’s complex problems. Since its emergence as a scientific discipline, the study of wetlands has frequently required interdisciplinary and integrated approaches. This interdisciplinary/integrated approach is largely the result of the fact that wetlands cannot be studied in isolation of upland areas that contribute surface and subsurface water, solutes, sediments, and nutrients into wetland basins. However, challenges still remain in thoroughly integrating the wetland sciences with scientific disciplines involved in upland studies, especially those involved with agriculture, development, and other land-conversion activities that influence wetland hydrology, chemistry, and sedimentation. One way to facilitate this integration is to develop an understanding of how human activities affect wetland ecosystem services, especially the trade-offs and synergisms that occur when land-use changes are made. Used in this context, an understanding of the real costs of managing for a particular ecosystem service or groups of services can be determined and quantified in terms of reduced delivery of other services and in overall sustainability of the wetland and the landscapes that support them. In this chapter, we discuss some of the more salient aspects of a few common wetland types to give the reader some background on the diversity of functions that wetlands perform and the specific ecosystem services they provide to society. Wetlands are among the most complex ecosystems on the planet, and it is often difficult to communicate to a diverse public all of the positive services wetlands provide to mankind. Our goal is to help the reader develop an understanding that management options can be approached as societal choices where decisions can be made within a spatial and temporal context to identify trade-offs, synergies, and effects on long-term sustainability of wetland ecosystems. This will be especially relevant as we move into alternate climate futures where our portfolio of management options for mitigating damage to ecosystem function or detrimental cascading effects must be diverse and effective.

Book chapter↗
USGS1976

Leasing policies for the extractive resources

Much of the available analysis of policies for the disposal of publicly held resources is based on comparatively straightforward extensions of the neoclassical pricing and allocation theory. As such, these analyses have to a large extent not fully incorporated the fact that firms normally acquire rights to these resources in sealed tender markets. In this paper, a simple bidding model is used to show that the choice of disposal policies can influence the firm's bid and also the public revenues obtained from the sale of the resource. It is additionally shown that the implications of such policy choices are conditioned by the firm's attitudes towards risk. Finally, it is argued that a modification of existing prescriptions may be necessary if a more realistic specification of the disposal problem taking account of the sealed tender market in which rights are obtained, is considered.

The Annals of Regional Science↗
USGS1995

Economics of mining law

Modern mining law, by facilitating socially and environmentally acceptable exploration, development, and production of mineral materials, helps secure the benefits of mineral production while minimizing environmental harm and accounting for increasing land-use competition. Mining investments are sunk costs, irreversibly tied to a particular mineral site, and require many years to recoup. Providing security of tenure is the most critical element of a practical mining law. Governments owning mineral rights have a conflict of interest between their roles as a profit-maximizing landowner and as a guardian of public welfare. As a monopoly supplier, governments have considerable power to manipulate mineral-rights markets. To avoid monopoly rent-seeking by governments, a competitive market for government-owned mineral rights must be created by artifice. What mining firms will pay for mineral rights depends on expected exploration success and extraction costs. Landowners and mining firms will negotlate respective shares of anticipated differential rents, usually allowing for some form of risk sharing. Private landowners do not normally account for external benefits or costs of minerals use. Government ownership of mineral rights allows for direct accounting of social prices for mineral-bearing lands and external costs. An equitable and efficient method is to charge an appropriate reservation price for surface land use, net of the value of land after reclamation, and to recover all or part of differential rents through a flat income or resource-rent tax. The traditional royalty on gross value of production, essentially a regressive income tax, cannot recover as much rent as a flat income tax, causes arbitrary mineral-reserve sterilization, and creates a bias toward development on the extensive margin where marginal environmental costs are higher. Mitigating environmental costs and resolving land-use conflicts require local evaluation and planning. National oversight ensures that the relative global avaliability of minerals and other values are considered, and can also promote adaptive efficiency by publicizing creative local solutions, providing technical support, and funding useful research. ?? 1995 Oxford University Press.

Nonrenewable Resources↗
USGS2003

Small-Scale Vertical Distribution of Bacterial Biomass and Diversity in Biological Soil Crusts from Arid Lands in the Colorado Plateau

We characterized, at millimeter resolution, bacterial biomass, diversity, and vertical stratification of biological soil crusts in arid lands from the Colorado Plateau. Microscopic counts, extractable DNA, and plate counts of viable aerobic copiotrophs (VAC) revealed that the top centimeter of crusted soils contained atypically large bacterial populations, tenfold larger than those in uncrusted, deeper soils. The plate counts were not always consistent with more direct estimates of microbial biomass. Bacterial populations peaked at the immediate subsurface (1-2 mm) in light-appearing, young crusts, and at the surface (0-1 mm) in well-developed, dark crusts, which corresponds to the location of cyanobacterial populations. Bacterial abundance decreased with depth below these horizons. Spatially resolved DGGE fingerprints of Bacterial 16S rRNA genes demonstrated the presence of highly diverse natural communities, but we could detect neither trends with depth in bacterial richness or diversity, nor a difference in diversity indices between crust types. Fingerprints, however, revealed the presence of marked stratification in the structure of the microbial communities, probably a result of vertical gradients in physicochemical parameters. Sequencing and phylogenetic analyses indicated that most of the naturally occurring bacteria are novel types, with low sequence similarity (83-93%) to those available in public databases. DGGE analyses of the VAC populations indicated communities of lower diversity, with most types having sequences more than 94% similar to those in public databases. Our study indicates that soil crusts represent small-scale mantles of fertility in arid ecosystems, harboring vertically structured, little-known bacterial populations that are not well represented by standard cultivation methods.

Microbial Ecology↗