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Results for “Biodiversity Letters”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

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33 records · Page 2Linked to original sources
USGS2011

Forest species diversity reduces disease risk in a generalist plant pathogen invasion

Empirical evidence suggests that biodiversity loss can increase disease transmission, yet our understanding of the 'diversity-disease hypothesis' for generalist pathogens in natural ecosystems is limited. We used a landscape epidemiological approach to examine two scenarios regarding diversity effects on the emerging plant pathogen Phytophthora ramorum across a broad, heterogeneous ecoregion: (1) an amplification effect exists where disease risk is greater in areas with higher plant diversity due to the pathogen's wide host range, or (2) a dilution effect where risk is reduced with increasing diversity due to lower competency of alternative hosts. We found evidence for pathogen dilution, whereby disease risk was lower in sites with higher species diversity, after accounting for potentially confounding effects of host density and landscape heterogeneity. Our results suggest that although nearly all plants in the ecosystem are hosts, alternative hosts may dilute disease transmission by competent hosts, thereby buffering forest health from infectious disease.

Ecology Letters↗
USGS2024

Identifying Pareto-efficient eradication strategies for invasive populations

Invasive species are a major cause of biodiversity loss and are notoriously expensive and challenging to manage. We developed a decision-analytic framework for evaluating invasive species removal strategies, given objectives of maximizing eradication probability and minimizing costs. The framework uses an existing estimation model for spatially referenced removal data—one of the most accessible types of invasive species data—to obtain estimates of population growth rate, movement probability, and detection probability. We use these estimates in simulations to identify Pareto-efficient strategies—strategies where increases in eradication probability cannot be obtained without increases in cost—from a set of proposed strategies. We applied the framework post hoc to a successful eradication of veiled chameleons ( Chamaeleo calyptratus ) and identified the potential for substantial improvements in efficiency. Our approach provides managers and policymakers with tools to identify cost-effective strategies for a range of invasive species using only prior knowledge or data from initial physical removals.

Hawaii↗
USGS1997

Gradients, vegetation and climate: spatial and temporal dynamics in the Olympic Mountains, USA

The steep environmental gradients of mountains result in the juxtaposition of diverse vegetation associations with narrow ecotones because life zones are compressed. Variation in geologic substrate, landforms, and soils, in combination with steep environmental gradients, create habitat diversity across spatial scales from 10 6 ha to <10 m 2 . This leads to higher biodiversity in a smaller space than in landscapes with less topographic variation. Mountains are often considered to be refuges for biological diversity at the regional scale, although variation in landscape features creates refuges at a fine scale as well. Mountains should also be considered a source of biological diversity, because they provide the germplasm for migration into lowland areas following glacial recession. Many taxa are distributed over a broad range of elevations and habitats, which maximizes the potential to respond to environmental perturbations. Reorganization of species distribution and abundance as a result of climatic change may be impacted considerably by human-caused fragmentation of landscape features, especially at lower elevations. This paper uses palaeoecological and biogeographical data to investigate the spatial and temporal vegetation dynamics of a steep maritime range, the Olympic Mountains (USA). The role of resource management in protecting vegetation in a fragmented landscape is discussed, with emphasis on how to address uncertainties such as climatic change.

Washington↗
USGS2019

Conservation challenges emerging from free-roaming horse management: a vexing social-ecological mismatch

Horses have been associated with human societies for millennia, and for many have come to symbolize wildness, power, resilience, and freedom. Although equids were extirpated from North America 10 000-12 000 years ago, descendants of domestic horses now roam freely in the USA and 17 other countries across six continents. In landscape-scale and experimental investigations, free-roaming horses (Equus caballus) have been shown to induce numerous alterations to native-ecosystem components and processes through influences on soil, water, plants, native ungulates, small mammals, birds, reptiles, and other aspects of biodiversity. However, we argue that the management of free-roaming horses both in the U.S. and globally has been complicated by “socio-ecological mismatches.” These three mismatches stem from discrepancies between: 1) steady-state (horse-management) goals vs. a stochastically variable environment; 2) different methods to evaluate evidence, resolve conflicting beliefs, and achieve objectives, in scientific vs. political processes; and 3) differing spatial and temporal scales between policy and management, and values of science vs. values of the general public. Such mismatches arise from an inability to reconcile conflicting processes and functions in a social-ecological system, often reflecting differences in the spatio-temporal scales at which diverse components operate. Here, we describe three types of mismatches, and illustrate how the ecological dynamics of aridlands generally fit poorly with existing approaches to horse management and policy. Such mismatches complicate cost-effective management of free-roaming horses and the ecosystems they inhabit, and reduce the palette of potential solutions.

Conservation Letters↗
USGS2021

A combined microbial and ecosystem metric of carbon retention efficiency explains land cover-dependent soil microbial biodiversity–ecosystem function relationships

While soil organic carbon (C) is the foundation of productive and healthy ecosystems, the impact of the ecology of microorganisms on C-cycling remains unknown. We manipulated the diversity, applied here as species richness, of the microbial community present in similar soils on two contrasting land-covers—an adjacent pasture and forest—and observed the transformations of plant detritus and soil organic matter (SOM) using stable isotope ( 13 C) tracing coupled with a novel nuclear magnetic resonance (NMR) experiment. The amount of detritus-C degraded was not affected by the microbial diversity (p > 0.05), however the fate of detritus- and SOM-C across the diversity gradient was complex and land cover-dependent. For example, in the pasture soil, higher diversity led to lower CO 2 production (p = 0.001), a trend driven solely by SOM-C mineralization. There was no relationship between diversity and detritus-C mineralization or production of new mineral-associations after one year (p > 0.05). In contrast, in the forest soil higher diversity resulted in increased detritus-C (p = 0.01) and SOM-C (p = 0.0008) mineralization and decreased mineral-associated organic matter formation (p = 0.02). In both land cover types, retention efficiency—a measure that integrates both microbial physiology and the ability of the ecosystem to retain C—explained C loss and transformation trends. Overall, this demonstrates that the trajectory of C gained and lost is altered by land management-induced changes to microbial communities, soil structure, and chemical characteristics underlying SOM persistence.

Biogeochemistry Letters↗
USGS2015

Improving conservation outcomes with a new paradigm for understanding species’ fundamental and realized adaptive capacity

Worldwide, many species are responding to ongoing climate change with shifts in distribution, abundance, phenology, or behavior. Consequently, natural-resource managers face increasingly urgent conservation questions related to biodiversity loss, expansion of invasive species, and deteriorating ecosystem services. We argue that our ability to address these questions is hampered by the lack of explicit consideration of species&rsquo; adaptive capacity (AC). AC is the ability of a species or population to cope with climatic changes and is characterized by three fundamental components: phenotypic plasticity, dispersal ability, and genetic diversity. However, few studies simultaneously address all elements; often, AC is confused with sensitivity or omitted altogether from climate-change vulnerability assessments. Improved understanding, consistent definition, and comprehensive evaluations of AC are needed. Using classic ecological-niche theory as an analogy, we propose a new paradigm that considers fundamental and realized AC: the former reflects aspects inherent to species, whereas the latter denotes how extrinsic factors constrain AC to what is actually expressed or observed. Through this conceptualization, we identify ecological attributes contributing to AC, outline areas of research necessary to advance understanding of AC, and provide examples demonstrating how the inclusion of AC can better inform conservation and natural-resource management.

Conservation Letters↗
USGS2024

Multinational evaluation of genetic diversity indicators for the Kunming-Montreal Global Biodiversity Framework

Under the recently adopted Kunming-Montreal Global Biodiversity Framework, 196 Parties committed to reporting the status of genetic diversity for all species. To facilitate reporting, three genetic diversity indicators were developed, two of which focus on processes contributing to genetic diversity conservation: maintaining genetically distinct populations and ensuring populations are large enough to maintain genetic diversity. The major advantage of these indicators is that they can be estimated with or without DNA-based data. However, demonstrating their feasibility requires addressing the methodological challenges of using data gathered from diverse sources, across diverse taxonomic groups, and for countries of varying socio-economic status and biodiversity levels. Here, we assess the genetic indicators for 919 taxa, representing 5271 populations across nine countries, including megadiverse countries and developing economies. Eighty-three percent of the taxa assessed had data available to calculate at least one indicator. Our results show that although the majority of species maintain most populations, 58% of species have populations too small to maintain genetic diversity. Moreover, genetic indicator values suggest that IUCN Red List status and other initiatives fail to assess genetic status, highlighting the critical importance of genetic indicators.

Ecology Letters↗
USGS2018

Fire and tree death: Understanding and improving modeling of fire-induced tree mortality

Each year wildland fires kill and injure trees on millions of forested hectares globally, affecting plant and animal biodiversity, carbon storage, hydrologic processes, and ecosystem services. The underlying mechanisms of fire-caused tree mortality remain poorly understood, however, limiting the ability to accurately predict mortality and develop robust modeling applications, especially under novel future climates. Virtually all post-fire tree mortality prediction systems are based on the same underlying empirical model described in Ryan and Reinhardt (1988 Can. J. For. Res. 18 1291–7), which was developed from a limited number of species, stretching model assumptions beyond intended limits. We review the current understanding of the mechanisms of fire-induced tree mortality, provide recommended standardized terminology, describe model applications and limitations, and conclude with key knowledge gaps and future directions for research. We suggest a two-pronged approach to future research: (1) continued improvements and evaluations of empirical models to quantify uncertainty and incorporate new regions and species and (2) acceleration of basic, physiological research on the proximate and ultimate causes of fire-induced tree mortality to incorporate processes of tree death into models. Advances in both empirical and process fire-induced tree modeling will allow creation of hybrid models that could advance understanding of how fire injures and kills trees, while improving prediction accuracy of fire-driven feedbacks on ecosystems and landscapes, particularly under novel future conditions.

Environmental Research Letters↗
USGS2022

Using ecosystem services to identify inequitable outcomes in migratory species conservation

Biodiversity conservation efforts have been criticized for generating inequitable socio-economic outcomes. These equity challenges are largely analyzed as place-based problems affecting local communities directly impacted by conservation programs. The conservation of migratory species extends this problem geographically since people in one place may benefit while those in another bear the costs of conservation. The spatial subsidies approach offers an effective tool for analyzing such relationships between places connected by migratory species. Designed to quantify ecosystem services provided and received in specific locations across a migratory species’ range—and the disparities between them—the spatial subsidies approach highlights three axes of inequity: between indigenous and settler colonial societies, between urban and rural populations, and between the Global North and Global South. Recognizing these relationships is critical to achieving two mutually reinforcing policy goals: avoiding inequitable conservation outcomes in efforts to conserve migratory species, and ensuring effective long-term conservation of migratory species. In demonstrating how the spatial subsidies approach enables the identification and quantification of inequities involving three migratory species (northern pintail ducks, monarch butterflies, and Mexican free-tailed bats), we argue that a spatial subsidies approach could apply to migratory species conservation efforts worldwide under the context of “payments for ecosystem services.”

Conservation Letters↗
USGS2011

Abundance of introduced species at home predicts abundance away in herbaceous communities

Many ecosystems worldwide are dominated by introduced plant species, leading to loss of biodiversity and ecosystem function. A common but rarely tested assumption is that these plants are more abundant in introduced vs. native communities, because ecological or evolutionary-based shifts in populations underlie invasion success. Here, data for 26 herbaceous species at 39 sites, within eight countries, revealed that species abundances were similar at native (home) and introduced (away) sites - grass species were generally abundant home and away, while forbs were low in abundance, but more abundant at home. Sites with six or more of these species had similar community abundance hierarchies, suggesting that suites of introduced species are assembling similarly on different continents. Overall, we found that substantial changes to populations are not necessarily a pre-condition for invasion success and that increases in species abundance are unusual. Instead, abundance at home predicts abundance away, a potentially useful additional criterion for biosecurity programmes.

Ecology Letters↗
USGS2021

Carbon and ecohydrological priorities in managing woody encroachment: UAV perspective 63 years after a control treatment

Woody encroachment, including both woody species expansion and density increase, is a globally observed phenomenon that deteriorates arid and semi-arid rangeland health, biodiversity, and ecosystem services. Mechanical and chemical control treatments are commonly performed to reduce woody cover and restore ecohydrologic function. While the immediate impacts of woody control treatments are well documented in short-term studies, treatment impacts at decadal scales are not commonly studied. Using a controlled herbicide treatment from 1954 in the Sierra Ancha Experimental Forest in central Arizona, USA, we quantify woody encroachment and associated aboveground carbon accumulation in treated and untreated watersheds. Woody encroachment and aboveground carbon are estimated using high resolution multispectral images and photogrammetric data from a fixed-wing unmanned aerial vehicle (UAV). We then combine the contemporary UAV image-derived estimates with historical records from immediately before and after the treatment to consider long-term trends in woody vegetation cover, aboveground carbon, water yield, and sedimentation. Our results indicate that the treatment has had a lasting impact. More than six decades later, woody cover in two treated watersheds are still significantly lower compared to two control watersheds, even though woody cover increased in all four drainages. Aboveground woody carbon in the treated watersheds is approximately one half that accumulated in the control watersheds. The historical records indicate that herbicide treatment also increased water yield and reduced annual sedimentation. Given the sustained reduction in woody cover and aboveground woody biomass in treated watersheds, we infer that the herbicide treatment has had similarly long lasting impacts on ecohydrological function. Land managers can consider legacy impacts from control treatments to better balance carbon and ecohydrological consequences of woody encroachment and treatment activities.

Environmental Research Letters↗
USGS2024

Range-wide salamander densities reveal a key component of terrestrial vertebrate biomass in eastern North American forests

Characterizing the population density of species is a central interest in ecology. Eastern North America is the global hotspot for biodiversity of plethodontid salamanders, an inconspicuous component of terrestrial vertebrate communities, and among the most widespread is the eastern red-backed salamander, Plethodon cinereus . Previous work suggests population densities are high with significant geographic variation, but comparisons among locations are challenged by lack of standardization of methods and failure to accommodate imperfect detection. We present results from a large-scale research network that accounts for detection uncertainty using systematic survey protocols and robust statistical models. We analysed mark–recapture data from 18 study areas across much of the species range. Estimated salamander densities ranged from 1950 to 34 300 salamanders ha −1 , with a median of 9965 salamanders ha −1 . We compared these results to previous estimates for P. cinereus and other abundant terrestrial vertebrates. We demonstrate that overall the biomass of P. cinereus , a secondary consumer, is of similar or greater magnitude to widespread primary consumers such as white-tailed deer ( Odocoileus virginianus ) and Peromyscus mice, and two to three orders of magnitude greater than common secondary consumer species. Our results add empirical evidence that P. cinereus , and amphibians in general, are an outsized component of terrestrial vertebrate communities in temperate ecosystems.

Biology Letters↗
USGS2026

The Zooplankton International Geospatial (ZIG) dataset: A global repository of spatiotemporal freshwater zooplankton community composition data from lakes and reservoirs to support ecological research

Zooplankton transfer substantial energy in aquatic food webs and are used as indicators of environmental change. Syntheses of zooplankton community dynamics globally require datasets that span a wide range of environmental gradients; however, these datasets are limited due to methodological differences across programs, taxonomic inconsistencies, and a lack of standardized metadata. To reconcile these challenges, we created the Zooplankton International Geospatial (ZIG) dataset, which includes original zooplankton, water physical and chemical variables, and lake morphometric data from 311 inland lakes and reservoirs. ZIG includes waterbodies ranging in size from 0.005 to 82,100 km 2 and spanning broad latitudinal (−47.26 to 64.90) and longitudinal ranges (−165.04 to 176.53). Temporal coverage for individual waterbodies ranges between 1 and 60 yr with sampling frequency ranging from annually to weekly. With its extensive coverage and content, we consider ZIG to be a cornerstone for future investigations of global scale lake biodiversity change.

Limnology & Oceanography - Letters↗
USGS2022

Globally, tree fecundity exceeds productivity gradients

Lack of tree fecundity data across climatic gradients precludes the analysis of how seed supply contributes to global variation in forest regeneration and biotic interactions responsible for biodiversity. A global synthesis of raw seedproduction data shows a 250-fold increase in seed abundance from cold-dry to warm-wet climates, driven primarily by a 100-fold increase in seed production for a given tree size. The modest (threefold) increase in forest productivity across the same climate gradient cannot explain the magnitudes of these trends. The increase in seeds per tree can arise from adaptive evolution driven by intense species interactions or from the direct effects of a warm, moist climate on tree fecundity. Either way, the massive differences in seed supply ramify through food webs potentially explaining a disproportionate role for species interactions in the wet tropics.

Ecology Letters↗
USGS2004

Demographic estimation methods for plants with dormancy

Demographic studies in plants appear simple because unlike animals, plants do not run away. Plant individuals can be marked with, e.g., plastic tags, but often the coordinates of an individual may be sufficient to identify it. Vascular plants in temperate latitudes have a pronounced seasonal life–cycle, so most plant demographers survey their study plots once a year often during or shortly after flowering. Life–states are pervasive in plants, hence the results of a demographic study for an individual can be summarized in a familiar encounter history, such as 0VFVVF000. A zero means that an individual was not seen in a year and a letter denotes its state for years when it was seen aboveground. V and F here stand for vegetative and flowering states, respectively. Probabilities of survival and state transitions can then be obtained by mere counting. Problems arise when there is an unobservable dormant state, i.e., when plants may stay belowground for one or more growing seasons. Encounter histories such as 0VF00F000 may then occur where the meaning of zeroes becomes ambiguous. A zero can either mean a dead or a dormant plant. Various ad hoc methods in wide use among plant ecologists have made strong assumptions about when a zero should be equated to a dormant individual. These methods have never been compared among each other. In our talk and in Kéry et al. (submitted), we show that these ad hoc estimators provide spurious estimates of survival and should not be used. In contrast, if detection probabilities for aboveground plants are known or can be estimated, capturerecapture (CR) models can be used to estimate probabilities of survival and state–transitions and the fraction of the population that is dormant. We have used this approach in two studies of terrestrial orchids, Cleistes bifaria (Kéry et al., submitted) and Cypripedium reginae (Kéry & Gregg, submitted) in West Virginia, U.S.A. For Cleistes, our data comprised one population with a total of 620 marked ramets over 10 years, and for Cypripedium , two populations with 98 and 258 marked ramets over 11 years. We chose the ramet (= single stem or shoot) as the demographic unit of our study since there was no way distinguishing among genets (genet = genetical individual, i.e., the “individual” that animal ecologists are mostly concerned with). This will introduce some non–independence into the data, which can nevertheless be dealt with easily by correcting variances for overdispersion. Using ramets instead of genets has the further advantage that individuals can be assigned to a state such as flowering or vegetative in an unambiguous manner. This is not possible when genets are the demographic units. In all three populations, auxiliary data was available to show that detection probability of aboveground plants was m 0.995 We fitted multistate models in program MARK by specifying three states (D, V, F), even though the dormant state D does not occur in the encounter histories. Detection probability is fixed at 1 for the vegetative (V) and the flowering state (F) and at zero for the dormant state (D). Rates of survival and of state transitions as well as slopes of covariate relationships can be estimated and LRT or the AIC machinery be used to select among models. To estimate the fraction of the population in the unobservable dormant state, the encounter histories are collapsed to 0 (plant not observed aboveground) and 1 (plant observed aboveground). The Cormack–Jolly–Seber model without constraints on detection probability is used to estimate detection probability, the complement of which is the estimated fraction of the population in the dormant state. Parameter identifiability is an important issue in multi state models. We used the Catchpole–Morgan–Freeman approach to determine which parameters are estimable in principle in our multi state models. Most of 15 tested models were indeed estimable with the notable exception of the most general model, which has fully interactive state- and time-dependent survival and state transition rates. This model would become identifiable if at least some plants would be excavated in years when they do not show up aboveground. Our analyses for three analyzed populations of Cleistes and Cypripedium yielded annual ramet survival rates ranging from 0.86–0.96. Estimates of the average fraction dormant ranged from 0.02–0.30, but with up to half a population in the dormant state in some years. Ultrastructural modeling enables interesting hypotheses to be tested about the relationships of demographic rates with climatic covariates for instance. Such covariate modeling makes the CR approach particularly interesting for evolutionary–ecological questions about, e.g., the adaptive significance of the dormant state.

Animal Biodiversity and Conservation↗