Geology Reports⌕ Search

SEARCH · Geology Reports

Results for “Climate Change Responses”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 865 records · Page 48Linked to original sources
USGS2019

Evaluating community-level response to management actions across a diverse Hawaiian forest bird community

Although species‐specific approaches are necessary to understand the dynamics of individual species composing a community, they do not offer a framework for making optimal management decisions at the community level. Here, we present a simple framework for comparing the response of entire communities to multiple management scenarios. Our approach uses a weighted average of standardized species‐specific responses to produce a single integrative measure of the community response and employs mixed‐effect linear models to quantify the increase in the community response due to each management action, or combination of actions. We demonstrate our approach with a simulation study assessing the potential benefits of multiple management actions on the avian community of Hakalau Forest National Wildlife Refuge, Hawaiʻi, which is composed of eight native species with conservation status varying from endangered to least concern. Management actions considered included a reduction of avian malaria transmission risk, reducing rat predation, and increasing forest habitat. We used three different prioritization (weighting) schemes to assess whether the response to management actions differed along a conservation gradient (from endangered to least concern). We also investigated whether future changes in disease distribution as a result of climate change will alter the relationship between management practices and community response. Our community‐level analysis produced three important insights, highlighting the need to consider the response from multiple species to changing threats and management actions. First, increasing the amount of habitat always had the greatest positive impact on the avian community, regardless of the weighting scheme. Second, the community response to management was different under current vs. future conditions, with increased benefit in the future when disease risks were higher. Third, the response to management varied along the conservation gradient. Reducing malaria transmission risk in 2100 had the greatest benefit to endangered species, while increasing forest habitat had the greatest benefit to “least concern” species. However, reducing rat predation appeared to benefit a subset of species based on ecological factors unrelated to rarity, such as nest accessibility. Our approach is widely applicable using experimental, observational, or simulation‐based data, allowing managers to consider the response of all species while weighting their priority levels.

Hawaii↗
USGS2012

High-resolution tephrochronology of the Wilson Creek Formation (Mono Lake, California) and Laschamp event using 238 U- 230 Th SIMS dating of accessory mineral rims

Sediments of the Wilson Creek Formation surrounding Mono Lake preserve a high-resolution archive of glacial and pluvial responses along the eastern Sierra Nevada due to late Pleistocene climate change. An absolute chronology for the Wilson Creek stratigraphy is critical for correlating the paleoclimate record to other archives in the western U.S. and the North Atlantic region. However, multiple attempts to date the Wilson Creek stratigraphy using carbonates and tephras yield discordant results due to open-system effects and radiocarbon reservoir uncertainties as well as abundant xenocrysts. New ion microprobe 238 U- 230 Th dating of the final increments of crystallization recorded by allanite and zircon autocrysts from juvenile pyroclasts yield ages that effectively date eruption of key tephra beds and delimit the timing of basal Wilson Creek sedimentation to the interval between 26.8±2.1 and 61.7±1.9 ka. Tephra (Ash 15) erupted during the geomagnetic excursion originally designated the Mono Lake excursion yields an age of 40.8±1.9 ka, indicating that the event is instead the Laschamp excursion. The new ages support a depositional chronology from magnetostratigraphy that indicates quasi-synchronous glacial and hydrologic responses in the Sierra Nevada and Mono Basin to regional climate change, with intervals of lake filling and glacial-snowpack melting that are in phase with peaks in spring insolation.

California↗
USGS2010

Perspectives: Gene Expression in Fisheries Management

Functional genes and gene expression have been connected to physiological traits linked to effective production and broodstock selection in aquaculture, selective implications of commercial fish harvest, and adaptive changes reflected in non-commercial fish populations subject to human disturbance and climate change. Gene mapping using single nucleotide polymorphisms (SNPs) to identify functional genes, gene expression (analogue microarrays and real-time PCR), and digital sequencing technologies looking at RNA transcripts present new concepts and opportunities in support of effective and sustainable fisheries. Genomic tools have been rapidly growing in aquaculture research addressing aspects of fish health, toxicology, and early development. Genomic technologies linking effects in functional genes involved in growth, maturation and life history development have been tied to selection resulting from harvest practices. Incorporating new and ever-increasing knowledge of fish genomes is opening a different perspective on local adaptation that will prove invaluable in wild fish conservation and management. Conservation of fish stocks is rapidly incorporating research on critical adaptive responses directed at the effects of human disturbance and climate change through gene expression studies. Genomic studies of fish populations can be generally grouped into three broad categories: 1) evolutionary genomics and biodiversity; 2) adaptive physiological responses to a changing environment; and 3) adaptive behavioral genomics and life history diversity. We review current genomic research in fisheries focusing on those that use microarrays to explore differences in gene expression among phenotypes and within or across populations, information that is critically important to the conservation of fish and their relationship to humans.

Current Zoology↗
USGS2026

Linking community-climate disequilibrium to ecosystem function

Turnover in species composition often lags behind the pace of climate change, resulting in mismatches between climate and communities. However, the impact of these community-climate disequilibria on ecosystem functions is rarely considered, and current methods for measuring disequilibria assume that species ranges were, until recently, in equilibrium with climate. Here, we develop a simple theoretical model to address both of these problems by linking community-climate disequilibrium with ecosystem functioning. We show how disequilibrium can impair functioning in the near-term even when climate change is expected to enhance functioning in the long-term. Responses are most likely to change over time in communities where turnover is slow, the impact of disequilibrium counteracts the direct effects of climate on ecosystem function, and pre-existing disequilibrium is large. These findings emphasise the importance of precise and unbiased estimates of community-climate disequilibria for improving ecological forecasts. By fitting our model to time series of both climate and ecosystem function from a metacommunity simulation, we show the potential for community-climate disequilibrium to be inferred without direct knowledge about species' distributions or climatic tolerances. We end by outlining a research agenda to apply dynamic disequilibrium concepts and test novel hypotheses across diverse ecosystems.

Ecology Letters↗
USGS2018

Land cover and land use change

Climate can affect and be affected by changes in land cover (the physical features that cover the land such as trees or pavement) and land use (human management and activities on land, such as mining or recreation). A forest, for instance, would likely include tree cover but could also include areas of recent tree removals currently covered by open grass areas. Land cover and use are inherently coupled: changes in land-use practices can change land cover, and land cover enables specific land uses. Understanding how land cover, use, condition, and management vary in space and time is challenging. Changes in land cover can occur in response to both human and climate drivers. For example, demand for new settlements often results in the permanent loss of natural and working lands, which can result in localized changes in weather patterns, temperature, and precipitation. Aggregated over large areas, these changes have the potential to influence Earth’s climate by altering regional and global circulation patterns, changing the albedo (reflectivity) of Earth’s surface, and changing the amount of carbon dioxide (CO 2 ) in the atmosphere. Conversely, climate change can also influence land cover, resulting in a loss of forest cover from climate-related increases in disturbances, the expansion of woody vegetation into grasslands, and the loss of beaches due to coastal erosion amplified by rises in sea level. Land use is also changed by both human and climate drivers. Land-use decisions are traditionally based on short-term economic factors. Land-use changes are increasingly being influenced by distant forces due to the globalization of many markets. Land use can also change due to local, state, and national policies, such as programs designed to remove cultivation from highly erodible land to mitigate degradation, legislation to address sea level rise in local comprehensive plans, or policies that reduce the rate of timber harvest on federal lands. Technological innovation has also influenced land-use change, with the expansion of cultivated lands from the development of irrigation technologies and, more recently, decreases in demand for agricultural land due to increases in crop productivity. The recent expansion of oil and gas extraction activities throughout large areas of the United States demonstrates how policy, economics, and technology can collectively influence and change land use and land cover. Decisions about land use, cover, and management can help determine society’s ability to mitigate and adapt to climate change.

Report↗
USGS2008

Loess record of the Pleistocene-Holocene transition on the northern and central Great Plains, USA

Various lines of evidence support conflicting interpretations of the timing, abruptness, and nature of climate change in the Great Plains during the Pleistocene-Holocene transition. Loess deposits and paleosols on both the central and northern Great Plains provide a valuable record that can help address these issues. A synthesis of new and previously reported optical and radiocarbon ages indicates that the Brady Soil, which marks the boundary between late Pleistocene Peoria Loess and Holocene Bignell Loess, began forming after a reduction in the rate of Peoria Loess accumulation that most likely occurred between 13.5 and 15 cal ka. Brady Soil formation spanned all or part of the B??lling-Aller??d episode (approximately 14.7-12.9 cal ka) and all of the Younger Dryas episode (12.9-11.5 cal ka) and extended at least 1000 years beyond the end of the Younger Dryas. The Brady Soil was buried by Bignell Loess sedimentation beginning around 10.5-9 cal ka, and continuing episodically through the Holocene. Evidence for a brief increase in loess influx during the Younger Dryas is noteworthy but very limited. Most late Quaternary loess accumulation in the central Great Plains was nonglacigenic and was under relatively direct climatic control. Thus, Brady Soil formation records climatic conditions that minimized eolian activity and allowed effective pedogenesis, probably through relatively high effective moisture. Optical dating of loess in North Dakota supports correlation of the Leonard Paleosol on the northern Great Plains with the Brady Soil. Thick loess in North Dakota was primarily derived from the Missouri River floodplain; thus, its stratigraphy may in part reflect glacial influence on the Missouri River. Nonetheless, the persistence of minimal loess accumulation and soil formation until 10 cal ka at our North Dakota study site is best explained by a prolonged interval of high effective moisture correlative with the conditions that favored Brady Soil formation. Burial of both the Brady Soil and the Leonard Paleosol by renewed loess influx probably represents eolian system response that occurred when gradual change toward a drier climate eventually crossed the threshold for eolian activity. Overall, the loess-paleosol sequences of the central and northern Great Plains record a broad peak of high effective moisture across the late Pleistocene to Holocene boundary, rather than well-defined climatic episodes corresponding to the B??lling-Aller??d and Younger Dryas episodes in the North Atlantic region. ?? 2008 Elsevier Ltd. All rights reserved.

Quaternary Science Reviews↗
USGS2008

Glaciers of North America - Glaciers of Alaska

Glaciers cover about 75,000 km 2 of Alaska, about 5 percent of the State. The glaciers are situated on 11 mountain ranges, 1 large island, an island chain, and 1 archipelago and range in elevation from more than 6,000 m to below sea level. Alaska's glaciers extend geographically from the far southeast at lat 55 deg 19'N., long 130 deg 05'W., about 100 kilometers east of Ketchikan, to the far southwest at Kiska Island at lat 52 deg 05'N., long 177 deg 35'E., in the Aleutian Islands, and as far north as lat 69 deg 20'N., long 143 deg 45'W., in the Brooks Range. During the 'Little Ice Age', Alaska's glaciers expanded significantly. The total area and volume of glaciers in Alaska continue to decrease, as they have been doing since the 18th century. Of the 153 1:250,000-scale topographic maps that cover the State of Alaska, 63 sheets show glaciers. Although the number of extant glaciers has never been systematically counted and is thus unknown, the total probably is greater than 100,000. Only about 600 glaciers (about 1 percent) have been officially named by the U.S. Board on Geographic Names (BGN). There are about 60 active and former tidewater glaciers in Alaska. Within the glacierized mountain ranges of southeastern Alaska and western Canada, 205 glaciers (75 percent in Alaska) have a history of surging. In the same region, at least 53 present and 7 former large ice-dammed lakes have produced jokulhlaups (glacier-outburst floods). Ice-capped volcanoes on mainland Alaska and in the Aleutian Islands have a potential for jokulhlaups caused by subglacier volcanic and geothermal activity. Because of the size of the area covered by glaciers and the lack of large-scale maps of the glacierized areas, satellite imagery and other satellite remote-sensing data are the only practical means of monitoring regional changes in the area and volume of Alaska's glaciers in response to short- and long-term changes in the maritime and continental climates of the State. A review of the literature for each of the 11 mountain ranges, the large island, the island chain, and the archipelago was conducted to determine both the individual and the regional status of Alaskan glaciers and to characterize changes in thickness and terminus position of representative glaciers in each mountain range or island group. In many areas, observations used for determining changes date from the late 18th or early 19th century. Temperature records at all Alaskan meteorological recording stations document a 20th century warming trend. Therefore, characterizing the response of Alaska's glaciers to changing climate helps to quantify potential sea-level rise from past, present, and future melting of glacier ice (deglaciation of the 14 glacierized regions of Alaska), understand present and future hydrological changes, and define impacts on ecosystems that are responding to deglacierization. Many different types of data were scrutinized to determine baselines and to assess the magnitude of glacier change. These data include the following: published descriptions of glaciers (1794-2000), especially the comprehensive research by Field (1975a) and his colleagues in the Alaska part of Mountain Glaciers of the Northern Hemisphere, aerial photography (since 1926), ground photography (since 1884), airborne radar (1981-91), satellite radar (1978-98), space photography (1984-94), multispectral satellite imagery (since 1972), aerial reconnaissance and field observations made by many scientists during the past several decades, and various types of proxy data. The published and unpublished data available for each glacierized region and individual glacier varied significantly. Geospatial analysis of digitized U.S. Geological Survey (USGS) topographic maps is used to statistically define selected glaciological parameters in the eastern part of the Alaska Range. The analysis determined that every mountain range and island group investigated can be characterized by significant glacier retreat, thinning, and (or) stagnation, especially those glaciers that end at lower elevations. At some locations, glaciers completely disappeared during the 20th century. In other areas, retreat that started as early as the early 18th century has continued into the 21st century. Ironically, in several areas, retreat is resulting in an increase in the total number of glaciers; even though individual glaciers are separating, the volume and area of ice continue to decrease.

Alaska↗
USGS2016

Detecting sea-level hazards: Simple regression-based methods for calculating the acceleration of sea level

This report documents the development of statistical tools used to quantify the hazard presented by the response of sea-level elevation to natural or anthropogenic changes in climate and ocean circulation. A hazard is a physical process (or processes) that, when combined with vulnerability (or susceptibility to the hazard), results in risk. This study presents the development and comparison of new and existing sea-level analysis methods, exploration of the strengths and weaknesses of the methods using synthetic time series, and when appropriate, synthesis of the application of the method to observed sea-level time series. These reports are intended to enhance material presented in peer-reviewed journal articles where it is not always possible to provide the level of detail that might be necessary to fully support or recreate published results. The purpose of this report is to document and compare three simple methodologies that have previously been used to provide estimates with associated errors of the acceleration of sea-level elevation. These techniques have been used by coastal scientists and planners in assessing coastal risk over a wide range of spatial and temporal scales. Because relative sea-level (SL) elevation time series contain energetic fluctuations at many time scales, extracting what can be relatively small rate and acceleration signals (along with estimates of the error) from much larger “noise” has proven to be both difficult and controversial. Acceleration is a preferred measure of SL response to recent changes in the Earth’s climate because over time scales of 100 years or less slow vertical land motions (such as glacial isostatic adjustment) contribute only to the linear signal and not to acceleration, thus reducing the complexity of the analysis. Hence acceleration is useful if the goal of a study is to characterize and quantify the hazard associated with the changing relative elevation of water with respect to land on decadal time scales. Although in some cases it may be necessary to determine the cause of relative sea level rise, as a first step, it is important to accurately estimate the magnitude of the threat. Most researchers agree that global sea level (GSL) rose persistently through much of the 20th century at about 1.5–2.0 millimeters per year (mm/yr). There is far less agreement about whether the rate of sea-level rise (SLR) is increasing (that is, an acceleration in SL). Recent studies, and most of their predecessors, use tide gage data to quantify SL acceleration, A SL (t). In the current study, three techniques were used to calculate acceleration from tide gage data, and of those examined, it was determined that the two techniques based on sliding a regression window through the time series are more robust compared to the technique that fits a single quadratic form to the entire time series, particularly if there is temporal variation in the magnitude of the acceleration. The single-fit quadratic regression method has been the most commonly used technique in determining acceleration in tide gage data. The inability of the single-fit method to account for time-varying acceleration may explain some of the inconsistent findings between investigators. Properly quantifying A SL (t) from field measurements is of particular importance in evaluating numerical models of past, present, and future SLR resulting from anticipated climate change.

Open-File Report↗
USGS2018

Plant production responses to precipitation differ along an elevation gradient and are enhanced under extremes

The sensitivity of plant production to precipitation underlies the functioning of ecosystems. Studies that relate long-term mean annual precipitation and production across multiple sites (spatial relationship) or examine interannual linkages within a site (temporal relationship) can reveal biophysical controls over ecosystem function but have limited ability to infer responses to extreme changes in precipitation that may become more common under climate change. To overcome limitations of using a single approach, we integrated satellite- and ground-based estimates of production with a standardized, multi-site precipitation manipulation experiment across a grassland elevation gradient in the southwestern USA. The responsiveness of production to changes in precipitation followed the order: temporal (0.06–0.13 g m −2 mm −1 ) < spatial (0.21 g m −2 mm −1 ) < experimental relationship (0.25–0.42 g m −2 mm −1 ), suggesting that spatial and temporal relationships determined with satellite- and ground-based estimates cannot be extrapolated to determine the effect of extreme events. A strong production response to differences in mean annual precipitation across sites reinforces a regional control of water availability. Interannual sensitivity to precipitation was strongest at the low elevation grasslands, and the high elevation mixed conifer meadow had a large reduction in production in a drought year. Extreme experimental drought strongly reduced production in low elevation grasslands, but water addition had mixed effects. High elevation meadows were insensitive to both extreme drought and water addition. Our results highlight the importance of accounting for extreme climate regimes and site-level factors when scaling climate change effects up to regional and global scales.

Ecosystems↗
USGS2024

International Ocean Discovery Program Expedition 389 preliminary report: Hawaiian drowned reefs

Our understanding of the mechanisms controlling eustatic sea level and global climate changes has been hampered by a lack of appropriate fossil coral records over the last 500 ky, particularly into and out of the glacial periods. This problem was addressed by International Ocean Discovery Program Expedition 389 by drilling a unique succession of Hawaiian drowned coral reefs now at 110–1300 meters below sea level (mbsl). The four objectives are to investigate (1) the timing, rate, and amplitude of sea level variability to examine cryosphere and geophysical processes, including the assessment of abrupt sea level change events; (2) the processes that determine changes in mean and high-frequency (seasonal–interannual) climate variability from times with different boundary conditions (e.g., ice sheet size, p CO 2 , and solar forcing); (3) the response of coral reef systems to abrupt sea level and climate changes; and (4) the variation through space and time of the subsidence and the volcanic evolution of the island. To achieve these objectives, 35 holes at 16 sites ranging 131.9–1241.8 mbsl were drilled during the expedition. A total of 425 m of core was recovered, comprising reef (83%) and volcanic (17%) material. Average core recoveries were 66%, with numerous intervals characterized by very well preserved mixtures of coralgal and microbialite frameworks with recoveries >90%. Some science-critical shallow sites were not drilled due to a failure to secure permits to operate in Hawaiian state waters. Furthermore, apart from one site the target penetration depths were not achieved. Preliminary radiometric dates indicate that the recovered reef deposits are from 488 to 13 ka in age. The Onshore Science Party took place in February 2024. Cores were CT and hyperspectral scanned and described. Standard measurements were made, and samples were taken for postcruise research. Preliminary assessment of the age and quality of the reef and basalt cores suggest that many of the expedition objectives will be met.

Hawaii↗
USGS1993

Elk Lake in perspective

Elk Lake is located in the forested region of north-central Minnesota at the headwaters of the Mississippi River and occupies one of countless basins left behind as the last great Pleistocene ice sheet retreated northward into Canada. In this respect it resembles many other moderately deep, dimictic, hard-water lakes in the north-central United States, the sediments of which contain a history of postglacial and Holocene climatic and environmental change. Elk Lake is different, however, because the Holocene sediments in the deeper part of the lake form an uninterrupted sequence of annual laminations or varves. The varves are a chronometer for timing precisely the biologic, geochemical, and sedimentological responses in the lake to cyclic and progressive changes in climate. The varves also, through profound changes in their composition, divide the history of Elk Lake into three, sharply defined episodes; a postglacial lake, a prairie lake, and a modern, mesic-forest lake. We use these episodes and the character of the varves as a framework to guide the reader to the chapters and discussions found in this volume.

Minnesota↗
USGS2025

Weather drivers of reproductive variability in perennial plants and their implications for climate change risks

Seed production in perennial plants often shows strong year-to-year variation, a phenomenon known as masting. Masting is typically adaptive and driven by weather cues that synchronize reproduction by promoting or suppressing flowering and seed set. These cues, involving temperature, precipitation, and drought, differ across species and regions, yet a global synthesis is needed. Understanding such patterns is crucial, as reproductive responses to climate interact with resource constraints to shape plant fitness under climate change. Here, we analyze climate-reproduction relationships in 746 populations of 331 species worldwide using moving-window methods. We find that temperature is the dominant cue for reproductive investment, though its influence is weaker in the wettest and driest climates. In temperate and boreal regions, reproduction is most often linked to warmer conditions, whereas in the tropics, reproduction is disproportionately linked to cooler temperatures. Therefore, we expect rising temperatures to increase reproductive failures in the tropics, but to reduce interannual variability in temperate and boreal zones as favorable cues become more frequent. These results confirm long-standing theoretical predictions and provide a global framework for evaluating climate change risks to mast seeding.

Nature Communications↗
USGS2024

Incorporating climate data into emergency planning and exercises: A primer for emergency management practioners and data developers

Climate change has and will continue to sharpen climate-related risks to communities and natural resources in California and elsewhere, as the probabilities of more extreme weather, floods, and fires continue to increase. This poses a problem of novel situations for emergency management. Progress has been made in terms of formally incorporating climate projections, data, and research on expected changes in climate-driven hazards into long-term hazard mitigation and climate adaptation strategies at both state and national levels. However, there are fewer examples of how climate change considerations have, or could be, incorporated into shorter-term emergency preparedness and response strategies. This is an important gap to fill, as climate resilience depends not only on mitigation and prevention measures, but also on the ability of agencies to coordinate and effectively minimize impacts when prevention measures fall short. The goal of this primer is to provide guidance on how to incorporate the best available information on climate variability and change into emergency management planning, with a focus on the development and use of extreme weather event scenarios for use in exercises. The first section is aimed toward a broad audience, including emergency management practitioners who use extreme weather event scenarios. It provides an overview of available data and tools that can inform scenario design as well as techniques for scenario design based on the hazard of interest, the audience and application, and the technical skills and resources required to develop, summarize, and/or visualize the data. This section concludes with an overview of approaches and lessons learned related to extreme event response planning and exercise design. Overall, this section highlights the advantages of developing quantitative scenarios based on spatial data, which allows visualizations and interactive data explorations that can provide greater specificity in discussions related to preparedness and response strategies. It further highlights the advantages of developing a core expert working group to guide planning, holding pre-exercise workshops to engage diverse communities outside of the emergency management sector, and engaging decisionmakers post-exercise to communicate key issues and outcomes as well as potential approaches for mitigating consequences that were identified by participants. The second section is aimed toward the scientific community and data developers involved in the creation of extreme weather event scenarios. This section provides technical guidance and detailed descriptions of four types of data resources and five analytical approaches that can be used to create extreme weather event scenarios based on the design considerations highlighted in section one. The computational resources and expertise required varies substantially across the options presented and is a primary consideration. These requirements, in addition to considerations related to audience and application, may determine the novelty and detail of the event, the detail of weather forecast information that can be provided, and the spatial extent across which the event can reasonably be modeled. The importance of, and approaches for, delivering information in a form that is accessible to emergency management practitioners is also discussed.

Report↗
USGS2026

Mechanisms of Devils Lake’s responses to recent climatic wetting: Insights from a physically based hydrologic model

Study region Devils Lake Basin of the Northern Great Plains (NGP) region, North Dakota, USA Study focus Understanding the mechanism of Devils Lake’s responses and basin-wide hydrologic change under a wet-climatic regime using a process-based and cold region hydrologic model. New hydrologic insights Model results illustrate that three distinct hydroclimatic periods occurred during the study: Water Years 2002–05, 2006–11, and 2012–18. Following a brief time of contraction and growth, the latter two periods provide a complete picture of a wetting to drying cycle during an overall wetting regime. From 2006–2011, Devils Lake (DL) grew primarily due to lateral inflow, driven by strong precipitation and high frozen soil content leading up to the 2011 floods. In addition, during wet years, the snowmelt streamflow from the eastern and central parts of the DL Basin contributes significantly to lake growth compared to the western part. By contrast, from 2012 to 18, DL entered a contraction period, dominated by evaporation losses and anthropogenic flood control operations. Contributors to upstream drying included low precipitation, minimal snowpack accumulation, slightly lower frozen soil ratios, and minimal snowmelt runoff.

North Dakota↗
USGS2016

Molluscan extinction patterns across the Cenomanian-Turonian Stage boundary in the western interior of the United States

High-resolution stratigraphic analysis of 18 sections spanning the Cenomanian–Turonian Stage boundary in the western interior of the United States has allowed determination of the magnitude and pattern of molluscan extinction and disruption. Composite range data from all sections show that the faunal turnover across the stage boundary occurs in a series of narrow stratigraphic zones, defined by multiple first and last occurrences, separated by intervals displaying little or no taxonomic turnover. Two of the apparent extinction steps (bottom and top of the Neocardioceras juddii Zone) may be intercontinentally developed. The additional steps apparently reflect cyclic changes in water mass and substrate characteristics in the western interior basin produced in response to orbital forcing of climate. An interval (ca. 10-100 k.y. duration) of changing community structure and general biotic deterioration is found below each of the two potentially intercontinentally developed extinction steps. The most affected mollusks were those having intercontinental distributions (ammonites and inoceramid bivalves), suggesting that disruption of planktotrophic larval dispersal may have played a role in increasing extinction and speciation rates near the C–T boundary. The nekto-benthic ammonites were affected earlier and to a greater degree than the pelagic forms, implying progressive upward expansion of the oxygen minimum zone preceding the stage boundary.

Paleobiology↗
USGS1996

Waterfowl communities in the northern plains: Chapter 13

Features that determine the composition of avian communities have received extensive and enthusiastic attention, both empirically and theoretically (e.g., Cody 1974; Strong et al. 1984; Wiens, 1989a,b). Interspecific competition for limited resources is one influence widely regarded as critical, but others include species-specific responses to environmental conditions, predation, parasitism, commensal and mutualistic interactions, disturbance and chance, and historical events (Wiens, 1989b). Despite the attention they have received, the relative importance of the different features remains highly controversial. Certainly the community of birds present in an area will be but a subset of the total population of each constituent species; thus, the total population size of each species is a potential influence on local communities. Since many bird communities in the temperate zone are reconstituted annually with migrants, the geographical location of a site within the breeding range is an important feature; clearly, an avian community outside the normal breeding range of a particular species is unlikely to include that species, irrespective of the suitability of vegetation and other habitat features. Further, suitable habitat encountered earlier in spring migration is more likely to be occupied than is habitat encountered later. And the breeding ranges of birds are known to shift from year to year, depending on climatic conditions, a phenomenon that represents a modification of the general breeding range at a finer scale of resolution. The return of migrant birds to areas from which they fledged or where they previously bred modifies the occupancy of a particular habitat (HildTn 1964); likewise, traditional use of breeding sites by birds can induce species to persist in unsuitable habitat (Wiens 1985). Thus site fidelity can weaken the relationship between habitat quality and number of birds on an area (Wiens 1985). Waterfowl have received less attention from community ecologists than have many other groups of birds despite the importance attributed to waterfowl by biologists more generally, as well as by the public. Exceptions include work by Nudds and colleagues in Canada and by P?ysS and colleagues in Finland (see Nudds 1992 and references contained therein). Further, waterfowl are important ecologically; in much of the prairie of the North American midcontinent, waterfowl are numerically among the most common bird species and are certainly dominant in terms of biomass. This chapter addresses some influences on waterfowl communities in mixed-grass prairie pothole habitat. It takes a temporal perspective, based on annual censuses of breeding ducks for 25 years on a specific study area at Woodworth, North Dakota. Any changes in the structural features of the habitat that may have occurred during this period at the census site were at most gradual. I examine how the waterfowl communities varied in response to influences that did change annually, such as climate, conditions of the wetlands on the study area, the regional populations of birds from which the communities were constituted, and the population at Woodworth during the previous year. The results of the analyses are interpreted relative to individual characteristics of 11 waterfowl species: Mallard ( Anas platyrhynchos ), Gadwall ( Anas strepera ), Green-winged Teal ( Anas crecca ), Blue-winged Teal ( Anas discors ), Northern Pintail ( Anas acuta ), Northern Shoveler ( Anas clypeata ), American Wigeon ( Anas americana ), Canvasback ( Aythya valisineria ), Redhead ( Aythya americana ), Lesser Scaup ( Aythya affinis ), and Ruddy Duck ( Oxyura jamaicensis ).

Book chapter↗
USGS2017

Variable effects of climate on forest growth in relation to climate extremes, disturbance, and forest dynamics

Changes in the frequency, duration, and severity of climate extremes are forecast to occur under global climate change. The impacts of climate extremes on forest productivity and health remain difficult to predict due to potential interactions with disturbance events and forest dynamics—changes in forest stand composition, density, size and age structure over time. Such interactions may lead to non-linear forest growth responses to climate involving thresholds and lag effects. Understanding how forest dynamics influence growth responses to climate is particularly important given stand structure and composition can be modified through management to increase forest resistance and resilience to climate change. To inform such adaptive management, we develop a hierarchical Bayesian state space model in which climate effects on tree growth are allowed to vary over time and in relation to past climate extremes, disturbance events, and forest dynamics. The model is an important step toward integrating disturbance and forest dynamics into predictions of forest growth responses to climate extremes. We apply the model to a dendrochronology data set from forest stands of varying composition, structure, and development stage in northeastern Minnesota that have experienced extreme climate years and forest tent caterpillar defoliation events. Mean forest growth was most sensitive to water balance variables representing climatic water deficit. Forest growth responses to water deficit were partitioned into responses driven by climatic threshold exceedances and interactions with insect defoliation. Forest growth was both resistant and resilient to climate extremes with the majority of forest growth responses occurring after multiple climatic threshold exceedances across seasons and years. Interactions between climate and disturbance were observed in a subset of years with insect defoliation increasing forest growth sensitivity to water availability. Forest growth was particularly sensitive to climate extremes during periods of high stem density following major regeneration events when average inter-tree competition was high. Results suggest the resistance and resilience of forest growth to climate extremes can be increased through management steps such as thinning to reduce competition during early stages of stand development and small-group selection harvests to maintain forest structures characteristic of older, mature stands.

Minnesota, Wisconsin↗
USGS2022

High resolution spatiotemporal patterns of flow at the landscape scale in montane non-perennial streams

Intermittent and ephemeral streams in dryland environments support diverse assemblages of aquatic and terrestrial life. Understanding when and where water flows provide insights into the availability of water, its response to external controlling factors, and potential sensitivity to climate change and a host of human activities. Knowledge regarding the timing of drying/wetting cycles can also be useful to map critical habitats for species and ecosystems that rely on these temporary water sources. However, identifying the locations and monitoring the timing of streamflow and channel sediment moisture remains a challenging endeavor. In this paper, we analyzed daily conductivity from 37 sensors distributed along 10 streams across an arid mountain front in Arizona (United States) to assess spatiotemporal patterns in flow permanence, defined as the timing and extent of water in streams. Conductivity sensors provide information on surface flow and sediment moisture, supporting a stream classification based on seasonal flow dynamics. Our results provide insight into flow responses to seasonal rainfall, highlighting stream reaches very reactive to rainfall versus those demonstrating more stable streamflow. The strength of stream responses to precipitation are explored in the context of surficial geology. In summary, conductivity data can be used to map potential stream habitat for water-dependent species in both space and time, while also providing the basis upon which sensitivity to ongoing climate change can be evaluated.

Arizona↗