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USGS2019

Report on the workshop 'Global modelling of biodiversity and ecosystem services'

A three-day workshop on ‘Global Modelling of Biodiversity and Ecosystem Services’, was held in the Hague, Netherlands, from 24th to 26th June 2019. The workshop, attended by 35 modelling and scenario-building experts, was organised on behalf of the former IPBES1 expert group on scenarios and models of the first IPBES work programme by its interim technical support unit, and hosted by the PBL Netherlands Environmental Assessment Agency. The workshop drew on the ‘nature futures’ participatory scenario-building exercise initiated by the IPBES expert group on scenarios and models, and other biodiversity modelling initiatives such as the ISIMIP project2 working on adding biodiversity to the Shared Socioeconomic Pathways (SSPs) scenarios framework, the 'bending the curve' initiative3 led by IIASA4 and WWF5, and GEOBON6 working on modelling Essential Biodiversity Variables. The workshop was a step towards coordinating across biodiversity modelling initiatives, to build on each other’s work, and to seek synergies for the production of innovative scenarios on biodiversity and ecosystem services to inform the post-2020 agenda of the Convention on Biological Diversity, as well as the Sustainable Development Goals. The aims of the workshop were to: 1. Compile material as input for a first draft of the fifth Global Biodiversity Outlook (GBO-5) based on recent scenario work, including the ‘bending the curve’ scenarios and the newly developed PBL scenarios (modified from the Rio+20 scenarios), and existing models (to be completed by August 2019) 2. Develop a protocol for modelling trends and near term projections on indicators relevant to the Nature Futures Framework7 using models that are readily available (to be completed by early 2020) 3. Set the agenda and define the aims for a larger meeting at the end of 2019 to discuss the long term strategy towards the development of appropriate indicators and models to produce Nature Futures scenarios (to continue beyond Jan 2020)

Report↗

USGS1993

Proceedings of the symposium on restoration planning for the rivers of Mississippi River ecosystem

This volume presents over 25 papers containing the proceedings of a symposium held at the 122nd annual meeting of the American Fisheries Society in September 1992. The symposium was organised to review the status of fish and wildlife resources and restoration planning for the Mississippi river ecosystem. The objectives of the symposia were as follows: to present existing information of the biota and values associated with riverine resources throughout the basin; to identify existing or planned actions that might be useful for fisheries management in rivers within the basin and to identify minimal requirements for the restoration of important fish stocks, other aquatic resources and entire ecosystems. Papers included in this issue cover the following topics: thee impacts of altered hydrologic sediment and organic matter cycles; the availability of woody debris in the river cross-section, loss of floodplain and side-arm connection, and changing water quality.

Mississippi River Basin↗

USGS2021

A reassessment of Chao2 estimates for population monitoring of grizzly bears in the Greater Yellowstone Ecosystem

The Yellowstone Ecosystem Subcommittee (YES) asked the Interagency Grizzly Bear Study Team (IGBST) to re-assess a technique used in annual population estimation and trend monitoring of grizzly bears in the Greater Yellowstone Ecosystem (GYE). This technique is referred to as the Chao2 approach and estimates the number of females with cubs-of-the-year (hereafter, females with cubs) and, in association with other demographic data, is used by the IGBST to produce annual population estimates. Females with cubs are an easily recognizable population segment, and trends for this reproductive segment of the population are assumed to be representative of trend for the entire population. The overarching objective of the analyses presented in this report was to provide a more accurate representation of the GYE grizzly bear population using the current methodologies in place. Specifically, we addressed two limitations of the current Chao2 approach: 1) underestimation bias associated with a distance criterion used to differentiate annual sightings of females with cubs into unique individuals and 2) limitations of the model-averaging approach to effectively distinguish among potential future population trajectories (decline, stability, and growth). The first issue addressed in this report is the underestimation bias associated with the rule set that Knight et al. (1995) developed to differentiate sightings of females with cubs into unique individuals (i.e., unique family groups). The rule set was originally designed to be conservative by reducing the risk of identifying more females with cubs than actually existed, primarily through use of a distance criterion of 30 km to separate sightings of unique females. This approach resulted in an underestimation bias, and previous research demonstrated that this bias increases with increasing number of females with cubs. Using location data from radio-marked females with cubs, we evaluated alternative distance criteria by simulating scenarios with varying numbers of true females with cubs and sightings. Findings from these analyses demonstrate that bias in estimates of females with cubs can be substantially reduced by changing the 30-km distance criterion in the rule set to 16 km, which produced relatively unbiased estimates. Findings also indicate, however, the importance of adaptability with regard to the distance criteria because of the complex relationships and biases among the various parameters involved in estimation of unique females with cubs. The total number of annual sightings and the true number of females with cubs play particularly important roles. Whereas these analyses remind us that there is no perfect approach to estimating the number of females with cubs from sightings under various scenarios, they provide us with new tools to determine when and how to adapt the monitoring program. The second issue we were tasked to investigate was the potential for improvement of the technique referred to as model-averaging, which serves to smooth relatively high variation in annual estimates. This technique was chosen by YES as the basis for monitoring the Yellowstone grizzly bear population, as described in the 2016 Conservation Strategy. This choice was made in part because the technique has been well documented and population estimates derived from counts of females with cubs are conservative. Using simulations of population trends, we demonstrate why the model-averaging technique currently used cannot distinguish between plausible future trend scenarios. As a suitable alternative to model averaging, we propose the use of generalized additive models (GAMs). Using a suite of simulated trend dynamics relevant to management, we demonstrate GAM performance for tracking trends in females with cubs within the context of the annual monitoring program. We demonstrate the ability to not only document directional changes in population trend but also patterns of stabilization or resiliency after such changes. Furthermore, the proposed monitoring framework provides objective measures useful for early detection of directional changes in trend. The new framework is flexible, allowing retrospective analysis of Chao2-based estimates and future applications to time series of other population metrics, such as vital rates. The aforementioned updates provide us with new tools to determine when and how to adapt the monitoring program. Within the context of current monitoring protocols and effort, and considering the full suite of simulations presented in this report and previous studies, the IGBST plans to incorporate the following changes to the population monitoring protocol: 1) modify the distance criterion, starting with 16 km under current sampling conditions and 2) revise the population monitoring framework using GAMs as the basis for smoothing of annual estimates and detecting trends and changes in trend. Implementation of the 16-km distance criterion combined with use of GAM techniques would affect some of the population metrics (e.g., annual population size and uncertainty, population trend, mortality rates) used to inform management responses. A primary consideration is that the 16-km distance criterion results in total population estimates derived from the Chao2 estimates that are greater than those we have reported in the past. This increase is due to a change in the implementation of the technique and more accurately represents the number of females with cubs in the GYE grizzly bear population. Additionally, interpretation of retrospective trend patterns may change due to the combination of a different distance criterion and enhanced trend monitoring based on the GAM approach we present here. Implementation will require relatively minor changes in the monitoring protocols described in Appendices B and C of the 2016 Conservation Strategy. Finally, we note that the IGBST has ongoing investigations into the merits of an Integrated Population Model (IPM), for which annual Chao2-based estimates are important input data. The IGBST plans to continue those investigations using the 16-km distance criterion to derive Chao2 estimates.

Idaho, Montana, Wyoming↗

USGS2023

Nearshore ecosystems in the Gulf of Alaska

Nearshore ecosystem monitoring in western Prince William Sound, Kenai Fjords National Park, Kachemak Bay, and Katmai National Park and Preserve has been conducted as a single Nearshore Component of the Gulf Watch Alaska program over the past five years (2017-2021). This program builds on the previous five years and continues, in many cases, decades of preceding research and monitoring. During the 2017-2021 period of Gulf Watch Alaska, we successfully collected data on more than 200 nearshore metrics across all regions. These metrics were explicitly selected because of their value as trophically-connected features that offer insights into causes of changes through bottom-up and top-down forces within the nearshore food web. During these past 5 years, this study design has been applied to documenting and understanding several perturbations, including the Pacific Marine Heatwave and loss of sea stars due to sea star wasting. Continued monitoring will allow for a better understanding of change in nearshore ecosystems across the Gulf of Alaska and the status of spill injured resources, including greater perspective on oil spill effects and recovery relative to other types of perturbations. This information will be critical for anticipating and responding to ongoing and future changes in the region, as well as providing data for understanding global-scale variation in marine environments.

Alaska↗

USGS2020

Changing nitrogen inputs to the northern San Francisco Estuary: Potential ecosystem responses and opportunities for investigation

Anthropogenic activities have resulted in elevated ambient nitrogen (N) and phosphorus (P) concentrations in many regions of the Sacramento-San Joaquin Delta and Suisun Bay (northern San Francisco Estuary, (nSFE). The Sacramento Regional wastewater treatment plant (SRWTP WWTP) currently acts as the largest N point source to the system, discharging 13,000-15,000 kg/d of ammonium-N (NH4) near the nSFE’s northeastern boundary. By end of 2021, SRWTP will complete major upgrades that will reduce its effluent dissolved inorganic nitrogen (DIN) loads by >65% and release the remaining DIN as predominantly nitrate (NO3). This major change in nitrogen inputs provides a unique opportunity to study ecosystem-scale responses to an altered nutrient regime. While, in general, the nSFE has not experienced some classic symptoms of nutrient over-enrichment typical in other estuaries—e.g., large phytoplankton blooms and hypoxia—other concerning nutrient- related impacts have been hypothesized, including: occurrence of harmful algal blooms (HABs) and the production of cyanotoxins; excessive growth of invasive aquatic vegetation; and declines in the abundance and nutritional quality of phytoplankton. These impacts have repercussions for the system’s food web, habitat quality, and the way we manage for transportation, recreation, water conveyance, and drinking water quality. This report develops and applies a framework for i) identifying and examining ecosystem response scenarios to the forthcoming decreased N loads; and ii) identifying opportunities, and constraints or considerations, for investigating those responses, including key data needs or knowledge gaps. Through applying this framework, we identify a set of plausible response scenarios, and evaluate the feasibility of studying or observing those responses along with key study considerations and data and knowledge gaps.

California↗

USGS2024

Innovation in climate adaptation: Harnessing innovation for effective biodiversity and ecosystem adaptation

Climate change poses growing risks to species, ecosystems, and people, and is challenging many of the assumptions that underpin modern conservation practice. As climate impacts accelerate, conventional conservation approaches are being compromised and losing their effectiveness. As a result, there is an urgent need to not only center climate adaptation in conservation policy and practice, but for adaptation responses to be bolder and more innovative. Innovation in Climate Adaptation is designed to address this need by promoting creativity and innovation in the practice of climate adaptation for biodiversity and ecosystem conservation. The guide is not about promoting innovation for the sake of innovation; rather, it is intended to help policymakers, researchers, and resource managers harness the power of innovation to achieve more effective adaptation outcomes.

Report↗

USGS2024

Evaluating an improved systems approach to wetland crediting: Consideration of wetland ecosystem services

The Chesapeake Bay Agreement (CBA) has numerous direct goals for improving habitat, living resources, and water quality, conserving lands, engaging communities and addressing a changing climate. To date, the progress toward the wetlands outcome (creation/ restoration of 85,000 acres and enhancement of 150,000 acres) has been very slow and the outcome is projected to be off course for 2025. Two specific confounding issues arise in efforts to achieve the Bay wetlands goal: 1) the idea that restoration is driven, and incentivized and accounted for, in order to meet the TMDL’s water quality (WQ) benefits, leaving habitat benefits undervalued; and 2) there is often tension between competing restoration priorities and financial resources among different Best Management Practice (BMP) types that include wetlands, such as wetland restoration/creation/rehabilitation, stream restoration, and the creation or restoration of forest buffers. The collaborative workshop “ Evaluating an Improved Systems Approach to Wetland Crediting: Consideration of Wetland Ecosystem Services ” was held March 22-23, 2022 to explore the wetland accounting system and provide insight on improved approaches to promote wetland projects toward the wetlands outcome. Four sessions were organized around topics of 1) Accounting, 2) Landscape Systems Approach, 3) Wetlands Projects and Co-Benefits, and 4) Management Implications and Recommendation Development with 21 presentations, Q and A and facilitated discussions. Acknowledgement of the limitations of the current management framework to achieve significant gains in wetland area supports the conclusion that absent significant adaptive management of wetlands efforts, any outcome for net wetlands gains beyond 2025 will be similarly confounded. Workshop findings included suggestions for how to approach restoration projects at a systems level (e.g., creek, shoreline reach, watershed) in order to maximize synergies for multiple ecological outcomes and ecosystem services. Recommendations for improvement on existing efforts, as well as new processes, tools and partnerships are suggested from the workshop’s analysis of the state of the science as considerations to increase implementation of wetlands projects.

Chesapeake Bay watershed↗

USGS2006

State-parameter estimation of ecosystem models using a smoothed ensemble Kalman filter

Much of the effort in data assimilation methods for carbon dynamics analysis has focused on estimating optimal values for either model parameters or state variables. The main weakness of estimating parameter values alone (i.e., without considering state variables) is that all errors from input, output, and model structure are attributed to model parameter uncertainties. On the other hand, the accuracy of estimating state variables may be reduced if the temporal evolution of parameter values is not incorporated. This research develops a smoothed ensemble Kalman filter (SEnKF) to estimate simultaneously the system states and model parameters of an eddy flux partition model. The approach is used to assimilate observed fluxes of carbon and major driving forces at an AmeriFlux forest station: Howland, Maine, USA. The aim of applying a kernel-smoothing algorithm to an ensemble Kalman filter is to overcome the dramatic, sudden change of parameter values in time and the loss of continuity between two consecutive points in time. Our analysis demonstrates that model parameters, such as light use efficiency, respiration coefficients, minimum and optimum temperatures for photosynthetic activity, and so on, are highly constrained by eddy flux data at daily-to-seasonal time scales. The SEnKF stabilizes parameter values quickly regardless of the initial values of the parameters. Potential ecosystem light use efficiency demonstrates a strong seasonality. Results show that the simultaneous parameter estimation procedure significantly improves model predictions. Results also show that the SEnKF can dramatically reduce variance in state variables stemming from the uncertainty of parameters and driving variables. The SEnKF is a robust and effective algorithm in evaluating and developing ecosystem models and in improving understanding and quantification of carbon cycle parameters and processes.

Conference Paper↗

USGS2025

Photographic guide to the leaf litter arthropod community of the lowland wet forest ecosystem of the Island of Hawaiʻi

Leaf litter arthropods are important components of the food web in forests, and their presence and diversity can provide information on forest health. There has been very little documentation of the leaf litter arthropods in Hawaiian forest ecosystems. This technical report is a photographic guide to some common arthropods collected from forest leaf litter at the Liko Nā Pilina Hybrid Ecosystems Project study site, a lowland wet forest in Hilo, Island of Hawaiʻi, USA. Leaf litter samples were collected from plots of invaded and experimental restoration communities using two complementary methods (litterbags and quadrats), and arthropods were extracted using Berlese funnels. The field site contained many morphospecies that were rare and locally distributed across plots, and only a few that were very common and widely distributed. The majority of the morphospecies identified were mites. This photoguide is designed to help identify arthropods found in plant litter in Hawaiian lowland forests and it may assist with research and education efforts concerned with the diversity, ecology, or conservation of litter arthropods across the Hawaiian archipelago and other Pacific islands.

Hawaii↗

USGS2025

Effects of climate change on midwestern ecosystems: North American bog and fen

The North American Bog and Fen ecosystem may be increasingly vulnerable to climate stressors, particularly water deficits and warming temperatures. These peat-forming wetlands, found at the southern extent of their range in the Midwest, depend on relatively stable hydrological and thermal conditions. Climate change may disrupt these conditions through projected declines in summer precipitation, increases in summer vapor pressure deficit and temperature, and longer periods of warmth throughout the year. These changes could lower water tables, accelerate aerobic decomposition, and alter peat-accumulating processes that define bogs and fens. Water deficits, compounded by warmer conditions, may reduce moss and sedge productivity and promote peat subsidence and compaction. Collectively, these impacts may compromise the structural integrity of this ecosystem and reduce its capacity to store carbon, maintain unique microhabitats, and support moisture-dependent species.

Illinois, Indiana, Iowa, Michigan, Minnesota, Miss↗

USGS2025

Effects of climate change on midwestern ecosystems: Eastern North American temperate freshwater marsh, wet meadow and shrubland

The Eastern North American Temperate Freshwater Marsh, Wet Meadow and Shrubland is a hydrologically dynamic ecosystem highly sensitive to shifts in water availability. Across the Midwest, climate change is expected to intensify two primary stressors, flooding and drought, resulting in increased hydrologic variability that may threaten the persistence of these wetlands. Increased spring precipitation and more frequent extreme rainfall events are projected to cause deeper, longer-lasting inundation, while rising temperatures, reduced snowpack, and heightened evaporative demand are likely to increase the frequency and severity of droughts. Changes in hydrology may significantly alter both habitat structure and community composition. Physical disturbance from scouring and erosion may intensify, while nutrient and sediment loading from surrounding land uses may lead to eutrophication and terrestrialization. Vegetation zonation is likely to become destabilized under more extreme hydrological conditions, with flood-tolerant or droughtadapted species replacing those with narrower hydrologic tolerances. The two habitat groups within this broader ecosystem show differing vulnerabilities. The Eastern North American Freshwater Marsh, including both Great Lakes coastal and inland systems, is considered among the most hydrologically dynamic and disturbance-prone wetland types. Vegetation in these marshes is typically stratified along water depth gradients, forming distinct zones that depend on variable hydrology to persist, but deep or prolonged inundation can disrupt this zonation and reduce plant diversity. In contrast, the Midwest Wet Prairie, Wet Meadow and Shrub Swamp, generally lacks persistent surface water and relies on precipitation and snowmelt to maintain seasonal saturation. As a result, this habitat group is especially prone to drying and potentially susceptible to woody encroachment and shifts toward drier-adapted plant communities. Across both habitat groups, invasive species are expected to gain a competitive edge under future climate conditions. Invasive wetland plants often exhibit high plasticity and can tolerate a wide range of disturbances and hydrologic conditions, allowing them to expand rapidly during both flood and drought periods. Interacting pressures underscore the growing vulnerability of the Eastern North American Temperate Freshwater Marsh, Wet Meadow and Shrubland under future climate scenarios.

Illinois, Indiana, Iowa, Michigan, Minnesota, Miss↗

USGS1997

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

About 100 species of mammals are endemic to the southeastern United States, an area of diverse habitat types and high biodiversity. Many of these species are either formally considered aquatic or semi-aquatic, or they are otherwise closely associated with aquatic ecosystems. In the southeastern United States, greater than 80 percent of mammalian species are listed in some category of concern throughout all or at least a portion of their ranges (i.e., endangered, threatened, under review for possible listing as endangered or threatened, species of special concern, species deemed in need of management, etc.). Almost all of these species are imperiled because their populations have declined to dangerously low levels due to habitat loss, habitat degradation, or other human-related factors. Most imperiled mammal taxa can be categorized as belonging to one of two general groups: habitat generalists or habitat specialists. Typically, habitat generalists have become imperiled mainly due to human exploitation, while habitat specialists have suffered primarily from habitat loss or habitat degradation. The passage of the U.S. Endangered Species Act of 1973 resulted in an increased need for information concerning distribution and status of all native species. However, relatively little is known concerning the historical distribution and current status of many mammalian taxa, and this is particularly so for small non-game species. In this chapter we provide species accounts of mammals commonly associated with aquatic ecosystems that we consider to be imperiled in the southeastern United States. In these accounts we have included information which we feel is valuable toward best understanding the threats that challenge each considered taxon.

Book chapter↗

USGS1997

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

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

Book chapter↗

USGS2023

Forage fish species prefer habitat within designated offshore wind energy areas on the US Northeast Shelf ecosystem

As the world develops sources of renewable energy, there is an intensifying interest in offshore wind energy production. The Northeast U.S. Continental Shelf (NES) ecosystem has favorable wind dynamics, with active development of wind energy. In this study, we present species distribution models that consider both occupancy and biomass responses for a broad spectrum of fish and macroinvertebrate taxa ( n = 177). Building upon prior analyses, habitat was differentiated into overall and core habitats based on statistical distributions of habitat scores. Overall habitat was used to show each species' regional distribution based on fishery-independent survey captures between 1976 and 2019, whereas core habitat represented where the focus of the species' abundance was located as a subset of overall habitat. Wind energy developments may modify the water column in ways that impact lower-trophic-level productivity; therefore, added attention was given to the response of forage species. Over 20% of species showed preferential use of putative and potential wind development areas, including a disproportionate number of forage taxa. Principal usage varied by season, with forage species like Atlantic Menhaden Brevoortia tyrannus and Atlantic Mackerel Scomber scombrus preferentially using the lease areas in spring and Round Herring Etrumeus teres and longfin inshore squid Doryteuthis pealeii using lease areas in autumn. For species with relatively low usage of the lease areas, there was a tendency for the usage related to overall habitat to be lower than usage for core habitat; in contrast, for species with high usage of the lease areas, that usage was higher for overall habitat than for core habitat. The area of habitat tended to have positive trends across species, with these positive trends being disproportionately higher among forage taxa. These results frame the importance of wind lease areas for species in the NES, particularly forage taxa that fulfill many important ecological functions.

Marine and Coastal Fisheries: Dynamics, Management↗

USGS1995

Top-level carnivores and ecosystem effects: Questions and approaches

Top-level carnivores comprise a diverse array of taxa and occur in most natural ecosystems. This chapter considers three main questions: What are the ecological and evolutionary effects of top-level carnivores, how general are they, and under what conditions do they occur? To answer these questions one first must determine whether a food web is under top-down control, and ultimately, the species, systems, and circumstances for which top-down control exists. For systems affected by top-down forces, the cascading effect of carnivory on autotrophs is expected to vary with the order of trophic complexity. Given this conceptual framework, three more specific questions are explored. First, how general are the direct and indirect effects of top-level carnivores? Second, what is the breadth of trophic influence from the direct impact of carnivory? Broadly ranging effects are expected for systems in which (1) top-level carnivores occupy odd-numbered trophic levels and (2) the food web is strongly linked. (3) what are the evolutionary consequences of trophic cascades on species lower in the food web? These questions can best be answered via manipulative or natural experiments in which the presence or absence of carnivores varies in space or time. Natural experiments are advocated as the only practical means of addressing these questions for many species and systems, in particular those in which the key players are large and highly mobile, or those in which the manipulation of predators has legal, political, or social ramifications.

Linking Species and Ecosystems↗

USGS2008

Fine root dynamics and forest production across a calcium gradient in northern hardwood and conifer ecosystems

Losses of soil base cations due to acid rain have been implicated in declines of red spruce and sugar maple in the northeastern USA. We studied fine root and aboveground biomass and production in five northern hardwood and three conifer stands differing in soil Ca status at Sleepers River, VT; Hubbard Brook, NH; and Cone Pond, NH. Neither aboveground biomass and production nor belowground biomass were related to soil Ca or Ca:Al ratios across this gradient. Hardwood stands had 37% higher aboveground biomass (P = 0.03) and 44% higher leaf litter production (P < 0.01) than the conifer stands, on average. Fine root biomass (<2 mm in diameter) in the upper 35 cm of the soil, including the forest floor, was very similar in hardwoods and conifers (5.92 and 5.93 Mg ha-1). The turnover coefficient (TC) of fine roots smaller than 1 mm ranged from 0.62 to 1.86 y-1 and increased significantly with soil exchangeable Ca (P = 0.03). As a result, calculated fine root production was clearly higher in sites with higher soil Ca (P = 0.02). Fine root production (biomass times turnover) ranged from 1.2 to 3.7 Mg ha-1 y-1 for hardwood stands and from 0.9 to 2.3 Mg ha-1 y -1 for conifer stands. The relationship we observed between soil Ca availability and root production suggests that cation depletion might lead to reduced carbon allocation to roots in these ecosystems. ?? 2008 Springer Science+Business Media, LLC.

Ecosystems↗

USGS2011

Twenty Years After the 1988 Yellowstone Fires: Lessons About Disturbance and Ecosystems

The 1988 Yellowstone fires were among the first in what has proven to be an upsurge in large severe fires in the western USA during the past 20 years. At the time of the fires, little was known about the impacts of such a large severe disturbance because scientists had had few previous opportunities to study such an event. Ecologists predicted short- and long-term effects of the 1988 fires on vegetation, biogeochemistry, primary productivity, wildlife, and aquatic ecosystems based on scientific understanding of the time. Twenty-plus years of subsequent study allow these early predictions to be evaluated. Most of the original predictions were at least partially supported, but some predictions were refuted, others nuanced, and a few postfire phenomena were entirely unexpected. Post-1988 Yellowstone studies catalyzed advances in ecology focused on the importance of spatial and temporal heterogeneity, contingent influences, and multiple interacting drivers. Post-1988 research in Yellowstone also has changed public perceptions of fire as an ecological process and attitudes towards fire management. Looking ahead to projected climate change and more frequent large fires, the well-documented ecological responses to the 1988 Yellowstone fires provide a foundation for detecting and evaluating potential changes in fire regimes of temperate mountainous regions. ?? 2011 Springer Science+Business Media, LLC.

Ecosystems↗

USGS2015

Prediction of plant vulnerability to salinity increase in a coastal ecosystem by stable isotopic composition (δ 18 O) of plant stem water: a model study

Sea level rise and the subsequent intrusion of saline seawater can result in an increase in soil salinity, and potentially cause coastal salinity-intolerant vegetation (for example, hardwood hammocks or pines) to be replaced by salinity-tolerant vegetation (for example, mangroves or salt marshes). Although the vegetation shifts can be easily monitored by satellite imagery, it is hard to predict a particular area or even a particular tree that is vulnerable to such a shift. To find an appropriate indicator for the potential vegetation shift, we incorporated stable isotope 18 O abundance as a tracer in various hydrologic components (for example, vadose zone, water table) in a previously published model describing ecosystem shifts between hammock and mangrove communities in southern Florida. Our simulations showed that (1) there was a linear relationship between salinity and the δ 18 O value in the water table, whereas this relationship was curvilinear in the vadose zone; (2) hammock trees with higher probability of being replaced by mangroves had higher δ 18 O values of plant stem water, and this difference could be detected 2 years before the trees reached a tipping point, beyond which future replacement became certain; and (3) individuals that were eventually replaced by mangroves from the hammock tree population with a 50% replacement probability had higher stem water δ 18 O values 3 years before their replacement became certain compared to those from the same population which were not replaced. Overall, these simulation results suggest that it is promising to track the yearly δ 18 O values of plant stem water in hammock forests to predict impending salinity stress and mortality.

Ecosystems↗