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At least 1,171 records · Page 65Linked to original sources

USGS2009

Seed dispersal and seedling emergence in a created and a natural salt marsh on the Gulf of Mexico coast in Southwest Louisiana, U.S.A

Early regeneration dynamics related to seed dispersal and seedling emergence can contribute to differences in species composition among a created and a natural salt marsh. The objectives of this study were to determine (1) whether aquatic and aerial seed dispersal differed in low and high elevations within a created marsh and a natural marsh and (2) whether seedling emergence was influenced by marsh, the presence of openings in the vegetation, and seed availability along the northern Gulf of Mexico coast. Aerial seed traps captured a greater quantity of seeds than aquatic traps. Several factors influenced aquatic and aerial seed dispersal in a created and a natural salt marsh, including distance from the marsh edge, cover of existing vegetation, and water depth. The natural marsh had a high seed density of Spartina alterniflora and Distichlis spicata, the low-elevation created marsh had a high seed density of S. alterniflora, and the high-elevation created marsh had a high seed density of Aster subulatus and Iva frutescens. The presence of adult plants and water depth above the marsh surface influenced seed density. In the natural marsh, openings in vegetation increased seedling emergence for all species, whereas in the low-elevation created marsh, S. alterniflora had higher seedling density under a canopy of vegetation. According to the early regeneration dynamics, the future vegetation in areas of the low-elevation created marsh may become similar to that in the natural marsh. In the high-elevation created marsh, vegetation may be upland fringe habitat dominated by high-elevation marsh shrubs and annual herbaceous species. ?? 2009 Society for Ecological Restoration International.

Restoration Ecology↗

USGS2024

Expanded conceptual risk framework for uranium mining in Grand Canyon watershed—Inclusion of the Havasupai Tribe perspective

In 2012, the Secretary of the U.S. Department of the Interior placed a 20-year limit on mineral extraction on Federal lands in the Grand Canyon watershed to permit further study of the environmental effects of uranium mining. Tribal concerns were also noted by the U.S. Department of the Interior and included in the rationale for the decision stating Tribal resource impacts could not be mitigated and cultural degradation may result should mining occur within sacred and traditional places of Tribal peoples. The U.S. Geological Survey previously developed a conceptual framework for a uranium mine in the region that defined contaminant sources and physical, chemical, and biological processes that affect contaminant transport to ecological receptors. However, published risk models have largely ignored exposure pathways relevant to Tribal communities in terms of traditional uses and existential values of the resources included. This report presents an updated conceptual risk framework for uranium mining that includes indigenous knowledge components informed by the Havasupai Tribe perspective. The expansion of the framework relied on connecting to the foundations of the Havasupai ceremonial wheel—food, environment, belief system, and ceremony. The framework is applied to uranium development near Red Butte, an important gathering place for multiple federally recognized Tribes including the Havasupai, Hopi, Navajo, and Zuni. Plants and animals important to the Havasupai for subsistence, ceremonial, and medicinal practices and how mining affects these practices are described. The final framework is presented in English and Havasupai to aid Tribal members in understanding how the framework relates to their community and to help preserve the language and historical cultural practices for future generations. New or expanded exposure pathways include inhalation, ingestion, and absorption from traditional food and medicines as well as ceremonial practices. The updated framework has allowed the U.S. Geological Survey to take first steps in understanding resources important to the Havasupai and to build relationships to improve co-production in our research. Ideally, the framework and other research can be used, along with indigenous knowledge, in Federal research and decision making for mining in the Grand Canyon region.

Open-File Report↗

USGS2017

When perception reflects reality: Non-native grass invasion alters small mammal risk landscapes and survival

Modification of habitat structure due to invasive plants can alter the risk landscape for wildlife by, for example, changing the quality or availability of refuge habitat. Whether perceived risk corresponds with actual fitness outcomes, however, remains an important open question. We simultaneously measured how habitat changes due to a common invasive grass (cheatgrass, Bromus tectorum ) affected the perceived risk, habitat selection, and apparent survival of a small mammal, enabling us to assess how well perceived risk influenced important behaviors and reflected actual risk. We measured perceived risk by nocturnal rodents using a giving-up density foraging experiment with paired shrub (safe) and open (risky) foraging trays in cheatgrass and native habitats. We also evaluated microhabitat selection across a cheatgrass gradient as an additional assay of perceived risk and behavioral responses for deer mice ( Peromyscus maniculatus ) at two spatial scales of habitat availability. Finally, we used mark-recapture analysis to quantify deer mouse apparent survival across a cheatgrass gradient while accounting for detection probability and other habitat features. In the foraging experiment, shrubs were more important as protective cover in cheatgrass-dominated habitats, suggesting that cheatgrass increased perceived predation risk. Additionally, deer mice avoided cheatgrass and selected shrubs, and marginally avoided native grass, at two spatial scales. Deer mouse apparent survival varied with a cheatgrass–shrub interaction, corresponding with our foraging experiment results, and providing a rare example of a native plant mediating the effects of an invasive plant on wildlife. By synthesizing the results of three individual lines of evidence (foraging behavior, habitat selection, and apparent survival), we provide a rare example of linkage between behavioral responses of animals indicative of perceived predation risk and actual fitness outcomes. Moreover, our results suggest that exotic grass invasions can influence wildlife populations by altering risk landscapes and survival.

Wyoming↗

USGS2018

Leaf to landscape responses of giant sequoia to hotter drought: An introduction and synthesis for the special section

Hotter droughts are becoming more common as climate change progresses, and they may already have caused instances of forest dieback on all forested continents. Learning from hotter droughts, including where on the landscape forests are more or less vulnerable to these events, is critical to help resource managers proactively prepare for the future. As part of our Leaf to Landscape Project, we measured the response of giant sequoia, the world’s largest tree species, to the extreme 2012–2016 hotter drought in California. The project integrated leaf-level physiology measurements, crown-level foliage dieback surveys, and remotely sensed canopy water content (CWC) to shed light on mechanisms and spatial patterns in drought response. Here we summarize initial findings, present a conceptual model of drought response, and discuss management implications; details are presented in the other four articles of the special section on Giant Sequoias and Drought. Giant sequoias exhibited both leaf- and canopy-level responses that were effective in protecting whole-tree hydraulic integrity for the vast majority of individual sequoias. Very few giant sequoias died during the drought compared to other mixed conifer tree species; however, the magnitude of sequoia drought response varied across the landscape. This variability was partially explained by local site characteristics, including variables related to site water balance . We found that low CWC is an indicator of recent foliage dieback, which occurs when stress levels are high enough that leaf-level adjustments alone are insufficient for giant sequoias to maintain hydraulic integrity. CWC or change in CWC may be useful indicators of drought stress that reveal patterns of vulnerability to future hotter droughts. Future work will measure recovery from the drought and strengthen our ability to interpret CWC maps. Our ultimate goal is to produce giant sequoia vulnerability maps to help target management actions, such as reducing other stressors, increasing resistance to hotter drought through prescribed fire or mechanical thinning, and planting sequoias in projected future suitable habitat, which may occur outside current grove distributions. We suggest that managers compare different types of vulnerability assessments and combine vulnerability maps with other sources of information to inform decisions.

California↗

USGS2025

Costs of land treatments on public lands in the western United States

Public land managers often conduct rehabilitation and restoration actions to achieve desired conditions or specific natural resource objectives. These “land treatments” include a variety of techniques, such as biomass removal or manipulation, seeding, and herbicide application. Limited information exists on the costs of conducting many common types of land treatments, but such information can be paired with treatment effectiveness data to prioritize application of limited resources where they may have the greatest benefit and improve efficiency. Here, we investigated cost information recorded in the Land Treatment Digital Library, a catalog of legacy land treatment information on public lands managed by the U.S. Department of the Interior's Bureau of Land Management. Based on 1,701 treatment records across eleven western U.S. states, we developed empirical per-acre cost estimates for representative land treatments in eight categories: three seeding categories (aerial seeding, drill seeding, and seedling planting), prescribed burning, soil disturbance, soil stabilization, vegetation disturbance, and weed control. We evaluated spatio-temporal factors that may be associated with variation in treatment costs and found strong evidence for nonlinear decreases in per-acre costs as treatment areas increased and that per-acre treatment costs have increased in real terms in recent decades. We also found evidence that per-acre costs for drill seeding, prescribed burns, and soil stabilization increased with the average slope of the terrain of a treated area and that per-acre costs for prescribed burns, seedling planting, and soil stabilization were influenced by distance to urban areas or major roads. These results can inform planning, prioritization, and assessment of common land treatments on public lands in the western United States, in particular supporting greater consideration of costs and cost effectiveness.

Rangeland Ecology & Management↗

USGS2015

Understory vegetation as an indicator for floodplain forest restoration in the Mississippi River Alluvial Valley, U.S.A.

In the Mississippi River Alluvial Valley (MAV), complete alteration of river-floodplain hydrology allowed for widespread conversion of forested bottomlands to intensive agriculture, resulting in nearly 80% forest loss. Governmental programs have attempted to restore forest habitat and functions within this altered landscape by the methods of tree planting (afforestation) and local hydrologic enhancement on reclaimed croplands. Early assessments identified factors that influenced whether planting plus tree colonization could establish an overstory community similar to natural bottomland forests. The extent to which afforested sites develop typical understory vegetation has not been evaluated, yet understory composition may be indicative of restored site conditions. As part of a broad study quantifying the ecosystem services gained from restoration efforts, understory vegetation was compared between 37 afforested sites and 26 mature forest sites. Differences in vegetation attributes for species growth forms, wetland indicator classes, and native status were tested with univariate analyses; floristic composition data were analyzed by multivariate techniques. Understory vegetation of restoration sites was generally hydrophytic, but species composition differed from that of mature bottomland forest because of young successional age and differing responses of plant growth forms. Attribute and floristic variation among restoration sites was related to variation in canopy development and local wetness conditions, which in turn reflected both intrinsic site features and outcomes of restoration practices. Thus, understory vegetation is a useful indicator of functional progress in floodplain forest restoration.

Arkansas, Louisiana, Mississippi, Tennessee↗

USGS2013

Linking phenology and biomass productivity in South Dakota mixed-grass prairie

Assessing the health of rangeland ecosystems based solely on annual biomass production does not fully describe plant community condition; the phenology of production can provide inferences on species composition, successional stage, and grazing impacts. We evaluate the productivity and phenology of western South Dakota mixed-grass prairie using 2000 to 2008 Moderate Resolution Imaging Spectrometer (MODIS) normalized difference vegetation index (NDVI) satellite imagery at 250 m spatial resolution. Growing season NDVI images were integrated weekly to produce time-integrated NDVI (TIN), a proxy of total annual biomass production, and integrated seasonally to represent annual production by cool (C3) and warm (C4) season species. Additionally, a variety of phenological indicators including cool season percentage of TIN were derived from the seasonal profiles of NDVI. Cool season percentage and TIN were combined to generate vegetation classes, which served as proxies of plant community condition. TIN decreased with precipitation from east to west across the study area. Alternatively, cool season percentage increased from east to west, following patterns related to the reliability (interannual coefficient of variation [CV]) and quantity of mid-summer precipitation. Cool season TIN averaged 76.8% of total. Seasonal accumulation of TIN corresponded closely (R2 > 0.90) to that of gross photosynthesis data from a carbon flux tower. Field-collected biomass and community composition data were strongly related to the TIN and cool season percentage products. The patterns of vegetation classes were responsive to topographic, edaphic, and land management influences on plant communities. Accurate maps of biomass production, cool/warm season composition, and vegetation classes can improve the efficiency of land management by adjusting stocking rates and season of use to maximize rangeland productivity and achieve conservation objectives. Further, our results clarify the spatial and temporal dynamics of phenology and TIN in mixed-grass prairie.

South Dakota↗

USGS2016

Synthesis of common management concerns associated with dam removal

Managers make decisions regarding if and how to remove dams in spite of uncertainty surrounding physical and ecological responses, and stakeholders often raise concerns about certain negative effects, regardless of whether or not these concerns are warranted at a particular site. We used a dam-removal science database supplemented with other information sources to explore seven frequently-raised concerns, herein Common Management Concerns (CMCs). We investigate the occurrence of these concerns and the contributing biophysical controls. The CMCs addressed are: degree and rate of reservoir sediment erosion, excessive channel incision upstream of reservoirs, downstream sediment aggradation, elevated downstream turbidity, drawdown impacts on local water infrastructure, colonization of reservoir sediments by non-native plants, and expansion of invasive fish. Biophysical controls emerged for some of the concerns, providing managers with information to assess whether a given concern is likely to occur at a site. To fully assess CMC risk, managers should concurrently evaluate site conditions and identify the ecosystem or human uses that will be negatively affected if the biophysical phenomenon producing the CMC occurs. We show how many CMCs have one or more controls in common, facilitating the identification of multiple risks at a site, and demonstrate why CMC risks should be considered in the context of other factors like natural watershed variability and disturbance history.

Journal of the American Water Resources Associatio↗

USGS2013

Consumption of freshwater bivalves by muskrats in the Green River, Kentucky

Muskrats (Ondatra zibethicus) are known to prey on freshwater bivalves (mussels and clams) and can negatively impact imperiled mussel species. However, factors that influence muskrat predation on bivalves are poorly understood. We evaluated the feeding ecology of muskrats in the Green River, Kentucky, by using stable isotope analysis of muskrat hair samples and by monitoring bivalve shell deposition at muskrat middens. Bayesian mixing-model analysis of stable isotope δ 15 N and δ 13 C ratios revealed that the median muskrat biomass derived from bivalves was 51.4% (5th and 95th percentiles were 39.1 to 63.4%, respectively), a much higher dietary proportion than previously reported. Shell depositions by muskrats at middens decreased with the availability of seasonal emergent vegetation, suggesting that the consumption of animal matter is in response to a scarcity of plant foods, perhaps exacerbated by the altered flow regimes on the Green River. Our results add to the growing body of evidence that muskrats have the potential to impact mussel population growth and recovery in some environments.

Kentucky↗

USGS2017

Final Report fr critical thresholds and ecosystem services for coastal ecological and human climate adaptation

Understanding how climate change will impact natural and human communities is a crucial part of decision making and management related to the protection of our coasts. As the effects of climate change on ecological communities grow, the possibility of crossing tipping points or thresholds of viability increases the potential for rapid and possibly irreversible changes in ecosystems. Therefore, understanding thresholds related to climate change is critical for facilitating conservation and management actions, which could help to prevent more costly and possibly catastrophic effects in the future. As part of a broad effort to synthesize and deliver coastal resilience information through the Landscape Conservation Cooperatives (LCCs), Climate Science Centers, states, and other partners along the Atlantic and Gulf Coasts, we synthesized existing quantitative threshold information for 45 priority coastal fish, wildlife, and plant species and habitats in response to sea level rise and storm projections. Additional information was synthesized on climate change adaptation actions that can increase the persistence and resilience of species and their habitats and how these actions relate to human community resilience. In addition to two peer-reviewed manuscripts, results from these synthesis efforts were disseminated online through easily accessible, topic-specific web pages in the Massachusetts Wildlife Climate Action Tool (climateactiontool.org) to make this information more easily accessible to stakeholders across the region. The compilation and dissemination of species and habitat threshold information will help to develop a more comprehensive understanding of how natural systems will respond to climate change and how land and resource management decisions could potentially help these species.

Report↗

USGS2014

Dynamics and ecological consequences of the 2013−2014 koa moth outbreak at Hakalau Forest National Wildlife Refuge.

A massive outbreak of the koa moth (Geometridea: Scotorythra paludicola) defoliated more than a third of the koa (Acacia koa) forest on Hawai‘i Island during 2013−2014. This was the largest koa moth outbreak ever recorded and the first on the island since 1953. The outbreak spread to sites distributed widely around the island between 800−2,000 m elevation and in wet rainforest to dry woodland habitats. We monitored the outbreak at two windward forest sites (Laupāhoehoe and Saddle Road Kīpuka) and one leeward forest site (Kona), and we studied the dynamics of the outbreak and its impacts on the forest ecosystem at Hakalau Forest National Wildlife Refuge, our higher elevation windward site. Study sites at Hakalau included two stands of koa that were planted (reforestation stands) in former cattle pastureland about 20 years earlier and two stands of koa that were dominated by ‘ōhi‘a (Metrosideros polymorpha) and that were naturally recovering from cattle grazing (forest stands). We observed one outbreak at Hakalau, multiple outbreaks at the two other windward sites, but no outbreak at the leeward site. Caterpillars at Hakalau reached peak estimated abundances of more than 250,000 per tree and 18,000,000 per hectare, and they removed between 64−93% of the koa canopy in managed forest stands. Defoliation was more extensive in naturally recovering forest, where ‘ōhi‘a dominated and koa was less abundant, compared to the planted stands, where koa density was high. Koa trees were still growing new foliage six months after being defoliated, and leaves were produced in greater proportion to phyllodes, especially by small koa (≤ 8 cm dbh) and by larger trees in forest stands, where light levels may have remained relatively low after defoliation due to the high cover of ‘ōhi‘a. Small branches of many trees apparently died, and canopy regrowth was absent or low in 9% of koa trees and seedlings, which indicates the likely level of mortality. Between 2,000−5,000 kg/ha of frass fell during the defoliation event, resulting in the deposition of up to 200 kg/ha of highly labile nitrogen on the forest floor in less than two months. The deposition of nitrogen was detected as pulses in resin-available nitrogen in the top 5−10 cm of soil at two of three sites. These sites showed elevated soil nitrogen for about seven months. Nitrogen content of understory plant foliage, which is indicative of nitrogen uptake, suggested weak and variable effects of nitrogen deposition in the soil. Foliar nitrogen increased slightly in alien pasture grasses four months after the deposition of frass, although distinctive increases were not detected in native woody species. Birds responded to the abundance of caterpillars by increasing their activity in koa during the buildup of caterpillars and decreasing their use of koa after defoliation. During the outbreak, caterpillars increased in the diets of the two generalist insectivores we examined, and nearly all species gained weight. Bats responded to the abundance of moths by compression of active foraging into the first three hours of darkness each night after presumably having reached a digestive bottleneck. Reduced foraging activity by bats also resulted in lower indices of detectability based upon acoustic monitoring when compared to non-outbreak years. Parasitoid wasps tracked caterpillar abundance, but the low rate at which they attacked caterpillars suggests that they had little influence on the population. The predatory yellowjacket (Vespula pensylvanica) did not respond to the outbreak. Although a single, protracted outbreak occurred at Hakalau, multiple outbreaks and defoliations occurred at lower elevations. Our results provide a broad foundation for evaluating the dynamics and impacts of future Scotorythra outbreaks.

Hawaii↗

USGS2007

Wildlife species associated with non-coniferous vegetation in Pacific Northwest conifer forests: A review

Non-coniferous vegetation, including herbs, shrubs, and broad-leaved trees, makes a vital contribution to ecosystem function and diversity in Pacific Northwest conifer forests. However, forest management has largely been indifferent or detrimental to shrubs and trees that have low commercial value, in spite of a paradigm shift towards more holistic management in recent decades. Forest management practices that are detrimental to broad-leaved trees and shrubs are likely to decrease habitat diversity for wildlife, but the number of species that may be affected has not previously been enumerated. I reviewed life history accounts for forest-dwelling vertebrate wildlife species and derived a list of 78 species in Oregon and Washington that are associated with non-coniferous vegetation. The diversity of direct and indirect food resources provided was the primary functional basis for associations of most species with non-coniferous vegetation. Thus, a diversity of herbs and broad-leaved trees and shrubs provides the foundation for food webs that contribute to diversity at multiple trophic levels in Pacific Northwest conifer forests. Given the number of species associated with non-coniferous vegetation in conifer-dominated forests, maintaining habitats that support diverse plant communities, particularly broad-leaved trees and shrubs, will be an important component of management strategies intended to foster biodiversity. Silvicultural practices such as modified planting densities, and pre-commercial and commercial thinning, can be used to control stand density in order to favor the development of understory herbs, shrubs, and a diversity of tree species within managed stands. Allowing shrubs and hardwood trees to develop and persist in early seral stands by curtailing vegetation control also would benefit many species associated with non-coniferous vegetation.

Forest Ecology and Management↗

USGS2005

Inventory of the mosses, liverworts, and lichens of Olympic National Park, Washington- Species list

The identification of non-vascular cryptogam species (lichens, mosses, liverworts, and hornworts) is especially challenging because of their small size, their often microscopic or chemical distinguishing features, and their enormous diversity. Consequently, they are a poorly known component of Olympic National Park, despite their ecological and aesthetic importance. This project is the first attempt at a systematic, comprehensive survey of non-vascular cryptogams in the Park and presents the current species list with descriptions of the substrate and vascular vegetation type where they were observed. The authors strove to collect from as many park environments as feasible, and distributed collections along important environmental gradients in different regions of the park using vascular vegetation as an environmental indicator. They also collected opportunistically when interesting habitats or microhabitats were encountered. Finally, the authors updated the nomenclature in the Park’s previous collection of nonvascular plants. This study identified approximately 13,200 bryophyte and lichen species, adding approximately 425 new species to the Olympic National Park Herbarium. These data, combined with select literature reports and personal data from Martin and Karen Hutten, added more than 350 species to the previously documented Olympic Peninsula lichen and bryophyte list. The authors discuss the list in a local, regional, and global context of rarity, as well as cryptogam conservation and further work needed in Olympic National Park. The improved inventory of Olympic National Park cryptogams represented by this project enables Olympic National Park to protect populations of rare and sensitive species, assess the damage caused by illegal harvest, and contribute information to the Bureau of Land Management and U.S. Forest Service Sensitive Species Programs.

Scientific Investigations Report↗

USGS1975

Water and the South Florida environment

Ecological problems are a major concern to Florida as well as to the Nation. National attention was focused on these problems in September 1968, when the Port Authority of Dade County began to con- struct a jetport for supersonic aircraft on a 39-square-mile tract 6 miles north of Everglades National Park and on the east edge of the Big Cypress Swamp. Conservation groups and citizens raised questions as to the effects of a regional jetport and the attendant satellite growth on the water resources and biological communities of the National Park. The Department of the Interior began studies to investigate the situation. One study, Leopold (1969), reported on the unfavorable ecological effects of the attendant satellite growth. Then Secretary of the Interior, Walter J. Hickel, directed the U.S. Geological Survey to study the water resources of the Big Cypress to determine which parts of the Big Cypress contribute the major part of the water necessary to maintain adequate water supplies for Everglades National Park. This was done in a report by Klein and others (1970). At about the same time, the Departments of interior and Transportation, the State of Florida, and the Dade County Port Authority con-curred in assigning to the Secretary of the Interior certain responsibilities for planning, developing, and coordinating an ecological study of south Florida. A primary objective of the ecological study is to provide information that will assist in the formulation of land-use policy consistent with the protection of the environment of Everglades National Park, the adjacent estuaries, and the public water supplies. The part of the investigation describing the surface-water and ground-water resources of south Florida was assigned to the Geological Survey. The quantity and quality of surface water and ground water and their interrelation with estuarine and marine waters are here considered. Also considered are the problems, present or future, related to the hydrologic environment that involve human, animal, and plant life. Changes taking place, apparent trends, and projections for the future are also considered, as well as alternatives for water management. The Geological Survey effort began in January 1971, when aerial photography and selected qualitative hydrologic data were obtained. However, most of the information upon which this report Is based was obtained by the Geological Survey in cooperative programs with several local, State, and Federal agencies since about 1940. The long-term support of the U.S. Army Corps of Engineers, the National Park Service, U.S. Navy, Florida Department of Natural Resources, Central and Southern Florida Flood Control District, Dade, Broward, Palm Beach and Collier Counties, Miami and Miami Beach, Ft. Lauderdale, Naples and others in the collection of data is gratefully acknowledged. A prolonged drought throughout south Florida from September 1970 to May 1971 accentuated the importance and timeliness of the study. The drought brought about a readvance of sea-water intrusion in many coastal areas, which necessitated restrictions on water use. The effect of drought on the regional water supply, continued population growth and increased water demands, and deterioration of the water quality in many of the canals and waterways of the urban areas accentuated the need for improved water management and land-use planning. As a result of the water crisis, the Governor of Florida called a special conference in September 1971. The conference, attended by foremost scientific and government personnel, proposed creation of an agency that would develop and implement comprehensive land and water-use plans for south Florida that would minimize environmental degradation.

Florida↗

USGS2015

Bistability of mangrove forests and competition with freshwater plants

Halophytic communities such as mangrove forests and buttonwood hammocks tend to border freshwater plant communities as sharp ecotones. Most studies attribute this purely to underlying physical templates, such as groundwater salinity gradients caused by tidal flux and topography. However, a few recent studies hypothesize that self-reinforcing feedback between vegetation and vadose zone salinity are also involved and create a bistable situation in which either halophytic dominated habitat or freshwater plant communities may dominate as alternative stable states. Here, we revisit the bistability hypothesis and demonstrate the mechanisms that result in bistability. We demonstrate with remote sensing imagery the sharp boundaries between freshwater hardwood hammock communities in southern Florida and halophytic communities such as buttonwood hammocks and mangroves. We further document from the literature how transpiration of mangroves and freshwater plants respond differently to vadose zone salinity, thus altering the salinity through feedback. Using mathematical models, we show how the self-reinforcing feedback, together with physical template, controls the ecotones between halophytic and freshwater communities. Regions of bistability along environmental gradients of salinity have the potential for large-scale vegetation shifts following pulse disturbances such as hurricane tidal surges in Florida, or tsunamis in other regions. The size of the region of bistability can be large for low-lying coastal habitat due to the saline water table, which extends inland due to salinity intrusion. We suggest coupling ecological and hydrologic processes as a framework for future studies.

Florida↗

USGS2023

California State waters map series—Benthic habitat characterization in the region offshore of Morro Bay, California

Coastal and Marine Ecological Classification Standard geoform, substrate, and biotic component geographic information system products were developed for the California State waters of south-central California in the region offshore of Morro Bay. The study was motivated by interest in development of offshore wind-energy capacity and infrastructure in Federal waters offshore. The Bureau of Ocean Energy Management, in coordination with the State of California and many other members of the California Intergovernmental Renewable Energy Task Force, issued calls for information in 2018 for the study area offshore of Morro Bay, California. The study area is adjacent to a nuclear power plant (currently scheduled for decommissioning) with a developed electric grid connection, and in an area of high wind resource potential. The Bureau of Ocean Energy Management is the lead agency responsible for planning and leasing in the U.S. Exclusive Economic Zone and funded this project to assess baseline conditions of, and the potential effects on, the seafloor environment. This project, carried out by the U.S. Geological Survey, resulted in three data releases for individual map blocks that are part of the California State Waters Map Series: (1) Offshore of Point Estero, (2) Offshore of Morro Bay, and (3) Offshore of Point Buchon. The study area consists of 341 square kilometers (km 2 ) of multibeam echo sounder (MBES) data acquired by Fugro, Inc., in 2010. Towed camera-sled video was acquired in 2012 to supervise the classification of the MBES data into habitats. There were 935 annotations of organisms and habitat made from 22 video transects. Using video observations of habitat as ground truth, derivatives of the MBES data were classified into 3 seafloor character types (hard-rugged, hard-flat, and soft-flat), 25 modifier groups, and 9 geoforms. The study area substrate is predominantly soft-flat sediment (mud and fine sand) covering 191.3 km 2 (56.1 percent) of the area. Hard-flat substrate areas, predominantly coarse sediment in scour depressions, cover 52.2 km 2 (15.3 percent) of the study area. The hard-rugged substrate areas are primarily outcrops of layered sedimentary bedrock and constitute 97.5 km 2 of the study area (28.6 percent). After classification of bathymetry and backscatter raster images according to substrate, false-positive hard areas produced by noise artifacts were removed by manual editing. Nine geoforms were then identified in the analysis. The predominant geoforms mirror the seafloor character results, shelf geoforms (flat areas covered in soft sediment), rock outcrop geoforms (hard, rugged areas), and scour depression geoforms (flat areas covered in coarse sediment formed by bottom currents).

California↗

USGS2005

Managing vegetation in surface-flow wastewater-treatment wetlands for optimal treatment performance

Constructed wetlands that mimic natural marshes have been used as low-cost alternatives to conventional secondary or tertiary wastewater treatment in the U.S. for at least 30 years. However, the general level of understanding of internal treatment processes and their relation to vegetation and habitat quality has not grown in proportion to the popularity of these systems. We have studied internal processes in surface-flow constructed wastewater-treatment wetlands throughout the southwestern U.S. since 1990. At any given time, the water quality, hydraulics, water temperature, soil chemistry, available oxygen, microbial communities, macroinvertebrates, and vegetation each greatly affect the treatment capabilities of the wetland. Inside the wetland, each of these components plays a functional role and the treatment outcome depends upon how the various components interact. Vegetation plays a uniquely important role in water treatment due to the large number of functions it supports, particularly with regard to nitrogen transformations. However, it has been our experience that vegetation management is critical for achieving and sustaining optimal treatment function. Effective water treatment function and good wildlife quality within a surface-flow constructed wetland depend upon the health and sustainability of the vegetation. We suggest that an effective tool to manage and sustain healthy vegetation is the use of hummocks, which are shallow emergent plant beds within the wetland, positioned perpendicular to the water flow path and surrounded by water sufficiently deep to limit further emergent vegetation expansion. In this paper, we describe the use of a hummock configuration, in conjunction with seasonal water level fluctuations, to manage the vegetation and maintain the treatment function of wastewater-treatment wetlands on a sustainable basis.

Ecological Engineering↗

USGS2014

Functional diversity supports the physiological tolerance hypothesis for plant species richness along climatic gradients

1. The physiological tolerance hypothesis proposes that plant species richness is highest in warm and/or wet climates because a wider range of functional strategies can persist under such conditions. Functional diversity metrics, combined with statistical modeling, offer new ways to test whether diversity-environment relationships are consistent with this hypothesis. 2. In a classic study by R. H. Whittaker (1960), herb species richness declined from mesic (cool, moist, northerly) slopes to xeric (hot, dry, southerly) slopes. Building on this dataset, we measured four plant functional traits (plant height, specific leaf area, leaf water content and foliar C:N) and used them to calculate three functional diversity metrics (functional richness, evenness, and dispersion). We then used a structural equation model to ask if ‘functional diversity’ (modeled as the joint responses of richness, evenness, and dispersion) could explain the observed relationship of topographic climate gradients to species richness. We then repeated our model examining the functional diversity of each of the four traits individually. 3. Consistent with the physiological tolerance hypothesis, we found that functional diversity was higher in more favorable climatic conditions (mesic slopes), and that multivariate functional diversity mediated the relationship of the topographic climate gradient to plant species richness. We found similar patterns for models focusing on individual trait functional diversity of leaf water content and foliar C:N. 4. Synthesis. Our results provide trait-based support for the physiological tolerance hypothesis, suggesting that benign climates support more species because they allow for a wider range of functional strategies.

Oregon↗