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USGS2019

Perspective: Developing flow policies to balance the water needs of humans and wetlands requires a landscape scale approach inclusive of future scenarios and multiple timescales

Maintenance of the natural flow regime is essential for continued wetland integrity; however, the flow regime is greatly influenced by both natural and anthropogenic forces. Wetlands may be particularly susceptible to altered flow regimes as they are directly impacted by water flows at a variety of time scales. In Puerto Rico, contemporary water management is decreasing freshwater recharge to wetlands and contributes to the salinization of important coastal wetlands as sea levels rise. Further, downscaled climate models predict an increase in drought frequency, intensity, and duration by mid-century. Conflicts over water allocation seem imminent between human and ecological needs. Current minimum flow policies are insufficient given the complexities of ecosystem processes and the changes in precipitation patterns and sea level rise that are expected in the future. Improved flow policies need to be established that reflect the functional relationships between specific representative ecological resources and components of the natural flow regime across all relevant time scales. Similarly, flow policies need to be developed within a landscape scale to implicitly address the socio-ecological trade-offs as well as the complexities of water management. Multi-disciplinary collaborations will be essential for increasing our resiliency to anticipated future changes.

Wetlands↗

USGS1983

Some observations on the use of discriminant analysis in ecology

The application of discriminant analysis in ecological investigations is discussed. The appropriate statistical assumptions for discriminant are illustrated, and both classification and group separation approaches are outlined. Three assumptions that are crucial in ecological studies are discussed at length, and the consequences of their violation are developed. These assumptions are: (1) equality of dispersions, (2) identifiability of prior probabilities, and (3) precise and accurate estimation of means and dispersions. The use of discriminant functions for purposes of interpreting ecological relationships is also discussed. It is suggested that the common practice of imputing ecological m eaning to the signs and magnitudes of coefficients be replaced by an assessment of s tructure coefficients. Finally, the potential and limitations of representation of data in canonical space are considered, and some cautionary points are made concerning ecological interpretation of patterns in canonical space.

Ecology↗

USGS2019

Local scale spatial patterns of freshwater mussels in the Upper Mississippi River

Multiple physical and biological factors contribute to the structure of freshwater mussel communities in large rivers. Mussel distributions are frequently described as clumped or patchy. However, few surveys of mussel populations have been designed to quantify these spatial patterns. We used indicators of spatial autocorrelation to quantify spatial patterns of adult and juvenile (≤ 5 years of age) freshwater mussels at local scales (i.e., < 300 m), within 14 sites along ~700 km of the Upper Mississippi River, USA. Juveniles were patchily distributed in 43% of the sites, and adults were patchily distributed in 50%. Within sites, juveniles and adults displayed the same spatial pattern in 64% of the sites. At half of the sites, hotspots of adults and juveniles overlapped suggesting spatial and temporal persistence of habitat. Mussels have an important ecological role in rivers, and information on their spatial patterns aid our understanding of the spatial structure and function of riverine ecosystems, and the ecological consequences of population declines.

Illinois, Iowa, Minneapolis, Wisconsin↗

USGS2010

Landscape genetics of high mountain frog metapopulations

Explaining functional connectivity among occupied habitats is crucial for understanding metapopulation dynamics and species ecology. Landscape genetics has primarily focused on elucidating how ecological features between observations influence gene flow. Functional connectivity, however, may be the result of both these between‐site (landscape resistance) landscape characteristics and at‐site (patch quality) landscape processes that can be captured using network based models. We test hypotheses of functional connectivity that include both between‐site and at‐site landscape processes in metapopulations of Columbia spotted frogs ( Rana luteiventris ) by employing a novel justification of gravity models for landscape genetics (eight microsatellite loci, 37 sites, n = 441). Primarily used in transportation and economic geography, gravity models are a unique approach as flow (e.g. gene flow) is explained as a function of three basic components: distance between sites, production/attraction (e.g. at‐site landscape process) and resistance (e.g. between‐site landscape process). The study system contains a network of nutrient poor high mountain lakes where we hypothesized a short growing season and complex topography between sites limit R. luteiventris gene flow. In addition, we hypothesized production of offspring is limited by breeding site characteristics such as the introduction of predatory fish and inherent site productivity. We found that R. luteiventris connectivity was negatively correlated with distance between sites, presence of predatory fish (at‐site) and topographic complexity (between‐site). Conversely, site productivity (as measured by heat load index, at‐site) and growing season (as measured by frost‐free period between‐sites) were positively correlated with gene flow. The negative effect of predation and positive effect of site productivity, in concert with bottleneck tests, support the presence of source–sink dynamics. In conclusion, gravity models provide a powerful new modelling approach for examining a wide range of both basic and applied questions in landscape genetics.

Idaho↗

USGS2021

Ontogenetic trait shifts: Seedlings display high trait variability during early stages of development

Characterizing variation in plant functional traits is often key to understanding community-level processes and predicting ecosystem responses to environmental change. Trait-based ecology has focused on interspecific trait variation, but sources and consequences of within-species ontogenetic trait variation, particularly during early stages of development, remain understudied. Using a manipulative greenhouse experiment, we investigated trait variation during early stages of seedling development in seven dominant perennial plant species in the western United States. We examined variability in key trait values (i.e. SLA, root:shoot ratio (RSR), specific root length (SRL) and root dry matter content (RDMC)) of 20- to 62-day-old seedlings grown under low and high levels of water availability. We also compared these to compiled trait databases to assess how representative these readily available data sources are of seedling trait values. Early seedling trait values shifted greatly during early stages of development and generally differed from average plant trait database values. Trait shifts were greatest in forbs versus grasses. Overall, observed trait shifts suggested a transition from fast-growing resource acquisitional strategies towards more slow-growing conservative strategies over time. For example, seedling SLA decreased while RSR and RDMC increased over time. That seedling trait values aconsistently differed from trait database values indicates that plant trait database values may be poor predictors of seedling trait values. Such mismatches in species trait information could result in inaccurate predictions of community assembly outcomes or incongruities between seedling traits and environmental filters experienced by seedlings during early stages of recruitment in applied settings. We suggest that additional work is needed to characterize intraspecific trait variation across plant ontogeny, and that this information should be incorporated into studies ranging from understanding early plant growth and survival to evaluating the outcomes of ecological restoration.

Functional Ecology↗

USGS2012

Global Change and the Function and Distribution of Wetlands

The Global Change Ecology and Wetlands book series will highlight the latest research from the world leaders in the field of climate change in wetlands. Global Change and the Function and Distribution of Wetlands highlights information of importance to wetland ecologists. The chapters include syntheses of international studies on the effects of drought on function and regeneration in wetlands, sea level rise and the distribution of mangrove swamps, former distributions of swamp species and future lessons from paleoecology, and shifts in atmospheric emissions across geographical regions in wetlands. Overall, the book will contribute to a better understanding of the potential effects of climate change on world wetland distribution and function.

Book↗

USGS2020

Characterizing benthic macroinvertebrate and algal biological condition gradient models for California wadeable Streams, USA

The Biological Condition Gradient (BCG) is a conceptual model that describes changes in aquatic communities under increasing levels of anthropogenic stress. The BCG helps decision-makers connect narrative water quality goals (e.g., maintenance of natural structure and function) to quantitative measures of ecological condition by linking index thresholds based on statistical distributions (e.g., percentiles of reference distributions) to expert descriptions of changes in biological condition along disturbance gradients. As a result, the BCG may be more meaningful to managers and the public than indices alone. To develop a BCG model, biological response to stress is divided into 6 levels of condition, represented as changes in biological structure (abundance and diversity of pollution sensitive versus tolerant taxa) and function. We developed benthic macroinvertebrate (BMI) and algal BCG models for California perennial wadeable streams to support interpretation of percentiles of reference-based thresholds for bioassessment indices (i.e., the California Stream Condition Index [CSCI] for BMI and the Algal Stream Condition Index [ASCI] for diatoms and soft-bodied algae). Two panels (one of BMI ecologists and the other of algal ecologists) each calibrated a general BCG model to California wadeable streams by first assigning taxa to specific tolerance and sensitivity attributes, and then independently assigning test samples (264 BMI and 248 algae samples) to BCG Levels 1–6. Consensus on the assignments was developed within each assemblage panel using a modified Delphi method. Panels then developed detailed narratives of changes in BMI and algal taxa that correspond to the 6 BCG levels. Consensus among experts was high, with 81% and 82% expert agreement within 0.5 units of assigned BCG level for BMIs and algae, respectively. According to both BCG models, the 10th percentiles index scores at reference sites corresponded to a BCG Level 3, suggesting that this type of threshold would protect against moderate changes in structure and function while allowing loss of some sensitive taxa. The BCG provides a framework to interpret changes in aquatic biological condition along a gradient of stress. The resulting relationship between index scores and BCG levels and narratives can help decision-makers select thresholds and communicate how these values protect aquatic life use goals.

California↗

USGS2017

Ecological impacts of winter water level drawdowns on lake littoral zones: A review

Freshwater littoral zones harbor diverse ecological communities and serve numerous ecosystem functions that are controlled, in part, by natural water level fluctuations. However, human alteration of lake hydrologic regimes beyond natural fluctuations threaten littoral zone ecological integrity. One type of hydrologic alteration in lakes is winter water level drawdowns, which are frequently employed for hydropower, flood control, and macrophyte control, among other purposes. Here, we synthesize the abiotic and biotic responses to annual and novel winter water level drawdowns in littoral zones of lakes and reservoirs. The dewatering, freezing, and increased erosion of exposed lakebeds drive changes in the littoral zone. Shoreline-specific physicochemical conditions such as littoral slope and shoreline exposure further induce modifications. Loss of fine sediment decreases nutrient availability over time, but desiccation may promote a temporary nutrient pulse upon re-inundation. Annual winter drawdowns can decrease taxonomic richness of macrophytes and benthic invertebrates and shift assemblage composition to favor taxa with r-selected life history strategies and with functional traits resistant to direct and indirect drawdown effects. Fish assemblages, though less directly affected by winter drawdowns (except where there is critically low dissolved oxygen), experience negative effects via indirect pathways like decreased food resources and spawning habitat. We identify eight general research gaps to guide future research that could improve our understanding about the complex effects of winter drawdowns on littoral zone ecology.

Aquatic Sciences↗

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

Predicting wildfire impacts on the prehistoric archaeological record of the Jemez Mountains, New Mexico, USA

Wildfires of uncharacteristic severity, a consequence of climate changes and accumulated fuels, can cause amplified or novel impacts to archaeological resources. The archaeological record includes physical features associated with human activity; these exist within ecological landscapes and provide a unique long-term perspective on human–environment interactions. The potential for fire-caused damage to archaeological materials is of major concern because these resources are irreplaceable and non-renewable, have social or religious significance for living peoples, and are protected by an extensive body of legislation. Although previous studies have modeled ecological burn severity as a function of environmental setting and climate, the fidelity of these variables as predictors of archaeological fire effects has not been evaluated. This study, focused on prehistoric archaeological sites in a fire-prone and archaeologically rich landscape in the Jemez Mountains of New Mexico, USA, identified the environmental and climate variables that best predict observed fire severity and fire effects to archaeological features and artifacts.

New Mexico↗

USGS2020

Research is needed to inform environmental management of hydrothermally inactive and extinct polymetallic sulfide (PMS) deposits

Polymetallic sulfide (PMS) deposits produced at hydrothermal vents in the deep sea are of potential interest to miners. Hydrothermally active sulfide ecosystems are valued for the extraordinary chemosynthetic communities that they support. Many countries, including Canada, Portugal, and the United States, protect vent ecosystems in their Exclusive Economic Zones. When hydrothermal activity ceases temporarily (dormancy) or permanently (extinction), the habitat and associated ecosystem change dramatically. Until recently, so-called “inactive sulfide” habitats, either dormant or extinct, received little attention from biologists. However, the need for environmental management of deep-sea mining places new imperatives for building scientific understanding of the structure and function of inactive PMS deposits. This paper calls for actions of the scientific community and the emergent seabed mining industry to i) undertake fundamental ecological descriptions and study of ecosystem functions and services associated with hydrothermally inactive PMS deposits, ii) evaluate potential environmental risks to ecosystems of inactive PMS deposits through research, and iii) identify environmental management needs that may enable mining of inactive PMS deposits. Mining of some extinct PMS deposits may have reduced environmental risk compared to other seabed mining activities, but this must be validated through scientific research on a case-by-case basis.

Marine Policy↗

USGS2017

Impacts of coastal land use and shoreline armoring on estuarine ecosystems: An introduction to a special issue

The nearshore land-water interface is an important ecological zone that faces anthropogenic pressure from development in coastal regions throughout the world. Coastal waters and estuaries like Chesapeake Bay receive and process land discharges loaded with anthropogenic nutrients and other pollutants that cause eutrophication, hypoxia, and other damage to shallow-water ecosystems. In addition, shorelines are increasingly armored with bulkhead (seawall), riprap, and other structures to protect human infrastructure against the threats of sea-level rise, storm surge, and erosion. Armoring can further influence estuarine and nearshore marine ecosystem functions by degrading water quality, spreading invasive species, and destroying ecologically valuable habitat. These detrimental effects on ecosystem function have ramifications for ecologically and economically important flora and fauna. This special issue of Estuaries and Coasts explores the interacting effects of coastal land use and shoreline armoring on estuarine and coastal marine ecosystems. The majority of papers focus on the Chesapeake Bay region, USA, where 50 major tributaries and an extensive watershed (~ 167,000 km 2 ), provide an ideal model to examine the impacts of human activities at scales ranging from the local shoreline to the entire watershed. The papers consider the influence of watershed land use and natural versus armored shorelines on ecosystem properties and processes as well as on key natural resources.

Estuaries and Coasts↗

USGS2000

What is “natural”? : Yellowstone elk population - A case study

Ecology analyzes the structure and function of ecosystems at all points along the continuum of human disturbance, from so-called pristine forests to urban backyards. Undisturbed systems provide reference points at one end of the spectrum, and nature reserves and parks are highly valued because they can provide unique examples of such ecosystems. Unfortunately the concept of “natural” or pristine is not that easy to define. Indeed, although ecologists have considered pre-Columbian, western-hemisphere ecosystems to have been largely unaltered by human action, and have termed their state “natural” or “pristine,” evidence from archaeology challenges this view. U.S. and Canadian national parks are charged with preserving the “natural,” and thus need to be able to understand and manage for the “natural.” A pivotal “natural” question in Yellowstone National Park management is the size of the northern-range, wintering elk population at Park establishment in 1872, argued both to have been small and large. Integrating and quantifying several sources of evidence provides a consistent picture of a low population (ca. 5,000–6,000), largely migrating out of the northern range in winter, with little vegetation impact. If we accept this conclusion about what is natural for the Yellowstone ecosystem, then it dramatically alters how we view management alternatives for the Park, which currently supports a northern wintering herd of up to ˜ 25,000 elk.

Wyoming↗

USGS2017

Advancing mangrove macroecology

Mangrove forests provide a wide range of ecosystem services to society, yet they are among the most anthropogenically impacted coastal ecosystems in the world. In this chapter, we discuss and provide examples for how macroecology can advance our understanding of mangrove ecosystems. Macroecology is broadly defined as a discipline that uses statistical analyses to investigate large-scale, universal patterns in the distribution, abundance, diversity, and organization of species and ecosystems, including the scaling of ecological processes and structural and functional relationships. Macroecological methods can be used to advance our understanding of how non-linear responses in natural systems can be triggered by human impacts at local, regional, and global scales. Although macroecology has the potential to gain knowledge on universal patterns and processes that govern mangrove ecosystems, the application of macroecological methods to mangroves has historically been limited by constraints in data quality and availability. Here we provide examples that include evaluations of the variation in mangrove forest ecosystem structure and function in relation to macroclimatic drivers (e.g., temperature and rainfall regimes) and climate change. Additional examples include work focused upon the continental distribution of aboveground net primary productivity and carbon storage, which are rapidly advancing research areas. These examples demonstrate the value of a macroecological perspective for the understanding of global- and regional-scale effects of both changing environmental conditions and management actions on ecosystem structure, function, and the supply of goods and services. We also present current trends in mangrove modeling approaches and their potential utility to test hypotheses about mangrove structural and functional properties. Given the gap in relevant experimental work at the regional scale, we also discuss the potential use of mangrove restoration and rehabilitation projects as macroecological studies that advance the critical selection and conservation of ecosystem services when managing mangrove resources. Future work to further incorporate macroecology into mangrove research will require a concerted effort by research groups and institutions to launch research initiatives and synthesize data collected across broad biogeographic regions.

Book chapter↗

USGS2023

Assessing community assembly controls over community-scale nutrient resorption responses to nitrogen deposition

Nutrient resorption is a fundamental physiological process in plants, with important ecological controls over numerous ecosystem functions. However, the role of community assembly in driving responses of nutrient resorption to perturbation remains largely unknown. Following the Price equation framework and the Community Assembly and Ecosystem Function framework, we quantified the contribution of species loss, species gain, and shared species to the reduction of community-level nutrient resorption efficiency in response to multi-level nitrogen (N) addition in a temperate steppe, after continuous N addition for seven years. Reductions of both N and phosphorus (P) resorption efficiency (NRE and PRE, respectively) were positively correlated with N addition levels. The dissimilarities in species composition between N-enriched and control communities increased with N addition levels, and N-enriched plots showed substantial species losses and gains. Interestingly, the reduction of community-scale NRE and PRE mostly resulted from N-induced decreases in resorption efficiency for the shared species in the control and N-enriched communities. There were negative correlations between the contributions of species richness effect and species identity effect and between the number and identity of species gained for the changes in both NRE and PRE following N enrichment. By simultaneously considering N-induced changes in species composition and in species-level resorption, our work presents a more complete picture of how different community assembly processes contribute to N-induced changes in community-level resorption.

Oecologia↗

USGS2015

Geographically isolated wetlands: Rethinking a misnomer

We explore the category “geographically isolated wetlands” (GIWs; i.e., wetlands completely surrounded by uplands at the local scale) as used in the wetland sciences. As currently used, the GIW category (1) hampers scientific efforts by obscuring important hydrological and ecological differences among multiple wetland functional types, (2) aggregates wetlands in a manner not reflective of regulatory and management information needs, (3) implies wetlands so described are in some way “isolated,” an often incorrect implication, (4) is inconsistent with more broadly used and accepted concepts of “geographic isolation,” and (5) has injected unnecessary confusion into scientific investigations and discussions. Instead, we suggest other wetland classification systems offer more informative alternatives. For example, hydrogeomorphic (HGM) classes based on well-established scientific definitions account for wetland functional diversity thereby facilitating explorations into questions of connectivity without an a priori designation of “isolation.” Additionally, an HGM-type approach could be used in combination with terms reflective of current regulatory or policymaking needs. For those rare cases in which the condition of being surrounded by uplands is the relevant distinguishing characteristic, use of terminology that does not unnecessarily imply isolation (e.g., “upland embedded wetlands”) would help alleviate much confusion caused by the “geographically isolated wetlands” misnomer.

Wetlands↗

USGS2011

Accounting for the ecosystem services of migratory species: Quantifying migration support and spatial subsidies

Migratory species support ecosystem process and function in multiple areas, establishing ecological linkages between their different habitats. As they travel, migratory species also provide ecosystem services to people in many different locations. Previous research suggests there may be spatial mismatches between locations where humans use services and the ecosystems that produce them. This occurs with migratory species, between the areas that most support the species' population viability – and hence their long-term ability to provide services – and the locations where species provide the most ecosystem services. This paper presents a conceptual framework for estimating how much a particular location supports the provision of ecosystem services in other locations, and for estimating the extent to which local benefits are dependent upon other locations. We also describe a method for estimating the net payment, or subsidy, owed by or to a location that balances benefits received and support provided by locations throughout the migratory range of multiple species. The ability to quantify these spatial subsidies could provide a foundation for the establishment of markets that incentivize cross-jurisdictional cooperative management of migratory species. It could also provide a mechanism for resolving conflicts over the sustainable and equitable allocation of exploited migratory species.

Ecological Economics↗

USGS2012

Physical modeling of river spanning rock structures: Evaluating interstitial flow, local hydraulics, downstream scour development, and structure stability

Rock weir and ramp structures uniquely serve a necessary role in river management: to meet water deliveries in an ecologically sound manner. Uses include functioning as low head diversion dams, permitting fish passage, creating habitat diversity, and stabilizing stream banks and profiles. Existing information on design and performance of in-stream rock structures does not provide the guidance necessary to implement repeatable and sustainable construction and retrofit techniques. As widespread use of rock structures increases, the need for reliable design methods with a broad range of applicability at individual sites grows as well. Rigorous laboratory testing programs were implemented at the U.S. Bureau of Reclamation (Reclamation) and at Colorado State University (CSU) as part of a multifaceted research project focused on expanding the current knowledge base and developing design methods to improve the success rate of river spanning rock structures in meeting project goals. Physical modeling at Reclamation is being used to measure, predict, and reduce interstitial flow through rock ramps. CSU is using physical testing to quantify and predict scour development downstream of rock weirs and its impact on the stability of rock structures. ?? 2009 ASCE.

Conference Paper↗