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At least 1,441 records · Page 80Linked to original sources
USGS2019

Pre‐fire vegetation drives post‐fire outcomes in sagebrush ecosystems: Evidence from field and remote sensing data

Understanding the factors that influence vegetation responses to disturbance is important because vegetation is the foundation of food resources, wildlife habitat, and ecosystem properties and processes. We integrated vegetation cover data derived from field plots and remotely sensed Landsat images in two focal areas over a 37‐yr period (1979–2016) to investigate how historical changes to community composition influence contemporary responses of vegetation to fire in sagebrush ecosystems in the Great Basin. Our objectives were (1) to quantify the magnitude and direction of change in the cover of native and exotic plant functional groups in relation to their exposure to fire; (2) to relate plant community changes to their historical composition, exposure to fire, and environmental conditions; and (3) to test for consistency of trends revealed by vegetation cover data derived from field plots and Landsat images. Historical (1979–1981) field data originated from 298 locations, Landsat‐derived data and contemporary (2011–2016) field data originated from 448 locations, and an expanded set of locations were included in some analyses of Landsat‐derived data. We found that areas burned by fire since the 1980s had higher annual herbaceous cover than unburned areas both historically and contemporarily. Models revealed a significant interaction between historical community composition and exposure to fire, which suggests that plots with historically high herbaceous cover were more susceptible to burning. Trends revealed by field and Landsat‐derived cover data were only partially consistent, potentially due in part to methods used to predict cover values from Landsat images, and the time period over which each data set was collected. Our results suggest that burned areas historically occupied by sagebrush‐dominated plant communities may have been invaded by exotic annuals prior to burning, possibly because of prior land uses, and after burning, have now transitioned to a persistent herbaceous‐dominated state. This type of state transition has important consequences for forage quality, wildlife habitat, soil nutrients, and future disturbances, such as drought and wildfire.

Oregon, Nevada↗
USGS1988

Use of "specific" inhibitors in biogeochemistry and microbial ecology

The above statement, although meant to be tongue in cheek, contains an essential truism: all work with inhibitors is inherently suspect. This fact has been known by biochemists for some time. However, use of chemical inhibitors of enzymic systems and membranes continues to be a common approach taken toward unraveling the biochemistry and biophysics of plants, animals, and microorganisms. Various types of “broad-spectrum” biochemical inhibitors (e.g., poisons, respiratory inhibitors, and uncouplers) have been employed by ecologists for many years in order to demonstrate the active participation of microbes in chemical reactions occurring in natural samples (e.g., soils, sediments, and water). In recent years, considerable advances have been made in our understanding of the biochemistry of microorganisms of biogeochemical interest. Concurrent with these advances have been the discoveries of novel types of compounds that will block the metabolism of one particular group of microbes, but have little disruptive effect on other physiological types. Thus, the term “specific inhibitor” has been applied to these types of compounds when they are used to probe the functions of mixed populations of microorganisms. These substances provide powerful experimental tools for investigating the activity and function of certain types of microorganisms in natural samples.

Book chapter↗
USGS2007

Evaluation of a non-point source pollution model, AnnAGNPS, in a tropical watershed

Impaired water quality caused by human activity and the spread of invasive plant and animal species has been identified as a major factor of degradation of coastal ecosystems in the tropics. The main goal of this study was to evaluate the performance of AnnAGNPS (Annualized Non-Point Source Pollution Model), in simulating runoff and soil erosion in a 48 km2 watershed located on the Island of Kauai, Hawaii. The model was calibrated and validated using 2 years of observed stream flow and sediment load data. Alternative scenarios of spatial rainfall distribution and canopy interception were evaluated. Monthly runoff volumes predicted by AnnAGNPS compared well with the measured data (R2 = 0.90, P < 0.05); however, up to 60% difference between the actual and simulated runoff were observed during the driest months (May and July). Prediction of daily runoff was less accurate (R2 = 0.55, P < 0.05). Predicted and observed sediment yield on a daily basis was poorly correlated (R2 = 0.5, P < 0.05). For the events of small magnitude, the model generally overestimated sediment yield, while the opposite was true for larger events. Total monthly sediment yield varied within 50% of the observed values, except for May 2004. Among the input parameters the model was most sensitive to the values of ground residue cover and canopy cover. It was found that approximately one third of the watershed area had low sediment yield (0-1 t ha-1 y-1), and presented limited erosion threat. However, 5% of the area had sediment yields in excess of 5 t ha-1 y-1. Overall, the model performed reasonably well, and it can be used as a management tool on tropical watersheds to estimate and compare sediment loads, and identify "hot spots" on the landscape. ?? 2007 Elsevier Ltd. All rights reserved.

Environmental Modelling and Software↗
USGS2025

Geochemical assessment of the suitability of converting a coal-fired power plant reservoir to a drinking-water reservoir

There is an increasing need for additional water storage in the United States, especially in arid regions. Alternatives like decommissioned power plant raw-water reservoirs would be cheaper to use than creating new reservoirs; however, the biogeochemical pollution risk of these reservoirs is not well understood. The San Juan Generating Station power plant and the associated reservoir will be used as a sediment-settling basin to store drinking water. To evaluate whether the reservoir is appropriate for this use, inorganic and organic constituents of concern were measured in reservoir sediment cores, pore water, and reservoir water in 2020. Forty-six percent of sediment arsenic concentrations measured in core subsamples (8 to 12 mg/kg) were slightly above the New Mexico residential cancer threshold for soil of 7.07 mg/kg. One sediment sample contained elevated total barium concentrations (6020 mg/kg). The organic compounds analyzed were either below detection limits or below regulatory thresholds. Reservoir water had one sample with arsenic greater than the drinking water standard (10 µg/L). Overall, the reservoir sediment inorganic and organic analyte concentrations are within acceptable ranges. The few samples that have elevated concentrations are not of a sufficient magnitude that dilution and/or treatment processes would preclude the use of the reservoir for water storage. Our findings show potential for use of former coal power station raw-water reservoirs as drinking-water reservoirs after plant closure.

New Mexico↗
USGS1998

Mercury accumulation in transplanted Hypogymnia physodes lichens downwind of Wisconsin chlor-alkali plant

Emissions of mercury from a chlor-alkali plant in central Wisconsin have raised concern about possible effects on biota in the area. Samples of the lichen Hypogymnia physodes, which no longer grows in the area, were transplanted from a site in northeastern Wisconsin and positioned on plastic stands at varying distances up to 1250 m from the plant and sampled for Hg quarterly for one year to test the hypothesis that Hg would be taken up by the lichens and would decline with distance. Average tissue concentrations were elevated when first sampled at three months and continued to increase at the nearest sites until the study ended after one year. Average concentrations after a year of exposure ranged from 4418 ppb at 250 m from the plant to 403 ppb at 1250 m from the plant. The decrease over distance followed a negative exponential pattern. Background concentrations at a control site in northern Wisconsin averaged 155 ppb.

Wisconsin↗
USGS1981

Lower Eocene alluvial paleosols (Willwood Formation, Northwest Wyoming, U.S.A.) and their significance for paleoecology, paleoclimatology, and basin analysis

The lower Eocene Willwood Formation of northwest Wyoming is a 700 m thick accumulation of alluvial floodplain and channel mudstones and sandstones, nearly all of which show paleopedogenic modifications. Pedogenesis of Willwood sandstones is indicated by taproot and vertebrate and invertebrate bioturbation, early local cementation by calcium carbonate, and thin illuviation cutans on clastic grains. Pedogenesis in Willwood mudstones is indicated by plant bioturbation, insect and other invertebrate burrow casts and lebensspuren; free iron, aluminum, and manganese mobilization, including hydromorphic gleying; sesquioxide and calcareous glaebule formation in lower parts of the solum; presence of clay-rich and organic carbon-rich zones; and well differentiated epipedons and albic and spodic horizons. Probable A horizons are also locally well developed. Occurrence of variegated paleosol units in thick floodplain mudstone deposits and their association with thin, lenticular, and unconnected fluvial sandstones in the Willwood Formation of the central and southeast Bighorn Basin suggest that these soils formed during times of rapid sediment accumulation. The tabular geometry and lateral persistence of soil units as well as the absence of catenization indicate that Willwood floodplains were broad and essentially featureless. All Willwood paleosols were developed on alluvial parent materials and are complex in that B horizons of younger paleosols were commonly superimposed upon and mask properties of suspected A and B horizons of the next older paleosols. The soils appear to be wet varieties of the Spodosol and Entisol groups (aquods and ferrods, and aquents, respectively), though thick, superposed and less mottled red, purple, and yellow paleosols resemble some ultisols. Most Willwood paleosols resemble warm temperate to subtropical alluvial soils that form today under alternating wet and dry conditions and (or) fluctuating water tables. The up-section decrease in frequency of gley mottles, increase in numerical proportion and thickness of red versus orange coloration, and increase in abundance of calcrete glaebules indicate better drained soils and probably drier climate in late Willwood time. This drying is believed to be related to creation of rain shadows and spacing of rainfall (but not necessarily decrease in absolute rainfall) due to progressive tectonic structural elevation of the mountainous margins of the Bighorn Basin.

Wyoming↗
USGS2022

Small anthropogenic landforms from past charcoal production control moisture dynamics and chemistry in northcentral Appalachian soils

Throughout the northeastern United States (U.S.) and Europe, relict charcoal hearths (RCHs) are regularly being discovered in proximity to furnaces once used for the extraction of metal from ore or quick-lime production; charcoal produced in hearths was used as a furnace fuel. Given previous research has shown that topographic and subsurface disturbance can be great when a hearth is constructed, we hypothesize that hearth construction alters surface hydrology and soil chemistry in environments in and near hearths. We used a landscape classification process to identify 6,758 hearths near furnaces at Greenwood and Pine Grove Furnace State Park, central and southcentral Pennsylvania, U.S. Two types of digital elevation model wetness indexes were used to quantify surface hydrology effects in and around hearths. Modeled wetness conditions were compared to field soil volumetric water content in RCHs near Greenwood Furnace State Park. Modeled wetness indexes indicate that RCH interiors are significantly wetter than RCH rim areas; RCHs are acting as a landscape moisture sink. Results also indicate that RCHs on slopes result in downslope drier conditions below RCHs. Field measured volumetric water content indicates that as distance from the center of the hearth increases, soil moisture significantly decreases. Geomorphic position was found to not be related to RCH wetness. Soil from RCHs, compared to nearby native soils, has significantly higher total C, a lower Mehlich 3 extractable acidity, higher Ca and P. No trend was evident with RCH soil chemistry and geomorphic position. The high frequency of RCH occurrence, in proximity to the furnace’s RCHs supported, suggests that RCHs today could locally be an important niche for understory flora and fauna. Further research could explore how RCHs might be affecting surrounding plant populations and how within RCH patterns, especially on hillslopes, might represent a distinctly different scale of physical and chemical variability.

Pennsylvania↗
USGS1988

Tolerances of plants to drought and salinity in the western United States

Differing capacities of plant species to tolerate drought and salinity are causative factors for presence of species and communities in various habitats. It is proposed that minimum xylem pressure potentials measured are indicative of drought tolerance and that minimum cell osmotic potentials are indicative of salt tolerance of plant species. Of 85 species measured, Nuttall saltbush (Atriplex nuttallii nuttallii) was found to be the most drought tolerant. Saltbrush (Atriplex confertifolia, A. nuttallii, A. canescens, and A. torreyi) had the lowest cell osmotic potentials measured. Although pickleweed (Allenrolfea occidentalis) grows in the saltiest soil measured, it did not have the lowest cell osmotic potential. This apparent inconsistency may be explained by the succulent characteristics of pickleweed. (USGS)

Water-Resources Investigations Report↗
USGS2022

The role of microtopography and resident species in post-disturbance recovery of arid habitats in Hawaiʻi

Habitat-suitability indices (HSI) have been employed in restoration to identify optimal sites for planting native species. Often, HSI are based on abiotic variables and do not include biotic interactions, even though similar abiotic conditions can favor both native and nonnative species. Biotic interactions such as competition may be especially important in invader-dominated habitats because invasive species often have fast growth rates and can exploit resources quickly. In this study, we test the utility of an HSI of microtopography derived from airborne LiDAR to predict post-disturbance recovery and native planting success in native shrub-dominated and nonnative, invasive grass-dominated dryland habitats in Hawaiʻi. The HSI uses high-resolution digital terrain models to classify sites' microtopography as high, medium, or low suitability, based on wind exposure and topographic position. We used a split-plot before-after-control-impact design to implement a disturbance experiment within native shrub ( Dodonaea viscosa ) and nonnative, invasive grass ( Cenchrus clandestinus )-dominated ecosystems across three microtopography categories. In contrast to previous studies using the same HSI, we found that microtopography was a poor predictor of pre-disturbance conditions for soil nutrients, organic matter content, or foliar C:N, within both Dodonaea and Cenchrus vegetation types. In invader-dominated Cenchrus plots, microtopography helped predict cover, but not as expected (i.e., highest cover would be in high-suitability plots): D. viscosa had the greatest cover in low-suitability and C. clandestinus had the greatest cover in medium-suitability plots. Similarly, in native-dominated Dodonaea plots, microtopography was a poor predictor of D. viscosa , C. clandestinus , and total plant cover. Although we found some evidence that microtopography helped inform post-disturbance plant recovery of D. viscosa and total plant cover, vegetation type was a more important predictor. Important for considering the success of plantings, percent cover of D. viscosa decreased while percent cover of C. clandestinus increased within both vegetation types 20 months after disturbance. Our results are evidence that HSIs based on topographic features may prove most useful for choosing planting sites in harsh habitats or those already dominated by native species. In more productive habitats, competition from resident species may offset any benefits gained from “better” suitability sites.

Hawaii↗
USGS2019

Effects of white-tailed deer (Odocoileus virginianus) exclusion on plant recovery in overwash fans after a severe coastal storm

We documented the impacts of a hyper-abundant deer population on dune vegetation recovering from severe storm surge on a barrier island through use of permanent plots and a repeated measures analysis. Three years after landfall of the storm, vegetation cover was dominated by American beachgrass, Ammophila breviligulata, though we observed twelve plant species among plots surveyed. We documented significantly greater vegetation cover in fenced than unfenced plots in overwash fans in two consecutive years. The difference in species richness between fenced and unfenced plots was significant, though richness was consistently low (≤4 species per plot) and we did not detect a statistically significant difference between years. Both deer trampling and foraging effects were captured in this study, though separation between these effects was not possible. Because trampling effects are often exacerbated on sandy soils, trampling and foraging effects should be isolated and investigated in future assessments of deer impacts on coastal vegetation. Managing deer to lower abundance may enhance coastal resilience if vegetation is allowed to recover unimpeded by foraging and trampling, though a better understanding of the precise nature of deer impacts on dune vegetation is necessary.

AoB PLANTS↗
USGS2016

Controls on distribution patterns of biological soil crusts at micro- to global scales

Biocrusts are heterogeneously distributed in space. The drivers of their distribution patterns vary depending on the spatial scale of observation. Globally, there are about 1337 cyanobacteria, algae, bryophyte, and lichen species reported as components of biocrusts. At the broadest biogeographical scales, the degree and age of isolation of land masses may dictate distribution of these species and the similarities of the floras of different continents. At intra-continental and smaller scales, climate strongly influences abundance and community composition of biocrusts. Within drylands, biocrusts become more abundant as precipitation increases. The seasonality of rainfall is about equally important, with regions receiving most precipitation as winter rain and snow exhibiting the highest abundance and greatest relative cover of bryophyte and lichens vs. cyanobacteria. Temperature gradients may dictate the dominant cyanobacterium present in the community. At eco-regional and smaller scales, edaphic gradients determined by either soil parent materials or geomorphology or both become particularly influential. Globally, the most significant soil properties influencing the eco-regional scale cover and richness of biocrusts in dryland environments are soil texture, pH, and soil CaCO3 content. Sandier soils tend to favour development of cyanobacterial biocrusts, whereas mosses and lichens tend to be more abundant on finer textured soils. The alkalinity and CaCO3 content of soils are associated with greater bioocrust abundance in some regions, and dictates the species composition in the bryophyte and lichen component. Globally, gypsiferous soils are often associated with distinct floras and high abdundances of biocrusts, especially lichens. At local to micro-scales, biocrusts often are better developed in habitats with lower radiation loads such as polar-oriented slopes, or shaded habitats. Also at small scales, vascular plant canopies buffer microclimate for biocrusts, but also exert negative influences such as burial by litter. While our knowledge of biocrust distribution has advanced rapidly, there are considerable geographic and taxonomic gaps in our knowledge and a pronounced lack of truly global studies.

Book chapter↗
USGS2014

Effects of disturbance associated with seismic exploration for oil and gas reserves in coastal marshes

Anthropogenic disturbances in wetland ecosystems can alter the composition and structure of plant assemblages and affect system functions. Extensive oil and gas extraction has occurred in wetland habitats along the northern Gulf of Mexico coast since the early 1900s. Activities involved with three-dimensional (3D) seismic exploration for these resources cause various disturbances to vegetation and soils. We documented the impact of a 3D seismic survey in coastal marshes in Louisiana, USA, along transects established before exploration began. Two semi-impounded marshes dominated by Spartina patens were in the area surveyed. Vegetation, soil, and water physicochemical data were collected before the survey, about 6 weeks following its completion, and every 3 months thereafter for 2 years. Soil cores for seed bank emergence experiments were also collected. Maximum vegetation height at impact sites was reduced in both marshes 6 weeks following the survey. In one marsh, total vegetation cover was also reduced, and dead vegetation cover increased, at impact sites 6 weeks after the survey. These effects, however, did not persist 3 months later. No effects on soil or water properties were identified. The total number of seeds that germinated during greenhouse studies increased at impact sites 5 months following the survey in both marshes. Although some seed bank effects persisted 1 year, these effects were not reflected in standing vegetation. The marshes studied were therefore resilient to the impacts resulting from 3D seismic exploration because vegetation responses were short term in that they could not be identified a few months following survey completion.

Louisiana↗
USGS2016

Ecosystem development on terraces along the Kugururok River, northwest Alaska

Riverside terraces along the Kugururok River in the Noatak National Preserve provided an opportunity to study primary succession, considering general trends that apply across all terraces, and unique events that influence individual terraces. The 30-year-old willow/poplar (Salix spp., Populus balsamifera L.) terrace had no trees taller than 1.5 m; the abundant spruce trees were not tall enough to emerge from the canopy height of the willows and poplars, and moose (Alces alces [Clinton]) browsing limited the canopy height of these plants. The 75-year-old poplar/spruce (Picea glauca [Moench] Voss) terrace had a high density of poplars (> 1000/ha) and low density of spruce (125/ha); heavy browsing by moose reduced the density of poplar by about one-half. The removal of the poplar by moose in this stand resulted in sustained increases in growth of individual spruce trees. The 100-year-old younger spruce/poplar terrace had about twice as many spruce trees (1250/ha) as poplar trees (500/ha), and the spruce trees were larger on average than the poplar trees. In the 220+ year-old older spruce/poplar type, only a few poplars remained (about 25/ha), and the number of spruce trees (600/ha) was only half that of the younger stage, either from lower initial spruce density on this terrace, or increased mortality of spruce. The 240+ year-old spruce type was a second-generation forest, characterized by a high density (1950/ha) of small spruce trees, some of which were tilted, indicating discontinuous permafrost. Plant litterfall mass showed no strong trend with terrace age, although N content of litterfall appeared to decline by about 1/3 in the spruce-dominated stages. Fungal biomass increased with ecosystem age, whereas bacterial biomass and microfauna declined. We found no evidence of declining soil N supply in older stages, but fertilization experiments would be needed to determine if N limitation of productivity changed with ecosystem development. We conclude that the general successional trend of increased spruce dominance is robust for this location, but that unique events play important roles in determining tree densities and the timing of the shift in dominance from poplar to spruce. The arrival of moose in the 1970s accelerated dominance by spruce on young terraces.

Écoscience↗
USGS2005

Southern marl prairies conceptual ecological model

About 190,000 ha of higher-elevation marl prairies flank either side of Shark River Slough in the southern Everglades. Water levels typically drop below the ground surface each year in this landscape. Consequently, peat soil accretion is inhibited, and substrates consist either of calcitic marl produced by algal periphyton mats or exposed limestone bedrock. The southern marl prairies support complex mosaics of wet prairie, sawgrass sawgrass ( Cladium jamaicense ), tree islands, and tropical hammock communities and a high diversity of plant species. However, relatively short hydroperiods and annual dry downs provide stressful conditions for aquatic fauna, affecting survival in the dry season when surface water is absent. Here, we present a conceptual ecological model developed for this landscape through scientific consensus, use of empirical data, and modeling. The two major societal drivers affecting the southern marl prairies are water management practices and agricultural and urban development. These drivers lead to five groups of ecosystem stressors: loss of spatial extent and connectivity, shortened hydroperiod and increased drought severity, extended hydroperiod and drying pattern reversals, introduction and spread of non-native trees, and introduction and spread of non-native fishes. Major ecological attributes include periphyton mats, plant species diversity and community mosaic, Cape Sable seaside sparrow ( Ammodramus maritimus mirabilis ), marsh fishes and associated aquatic fauna prey base, American alligator ( Alligator mississippiensis ), and wading bird early dry season foraging. Water management and development are hypothesized to have a negative effect on the ecological attributes of the southern marl prairies in the following ways. Periphyton mats have decreased in cover in areas where hydroperiod has been significantly reduced and changed in community composition due to inverse responses to increased nutrient availability. Plant species diversity and community mosaics have changed due to shifting gradients to more terrestrial or more aquatic communities, displacement of native communities by non-natives, expansion of woody plants, high-intensity dry season fires, tree-island burnout, and reduced microtopography resulting from alligator population decline. Cape Sable seaside sparrow populations are threatened by nest destruction resulting from extended hydroperiods, drying pattern reversals, and high intensity dry season fires, as well as by the expansion of woody plants into graminoid wetland habitats. Populations of marsh fishes and associated aquatic fauna that constitute the aquatic prey base for higher vertebrates have decreased in density and changed in species composition and size structure due to loss of wetland spatial extent, shortened hydroperiod, increased drought severity, loss of aquatic drought refugia in solution holes and alligator holes, and spread of exotic fishes. American alligator populations have declined in the Rocky Glades, and alligator holes have filled with sediment, as a result of shortened hydroperiod and increased drought severity. Habitat options for wading birds to forage during the early dry season and during unusually wet years have been reduced due to loss of spatial extent and shortened hydroperiod.

Wetlands↗
USGS2017

Water quality, sources of nitrate, and chemical loadings in the Geronimo Creek and Plum Creek watersheds, south-central Texas, April 2015–March 2016

Located in south-central Texas, the Geronimo Creek and Plum Creek watersheds have long been characterized by elevated nitrate concentrations. From April 2015 through March 2016, an assessment was done by the U.S. Geological Survey, in cooperation with the Guadalupe-Blanco River Authority and the Texas State Soil and Water Conservation Board, to characterize nitrate concentrations and to document possible sources of elevated nitrate in these two watersheds. Water-quality samples were collected from stream, spring, and groundwater sites distributed across the two watersheds, along with precipitation samples and wastewater treatment plant (WWTP) effluent samples from the Plum Creek watershed, to characterize endmember concentrations and isotopic compositions from April 2015 through March 2016. Stream, spring, and groundwater samples from both watersheds were collected during four synoptic sampling events to characterize spatial and temporal variations in water quality and chemical loadings. Water-quality and -quantity data from the WWTPs and stream discharge data also were considered. Samples were analyzed for major ions, selected trace elements, nutrients, and stable isotopes of water and nitrate. The dominant land use in both watersheds is agriculture (cultivated crops, rangeland, and grassland and pasture). The upper part of the Plum Creek watershed is more highly urbanized and has five major WWTPs; numerous smaller permitted wastewater outfalls are concentrated in the upper and central parts of the Plum Creek watershed. The Geronimo Creek watershed, in contrast, has no WWTPs upstream from or near the sampling sites. Results indicate that water quality in the Geronimo Creek watershed, which was evaluated only during base-flow conditions, is dominated by groundwater, which discharges to the stream by numerous springs at various locations. Nitrate isotope values for most Geronimo Creek samples were similar, which indicates that they likely have a common source (or sources) of nitrate. Nitrate sources in the Geronimo Creek watershed include a predominance of nitrate from fertilizer applications, as well as a contribution from septic systems. Additional nitrate loading from these sources is ongoing. Chemical loadings of dissolved solids, chloride, and sulfate varied little among sampling events and were low at most sites because of low streamflow. In contrast to the Geronimo Creek watershed, nitrate sources in the Plum Creek watershed are dominated by effluent discharge from the major WWTPs in the upper and central parts of the watershed. Results indicate that discharge from these WWTPs accounts for the majority of base flow in the watershed. Nitrate concentrations in Plum Creek were dependent on flow conditions, with the highest concentrations measured at lower flows, when flow is dominated by WWTP effluent discharge. In addition to WWTP effluent discharge, the Plum Creek watershed, similar to the Geronimo Creek watershed, also is affected by historical and current loading of nitrate from fertilizer applications and from septic systems in the watershed. Chemical loadings of dissolved solids, chloride, sulfate, and nitrate in Plum Creek at lower flow conditions are highest at the upstream sites and decrease downstream as distance from the WWTPs increases, which is consistent with WWTP effluent as an important control on water quality. Under higher flow conditions, however, nitrate loads to Plum Creek increased by about a factor of three. These higher nitrate loads cannot be accounted for by WWTP effluent discharge from the five major WWTPs in the watershed. This additional loading indicates that nitrate is exported from the northeastern part of the watershed. In the lower part of the Plum Creek watershed, higher concentrations of dissolved solids, chloride, and sulfate occur, which might be affected by produced water associated with oil and gas exploration, or mixing with saline groundwater.

Texas↗
USGS1987

Use of no-till winter wheat by nesting ducks in North Dakota

Nesting of dabbling ducks (Anatinae) was studied in fields of no-till winter wheat (Triticum aestivum) in the prairie pothole region of North Dakota during 1984 and 1985. Total area of 59 fields searched in 1984 was 1,135 ha and total area of 70 fields searched in 1985 was 1,175 ha. Field sizes ranged from 3 ha to 110 ha. Nests of five duck species were found: blue-winged teal (Anas discors), 55 nests; northern pintail (A. acuta), 44; mallard (A. platyrhynchos), 29; gadwall (A. strepera), 15; and northern shoveler (A. clypeata), 8. The average number of nests found was 8/100 ha in 1984 and 6/100 ha in 1985. Nest success for all species averaged 26% in 1984 and 29% in 1985. Predation by mammals was the principal cause of nest destruction. No egg or hen mortality could be attributed to pesticide use. Only 6 of 151 nests (4%) were abandoned during the two years. We also found 29 nests of seven other ground-nesting bird species. The trend toward increased planting of no-till winter wheat in the prairie pothole region should benefit production of ducks and other ground-nesting birds.

Journal of Soil and Water Conservation↗
USGS2019

Fire, forests and city water supply

Forest landscapes generate 57 percent of runoff worldwide and supply water to more than 4 billion people (Millennium Ecosystem Assessment, 2005). As the world population continues to increase, there is a strong need to understand how forest processes link together in a cascade to provide people with water services like hydropower, aquaculture, drinking water and flood protection (Carvalho-Santos, Honrado and Hein, 2014). Wildfire is a major disturbance affecting forested watersheds and the water they provide (Box 1) (Paton et al., 2015). Several regions have experienced shifts in wildfires from natural ignition sources (primarily lightning) to ignitions dominated by human activities, especially in areas where populations are increasing (Moritz et al., 2014; Balch et al., 2017). Occasional wildfire is essential for the health and functioning of fire-adapted ecosystems through its effects on nutrient cycling, plant diversity and succession, and pest regulation (Pausas and Keeley, 2019). It also reduces the risk of subsequent wildfires until a forest has accumulated sufficient fuels and conditions are conducive for another fire. Extreme and hazardous wildfires, on the other hand, can cause erosion, gullying, soil loss and flooding – and, in severe cases, even debris flows and flash floods – by removing the protective functions of forests on hillsides (Ebel and Moody, 2017). Extreme wildfires have become more common after decades of fire suppression, allowing forests to become much denser with vegetation and causing more fuels to build up over time. Combined with increasing summer drought, this can have impacts on water yield and the ability of upstream forests to deliver high-quality water because forest vegetation uses less water immediately after fire and, in environments influenced by snow, more snow can accumulate in forest clearings (Kinoshita and Hogue, 2015; Hallema et al., 2019). Therefore, accounting for wildfire impacts on forests in water planning has become a priority for the nexus of fire, water and society or, in other words, the connection between fire risk and water security (Figure 1) (Martin, 2016). In this article, we discuss managed forest landscapes as nature-based solutions for water and explore how fire affects the provision of water-related services.

Unasylva↗
USGS2006

Seed germination of cirsium arvense and Lepidium latifolium: Implications for management of montane wetlands

Cirsium arvense and Lepidium latifolium are species that can aggressively invade wetland margins and potentially reduce biodiversity and alter ecosystem function. Although expansion of these species primarily occurs via rhizomatous growth, seeds are thought to be important in initial establishment. We conducted this study to investigate differences in seed germination of C. arvense and L. latifolium in montane wetlands of Colorado and Wyoming, USA. We used germination chambers to simulate environmental conditions (photoperiod, day/night temperature) during three periods of the growing season at each site and evaluated seed germination in relation to three soil moisture levels and two soil depths. A combination of shallow (<1 cm) seed burial and wet conditions resulted in the greatest germination probability of C. arvense (x = 63.0%), 95% CI = 41.2-80.5%), whereas deep (2-3 cm) seed burial and saturated moisture conditions resulted in almost no germination (x?? = 0.3%, 95% CI = 0.1-1.3%). The maximum germination probability of 44.0% (CI = 28.1-61.4%) for L. latifolium also occurred in the shallow burial and wet treatment; however, only effects of seed burial were significant (P < 0.05). The estimated mean germination probability of deeply buried seeds was <1.0% (CI = 0.3-1.4%) compared to 32% (CI = 19.7-47.9%) for shallowly buried seeds. Our results suggest that each species has the ability to germinate at similar rates throughout the growing season and across a large portion of the moisture gradient. This suggests that management actions, including water-level manipulations, at any time during the growing season may stimulate germination. Although burial of seed to depths of 2-3 cm reduced the germination potential of both species, the use of mechanical implements may be problematic in established stands because new plants of both species easily sprout from root buds. Further, disturbance resulting from such actions diminishes the density and vigor of other plants already present, which may ultimately decrease the competitive resistance of the disturbed environment to invasion by outside species. Detection of new invasions is a critical component of any integrated weed management program. Our results indicate that the incidence of C. arvense and L. latifolium germination is most likely in areas with seeds that are within 1 cm of the soil surface and soil moisture is 75-100% of field capacity for extended periods. ?? 2006, The Society of Wetland Scientists.

Wetlands↗