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At least 1,009 records · Page 56Linked to original sources
USGS2020

Exploring regional scale metamorphic fabrics in the Yukon Tanana terrane and environs using quantitative domain analyses

Metamorphic rock fabrics such as foliations and lineations provide a rock record of numerous deformational characteristics in the Earth’s crust. When spatial information is combined with fabric data collected at points on geologic maps, the nature and consistency of metamorphic fabrics can be explored through structural domain analysis. This is particularly useful in large regions where there is not well-established stratigraphy and where bedrock exposures are limited. Domains that contain distinctive orientations and patterns of fabrics can be constructed on the basis of several different parameters, but in folded, polydeformational regions cylindricity can be particularly useful. Distinct domains of cylindrical folding can sometimes be determined where poles to foliations show characteristic patterns on equal-area projections and lie perpendicular to a single axis in space. Additionally, the patterns of elements such as fold axes and mineral lineations can be used in conjunction with foliation data to refine domains and confirm parameters such as coaxiality.

Alaska, Yukon↗
USGS2004

Seedling growth of Wisconsin fast plants (Brassica rapa) in field environments

In this 3-week laboratory, students investigate the effects of an abiotic or biotic ecological factor on the growth or reproduction of rapid-cycling brassica ( Brassica rapa L. : Wisconsin Fast Plants) seedlings in the field. Measurable treatments include light, wind, herbivory, chemical or organic fertilizer, insecticides, and growth regulators (i.e., gibberellic acid spray, auxin paste). Students learn how to develop an hypothesis and apply the scientific method in a field setting. Students work in pairs and set up their experiments using previously prepared Wisconsin Fast Plant seedlings. One week later students harvest their plants during a return field trip after which they collect their data, write individual scientific reports, and present their findings in-class. This experiment is unique because Wisconsin Fast Plants are used in a field experiment instead of the usual laboratory setting.

Teaching Issues and Experiments in Ecology (TIEE)↗
USGS2018

Migration trends for king and common eiders and yellow-billed loons past Point Barrow in a rapidly changing environment

Most of the king ( Somateria spectabilis ) and common eiders ( S. mollissima v-nigra ) nesting in northern Alaska and northwestern Canada migrate past Point Barrow, Alaska, during the spring and fall migration. Yellow-billed loons ( Gavia adamsii ) also migrate past Point Barrow and are a species of international conservation concern. Spring migration counts of eiders have been conducted approximately every ten years at Point Barrow since 1976, and indicated that both eider species experienced population declines of approximately 50% between 1976 and 1996, and that the declines had stabilized by 2004. Population estimates derived from migration counts have not been previously estimated for yellow-billed loons. We conducted spring counts of eiders and loons in 2015 and 2016 to obtain population estimates to compare with those from 1994, 1995, 2003, and 2004 in order to evaluate long-term and current trends. We estimated (95% confidence intervals) that 796,419 (304,011) king and 96,775 (39,913) common eiders passed Point Barrow in 2015, and 322,381 (145,833) king and 130,390 (34,548) common eiders passed Point Barrow in 2016. Both and king and common eider population estimates increased from 1994 through 2016, however, the increase over time was not significant (F < 5.07, P > 0.087, df = 1). Our population estimates for king eiders were very different between the two years of this study, possibly due to a very short and intense migration peak in 2016, resulting in a population count that was biased low because sampling periods did not adequately capture the peak of migration. The numbers of common eiders were similar between the two years, as well as for the 12 years since the previous count. Photo analysis of flocks indicated that observer counts were on average 4% lower than photo counts (paired t-test; |t| = 3.26, df = 297, P < 0.001) for flocks less than 1400 individuals (observer count). Estimates of yellow-billed loon populations were very variable and are biased low as numbers of loons passing Pt. Barrow were still high when our counts ended in late May. It is important that counts continue to be conducted for these species of conservation and subsistence importance, but that techniques be refined to reduce bias and variability, and to find solutions to the increasing difficulty of conducting a count from the shore-fast ice in spring.

Alaska↗
USGS2021

Climate change implications for the conservation of amphibians in tropical environments.

The U.S. Fish and Wildlife Service and the Puerto Rico Department of Natural and Environmental Resources want to develop a plan of actions to protect 12 species of coqui frogs (Eleutherodactylus spp.) that are currently considered at risk of being considered threatened or endangered, requiring additional protections under the Endangered Species Act. Actions center on two possible adaptation strategies: a) translocations to suitable, unoccupied habitat, and b) identifying climate-resilient habitats to ensure the persistence of species. Knowledge required to implement these strategies includes understanding how microhabitat and microclimatic factors – the local environmental conditions around individual frogs influence their occupancy (distribution), abundance, and reproduction; these were estimated by focusing on four representative species (E. wightmanae, E. brittoni, E. antillensis, and E. coqui). The abundance of all species but E. antillensis was positively and strongly influenced by moisture levels. As expected, E. antillensis exhibited an opposite relationship. Similarly, the reproductive activity of E. coqui was influenced by higher relative humidity and the presence of a chorus of other individuals. We found that our four focal species were not affected (e.g., abundance, reproduction) by the passing of hurricane Maria in September 2017, possibly because fallen debris creates conditions of increased food and shelter. Our findings help to assess habitat suitability, potential climate refuges, and inform timing for managed translocations.

Final Report↗
USGS1998

Perspectives on the land use history of North America: A context for understanding our changing environment

Ecological change is constant and profound, yet it often occurs at temporal and spatial scales that are difficult to measure and interpret. This publication demonstrates how diverse data bases, archived in different formats and at numerous locations, can be brought together to provide an integrated perspective on the relationship between land use and landcover change. The authors provide the historical context for interpreting recent landcover change in several regions of North America and articulate the value of a comprehensive continental land-use history for guiding environmental policy and management decisions during the coming century and beyond.

Biological Science Report↗