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At least 307 records · Page 17Linked to original sources
USGS1986

Extinction and survival of plant life following the Cretaceous/Tertiary boundary event, Western Interior, North America

The palynological Cretaceous/Tertiary boundary is recognized in the northern part of the Western Interior by the abrupt disappearance of a few characteristic Cretaceous pollen genera, principally Proteacidites and Aquilapollenites . In the southern part, the boundary is recognized by the disappearance of a somewhat different group of pollen: Proteacidites , “ Tilia ” wodehousei , and Trisectoris . The abrupt change in both regions takes place precisely at the stratigraphic horizon at which boundary clay layers containing anomalously high concentrations of iridium (interpreted to be the result of an asteroid impact) are found. Although some characteristic Cretaceous taxa apparently became extinct, others were minimally affected by this boundary event and reappear in strata above. However, all the principal Cretaceous pollen genera (though not species) that disappear regionally have been reported from Tertiary rocks in other parts of North America. Differential apparent extinction and/or survival reflects a pronounced temporary disruption of plant life immediately after the event. Some Cretaceous plants must have persisted in refugia to have provided the propagules for the rapid recovery of the flora. No massive total extinction of plant genera at the end of the Cretaceous can be seen from the palynologic record.

Geology↗
USGS1987

Dinosaurs, spherules, and the “magic” layer: A new K-T boundary clay site in Wyoming

A new Cretaceous-Tertiary (K-T) boundary clay site has been found along Dogie Creek in Wyoming in the drainage of Lance Creek—the type area of the Lance Formation of latest Cretaceous age. The boundary clay was discovered in the uppermost part of the Lance Formation, 4–7 cm beneath the lowest lignite in the Paleocene Fort Union Formation and approximately 1 m above a fragmented dinosaur bone. The boundary clay consists of a basal kaolinitic claystone layer as much as 3 cm thick containing hollow goyazite spherules, overlain by a 2–3 mm smectitic layer (the “magic” layer) containing both shock-metamorphosed minerals and an iridium anomaly of 21 ppb. A palynological break coincides with the base of the claystone layer; numerous Late Cretaceous palynomorph species terminate at this boundary. The paleontological significance of this new boundary site lies in its close association with the well-studied assemblage of dinosaurs and other vertebrates and flora within the type area of the Lance Formation. The spherules at the Dogie Creek site are extremely well preserved by virtue of their replacement by the mineral goyazite. This preservation should facilitate the resolution of the origin of the spherules and of their host layer.

Wyoming↗
USGS1954

Stratigraphy and history of the Moenkopi formation of Triassic age

The Moenkopi formation of Triassic age is composed of a series of deposits that form a wedge thinning eastward from a maximum of about 2000 feet in western Utah and southern Nevada to the vanishing point along an irregular margin in western Colorado, northeastern Arizona, and western New Mexico. Partly marine and partly continental in the thick western sections, it is entirely continental in the east. Invertebrate faunas indicate that deposition began either during or preceding the middle of the Early Triassic (Meekoceras zone) and continued into late Early Triassic (Tirolites zone) and probably into Medial Triassic time. Vertebrate faunas also indicate an Early Triassic and probably, in part, a Medial Triassic age . Studies of the deposits indicate three major transgressions and three regressions across southern Utah and northern Arizona. Analysis of sedimentary rock types and original structures in them suggests a complex mixture of environments involved in the development of the formation : stream beds, lagoons, playas, flood plains or tidal flats, shallow sea floors, and others. Some types are clear cut and readily demonstrated; others are open to question. Evidence from flora, fauna, and sediments indicates a semiarid to arid climate. Except for uplift in the Uncompahgre region of Colorado indicated by conglomeratic beds in the Moenkopi near by, the entire region probably remained very low and flat during Moenkopi deposition.

Colorado, Arizona, New Mexico↗
USGS2008

Inland diatoms from the McMurdo Dry Valleys and James Ross Island, Antarctica

Diatom taxa present in the inland streams and lakes of the McMurdo Dry Valleys and James Ross Island, Antarctica, are presented in this paper. A total of nine taxa are illustrated, with descriptions of four new species (Luticola austroatlantica sp. nov., Luticola dolia sp. nov., Luticola laeta sp. nov., Muelleria supra sp. nov.). In the perennially ice-covered lakes of the McMurdo Dry Valleys, diatoms are confined to benthic mats within the photic zone. In streams, diatoms are attached to benthic surfaces and within the microbial mat matrix. One species, L. austroatlantica, is found on James Ross Island, of the southern Atlantic archipelago, and the McMurdo Dry Valleys. The McMurdo Dry Valley populations are at the lower range of the size spectrum for the species. Streams flow for 6-10 weeks during the austral summer, when temperatures and solar radiation allow glacial ice to melt. The diatom flora of the region is characterized by species assemblages favored under harsh conditions, with naviculoid taxa as the dominant group and several major diatom groups conspicuously absent. ?? 2008 NRC.

Botany↗
USGS2024

Observed and potential range shifts of native and non-native species with climate change

There is broad concern that the range shifts of global flora and fauna will not keep up with climate change, increasing the likelihood of population declines and extinctions. Many populations of nonnative species already have advantages over native species, including widespread human-aided dispersal and release from natural enemies. But do nonnative species also have an advantage with climate change? Here, we review observed and potential range shifts for native and nonnative species globally. We show that nonnative species are expanding their ranges orders of magnitude faster than native species, reflecting both traits that enable rapid spread and ongoing human-mediated introduction. We further show that nonnative species have large potential ranges and range expansions with climate change, likely due to a combination of widespread introduction and broader climatic tolerances. With faster spread rates and larger potential to persist or expand, nonnative populations have a decided advantage in a changing climate.

Annual Review of Ecology, Evolution, and Systemati↗
USGS1981

Upper Oligocene evaporites in basin fill of Sevier Desert region, western Utah

The basin fill beneath the Sevier Desert of western Utah contains evaporites that were deposited in a broad closed basin. All of the basin fill penetrated by the Gulf Oil 1 Gronning contains abundant volcanic detritus and its alteration products of Cenozoic age. Fission-track dating of tuffaceous sandstone yields ages of 26-28 m.y. Fossil pollen from mudstone in the evaporite-bearing strata includes forms no older than late Oligocene, in good agreement with the fission-track ages. Thus the age of evaporites is late Oligocene and younger. Anhydrite is present throughout approximately 900m of volcaniclastic rocks in the lower part of the section cut by the Gulf hole. Fossil pollen are indicative of an arid to semiarid flora.-from Authors

Utah↗
USGS1975

Stratigraphy of Atlantic coastal margin of United States north of Cape Hatteras: Brief survey

A synthesis of studies of sea-floor outcrops of the sedimentary wedge beneath the northeastern United States continental shelf and slope and a reassessment of coastal plain Mesozoic stratigraphy, particularly of the coastal margin, provide insight for estimating the oil and gas potential and provide geologic control for marine seismic investigations of the Atlantic continental margin. The oldest strata known to crop out on the continental slope are late Campanian in age. The Cretaceous-Tertiary contact along the slope ranges from a water depth of 0.6 to 1.5 km south of Georges Bank to 1.8 km in Hudson Canyon. Few samples are available from Tertiary and Late Cretaceous outcrops along the slope. Sediments of the Potomac Group, chiefly of Early Cretaceous age, constitute a major deltaic sequence in the emerged coastal plain. This thick sequence lies under coastal Virginia, Maryland, Delaware, southeastern New Jersey, and the adjacent continental shelf. Marine sands associated with this deltaic sequence may be present seaward under the outer continental shelf. South of the Norfolk arch, under coastal North Carolina, carbonate rocks interfinger with Lower Cretaceous clastic strata. From all available data, Mesozoic correlations in coastal wells between coastal Virginia and Long Island have been revised. The Upper-Lower Cretaceous boundary is placed at the transition between Albian and Cenomanian floras. Potential hydrocarbon source beds are present along the coast in the subsurface sediments of Cretaceous age. Potential reservoir sandstones are abundant in this sequence.

Atlantic coastal plain↗
USGS2014

Status of native stream fishes within selected protected areas of Niobrara River in western Nebraska

Lotic systems within the Great Plains are characterized by highly fluctuating conditions through both space and time. Fishes inhabiting these systems have adopted specific life-history strategies to survive in such environments; however, anthropogenic disturbance to prairie streams has resulted in declines and extirpation of many native stream fishes. Terrestrial protected areas (i.e., parks and reserves) are designated to support native flora and fauna and, it is assumed, to provide protection to native fishes. We assessed the presence and relative abundance of stream fish populations within protected areas along the Niobrara River in western Nebraska based on data collected during 1979, 1989, 2008, and 2011. The spatial extent of protection, landscape changes resulting in degraded physiochemical parameters, and introduced species may reduce the effectiveness of these terrestrial protected areas in protecting native fishes in Great Plains stream environments.

Great Plains Research↗
USGS2004

Population size and natural history of Mariana fruit bats (Chiroptera: Pteropodidae) on Sarigan, Mariana Islands

Based on count results, we estimated the population of Mariana fruit bats ( Pteropus mariannus Desmarest ) on Sarigan, Mariana Islands, to number 150-200 bats in 1999, 185-235 bats in 2000, and about 300-400 bats in 2001. Our results, plus those of two previous surveys, indicate that bat abundance on the island probably remained relatively stable at about 125-235 animals during much of the period from 1983 to 2000, then increased suddenly in 2001, most likely due to immigration from a neighboring island. Sarigan's population differs from those of larger islands in the archipelago by usually having smaller roost sizes, typically 3-75 bats, and large numbers of solitary bats that at times comprise up to half of the population. Colonies and smaller aggregations were composed primarily of harems with multiple females, whereas a nearly equal sex ratio occurred among solitary animals. Colonies roosted in isolated coconut trees in open grasslands and in native forest stands of various sizes, but avoided dense coconut forest. An estimated 30-50% of harem and solitary females possessed young in July 1999. Bats were recorded feeding on just six species of plants, which partly reflects the island's impoverished flora. We speculate that fruit bat abundance on Sarigan is limited primarily by food availability rather than hunting losses, in contrast to some other islands in the Marianas. Our study supports the contention that populations of P. mariannus in the northern Marianas are usually sedentary, but that interisland movements of larger numbers of bats may occur rarely.

Mariana Islands↗
USGS2016

Metabarcoding of fecal samples to determine herbivore diets: A case study of the endangered Pacific pocket mouse

Understanding the diet of an endangered species illuminates the animal’s ecology, habitat requirements, and conservation needs. However, direct observation of diet can be difficult, particularly for small, nocturnal animals such as the Pacific pocket mouse (Heteromyidae: Perognathus longimembris pacificus ). Very little is known of the dietary habits of this federally endangered rodent, hindering management and restoration efforts. We used a metabarcoding approach to identify source plants in fecal samples (N = 52) from the three remaining populations known. The internal transcribed spacers (ITS) of the nuclear ribosomal loci were sequenced following the Illumina MiSeq amplicon strategy and processed reads were mapped to reference databases. We evaluated a range of threshold mapping criteria and found the best-performing setting generally recovered two distinct mock communities in proportions similar to expectation. We tested our method on captive animals fed a known diet and recovered almost all plant sources, but found substantial heterogeneity among fecal pellets collected from the same individual at the same time. Observed richness did not increase with pooling of pellets from the same individual. In field-collected samples, we identified 4–14 plant genera in individual samples and 74 genera overall, but over 50 percent of reads mapped to just six species in five genera. We simulated the effects of sequencing error, variable read length, and chimera formation to infer taxon-specific rates of misassignment for the local flora, which were generally low with some exceptions. Richness at the species and genus levels did not reach a clear asymptote, suggesting that diet breadth remained underestimated in the current pool of samples. Large numbers of scat samples are therefore needed to make inferences about diet and resource selection in future studies of the Pacific pocket mouse. We conclude that our minimally invasive method is promising for determining herbivore diets given a library of sequences from local plants.

California↗
USGS2004

The future of fire in California ecosystems

This chapter reviews the concepts developed in the book and challenges Californians to accept the fact that they live in fire-prone ecosystems. California’s variety of fire regimes are products of its wide diversity of vegetation, climate, topography, and ignitions. The role fire plays in an ecosystem is characterized by the fire regime attributes that describe the pattern of fire occurrence, behavior, and effects. California has a diverse flora comprised of plants that have evolved under a variety of climates and evolutionary pressures. The most universal changes to California’s ecosystems during the historic period have been the alteration of past fire regimes and changes in the pattern of fire on the landscape. Ecosystems change, and it is a mistake to manage any complex, dynamic ecosystem for a single, static state or condition.

California↗
USGS2010

Lichen diversity changes along the Mississippi River in the Minneapolis-St. Paul urban area

Lichen diversity along the Mississippi River in the Minneapolis-St. Paul urban area was studied in 2008 by sampling 37 localities along the 110-kilometer river basin, resulting in 76 species, which are thought to represent 80% of the complete flora. A significant decrease in lichen diversity toward the urban part of the river basin, as well as the presence of only one cyanolichen suggests that urban factors, e.g. air pollutants and habitat destruction may be affecting lichen diversity. In addition, lichen diversity has significantly decreased from that of 112 years ago, when a study by Fink reported 113 species, and a higher number of genera represented by a single species.

Minnesota↗
USGS2012

Leopardus braccatus (Carnivora: Felidae)

Leopardus braccatus (Cope, 1889) is a small felid—not much larger than a domestic house cat—commonly called the Pantanal cat. No comprehensive surveys have been conducted to determine how many L. braccatus exist in the wild. It is found in humid, warm grasslands and wooded areas of extreme northwestern Argentina, southwestern and south- and north-central (newly reported ranges) Brazil, Paraguay, and Uruguay. Habitat loss and degradation are considered major threats throughout most of its range. It is uncommon in captivity and museum collections, listed with all Felidae under Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora, and considered “Near Threatened” by the International Union for Conservation of Nature and Natural Resources in the pampas cat group (= L. colocolo).

Mammalian Species↗
USGS2018

The nearshore benthic community of Kasatochi Island, one year after the 2008 volcanic eruption

A description is presented of the nearshore benthic community of Kasatochi Island 10–12 months after a catastrophic volcanic eruption in 2008. The eruption extended the coastline of the island approximately 400 m offshore, mainly along the south, southeast, and southwest shores, to roughly the 20 m isobath. Existing canopy kelp of Eualaria ( Alaria ) fistulosa , as well as limited understory algal species and associated fauna (e.g., urchin barrens) on the hard substratum were apparently buried following the eruption. Samples and observations revealed the substrate around the island in 2009 was comprised almost entirely of medium and coarse sands with a depauperate benthic community, dominated by opportunistic pontogeneiid amphipods. Comparisons of habitat and biological communities with other nearby Aleutian Islands, as well as with the Icelandic volcanic island of Surtsey, confirm dramatic reductions in flora and fauna consistent with an early stage of recovery from a large-scale disturbance event.

Arctic, Antarctic, and Alpine Research↗
USGS2014

Invasive Brown Treesnake movements at road edges indicate road-crossing avoidance

Roads have significant impacts on the dispersal of wildlife. Although this poses a threat to the abundance and diversity of desirable flora and fauna, it also affords some opportunity for enhancing control of invasive species. Roads are the most common terrain features that may affect the rate of landscape-scale movements of invasive Brown Treesnakes (Boiga irregularis) throughout Guam. We radio tracked 45 free-ranging Brown Treesnakes in close proximity to two roads in Guam and recorded instances where daily relocations of snakes spanned roads. Then we reconstructed observed movement histories with randomized turning angles, which served as a useful null hypothesis for assessing the effect of roads or road edge habitat on Brown Treesnake movement patterns. Random walk simulations demonstrated that Brown Treesnakes crossed these roads at a rate far lower than would be expected if snake movement was random with respect to roads and road edge habitat. We discuss two alternative hypotheses for these results: 1) habitat gaps posed by roads physically or behaviorally restrict snake movement; or 2) road edges provide preferred foraging habitat from which snakes are reluctant to depart. Because roads often form the boundaries of jurisdictional and management units, the effects of roads on the movement of invasive Brown Treesnakes will influence the prospects for success of future landscape-level suppression efforts.

Journal of Herpetology↗
USGS2017

Born of fire: In search of volcanoes in U.S. national parks, four striking examples

Geologic features, particularly volcanic features, have been protected by the National Park Service since its inception. Some volcanic areas were nationally protected even before the National Park Service was established. The first national park, Yellowstone National Park, is one of the most widely known geothermal and volcanic areas in the world. It contains the largest volcanic complex in North America and has experienced three eruptions which rate among the largest eruptions known to have occurred on Earth. Half of the twelve areas established as national parks before the 1916 Organic Act which created the National Park Service are centered on volcanic features. The National Park Service now manages lands that contain nearly every conceivable volcanic resource, with at least seventy-six managed lands that contain volcanoes or volcanic rocks. Given that so many lands managed by the National Park Service contain volcanoes and volcanic rocks, we cannot give an overview of the history of each one; rather we highlight four notable examples of parks that were established on account of their volcanic landscapes. These parks all helped to encourage the creation and success of the National Park Service by inspiring the imagination of the public. In addition to preserving and providing access to the nation's volcanic heritage, volcanic national parks are magnificent places to study and understand volcanoes and volcanic landscapes in general. Scientists from around the world study volcanic hazards, volcanic history, and the inner working of the Earth within U.S. national parks. Volcanic landscapes and associated biomes that have been relatively unchanged by human and economic activities provide unique natural laboratories for understanding how volcanoes work, how we might predict eruptions and hazards, and how these volcanoes affect surrounding watersheds, flora, fauna, atmosphere, and populated areas.

Earth Sciences History↗
USGS2011

Indigenous observations of climate change in the Lower Yukon River Basin, Alaska

Natural science climate change studies have led to an overwhelming amount of evidence that the Arctic and Subarctic are among the world's first locations to begin experiencing climate change. Indigenous knowledge of northern regions is a valuable resource to assess the effects of climate change on the people and the landscape. Most studies, however, have focused on coastal Arctic and Subarctic communities with relatively little focus on inland communities. This paper relates the findings from fieldwork conducted in the Lower Yukon River Basin of Alaska in the spring of 2009. Semi-structured interviews were conducted with hunters and elders in the villages of St. Mary's and Pitka's Point, Alaska to document observations of climate change. This study assumes that scientific findings and indigenous knowledge are complementary and seeks to overcome the false dichotomy that these two ways of knowing are in opposition. The observed changes in the climate communicated by the hunters and elders of St. Mary's and Pitka's Point, Alaska are impacting the community in ways ranging from subsistence (shifting flora and fauna patterns), concerns about safety (unpredictable weather patterns and dangerous ice conditions), and a changing resource base (increased reliance on fossil fuels). Here we attempt to address the challenges of integrating these two ways of knowing while relating indigenous observations as described by elders and hunters of the study area to those described by scientific literature.

Human Organization↗
USGS1998

Smoke-induced seed germination in California chaparral

The California chaparral community has a rich flora of species with different mechanisms for cuing germination to postfire conditions. Heat shock triggers germination of certain species but has no stimulatory effect on a great many other postfire species that are chemically stimulated by combustion products. Previous reports have shown that charred wood will induce germination, and here we report that smoke also induces germination in these same species. Smoke is highly effective, often inducing 100% germination in deeply dormant seed populations with 0% control germination. Smoke induces germination both directly and indirectly by aqueous or gaseous transfer from soil to seeds. Neither nitrate nor ammonium ions were effective in stimulating germination of smoke-stimulated species, nor were most of the quantitatively important gases generated by biomass smoke. Nitrogen dioxide, however, was very effective at inducing germination in Caulanthus heterophyllus (Brassicaceae), Emmenanthe penduliflora (Hydrophyllaceae), Phacelia grandiflora (Hydrophyllaceae), and Silene multinervia (Caryophyllaceae). Three species, Dendromecon rigida (Papaveraceae), Dicentra chrysantha, and Trichostema lanatum (Lamiaceae), failed to germinate unless smoke treatment was coupled with prior treatment of 1 yr soil storage. Smoke-stimulated germination was found in 25 chaparral species, representing 11 families, none of which were families known for heat-shock-stimulated germination. Seeds of smoke-stimulated species have many analogous characteristics that separate them from most heat-shock-stimulated seeds, including: (1) outer seed coats that are highly textured, (2) a poorly developed outer cuticle, (3) absence of a dense palisade tissue in the seed coat, and (4) a subdermal membrane that is semipermeable, allowing water passage but blocking entry of large (molecular mass > 500) solutes. Tentative evidence suggests that permeability characteristics of this subdermal layer are altered by smoke. While the mechanism behind smoke-induced germination is not known, it appears that smoke may be involved in overcoming different blocks to germination in different species. For example, in Emmenanthe penduliflora, NO 2 in smoke was sufficient to induce germination, and most forms of physical or chemical scarification also induced germination. For Romneya coulteri, NO 2 alone failed to induce germination, and scarified seeds required addition of gibberellic acid. In Dicentra chrysantha, none of these treatments, nor smoke alone, induced germination, but germination was triggered by a combination of soil burial followed by smoke treatment. Smoke-stimulated species differed substantially in the duration of smoke exposure required to induce germination, and this was inversely correlated with tolerance to smoke exposure. We suggest that such differences in response may affect postfire community structure.

California↗