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At least 1,261 records · Page 70Linked to original sources

USGS2022

Natural and anthropogenic factors influencing nesting ecology of the American crocodile in Florida, United States

Nesting ecology of American crocodiles ( Crocodylus acutus ) in Florida has been both positively and negatively influenced by anthropogenic and natural factors since the species was placed on the federally endangered species list in 1975. This includes a shift in nesting sites and an expansion of nesting to anthropogenic habitat. Using a 50-year record of monitoring data (1970-2020), we assessed factors influencing nesting ecology (number of nests, nest morphology, success rate, and habitat use) from a total of 3,013 nests recorded across South Florida. We detected a change in nesting success rate, increasing from 61% in the 1970’s to near 90% since 2010. Our hot spot analysis illustrates that nesting sites in northeastern Florida Bay and Flamingo/Cape Sable (Everglades National Park) were important for American crocodiles. Anthropogenic habitats, such as canals provided vital habitat nesting in areas such as Flamingo/Cape Sable (Everglades National Park), Turkey Point Power Plant, and Crocodile Lake National Wildlife Refuge for the current Florida population. Environmental parameters suspected to affect nesting success have shown an increasing trend over the past 50 years and minimum temperature and rainfall, during the summer season, are correlated with increased nesting success and temporal variation across South Florida. The adaptive capacity that American crocodiles exhibited in Florida gave the species advantages to face changes in climate and landscape over the last 50 years, however, it does not imply that the adaptive capacity of the species to face these changes (evolutionary potential) cannot reach a limit if changes continue. Here, we document C. acutus nesting ecology population responses to ecosystem restoration efforts in Florida; and further demonstrate the value of protecting and restoring habitat to support recovery of listed species.

Florida↗

USGS2013

Identification of metrics to monitor salt marsh integrity on National Wildlife Refuges in relation to conservation and management objectives

Executive Summary Most salt marshes in the US have been degraded by human activities, and threats from physical alterations, surrounding land-use, species invasions, and global climate change persist. Salt marshes are unique and highly productive ecosystems with high intrinsic value to wildlife, and many National Wildlife Refuges (NWRs) have been established in coastal areas to protect large tracts of salt marsh and wetland-dependent species. Various management practices are employed routinely on coastal NWRs to restore and enhance marsh integrity and ensure ecosystem sustainability. Prioritizing NWR salt marshes for application of management actions and choosing among multiple management options requires scientifically-based methods for assessing marsh condition. Monitoring is integral to structured decision-making (SDM), a formal process for decomposing a decision into its essential elements. Within a natural resource context, SDM involves identifying management objectives, alternative management actions, and expected management outcomes. The core of SDM is a set of criteria for measuring system performance and evaluating management responses. Therefore, use of SDM to frame natural resource decisions leads to logical selection of monitoring attributes that are linked explicitly to management needs. We used SDM to guide selection of variables for monitoring the ecological integrity of salt marshes within the National Wildlife Refuge System (NWRS). Our objectives were to identify indicators of salt marsh integrity that are effective across large geographic regions, responsive to a wide range of threats, and feasible to implement within funding and staffing constraints of the NWRS. In April, 2008, we engaged interdisciplinary experts in a week-long rapid prototyping SDM workshop to define the essential elements of salt marsh management decisions on refuges throughout the northeastern, southwestern, and northwestern US, corresponding to respective Regions 5, 2, and 1 of the US Fish and Wildlife Service (FWS). Through this process we identified measurable attributes for monitoring salt marsh ecosystems that are integrated into conservation practice and target management objectives. The following salt marsh attributes were identified through the SDM process either for describing state condition to determine management needs or for evaluating the achievement of management objectives: historical condition and geomorphic setting; ditch density; surrounding land use; ratio of open water area to vegetation area; rate of pesticide application; environmental contaminant concentration; change in marsh surface elevation relative to sea level rise; tidal range and groundwater level; surface topography; salinity; and species composition and abundance of vegetation, invasive species, invertebrates, nekton, and breeding and wintering birds. The identified attributes were too broadly defined to serve as operational monitoring variables. Therefore, we tested specific metrics for quantifying most of these attributes in summers of 2008 and 2009. The first four attributes in the above list can be characterized by office-based analysis of existing GIS data layers. The remaining attributes require field-based methods for assessment. We were forced to exclude a small number of attributes from field tests due to inconsistent data (pesticide application rate, environmental contaminant concentrations) or requirements that exceeded the scope of this project (change in marsh surface elevation; surface topography; benthic invertebrates; wintering birds). We evaluated potential metrics for evaluating all remaining field attributes. In partnership with NWRS biologists, we tested rapid versus intensive metrics for monitoring field attributes (tidal range and groundwater level; marsh surface elevation; salinity; and species composition and abundance of vegetation, invasive species, nekton, and breeding birds) at coastal refuges throughout FWS Region 5. Seven refuges participated in metric testing in 2008: Rachel Carson (ME), Parker River (MA), Wertheim (NY), E. B. Forsythe (NJ), Bombay Hook (DE), Prime Hook (DE), and Eastern Shore of Virginia Complex (VA). These seven and two additional refuges participated in metric testing in 2009: Rhode Island Complex (RI) and Stewart B. McKinney (CT). We based all field metrics on existing protocols for salt marsh assessment. Sampling locations were determined randomly within delineated marsh study units (MSUs) at each refuge. Detailed field methods are provided in appendices to this report. Measurements for individual metrics were averaged across samples within MSUs during each year of sampling. Each year, correlation or regression analysis was conducted on average measurements across MSUs within each attribute set to identify redundant metrics. Statistical redundancy between a pair of metrics within an attribute set (i.e., correlation or regression slopes with p-values < 0.05) was considered justification for eliminating one of the pair from the regional set of monitoring metrics. Decisions regarding metric elimination versus retention were based on feasibility of monitoring, considering such factors as sampling time, resources required, and potential for regional standardization in implementation. The result of these tests is a reduced suite of monitoring metrics that targets NWRS management decisions and is practicable for implementing on a regional scale. Based on these tests, we recommend the following list of metrics for monitoring integrity of NWRS salt marshes (marsh attribute category is in parentheses): (historical condition and geomorphic setting) position of marsh in the landscape, marsh shape, degree of fill and/or fragmentation, degree of tidal flushing, amount of aquatic edge; (ditch density) ranking of ditch density from none to severe; (surrounding land use) relative proportion of agricultural land in a 150-m buffer around the marsh, relative proportion of natural land in a 150-m buffer around the marsh, relative proportion of natural land in a 1-km buffer around the marsh; (ratio of open water area to vegetation area) ratio of open water to emergent herbaceous wetlands within the marsh; (marsh surface elevation) elevation referenced to NAVD88 in a representative area of the marsh; (tidal range and groundwater level) percent of time the marsh surface is flooded during deployment of a continuous water-level monitor at a representative marsh location, mean depth of surface flooding as measured by a continuous water-level monitor at a representative location; (salinity) salinity measured in surface water; (vegetation community) vegetation species richness using the point-intercept method in 100-m diameter survey plots, percent cover of various marsh community types within 100-m diameter survey plots; (invasive species abundance) percent cover of invasive plant species measured using the point-intercept method in 100-m diameter survey plots; (nekton community) nekton density, nekton species richness, length of Fundulus heteroclitus ; (breeding bird community) abundance of Willets counted per point during standard call-broadcast surveys, summed abundance of tidal marsh obligate species (Clapper Rail, Willet, Saltmarsh Sparrow, Seaside Sparrow) counted per point during standard call-broadcast surveys. Metrics describing the historical condition, geomorphic setting, and broad landscape features can be assessed using existing GIS databases. Our results support use of rapid methods to assess the majority of field metrics; only those used to describe the nekton community must be measured using intensive methods (throw traps or ditch nets, dependant on habitat configuration). Implementation of these metrics for quantitative assessment of NWRS salt marsh integrity in FWS Region 5 requires developing sampling designs for each refuge. Additionally, it is important to determine how the monitoring information will be used within a management context. SDM should be used to complete the analysis of salt marsh management decisions. The next steps would involve 1) prioritizing and weighting the management objectives; 2) predicting responses to individual management actions in terms of objectives and metrics; 3) using multiattribute utility theory to convert all measurable attributes to a common utility scale; 4) determining the total management benefit of each action by summing utilities across objectives; and 5) maximizing the total management benefits within cost constraints for each refuge. This process would allow the optimum management decisions for NWRS salt marshes to be selected and implemented based directly on monitoring data and current understanding of marsh responses to management actions. Monitoring the outcome of management actions would then allow new monitoring data to be incorporated into subsequent decisions.

Connecticut, Delaware, Maine, Massachusetts, New J↗

USGS2024

Colorado Delta riparian plant health improvement

The riparian corridor along Mexico’s arid Colorado River Delta is being affected by reduction in river flow and increases in heat, drought, human infrastructure, and disturbances. These disturbances can change riparian land cover by limiting water availability for riparian plant species, increasing fire intensity and frequency, and increasing soil and water salinities. In response to these forms of degradation, restoration efforts have begun to restore riparian habitats and native plant health, but vegetation greenness and corresponding plant water use continue to decline in unrestored reaches. Researchers from the U.S. Geological Survey (USGS) Southwest Biological Science Center are monitoring riparian plant health along the Colorado River Delta to support better ecohydrological decision-making. The researchers are helping a binational team to protect, restore, and maintain native vegetation within the 150-km long riparian corridor. Researchers are using Landsat 8 Operational Land Imager (OLI) data spanning 2014–2022 to measure greenness, a proxy for plant health, and actual evapotranspiration (ETa). Using an empirical model for ETa, evapotranspiration is estimated over each 16-day Landsat 8 OLI overpass period by considering the 8 days before and after the overpass date. In their paper, researchers noted an increase in vegetation greenness within the restoration sites over nine years, with an average increase of 41.3%, which may be partially due to targeted water deliveries at the restoration sites. Conversely, greenness in adjacent, unrestored control areas declined by 27.3%. The study showed a 22.1% increase in ETa in restored areas, compared to a 30.8% reduction in unrestored regions. Restored sites in one restored area experienced ETa increases up to 12.2%, whereas their unrestored counterparts showed a decline of 21.4%. These estimates of riparian greenness and water use may assist natural resource managers who are tasked with allocating water and managing habitats within similar riparian corridors.

Conference Paper↗

USGS2023

Forecasting natural regeneration of sagebrush after wildfires using population models and spatial matching

Context Addressing ecosystem degradation in the Anthropocene will require ecological restoration across large spatial extents. Identifying areas where natural regeneration will occur without direct resource investment will improve scalability of restoration actions. Objectives An ecoregion in need of large scale restoration is the Great Basin of the Western US, where increasingly large and frequent wildfires threaten ecosystem integrity and its foundational shrub species. We develop a framework to forecast where post-wildfire regeneration of sagebrush cover ( Artemisia spp.) is likely to occur within the burnt areas across the region (> 900,000 km 2 ). Methods First, we parameterized population models using Landsat satellite-derived time series of sagebrush cover. Second, we evaluated the out-of-sample performance by predicting natural regeneration in wildfires not used for model training. This model assessment reproduces a management-oriented scenario: making restoration decisions shortly after wildfires with minimal local information. Third, we asked how accounting for increasingly fine-scale spatial heterogeneity could improve model forecasting accuracy. Results Regional-level models revealed that sagebrush post-fire recovery is slow, estimating > 80-year time horizon to reach an average cover at equilibrium of 16.6% (CI95% 9–25). Accounting for wildfire and within-wildfire spatial heterogeneity improved out-of-sample forecasts, resulting in a mean absolute error of 3.5 ± 4.3% cover, compared to the regional model with an error of 7.2 ± 5.1% cover. Conclusions We demonstrate that combining population models and non-parametric spatial matching provides a flexible framework for forecasting plant population recovery. Models for population recovery applied to Landsat-derived time series will assist restoration decision-making, including identifying priority targets for restoration.

Great Basin↗

USGS2002

FTIR and py-GC-MS spectra of true-fern and seed-fern sphenopterids (Sydney Coalfield, Nova Scotia, Canada, Pennsylvanian)

Sphenopterid specimens from the Late Pennsylvanian of Sydney Coalfield, Canada, are investigated by FTIR and py-GC-MS techniques as part of an on-going research project into the biochemistry and chemotaxonomy of Pennsylvanian-age pteridophylls. Included in the investigation are samples of the true-fern species Oligocarpia brongniartii and Zeilleria delicatula that are preserved as naturally macerated cuticles (NMC), and the seed-fern Eusphenopteris neuropteroides that is also preserved as a compression/impression. FTIR spectra of NMC seed-fern E. neuropteroides, and fern sphenopterid O. brongniartii are very similar, except that the latter does not have aromatic bands in the 700-900 cm-1 out-of-plane region, py-GC-MS show more aromatic compounds for the seed fern than for the two true-fern sphenopterids. Another difference between seed-fern and true-fern sphenopterids is a lower ratio of CH2 to CH3 in chemically treated specimens (CTC) for the seed fern. These observations suggest slightly higher aromaticity for the seed ferns, perhaps related to some chemotaxonomic differences. Comparison of FTIR and py-GC-MS characteristics of sphenopterids and other plant groups shows that these two techniques have potential to identifying chemotaxonomic signals from Carboniferous pteridophylls in general, although more data are needed to confirm this. ?? 2002 Elsevier Science B.V. All rights reserved.

International Journal of Coal Geology↗

USGS2024

Climate-induced tree-mortality pulses are obscured by broad-scale and long-term greening

Vegetation greening has been suggested to be a dominant trend over recent decades, but severe pulses of tree mortality in forests after droughts and heatwaves have also been extensively reported. These observations raise the question of to what extent the observed severe pulses of tree mortality induced by climate could affect overall vegetation greenness across spatial grains and temporal extents. To address this issue, here we analyse three satellite-based datasets of detrended growing-season normalized difference vegetation index (NDVI GS ) with spatial resolutions ranging from 30 m to 8 km for 1,303 field-documented sites experiencing severe drought- or heat-induced tree-mortality events around the globe. We find that severe tree-mortality events have distinctive but localized imprints on vegetation greenness over annual timescales, which are obscured by broad-scale and long-term greening. Specifically, although anomalies in NDVI GS (ΔNDVI) are negative during tree-mortality years, this reduction diminishes at coarser spatial resolutions (that is, 250 m and 8 km). Notably, tree-mortality-induced reductions in NDVI GS (|ΔNDVI|) at 30-m resolution are negatively related to native plant species richness and forest height, whereas topographic heterogeneity is the major factor affecting ΔNDVI differences across various spatial grain sizes. Over time periods of a decade or longer, greening consistently dominates all spatial resolutions. The findings underscore the fundamental importance of spatio-temporal scales for cohesively understanding the effects of climate change on forest productivity and tree mortality under both gradual and abrupt changes.

Nature Ecology & Evolution↗

USGS2022

Divergent responses of butterflies and bees to burning and grazing management in tallgrass prairies

Butterflies and bees contribute significantly to grassland biodiversity and play important roles as pollinators and herbivores. Grassland conservation and management must be seen through the lens of insect conservation and management if these species are to thrive. In North America, grasslands are a product of climate and natural disturbances such as fire and grazing. These natural disturbances have changed considerably since European colonization and subsequent landscape fragmentation. The aim of this study was to better understand the impacts of fire and grazing management on butterfly and bee communities in tallgrass prairie, enabling land managers and conservationists to better protect and manage remnant prairie. We examined butterfly and bee abundance, species richness, and diversity in Minnesota tallgrass prairies managed by grazing or fire. In 2016 and 2017, we surveyed butterflies, bees, vegetation, and surrounding land use at 20 remnant prairies (10 burned and 10 grazed) with known management histories. Butterfly and bee abundance at our study sites were significantly negatively correlated. Butterfly abundance, but not species richness, was higher in burned than grazed prairies, and prairie-associated grass-feeding butterflies were more abundant at sites with higher plant species richness. Bee abundance was unrelated to management type but was higher at sites with sandier soils; bee species richness was positively associated with forb frequency. These findings highlight the challenges of designing management plans tailored to wide groups of pollinators and the potential pitfalls of using one group of pollinators as indicators for another. They also point to the importance of a mosaic of management practices across the prairie landscape.

Minnesota↗

USGS2018

Cadmium isotope fractionation during coal combustion: Insights from two U.S. coal-fired power plants

Coal combustion, one of the principal energy sources of electricity in the United States, produces over 100 million tons of coal combustion products (CCPs) per year in the U.S. The reuse and disposal of CCPs has the potential to release toxic trace elements, including cadmium (Cd), into the environment. In this study, we investigated CCPs, including bottom ash (BA), economizer fly ash (EFA), and fly ash (FA), as well as feed coal (FC) and pulverized coal (PC) collected from two U.S. coal-fired power plants in New Mexico and Ohio with different coal supplies. The New Mexico plant uses high volatile C bituminous, low-sulfur coals mined from the San Juan Basin (Cretaceous Fruitland Formation) and the Ohio plant uses high volatile A bituminous, high-sulfur central Appalachian Basin coals (Upper Pennsylvanian Monongahela Formation). Mineralogical and elemental analysis showed that these CCP samples consist of ∼70% amorphous Al-Si-rich glasses and ∼30% mineral phases of quartz (SiO 2 ) and mullite (Ai 6 Si 2 O 13 ). The Cd isotope compositions (δ 114 Cd, normalized to NIST Cd standard 3108) of FA and EFA samples (ranging from −0.51 to +0.47‰) are distinctively heavier than those of BA samples (−0.75 to −0.52‰) in both power plants. We interpret this Cd isotope difference as a result of Cd condensation from the gas phase during flue gas cooling, instead of evaporation of Cd phase during coal combustion. Cd condensation is the main process to generate the isotopically heavy Cd signatures that preferentially partition on the fine FA particles. We also investigated Cd isotope compositions in different leachate products from a series of batch-leaching experiments with these CCPs, using diluted acetic acid, hydroxyl ammonium chloride, hydrogen peroxide followed by ammonium acetate, and 5% nitric acid, as a possible means to identify CCP-released Cd in the environment. Unusually and significantly heavier Cd isotope compositions were observed in each leachate of FA samples (+1.10 to +7.09‰), which fall far outside from the range of Cd isotope ratios observed in natural soils and rocks, but less so for the EFA samples (−0.43 to +1.18‰). Such an observation is consistent with the interpretation that isotopically heavy Cd preferentially partitions on the fine FA particles after coal combustion and is readily to be released during these leaching experiments. This study demonstrates that high-temperature coal combustion can lead to a very large degree of fractionation of Cd isotopes that can be used as a unique tracer for identifying anthropogenic metal inputs in the environment. The major Cd isotope fractionation process occurs as the Cd gas phase condenses on fine FA particles during the flue gas cooling stage after coal combustion.

New Mexico, Ohio↗

USGS1998

Water-quality assessment of the Central Arizona Basins, Arizona and northern Mexico – Environmental setting and overview of water quality

The Central Arizona Basins study area in central and southern Arizona and northern Mexico is one of 60 study units that are part of the U.S. Geological Survey's National Water-Quality Assessment program. The purpose of this report is to describe the physical, chemical, and environmental characteristics that may affect water quality in the Central Arizona Basins study area and present an overview of water quality. Covering 34,700 square miles, the study area is characterized by generally north to northwestward-trending mountain ranges separated by broad, gently sloping alluvial valleys. Most of the perennial rivers and streams are in the northern part of the study area. Rivers and streams in the south are predominantly intermittent or ephemeral and flow in response to precipitation such as summer thunderstorms. Effluent-dependent streams do provide perennial flow in some reaches. The major aquifers in the study area are in the basin-fill deposits that may be as much as 12,000 feet thick. The 1990 population in the study area was about 3.45 million, and about 61 percent of the total was in Maricopa County (Phoenix and surrounding cities). Extensive population growth over the past decade has resulted in a twofold increase in urban land areas and increased municipal water use; however, agriculture remains the major water use. Seventy-three percent of all water with drawn in the study area during 1990 was used for agricultural purposes. The largest rivers in the study area-the Gila, Salt, and Verde-are perennial near their headwaters but become intermittent downstream because of impoundments and artificial diversions. As a result, the Central Arizona Basins study area is unique compared to less arid basins because the mean surface-water outflow is only 528 cubic feet per second from a total drainage area of 49,650 square miles. Peak flows in the northern part of the study area are the result of snowmelt runoff; whereas, summer thunderstorms account for the peak flows in the southern part. Ground water is the primary water supply in most of Arizona and the only source of drinking water used by communities in the southern half of the study area. Years of overpumping have caused water tables in basin fill to drop below once-perennial streams leaving streambeds dry, water too deep to pump economically, pumping of poorer quality water with depth, and earth fissures resulting from subsidence after dewatering of sediments. Natural processes-such as leaching of trace elements and major ions from geologic formations-and human activities-such as mining, agriculture, and urban development-have major effects on the quality of surface-water and ground-water resources in the Central Arizona Basins study area. Surface-water quality standards in Arizona are based on the designated use of the water such as full or partial body contact, fish consumption, aquatic and wildlife uses, and agriculture. Maintaining the biological integrity (health) of surface waters in Arizona is an important part of ensuring that these waters are suitable for designated uses. Important water-quality issues for surface water that are somewhat unique to Arizona include: (1) streamflows and riparian environments sustained by effluent from municipal wastewater-treatment plants that contains high concentrations of nutrients, potentially toxic trace elements and organic compounds, and fecal bacteria; (2) industrial, mining, agricultural, and municipal sources of contamination from Mexico; and (3) unpredictable high flows from major summer thunder storms causing stream-channel changes; high suspended-sediment concentrations and loads; sewage overflows; and breaching, erosion, and washout of landfills and mining operations. The quality of water in aquifers that are protected for drinking- water use is subject to standards that are in most cases equal to or more stringent than the primary drinking-water regulations of the U.S. Environmental Protection Agency. The general che

Arizona↗

USGS2013

Exotic plant colonization and occupancy within riparian areas of the Interior Columbia River and Upper Missouri River basins, USA

Exotic plant invasions into riparia often result in shifts in vegetative composition, altered stream function, and cascading effects to biota at multiple scales. Characterizing the distribution patterns of exotic plants is an important step in directing targeted research to identify mechanisms of invasion and potential management strategies. In this study, we employed occupancy models to examine the associations of landscape, climate, and disturbance attributes with the colonization and occupancy patterns for spotted knapweed ( Centaurea stoebe L.), Canada thistle ( Cirsium arvense L., Scop.), and cheatgrass ( Bromus tectorum L.) in the riparia of headwater streams ( n  = 1,091) in the Interior Columbia River and Upper Missouri River Basins. We found relatively low occupancy rates for cheatgrass (0.06, SE = 0.02) and spotted knapweed (0.04, SE = 0.01), but moderate occupancy of Canada thistle (0.28, SE = 0.05); colonization rates were low across all species (<0.01). We found the distributions of spotted knapweed, Canada thistle, and cheatgrass to exhibit significant associations with both ambient climate conditions and anthropogenic and natural disturbances. We attribute the low to moderate occupancy and colonization rates to the relatively remote locations of our sample sites within headwater streams and urge consideration of means to prevent further invasions.

Interior Columbia River and Upper Missouri River b↗

USGS2020

Trihalomethane precursors: Land use hot spots, persistence during transport, and management options

To meet drinking water regulations, rather than investing in costly treatment plant operations, managers can look for ways to improve source water quality; this requires understanding watershed sources and fates of constituents of concern. Trihalomethanes (THMs) are one of the major classes of regulated disinfection byproducts, formed when a specific fraction of the organic carbon pool—referred to as THM precursors—reacts with chorine and/or bromine during treatment. Understanding the source, fate, timing and duration of the organic compounds that react to form THMs will allow identification of targeted and effective management actions. In this study we evaluated THM precursor contributions from multiple land use categories and hydrologic contexts, including novel data for urban land uses that demonstrate strong potential to release water with high THM formation potential (THMFP; median 618 μg L −1 ): greater than storm runoff integrated across a mixed-use (1/3 natural, 2/3 agricultural) watershed (median 460 μg L −1 ), irrigation runoff from agricultural systems (357 μg L −1 ), or runoff from a natural forested (median 123 μg L −1 ) and shrubland/grassland (median 259 μg L −1 ) watersheds. While individual storm events released high THM precursor concentrations over short periods, dry season agricultural irrigation as well as urban landscapes have the potential to release water high in THM precursors for several months. Experimental bioassays and sampling along 333 miles of the California Aqueduct confirmed bioavailability and photooxidation potential of less than 10% for THM precursors, suggesting that rivers with residence times of days to weeks may act as THM precursor conduits, shuttling THM precursors from hundreds of miles away to drinking water intakes with minimal degradation. This finding has considerable implications for water managers, who may therefore consider THM precursor management strategies that target even sources located far upstream.

California↗

USGS1975

Chemical and biological quality of water in part of the Everglades, southeastern Florida

A comprehensive monitoring network was established in a part of the Everglades to evaluate the quality of water being delivered to Everglades National Park. Physical, chemical, and biological parameters were determined in surface water, bottom sediment, and bulk precipitation (rainfall and dry fallout). The geology of the area, bottom sediment, bulk precipitation, natural, urban, and agricultural runoff, and the characteristics of the hydrologic system in the Everglades influence the type and concentration of each chemical constituent and how it affects the water quality. The quality of surface water in the agricultural area between Lake Okeechobee and the water conservation areas is markedly different from that of other surface water in southeastern Florida. In general, the water in this area is higher in concentrations of most chemical constituents. Man has engaged in cultural activities, both agricultural and urban, which have affected the water quality in the northern and eastern segments of the area of investigation. The quality of the water improves, however, as it flows to the south and east because there is minimal input from man's activities and many of the constituents are assimilated by plants, sorbed on organic material and clay in the bottom sediments, and entrapped within the sediments. Dilution by rainfall and concentration by evapotranspiration are also important factors that influence the quality of surface water in the area of investigation. The area of investigation in the Everglades is a sink for macronutrients, trace metals, and chlorinated-hydrocarbon insecticides. These constituents do not move through the system freely. They become tied up in various complexes and for that reason, the water being delivered to Everglades National Park is of better quality than the water entering the northern edge of the water conservation areas. The various physical and biological processes and chemical reactions combine to improve the water quality as the water flows southward. The data presented in this report may be used as a baseline for determination of future changes in water quality at the several places in the Everglades where recurrent sampling of rainfall, surface water, and bottom sediments was undertaken during the course of the investigation.

Florida↗

USGS2016

Greenhouse gas emissions from a created brackish marsh in eastern North Carolina

Tidal marsh creation helps remediate global warming because tidal wetlands are especially proficient at sequestering carbon (C) in soils. However, greenhouse gas (GHG) losses can offset the climatic benefits gained from C storage depending on how these tidal marshes are constructed and managed. This study attempts to determine the GHG emissions from a 4–6 year old created brackish marsh, what environmental factors governed these emissions, and how the magnitude of the fluxes relates to other wetland ecosystems. The static flux chamber method was used to measure GHG fluxes across three distinct plant zones segregated by elevation. The major of soil GHG fluxes from the marsh were from CO 2 (−48–192 mg C m -2 h -1 ), although it was near the lower end of values reported from other wetland types having lower salinities, and would mostly be offset by photosynthetic uptake in this created brackish marsh. Methane flux was also low (−0.33–0.86 mg C m -2 h -1 ), likely inhibited by the high soil SO 4 2− and soil redox potentials poised above −150 mV in this in this created brackish marsh environment. Low N 2 O flux (−0.11–0.10 mg N m -2 h -1 ) was due to low soil NO 3 − and soil redox conditions favoring complete denitrification. GHG fluxes from this created brackish marsh were generally lower than those recorded from natural marshes, suggesting that C sequestration may not be offset by the radiative forcing from soil GHG emissions if projects are designed properly.

North Carolina↗

USGS2017

Macroclimatic change expected to transform coastal wetland ecosystems this century

Coastal wetlands, existing at the interface between land and sea, are highly vulnerable to climate change. Macroclimate (for example, temperature and precipitation regimes) greatly influences coastal wetland ecosystem structure and function. However, research on climate change impacts in coastal wetlands has concentrated primarily on sea-level rise and largely ignored macroclimatic drivers, despite their power to transform plant community structure and modify ecosystem goods and services. Here, we model wetland plant community structure based on macroclimate using field data collected across broad temperature and precipitation gradients along the northern Gulf of Mexico coast. Our analyses quantify strongly nonlinear temperature thresholds regulating the potential for marsh-to-mangrove conversion. We also identify precipitation thresholds for dominance by various functional groups, including succulent plants and unvegetated mudflats. Macroclimate-driven shifts in foundation plant species abundance will have large effects on certain ecosystem goods and services. Based on current and projected climatic conditions, we project that transformative ecological changes are probable throughout the region this century, even under conservative climate scenarios. Coastal wetland ecosystems are functionally similar worldwide, so changes in this region are indicative of potential future changes in climatically similar regions globally.

Nature Climate Change↗

USGS2014

Hydrologic alteration affects aquatic plant assemblages in an arid-land river

We evaluated the effects of long-term flow alteration on primary-producer assemblages. In 1962, Flaming Gorge Dam was constructed on the Green River. The Yampa River has remained an unregulated hydrologically variable river that joins the Green River 100 km downstream from Flaming Gorge Dam. In the 1960s before dam construction only sparse occurrences of two macroalgae, Cladophora and Chara , and no submerged vascular plants were recorded in the Green and Yampa rivers. In 2009–2010, aquatic plants were abundant and widespread in the Green River from the dam downstream to the confluence with the Yampa River. The assemblage consisted of six vascular species, Elodea canadensis , Myriophyllum sibiricum , Nasturtium officinale , Potamogeton crispus , Potamogeton pectinatus , and Ranunculus aquatilis , the macroalgae Chara and Cladophora , and the bryophyte, Amblystegium riparium . In the Green River downstream from the Yampa River, and in the Yampa River, only sparse patches of Chara and Cladophora growing in the splash zone on boulders were collected. We attribute the observed changes in the Green River to an increase in water transparency and a reduction in suspended and bed-load sediment and high flow disturbances. The lack of hydrophyte colonization downstream from the confluence with the Yampa River has implications for understanding tributary amelioration of dam effects and for designing more natural flow-regime schedules downstream from large dams.

Southwestern Naturalist↗

USGS2013

Vegetation classification and mapping, Vicksburg National Military Park, Mississippi

Executive Summary The National Park Service (NPS) Gulf Coast Inventory and Monitoring Network, with the support of the National Park Service Vegetation Inventory completed vegetation classification and mapping for Vicksburg National Military Park (VICK), in Warren County, Mississippi, from 2004 to 2010. VICK is one of more than 250 NPS units to be covered by the Vegetation Inventory. Methods and procedures follow those of the NPS Vegetation Inventory as of August, 2012 ( http://science.nature.nps.gov/im/inventory/veg/index.cfm ). Ecologists collected floristic and environmental data from 45 vegetation field plots and classified and described 13 plant community types corresponding to US National Vegetation Classification (USNVC) associations from these data. This classification was used to map 712 hectares (1,698 acres) of Vicksburg National Military Park, in ten map classes corresponding to vegetation associations and two non-vegetated land cover classes, from a digital orthomosaic created from 1:24,000 color infrared aerial photographs and digital elevation model (DEM) data. Methods used to delineate stands varied according to vegetation type and were a combination of incorporating stand boundaries from an existing map, new “heads-up” interpretation and modeling of digital environmental spatial data. A thematic accuracy assessment collected vegetation data from 118 field observations stratified across the vegetation classes. The overall accuracy of the vegetation map was estimated to be 60.5% at the thematic level of USNVC association and 92.4% at the thematic level of USNVC group. Estimates of areas of vegetation types, as adjusted for mapping error, were calculated for all types mapped and/or observed during the thematic accuracy assessment. An important finding of this study is that the composition of the forests of VICK is substantially different from that described by earlier, more qualitative, accounts. Implications of these findings and possible applications of the data for resource monitoring and management are presented. This report summarizes the methods and general results of the Vegetation Inventory for Vicksburg National Military Park. Appendices include descriptions of vegetation types, a field key to the types, a list of plant species, and accuracy assessment contingency tables. This report is supplemented by the project data, which include: spatial database containing map polygon attributes. Geospatial products are in Universal Transverse Mercator (UTM) projection, Zone 15, using the North American Datum of 1983. all field data (plot, observation point, and accuracy assessment point) stored in a Microsoft Access database metadata for all digital products The data and reports produced by this investigation reside at: https://irma.nps.gov/App/ and/or at: http://biology.usgs.gov/npsveg/

Mississippi↗

USGS2025

Water residence time and water depth influence on nutrient conditions, eutrophication endpoints and habitat quality in backwater lakes of a large floodplain river

Many eutrophication studies focus on the external supply of critical nutrients like nitrogen and phosphorus, but hydrology and geomorphology can enhance or dampen the effects of excessive nutrient supply. We studied six backwater lakes in the Upper Mississippi River that varied in water residence time and water depth. Eutrophication in these systems is responsible for negative impacts such as cyanobacterial blooms and toxicity, and floating plant and algal mats that disrupt recreational water uses. Increasing backwater residence time was associated with more nitrate removal and a greater likelihood of nitrogen limitation, as well as greater accumulations of duckweed. Backwaters with greater depth and lower nitrogen concentration had less likelihood of filamentous algal accumulations. The median water residence time of backwaters with low duckweed (11.7 days) and no filamentous algae (16.9 days) approached the 12-day target to maintain overwintering conditions in backwaters for fisheries survival, supporting that water residence times in this range would likely improve both winter and summer water quality. Mean depth in backwaters with low duckweed and no filamentous algae was ~1.3 m, while shallower backwaters were more likely to produce duckweed and filamentous algae mats. This indicates that deeper backwaters might reduce the likelihood of eutrophication impacts. Natural resource management at the local level may not always be able to answer global and regional threats, but habitat restoration of hydrology and geomorphology can possibly alleviate or reduce large-scale threats at the local level.

Minnesota, Wisconsin↗

USGS1985

Anomalous 13C enrichment in modern marine organic carbon

Marine organic carbon is heavier isotopically (13C enriched) than most land-plant or terrestrial organic C1. Accordingly, ??13C values of organic C in modern marine sediments are routinely interpreted in terms of the relative proportions of marine and terrestrial sources of the preserved organic matter2,3. When independent geochemical techniques are used to evaluate the source of organic matter in Cretaceous or older rocks, those rocks containing mostly marine organic C are found typically to have lighter (more-negative) ??13C values than rocks containing mostly terrestrial organic C. Here we conclude that marine photosynthesis in mid-Cretaceous and earlier oceans generally resulted in a greater fractionation of C isotopes and produced organic C having lighter ??13C values. Modern marine photosynthesis may be occurring under unusual geological conditions (higher oceanic primary production rates, lower PCO2) that limit dissolved CO2 availability and minimize carbon isotope fractionation4. ?? 1985 Nature Publishing Group.

Nature↗