Environmental Indicators and Impact Assessment Commons^™

Drought-Induced Shift Of A Forest–Woodland Ecotone: Rapid Landscape Response To Climate Variation, Craig Allen, David D. Breshears

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

In coming decades, global climate changes are expected to produce large shifts in vegetation distributions at unprecedented rates. These shifts are expected to be most rapid and extreme at ecotones, the boundaries between ecosystems, particularly those in semiarid landscapes. However, current models do not adequately provide for such rapid effects—particularly those caused by mortality—largely because of the lack of data from field studies. Here we report the most rapid landscape-scale shift of a woody ecotone ever documented: in northern New Mexico in the 1950s, the ecotone between semiarid ponderosa pine forest and pinon– juniper woodland shifted extensively (2 km or …

Idealwise Algebraic Independence For Elements Of The Completion Of A Local Domain, William Heinzer, Christel Rotthaus, Sylvia Wiegand

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

Over the past forty years many examples in commutative algebra have been constructed using the following principle: Let k be a field, let S k[xl Xn]x,xn) be a localized polynomial ring over k, and let a be an ideal in the completion S of S such that the associated prims of a are in the generic formal fiber of S; that is, p N S (0) for each p Ass(S/a):. Then S embeds in S/a, the fraction field Q(S) of S embeds in the fraction ring of S/a, and for certain choices of a, the intersection D Q(S) f3 (S/a) …

Relating United States Crop Land Use To Natural Resources And Climate Change, K. G. Hubbard, F. J. Flores-Mendoza

National Drought Mitigation Center: Faculty Publications

Crop production depends not only on the yield but also on the area harvested. The yield response to climate change has been widely examined, but the sensitivity of crop land use to hypothetical climate change has not been examined directly. Crop land-use regression models for estimating crop area indices (CAIs) - the percent of land used for corn, soybean, wheat, and sorghum production - are presented. Inputs to the models include available water-holding capacity of the soil, percent of land available for rain-fed agricultural production, annual precipitation, and annual temperature. The total variance of CAI explained by the models ranged …

The Potential Effects Of Climate Change On Summer Season Dairy Cattle Milk Production And Reproduction, Peggy L. Klinedinst, Donald A. Wilhite, G. Leroy Hahn, Kenneth G. Hubbard

National Drought Mitigation Center: Faculty Publications

The potential direct effects of possible global warming on summer season dairy production and re-production were evaluated for the United States and Europe. Algorithms used for milk production and conception rate were previously developed and validated. Three widely known global circulation models (GISS, GFDL, and UKMO) were used to represent possible scenarios of future climate. Milk production and conception rate declines were highest under the UKMO model scenario and lowest under the GISS model scenario. Predicted declines for the GCM scenarios are generally higher than either “l year in 10” probability-based declines or declines based on the abnormally hot summer …

Estimation Of Relative Pesticide Leaching In Nebraska Soils, P. J. Shea, L. N. Mielke, W. D. Nettleton

Nebraska Agricultural Experiment Station: Historical Research Bulletins

A computational procedure (RIPS, Relative Index for Pesticides and Soils) was developed as a conservative estimator of pesticide leaching and groundwater contamination based on soil and pesticide properties, and water table depth. RIPS values offer guidance in pesticide selection and identify situations where a detailed site-specific evaluation should be conducted.

Loss Of Biological Diversity: A Global Crisis Requiring International Solutions: A Report To The National Science Board, Craig Call Black, Perry L. Adkisson, Gardner Mallard Brown, Rita Rossi Colwell, Charles E. Hess, James B. Holderman, K. June Lindstedt-Siva, William A. Nierenberg, Peter Hamilton Raven, Theodore M. Smith, Edward O. Wilson, W. Franklin Harris

Harold W. Manter Laboratory of Parasitology: Library Materials

Executive Summary

Biological diversity refers to the variety and variability among living organisms and the ecological complexes in which they occur. Diversity can be defined as the number of different items and their relative frequency. For biological diversity, these items are organized at many levels, ranging from complete ecosystems to the chemical structures that are the molecular basis of heredity. Thus, the term encompasses different ecosystems, species, genes, and their relative abundance (OTA, 1987).

There is an ongoing, unprecedented loss of the variety as well as absolute numbers of organisms-from the smallest microorganism to the largest and most spectacular of …

Drought Management: The Role Of Near- Real Time Weather Data, Donald A. Wilhite, Kenneth G. Hubbard

National Drought Mitigation Center: Faculty Publications

The ability to collect weather data in near-real time has improved because of technological advances, enabling weather data users to obtain more weather data over wider areas, and in a more timely fashion. The number of near-real time climate networks is increasing as new applications are found for climate data. More than fifteen states in the United States have established automated weather station networks. This paper presents an overview of recent developments in automated weather data collection in the United States and gives a detailed description of the network in Nebraska.

Near-real time weather data has many applications in agricultural …

Cropstatus--A Computer Program To Assess The Effects Of Seasonal Weather Changes On Nebraska's Agriculture, R. E. Neild, Donald A. Wilhite, K. G. Hubbard

National Drought Mitigation Center: Faculty Publications

CROPSTATUS is a series of programs residing in Nebraska's AGNET system using daily weather data to assess seasonal changes in crops, livestock, and other agricultural conditions. Assessments are based on parameters developed from accumulations of current daily temperature and precipitation data collected from a network of synoptic, climate, and automated micrometeorological stations in Nebraska in comparison with daily normals. The daily normals were derived from monthly summaries using multiple regression models to compute daily values as a function of Julian day numbers. Crop phenology models based on growing degree days were used to monitor and forecast the progress of different …

Improving Projected Potential Evapotranspiration Estimates Using National Weather Service Forecasts, Steven J. Meyer, Kenneth G. Hubbard, Donald A. Wilhite

National Drought Mitigation Center: Faculty Publications

In a recent survey conducted by the University of Nebraska's Center for Agricultural Meteorology and Climatology of Agricultural Network (AGNET) users, the results of potential evapotranspiration (ET_p) projections (calculated using the Blaney-Criddle approach, which employs "normal" climatic data to project ET_p estimates up to three days into the future) were labeled "unrealistic." To improve these projections, National Weather Service (NWS) forecast variables were used as input into the Blaney-Criddle and Penman equations. ET_p projections calculated according to the Penman equation, with data measured by automated weather stations as input, were assumed to represent the "best" …

The Nebraska Agricultural Climate Situation Committee, R. E. Neild, K. G. Hubbard, Donald A. Wilhite

National Drought Mitigation Center: Faculty Publications

The Nebraska Agricultural Climate Situation Committee consisting of an interdisciplinary group of extension specialists provides up-to-date information and advice on seasonal changes in crop/ weather conditions. The committee meets each Monday during the growing season to review:

1. Maps and tabular data developed by a computer program CIS /Crop Weather Information System/ that is linked to a network of weather stations and computer terminals in county agent offices.

2. Insect, plant disease and weed surveys.

3. Weekly weather and crop reports from the State/Federal System.

4. Weather outlooks from the National Weather Service.

5. Climate probabilities.

Situation reports and advisories …

Government Response To Drought In The United States: With Particular Reference To The Great Plains, Donald A. Wilhite

National Drought Mitigation Center: Faculty Publications

Drought relief has become an expected response of the federal government to periods of widespread drought in the United States. A wide range of emergency, short-term and long-term drought programs were formulated to deal with the extreme drought of the 1930's. By 1977 there were 40 separate programs administered by 16 different federal agencies. This paper traces the development of federal drought relief bureaucracy, including drought designation criteria and procedures.

Two obvious deficiencies of past drought relief efforts in the United States are noted. First, drought relief organizations and programs have been hastily assembled during periods of crisis. This has …

Changing Fields: Agricultural Land Use Changes In Nebraska 1925-1974, Donald A. Wilhite

National Drought Mitigation Center: Faculty Publications

The series of graphs and maps which follow illustrate agricultural land use changes in Nebraska from 1925 to 1974. With these graphs and maps, the major agronomic crops of corn (dryland and irrigated), wheat, sorghum and soybeans are analyzed. The purpose of this analysis is to provide a pictorial history of Nebraska's ever-changing cropping system and, hopefully, to stimulate ideas and discussion with regard to trends and future directions. The Nebraska Water Resources Center is deeply interested in both the past and the future of Nebraska's agriculture because of the demands which agriculture places on the state's water resources. An …

Turbulence Spectra Above A Vegetated Surface Under Conditions Of Sensible Heat Advection, Raymond P. Motha, Shashi B. Verma, Norman J. Rosenberg

National Drought Mitigation Center: Faculty Publications

Spectra of vertical and horizontal velocity, air temperature and humidity fluctuations were analyzed from measurements made over a well-watered alfalfa crop under conditions of sensible heat advection. Vertical velocity and air temperature spectra as well as cospectra of momentum, sensible heat and water vapor were found to be dependent on atmospheric thermal stratification. These spectra and cospectra were shifted toward higher frequencies under advective as compared to lapse conditions. These results indicate that the predominant eddy sizes are relatively smaller under advective conditions. Humidity spectra, on the other hand, were independent of daytime thermal stratification conditions but were influenced by …

Extreme Evapotranspiration By Irrigated Alfalfa: A Consequence Of The 1976 Midwestern Drought, Norman J. Rosenberg, Shashi B. Verma

National Drought Mitigation Center: Faculty Publications

The rate of evapotranspiration by irrigated alfalfa at Mead, NE (41°09'Nj 96°30'W, elevation 354 m) reached record levels in 1976. Evapotranspiration was measured with precision weighing lysimeters in a field 1.9 ha in size. Evapotranspiration ranged during the growing season from 4.75 to 14.22 mm day^-l and exceeded 10 mm day^-I on one-third of the days studied. On each day of study the ratio of latent heat flux density (LE) to the sum of the net radiation and soil heat flux densities (Rn+S) was such that LE/ (Rn+S) > 1, indicating the occurrence of significant …

Finitely Generated Modules Over Bezout [email protected], Roger Wiegand, Sylvia Wiegand

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

Let R be a Bezout ring (a commutative ring in which all finitely generated ideals are principal), and let M be a finitely generated R -module. We will study questions of the following sort: (A) If every localization of M can be generated by n elements, can M itself be generated by n elements? (B) If M 0 R m = Rn for some m, n, is Af necessarily free? (C) If every localization of M has an element with zero annihilator, does M itself have such an element? We will answer these and related questions for various familiar classes …