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At least 919 records · Page 51Linked to original sources
USGS2004

Seismographs, sensors, and satellites: Better technology for safer communities

In the past 25 years, our ability to measure, monitor, and model the processes that lead to natural disasters has increased dramatically. Equally important has been the improvement in our technological capability to communicate information about hazards to those whose lives may be affected. These innovations in tracking and communicating the changes-floods, earthquakes, wildfires, volcanic eruptions-in our dynamic planet, supported by a deeper understanding of earth processes, enable us to expand our predictive capabilities and point the way to a safer future. ?? 2004 Elsevier Ltd. All rights reserved.

Technology in Society↗
USGS2023

Science to support conservation action in a large river system: The Willamette River, Oregon, USA

Management and conservation efforts that support the recovery and protection of large rivers are daunting, reflecting the complexity of the challenge and extent of effort (in terms of policy, economic investment, and spatial extent) needed to afford measurable change. These large systems have generally experienced intensive development and regulation, compromising their capacity to respond to disturbances such as climate change or wildfire. Functionally, large river and basin management require insights gained from social, ecological, geophysical, and hydrological sciences. This multi-disciplinary perspective can unveil the integrated relationship between a river network's biotic community and seasonally variable environmental conditions that are often influenced by human activities. Large rivers and their basins are constantly changing due to anthropogenic influences and as climate modifies patterns of temperature and precipitation. Because of these factors, the state of knowledge must advance to address changing conditions. The Willamette River, in western Oregon, USA, is a prime example of a basin that has experienced significant degradation and investment in rehabilitation in recent decades. Innovative science has facilitated development of fine-scale, spatially extensive datasets and models that can generate targeted conservation and rehabilitation actions that are prioritized across the entire river network. This prioritization allows investment decisions to be driven by site-specific conditions while simultaneously considering potentials for ecological improvement. Here, we review hydrologic, geomorphic, ecologic, and social conditions in the Willamette River basin through time—including pre-settlement, river development, and contemporary periods—and offer a future vision for consideration. Currently, detailed information about fish populations and habitat, hydrologic conditions, geomorphology, water quality, and land use can be leveraged to make informed decisions about protection, rehabilitation, and development. The time is ripe for strategic management and goal development for the entire Willamette River, and these efforts can be informed by comprehensive science realized through established institutions (e.g., public agencies, non-profit watershed groups, Tribes, and universities) focused on conservation and management. The approaches to science and social-network creation that were pioneered in the Willamette River basin offer insights into the development of comprehensive conservation-based planning that could be implemented in other large river systems globally.

Oregon↗
USGS2003

Introduction to the effects of wildland fire on aquatic ecosystems in the Western USA

The management of wildfire has long been controversial. The role of fire and fire-related management in terrestrial and aquatic ecosystems has become an important focus in recent years, but the general debate is not new. In his recent book, Stephen Pyne (2001 ) describes the political and scientific debate surrounding the creation of the U.S. Forest Service and the emergence of fire suppression as a central tenet of wildland management. Essentially, views in the first decade of the 20th century focused on fire as good or evil: a tool that might benefit other resources or interests (e.g. Indian burning) and mitigate larger more destructive fires, or a threat to the recruitment and productivity of newly designated forest reserves. The “great fires” in the Western USA in 1910 and the associated loss of human life and property largely forged the public and political will to suppress fire on a massive scale.

Forest Ecology and Management↗
USGS1997

Streamwater chemistry and nutrient budgets for forested watersheds in New England: Variability and management implications

Chemistry of precipitation and streamwater and resulting input-output budgets for nutrient ions were determined concurrently for three years on three upland, forested watersheds located within an 80 km radius in central New England. Chemistry of precipitation and inputs of nutrients via wet deposition were similar among the three watersheds and were generally typical of central New England. In contrast, chemistry and nutrient outputs in streamwater varied dramatically between watersheds, with chemistries ranging from acidic to alkaline. Comparisons with data reported for 159 other upland, forested watersheds in central New England show that our study watersheds span the regional range likely to be encountered in stream chemistry. The regional variability stems in part from past natural disturbances such as wildfire, and variations in source of soil parent material. An approach is presented for predicting the important influence of glacial till on stream chemistry, including acid-base relationships, aluminum content, and nutrient outputs. Knowledge of streamwater chemistry and controlling factors can serve as an index of how terrestrial and aquatic ecosystems will respond to forest management activities and atmospheric deposition.

Forest Ecology and Management↗
USGS2023

Effectiveness of a decade of treatments to reduce invasive buffelgrass (Pennisetum ciliare)

The invasion of nonnative grasses threatens biodiversity and ecosystem function globally through competition with native plant species and increases to wildfire frequency and intensity. Management actions to reduce buffelgrass [ Pennisetum ciliare (L.) Link], an invasive warm-season perennial bunchgrass, are widely implemented, with chemical and mechanical treatments extending over two decades within Saguaro National Park in the Sonoran Desert of North America. We assessed how the effectiveness of treatments to reduce P. ciliare cover spanning from 2011 to 2020 were influenced by stage of invasion, treatment type and intensity, and environmental conditions. An increase in treatment effectiveness was largely explained by high initial cover of P. ciliare , an indicator of a late invasion stage and associated with high treatment intensity. Treatments had potential to be effective in patches as small as 0.3-m 2 P. ciliare canopy per 400-m −2 area (<0.001% canopy cover) across treatment types and environmental gradients. Chemical treatments had higher or equal effectiveness compared with mechanical treatments, and greater reductions in P. ciliare were associated with shorter average years of treatment interruptions, or gaps, and to a lesser degree, total years of treatment. In many cases, P. ciliare was reduced with as little as 2 yr of treatment, but more than 3 average years of treatment gap could result in reduced treatment effectiveness. There was generally higher treatment effectiveness on shallow slopes, north- and east-facing aspects, and on higher elevations within one district of the park. Our findings highlight that resource-intensive treatments in all but the smallest patches of P. ciliare have largely been effective. Further opportunities for improvement include more frequent surveillance, limiting treatment gaps to ≤3 yr in areas of low P. ciliare cover, and comparison of treated with untreated areas.

Arizona↗
USGS2003

Population increase in Kirtland's warbler and summer range expansion to Wisconsin and Michigan's Upper Peninsula, USA

The threatened Kirtland's warbler Dendroica kirtlandii breeds in stands of young jack pine Pinus banksiana growing on well-drained soils in Michigan, USA. We summarize information documenting the range expansion of Kirtland's warbler due to increased habitat management in the core breeding range in the Lower Peninsula of Michigan during 1990–2000. We collected records and conducted searches for the species in Michigan's Upper Peninsula and Wisconsin over 1978–2000. During that time 25 males were found in Wisconsin and 90 males in the Upper Peninsula. We documented colonization of Michigan's Upper Peninsula by six ringed males from the Lower Peninsula of Michigan. Four ringed birds also moved back to the core breeding range, including two males that made two-way movements between the core breeding range and the Upper Peninsula. Thirty-seven females were observed with males from 1995 to 2000, all in Michigan. Nesting activities were noted for 25 pairs and at least nine nests fledged young. One male ringed as a fledgling returned to breed in two subsequent years. After a 19-year period of population stability, the Kirtland's warbler population increased four-fold during 1990–2000, most likely in response to a tripling in habitat area. This increase in sightings and documented breeding may be related to habitat availability in Michigan's Upper Peninsula and to saturation of habitat in the main breeding range. The increase in extra-limital records during 1995–1999 corresponds to the time when the population went from the minimum to the maximum projected population densities, and a decline in natural wildfire habitat was just offset by new managed habitat for the Kirtland's warbler.

Michigan, Wisconsin↗
USGS2026

Optimizing cryo-focused pyrolysis GC/MS for tracing soil organic matter across diverse ecosystems

The cycling of organic matter in terrestrial soils and sediments is central to a range of biogeochemical processes that regulate nutrient cycling, crop productivity, trace gas emissions, and contaminant transport. Pyrolysis-gas chromatography/mass spectrometry (py-GC/MS) is a powerful tool for characterizing bulk soil organic matter (SOM) at the molecular level. In this study, we used a cryo-focused py-GC/MS system to analyze soil samples from seven diverse ecosystems: vernal pool, prairie pothole, temperate forest, tropical forest, tundra, wildfire-affected boreal forest, and grassland. We addressed a key bottleneck in molecular-level SOM characterization by developing an automated data analysis pipeline to optimize py-GC/MS and complementary evolved gas analysis/mass spectrometry (EGA/MS) methods, incorporating advanced tools for data deconvolution, developing a custom compound class library, and implementing fragmentation spectrum-based molecular networking for the first time. This improved workflow was applied to soil samples from all seven ecosystems, including multiple depths and density fractions. Our findings demonstrate that ecosystem type plays a dominant role in shaping compositional differences in SOM. We also identified trends in the source of SOM compounds (e.g., microbial vs. plant-derived) across soil depth and density fractions, which are critical for understanding persistence and turnover of SOM. Our molecular networking analysis indicated that although many compounds are widespread across ecosystems, others are restricted to specific environments, such as wetlands. This underscores the utility of molecular-level data in elucidating the complexity of SOM composition and the environmental drivers that shape it. Such molecular-level insights can deepen our knowledge of biogeochemical SOM cycles.

Environmental Science and Technology↗
USGS2006

Concentration and dry deposition of mercury species in arid south central New Mexico (2001-2002)

This research was initiated to characterize atmospheric deposition of reactive gaseous mercury (RGM), particulate mercury (HgP; <2.5 &mu;m), and gaseous elemental mercury (Hg 0 ) in the arid lands of south central New Mexico. Two methods were field-tested to estimate dry deposition of three mercury species. A manual speciation sampling train consisting of a KCl-coated denuder, 2.5 &mu;m quartz fiber filters, and gold-coated quartz traps and an ion-exchange membrane (as a passive surrogate surface) were deployed concurrently over 24-h intervals for an entire year. The mean 24-h atmospheric concentration for RGM was 6.8 pg m -3 with an estimated deposition of 0.10 ng m -2 h -1 . The estimated deposition of mercury to the passive surrogate surface was much greater (4.0 ng m -2 h -1 ) but demonstrated a diurnal pattern with elevated deposition from late afternoon to late evening (1400&minus;2200; 8.0 ng m -2 h -1 ) and lowest deposition during the night just prior to sunrise (2200&minus;0600; 1.7 ng m -2 h -1 ). The mean 24-h atmospheric concentrations for HgP and Hg 0 were 1.52 pg m -3 and 1.59 ng m -3 , respectively. Diurnal patterns were observed for RGM with atmospheric levels lowest during the night prior to sunrise (3.8 pg m-3) and greater during the afternoon and early evening (8.9 pg m -3 ). Discernible diurnal patterns were not observed for either HgP or Hg 0 . The total dry deposition of Hg was 5.9 &mu;g m -2 year-1 with the contribution from the three species as follows:&thinsp; RGM (0.88 &mu;g m -2 year -1 ), HgP (0.025 &mu;g m -2 year -1 ), and Hg 0 (5.0 &mu;g m -2 year -1 ). The annual wet deposition for total mercury throughout the same collection duration was 4.2 &mu;g m -2 year -1 , resulting in an estimated total deposition of 10.1 &mu;g m -2 year -1 for Hg. On one sampling date, enhanced HgP (12 pg m -3 ) was observed due to emissions from a wildfire approximately 250 km to the east.

Environmental Science & Technology↗
USGS1997

Landscape characteristics of disturbed shrubsteppe habitats in southwestern Idaho (USA)

We compared 5 zones in shrubsteppe habitats of southwestern Idaho to determine the effect of differing disturbance combinations on landscapes that once shared historically similar disturbance regimes. The primary consequence of agriculture, wildfires, and extensive fires ignited by the military during training activities was loss of native shrubs from the landscape. Agriculture created large square blocks on the landscape, and the landscape contained fewer small patches and more large shrub patches than non-agricultural areas. In contrast, fires left a more fragmented landscape. Repeated fires did not change the distribution of patch sizes, but decreased the total area of remaining shrublands and increased the distance between remaining shrub patches that provide seed sources. Military training with tracked vehicles was associated with a landscape characterized by small, closely spaced, shrub patches. Our results support the general model hypothesized for conversion of shrublands to annual grasslands by disturbance. Larger shrub patches in our region, historically resistant to fire spread and large-scale fires because of a perennial bunchgrass understory, were more fragmented than small patches. Presence of cheatgrass (Bromus tectorum), an exotic annual, was positively related to landscape patchiness and negatively related to number of shrub cells. Thus, cheatgrass dominance can contribute to further fragmentation and loss of the shrub patch by facilitating spread of subsequent fires, carried by continuous fuels, through the patch. The synergistic processes of fragmentation of shrub patches by disturbance, invasion and subsequent dominance by exotic annuals, and fire are converting shrubsteppe in southwestern Idaho to a new state dominated by exotic annual grasslands and high fire frequencies.

Idaho↗
USGS2004

Chemistry of burning the forest floor during the FROSTFIRE experimental burn, interior Alaska, 1999

Wildfires represent one of the most common disturbances in boreal regions, and have the potential to reduce C, N, and Hg stocks in soils while contributing to atmospheric emissions. Organic soil layers of the forest floor were sampled before and after the FROSTFIRE experimental burn in interior Alaska, and were analyzed for bulk density, major and trace elements, and organic compounds. Concentrations of carbon, nutrients, and several major and trace elements were significantly altered by the burn. Emissions of C, N, and Hg, estimated from chemical mass balance equations using Fe, Al, and Si as stable constituents, indicated that 500 to 900 g C and up to 0 to 4 ?? 10-4 g Hg/M2 were lost from the site. Calculations of nitrogen loss range from -4 to +6 g/m2 but were highly variable (standard deviation 19), with some samples showing increased N concentrations post-burn potentially from canopy ash. Noncombustible major nutrients such as Ca and K also were inherited from canopy ash. Thermogravimetry indicates a loss of thermally labile C and increase of lignin-like C in char and ash relative to unburned counterparts. Overall, atmospheric impacts of boreal fires include large emissions of C, N and Hg that vary greatly as a function of severe fire weather and its access to deep organic layers rich in C, N, and Hg. In terrestrial systems, burning rearranges the vertical distribution of nutrients in fuels and soils, the proximity of nutrients and permafrost to surface biota, and the chemical composition of soil including its nutrient and organic constituents, all of which impact C cycling. Copyright 2004 by the American Geophysical Union.

Global Biogeochemical Cycles↗
USGS2011

Is the northern high-latitude land-based CO2 sink weakening?

Studies indicate that, historically, terrestrial ecosystems of the northern high-latitude region may have been responsible for up to 60% of the global net land-based sink for atmospheric CO2. However, these regions have recently experienced remarkable modification of the major driving forces of the carbon cycle, including surface air temperature warming that is significantly greater than the global average and associated increases in the frequency and severity of disturbances. Whether Arctic tundra and boreal forest ecosystems will continue to sequester atmospheric CO2 in the face of these dramatic changes is unknown. Here we show the results of model simulations that estimate a 41 Tg C yr-1 sink in the boreal land regions from 1997 to 2006, which represents a 73% reduction in the strength of the sink estimated for previous decades in the late 20th century. Our results suggest that CO 2 uptake by the region in previous decades may not be as strong as previously estimated. The recent decline in sink strength is the combined result of (1) weakening sinks due to warming-induced increases in soil organic matter decomposition and (2) strengthening sources from pyrogenic CO2 emissions as a result of the substantial area of boreal forest burned in wildfires across the region in recent years. Such changes create positive feedbacks to the climate system that accelerate global warming, putting further pressure on emission reductions to achieve atmospheric stabilization targets. Copyright 2011 by the American Geophysical Union.

Global Biogeochemical Cycles↗
USGS2011

Vulnerability of high-latitude soil organic carbon in North America to disturbance

This synthesis addresses the vulnerability of the North American high-latitude soil organic carbon (SOC) pool to climate change. Disturbances caused by climate warming in arctic, subarctic, and boreal environments can result in significant redistribution of C among major reservoirs with potential global impacts. We divide the current northern high-latitude SOC pools into (1) near-surface soils where SOC is affected by seasonal freeze-thaw processes and changes in moisture status, and (2) deeper permafrost and peatland strata down to several tens of meters depth where SOC is usually not affected by short-term changes. We address key factors (permafrost, vegetation, hydrology, paleoenvironmental history) and processes (C input, storage, decomposition, and output) responsible for the formation of the large high-latitude SOC pool in North America and highlight how climate-related disturbances could alter this pool's character and size. Press disturbances of relatively slow but persistent nature such as top-down thawing of permafrost, and changes in hydrology, microbiological communities, pedological processes, and vegetation types, as well as pulse disturbances of relatively rapid and local nature such as wildfires and thermokarst, could substantially impact SOC stocks. Ongoing climate warming in the North American high-latitude region could result in crossing environmental thresholds, thereby accelerating press disturbances and increasingly triggering pulse disturbances and eventually affecting the C source/sink net character of northern high-latitude soils. Finally, we assess postdisturbance feedbacks, models, and predictions for the northern high-latitude SOC pool, and discuss data and research gaps to be addressed by future research.

Journal of Geophysical Research G: Biogeosciences↗
USGS2019

Developing and testing physically based triggering thresholds for runoff‐generated debris flows

Runoff in steep channels is capable of transitioning into debris flows with hazardous implications for downstream communities and infrastructure, particularly in alpine landscapes with minimal vegetation and areas recently disturbed by wildfire. Here, we derive thresholds for the initiation of runoff‐generated debris flows based on critical values of dimensionless discharge and Shields stress. These thresholds are derived by using a numerical model to estimate the hydrodynamic conditions coinciding with the timing of debris flow activity in a recently burned basin. A benefit of hydrodynamic thresholds is that they can be used to assess debris flow likelihood based on measurable hydrologic and geomorphic parameters and therefore provide more universal criteria for quantifying the runoff‐to‐debris flow transition in landscape evolution studies and hazard assessments. We then demonstrate how hydrodynamic thresholds can be used to estimate rainfall intensity‐duration thresholds for runoff‐generated debris flows without the need for historic debris flow observations.

California↗
USGS2021

Watershed sediment yield following the 2018 Carr Fire, Whiskeytown National Recreation Area, northern California

Wildfire risk has increased in recent decades over many regions, due to warming climate and other factors. Increased sediment export from recently burned landscapes can jeopardize downstream infrastructure and water resources, but physical landscape response to fire has not been quantified for some at-risk areas, including much of northern California, USA. We measured sediment yield from three watersheds (13–29 km 2 ) that drain to Whiskeytown Lake, California, within the area burned by the 2018 Carr Fire. Structure-from-Motion photogrammetry on aerial images combined with sonar bathymetric mapping of submerged areas indicated first-year post-fire sediment yields of 4,080 ± 598 t/km 2 (Brandy Creek), 2,700 ± 527 t/km 2 (Boulder Creek), and 305 ± 58.0 t/km 2 (Whiskey Creek)—some of the first post-fire yields measured in northern California and 64, 42, and 4.8 times greater than pre-fire yields, respectively. These were measured during a wet year and resulted largely from rilling erosion and fluvial sediment transport, without post-fire debris flows. Rilling preferentially developed in contact with dirt roads, aided by thin soils and exposed bedrock, and on slopes vegetated by chaparral pre-fire. The second post-fire year (a dry year) was characterized by fluvial reworking and delta progradation of the first-year deposits and relatively little new sediment export. First-year sedimentation of 111,000 m 3 represented minor loss of storage capacity in Whiskeytown Lake but would be detrimental to smaller reservoirs; in general, increased sediment yields from western US watersheds as fire and extreme rainfall increase will likely pose risks to water quality and storage.

California↗
USGS2022

Elevated nitrogen deposition to fire-prone forests adjacent to urban and agricultural areas, Colorado front range, USA

As humans increasingly dominate the nitrogen cycle, deposition of reactive nitrogen (Nr) will continue to have adverse consequences for ecosystems. In the Rocky Mountains, Nr deposition remains elevated and has become increasingly dominated by ammonium, despite efforts to reduce emissions. Currently, spatial models of Nr deposition do not fully account for urban and agricultural emissions, sources that contribute to the observed high rates of ammonium deposition in adjacent ecosystems. To address this gap in the Colorado Front Range, we measured Nr deposition along a transect from urban and agricultural plains to subalpine forests. We found elevated values of wet Nr deposition at the urban and foothill sites (4.7 and 4.4 kg N ha −1 yr −1 , respectively), and lower values at the montane and subalpine sites (2.5–2.8 kg N ha −1 yr −1 ). Ammonium dominated wet and bulk Nr deposition, accounting for approximately 69% of bulk Nr deposition. Seasonally, bulk Nr deposition was highest in the spring months, when air masses from the plains are transported west into the mountains. Previous work has demonstrated that high elevations of the Colorado Front Range are especially sensitive to Nr deposition due to thin soil and minimal vegetation. Our results indicate that despite lower precipitation, the fire-prone forested foothills receive even greater Nr deposition than higher elevations, due to proximity to urban and agricultural Nr sources. The interaction between elevated Nr deposition and wildfire in this region may pose a risk to water supplies and ecosystems, and is an important topic for future research.

Colorado↗
USGS2024

Post-fire sediment yield from a central California watershed: Field measurements and validation of the WEPP model

In a warming climate, an intensifying fire regime and higher likelihood of extreme rain are expected to increase watershed sediment yield in many regions. Understanding regional variability in landscape response to fire and post-fire rainfall is essential for managing water resources and infrastructure. We measured sediment yield resulting from sequential wildfire and extreme rain and flooding in the upper Carmel River watershed (116 km 2 ), on the central California coast, USA, using changes in sediment volume mapped in a reservoir. We determined that the sediment yield after fire and post-fire flooding was 854–1,100 t/km 2 /yr, a factor of 3.5–4.6 greater than the long-term yield from this watershed and more than an order of magnitude greater than during severe drought conditions. In this first large-scale field validation test of the WEPPcloud/ wepppy framework for the Water Erosion Prediction Project (WEPP) model on a burned landscape, WEPP predicted 81%–106% of the measured sediment yield. These findings will facilitate assessing and predicting future fire effects in steep watersheds with a Mediterranean climate and indicate that the increasingly widespread use of WEPP is appropriate for evaluating post-fire hillslope erosion even across 100-km 2 scales under conditions without debris flows.

California↗
USGS2025

Post-fire sediment yield from a western Sierra Nevada watershed burned by the 2021 Caldor Fire

Watershed sediment yield commonly increases after wildfire, often causing negative impacts to downstream infrastructure and water resources. Post-fire erosion is important to understand and quantify because it is increasingly placing water supplies, habitat, communities, and infrastructure at risk as fire regimes intensify in a warming climate. However, measurements of post-fire sediment mobilization are lacking from many regions. We measured sediment yield from a forested, heavily managed 25.4-km 2 watershed in the western Sierra Nevada, California, over 2 years following the 2021 Caldor Fire, by repeat mapping of a reservoir where sediment accumulated from terrain with moderate to high soil burn severity. Sediment yield was less than the geochronology-derived long-term average in the first year post-fire (conservatively estimated at 21.8–28.0 t/km 2 ), low enough to be difficult to measure with uncrewed airborne system (UAS) and bathymetric sonar survey methods that are most effective at detecting larger sedimentary signals. In the second year post-fire the sediment delivery was 1,560–2,010 t/km 2 , an order of magnitude above long-term values, attributable to greater precipitation and intensive salvage logging. Hillslope erosion simulated by the Water Erosion Prediction Project (WEPP) model overestimated the measured amount by a factor of 90 in the first year and in the second year by a factor (1.9) that aligned with previously determined model performance in northern California. We encourage additional field studies, and validation of erosion models where feasible, to further expand the range of conditions informing post-fire hazard assessments and management decisions.

California↗