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Articles 1 - 10 of 10

Full-Text Articles in Life Sciences

Abundance, Distribution, And Diversity Of Buried Seed Populations In The Delta Marsh, Manitoba, Canada , Roger Lynn Pederson Jan 1983

Abundance, Distribution, And Diversity Of Buried Seed Populations In The Delta Marsh, Manitoba, Canada , Roger Lynn Pederson

Retrospective Theses and Dissertations

Several plant communities in the Delta Marsh were analyzed with respect to the distribution, abundance, diversity, and temporal variation in buried seed populations and annual seed rain. Numbers of germinable seeds were measured by placing substrate and seed trap soil samples under two simulated environmental conditions (drawdown and shallow-flooded) in an outdoor shelter;From the seed bank, four times as many seedlings and twice as many species occurred in substrate samples under the drawdown treatment as compared to samples under the shallow-flooded treatment. Many of the common species in the seed bank (Scirpus validus), (Scripus maritimus), Rumex maritimus, Aster brachyactis ...


Variation In Growth, Nitrogen Fixation, And Assimilate Allocation Among Selected Alnus Glutinosa (L.) Gaertn. Clones , Gregory Alan Miller Jan 1983

Variation In Growth, Nitrogen Fixation, And Assimilate Allocation Among Selected Alnus Glutinosa (L.) Gaertn. Clones , Gregory Alan Miller

Retrospective Theses and Dissertations

The purpose of this study was to gain a better understanding of genetic variation in growth characteristics of Alnus glutinosa (L.) Gaertn. Clones were selected from the largest and smallest individuals in one 14 and one 16 year-old plantation. The 20 selected clones plus 7 other clones of interest were propagated by softwood cuttings. Gas exchange measurements, both respiration and nitrogenase activity, of intact shoots and roots were attempted. However, due to limitations of facilities and the large number of measurements required, gas exchange measurements were foregone in favor of more detailed analysis of dry weight distribution, nitrogen fixation, and ...


Use Of Transformed Landsat Data In Regression Estimation Of Crop Acreages , Hsien-Ming Hung Jan 1983

Use Of Transformed Landsat Data In Regression Estimation Of Crop Acreages , Hsien-Ming Hung

Retrospective Theses and Dissertations

This study investigates the use of functions of a vector X as auxiliary variables in the regression estimation of the population mean with survey data. Functions of the vector X are estimated by estimating the unknown parameters of the transformation. Under certain assumptions, the error in the estimated parameters is order n('- 1/2), where n is the sample size. The effect of estimating the auxiliary variables is investigated under the assumption that the finite population is a random sample of an infinite population. Asymptotic properties of regression estimators of the finite population mean constructed with estimated auxiliary variables are ...


Factors Related To Selection Of Fish Scales For Growth Studies Of Yellow Perch, Perca Flavescens , Ahmad Hassan Abdu-Nabi Jan 1983

Factors Related To Selection Of Fish Scales For Growth Studies Of Yellow Perch, Perca Flavescens , Ahmad Hassan Abdu-Nabi

Retrospective Theses and Dissertations

Standardization of the body area for scale sampling for growth studies of fish becomes more essential if the a value in the Fraser-Lee equation is to be standardized as suggested by Carlander (1982). In a study on yellow perch (Perca flavescens) from West Okoboji Lake and Clear Lake in Iowa, the body area located at the tip of the pectoral fin below the lateral line was found to be the best area for scale sampling. This area exhibited the lowest variability in scale size and the lowest frequency of regenerated scales of the 10 areas sampled. The optimum number of ...


Behavior, Energetics And Management Of Refuging Waterfowl: A Simulation Model , Robert Beneke Frederick Jan 1983

Behavior, Energetics And Management Of Refuging Waterfowl: A Simulation Model , Robert Beneke Frederick

Retrospective Theses and Dissertations

A stochastic simulation model, designed to test the effects of alternative management schemes on refuging waterfowl populations, was constructed from data on fall-migrating snow geese (Chen c. caerulescens) at DeSoto National Wildlife Refuge, Iowa. Components of the model include goose population level, food density and distribution, food-searching flight characteristics, feeding rates, activity and energy budgets, migration rates, and the effects of weather, hunting pressure, and land management practices on the system. Independent data were collected to test model validity. The model validly describes movement from the refuge core to distant feeding areas and provides insight into factors affecting emigration. Refuge ...


The Effect Of Acid Rain On The Growth And Nutrient Content Of Two Species Of Hardwood Tree Seedlings, And On The Ph, Microflora And Nutrient Content Of The Soil , Doris Kathleen Patten Jan 1983

The Effect Of Acid Rain On The Growth And Nutrient Content Of Two Species Of Hardwood Tree Seedlings, And On The Ph, Microflora And Nutrient Content Of The Soil , Doris Kathleen Patten

Retrospective Theses and Dissertations

The increasing acidity of precipitation may cause foliage damage, decrease plant growth and leach essential nutrients from the soil. The purpose of this study was to determine the sensitivity of two hardwood tree species and three soils to simulated acid rain. The value of infecting tree seedlings with mycorrhizal fungi before transplanting into acid-leached soils was also examined;Dundas silt loam, Hayden loam and Luther loam supporting coleus and sorghum were leached three times each week for 20 weeks with a mixture of H(,2)SO(,4) and HNO(,3) adjusted by dilution to pH 5.5, 4.0 or ...


Effects Of Fenvalerate, A Synthetic Pyrethroid Insecticide, On Nontarget Organisms In An Old-Field Ecosystem , Richard Seigel Bennett Jan 1983

Effects Of Fenvalerate, A Synthetic Pyrethroid Insecticide, On Nontarget Organisms In An Old-Field Ecosystem , Richard Seigel Bennett

Retrospective Theses and Dissertations

Fenvalerate Pydrin('(REGTM)), cyano(3-phenoxybenzyl)-methyl 4-chloro-(alpha)-(1-methylethyl)benzeneacetate, a synthetic pyrethroid insecticide, was experimentally applied to 3 of 6 1-ha study plots on an old-field site. Two applications of 0.112 kg AI/ha (0.1 lbs/acre) were made during both 1980 and 1981. The effects of fenvalerate on arthropod and small mammal communities, and the degradation and movement of residues are reported;Arthropod populations were monitored with pitfall traps and sweep nets. No significant treatment differences were detected among ground arthropods. Most foliar arthropod populations were significantly reduced (P < 0.05) by fenvalerate, with varying degrees of population recovery, ranging from increases above control levels within 3 weeks by thrips (Thysanoptera) to essentially no recovery by beetle larvae. A few foliar arthropod groups were not reduced, but only springtails (Collembola) significantly increased in number after application;Nine small mammal species were captured in live traps during both years from grids in each plot. In 1980, 16,632 trap nights resulted in 1638 captures of 390 individuals, and in 1981, 14,700 trap nights produced 3911 captures of 787 individuals. Insecticide applications did not significantly affect population size, reproduction, age and sex ratios, or movement patterns for any species;The highest fenvalerate residues were detected on vegetation (12.1 ppm), with little evidence of drift into control plots. Residue concentrations declined exponentially with half-lives ranging from 5.9 to 10.6 days. All insect samples contained < 0.5 ppm fenvalerate. These residues also declined through time. The highest residue levels were found in short-horned grasshoppers ((LESSTHEQ) 0.33 ppm). Residues in ground beetles (Carabidae) were < 0.15 ppm. All mammalian samples contained (LESSTHEQ) 1.0 ppm, with the meadow voles (Microtus pennsylvanicus) containing higher residues than deermice (Peromyscus maniculatus). The low residue levels reflected the low application rate, rapid environmental degradation, and rapid mammalian metabolism of fenvalerate.


Small Area Estimation Using Nested-Error Models And Auxiliary Data , Rachel Margaret Harter Jan 1983

Small Area Estimation Using Nested-Error Models And Auxiliary Data , Rachel Margaret Harter

Retrospective Theses and Dissertations

A prediction approach to small area estimation is presented. The procedure uses survey and auxiliary data and is based on the assumption of a nested-error model. The mean squared error and the mean squared conditional bias of the predictor are given. Under the nested-error model, the best linear unbiased predictor of the small area mean has the form of a James-Stein estimator;Estimators for the variance components of the nested-error model are suggested. A generalized least squares procedure is given for constructing estimators of the variance components given prior estimators of the components. The asymptotic distribution of the estimated generalized ...


A Linear Programming Model Applied To The Supply Of Primary Hardwood Products In The United States 1990 To 2030, Francis Nwonwu Jan 1983

A Linear Programming Model Applied To The Supply Of Primary Hardwood Products In The United States 1990 To 2030, Francis Nwonwu

Retrospective Theses and Dissertations

A cost minimizing linear programming model was developed to determine the minimum cost of supplying hardwood lumber, veneer and plywood, and particleboard in each year of the period 1990 to 2030;The continental United States was divided into nine supply and three demand regions. Production, export, import and transportation activities were defined for demand regions. The total cost of producing, transporting, and importing the products was minimized subject to regional and national demand (consumption, export, and import) and resource (land, labor, and capital) constraints;The minimum costs (in 1972 dollars) of supplying the products in the years 1990, 2010 and ...


The Vegetation Of Ledges State Park, Boone County, Iowa, Cindy Lee Johnson-Groh Jan 1983

The Vegetation Of Ledges State Park, Boone County, Iowa, Cindy Lee Johnson-Groh

Retrospective Theses and Dissertations

No abstract provided.