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Aboveground Biomass And Net Primary Production Along A Virginia Barrier Island Dune Chronosequence, John Joseph Dilustro

Biological Sciences Theses & Dissertations

Aboveground biomass was examined along a chronosequence of dune communities on Hog Island, a Virginia Coast Reserve LTER site. The dominant species were Ammophila breviligulata and Spartina patens. Aboveground biomass was harvested monthly from ten quadrats on dunes 6, 24, 36, and 120 years old. Sampling was conducted from April to November 1993. Biomass values were greater for younger dunes. Total aboveground biomass decreased with increasing site age and ranged from 152 g m^-2 on the 120 year old dune to 205 g m^-2 on the 6 year old dune in October 1993. Spartina patens biomass was …

The Effect Of Nitrogen Fertilization On The Phenology Of Roots In A Barrier Island Sand Dune Community, Everett P. Weber

Biological Sciences Theses & Dissertations

Little work has been done on the phenology of root growth and senescence largely due to methodological difficulties. The application of minirhizotron technology has enabled the tracking of individual roots through an entire growing season. As a result, direct measures of turnover, root growth, and an analysis of cohorts were made. Small plots on a 36 year old dune on Hog Island, a barrier island in the Virginia Coast Reserve Long Term Ecological Research Site, were fertilized with nitrogen. Minirhizotron tubes were installed in each fertilized and control plot. Each tube was sampled monthly for nine months, March through October …

Chlorophyll Fluorescence As A Measure Of Ozone Induced Stress, Jerry L. Faulkner

Doctoral Dissertations

Chlorophyll fluorescence is a nondestructive, intrinsic probe of photosynthesis. It has been used in a variety of physiological and environmental research. This study attempted to investigate the usefulness of chlorophyll fluorescence as a monitor of ozone induced stress in Quercus rubra L.

Chlorophyll fluorescence measurements were taken from mature trees and seedlings in open top chambers located at the Tennessee Valley Authority Air Pollution Research Facility at Norris, Tennessee. Chambers reflected one of three ozone concentration treatments: sub-ambient, ambient, or twice ambient. Spring leaf expansion was also measured as was spring and autumn chlorophyll content of leaves from mature trees. …

Symbiotic Seed Germination Of Platanthera Integrilabia (Correll) Luer, An Endangered Terrestrial Orchid, Lawrence William Zettler

All Dissertations

No abstract provided.

Discussion And Measurement Of Soil Erosion In Iceland, Kimberly Jane Richardson

Undergraduate Honors Capstone Projects

Soil erosion has occurred since the beginning of time. It is a natural process, but one that has been increasing at an alarming rate. Once soil is eroded--whether it is blown out to sea or washed down a river to sedimentize a lake--it is lost. It is almost impossible to reestablish similar soil components and characteristics in a given system. Since soil and vegetation reestablishment is expensive, the prevention of soil erosion by controlling its causes has become the most cost-effective reclamation effort.

After spending six months in Iceland, I wrote this paper on the unique erosion problems facing that …

Influences Of Nitrogen Supply And Elevated Co2 On Nitrogen Consumption, Nitrogen Loss, Tissue Nitrogen Concentration, And Yield Of Hydroponic Wheat, Karl B. Ritchie

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Wheat was grown hydroponically for 23 days (early boot stage) in a controlled environment at NO₃^- concentrations of 100 and 1000 μmol and CO₂ levels of 360 and 1200 μmol mo1^-1. Nitrogen consumption and transpiration were measured daily. Tissue nitrogen concentration, total biomass, and percent root mass were measured at harvest. Nitrogen recovery and nitrogen use efficiency were calculated. Elevated CO₂ increased nitrogen consumption of the 100 μmol NO₃^- treatment by 13.6% and the 1000 μmol NO₃^- treatment by 21.3%. These increases were particularly evident during …

The Response Of Five Tropical Plant Species To Natural Solar Ultraviolet-B Radiation, Peter S. Searles

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Tropical regions currently receive the highest global levels of solar ultraviolet-B radiation (UV-B, 280-320 nm) even without ozone depletion. Thus, the influence of natural, present-day UV-B irradiance in the tropics was examined for five tropical species, including three native rainforest tree species and two economically important species. Solar UV-B radiation conditions were obtained vi using either a UV-B excluding plastic film or a near-ambient UV-B transmitting film in a small clearing on Barro Colorado Island (BCI), Panama (9 ° N). Significant differences were often exhibited as increased foliar UV-B absorbing compounds, increased leaf mass per area, and reduced leaf blade …

Dungpat Microenvironmental Effects On Germination And Establishment Of Crested Wheatgrass, Ghulam Akbar

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Complementary greenhouse and field studies investigated the effects of ambient environmental conditions on cattle dungpat moisture, temperature, nutrient concentration, and crust formation dynamics, which in turn influence seed germination and seedling establishment in dungpats. 'Hycrest' crested wheatgrass [Agropyron desertorum (Fisch. ex Link) X A. cristatum (L.) Gaert.] was used as a representative revegetation species.

After collecting feces from Holstein steers that had been fed crested wheatgrass seeds, uniform dungpats were prepared and placed on two soil types (loam and coarse sand) in containers under three watering treatments (field capacity, 1/2 field capacity, and no water) in the greenhouse. Dungpat …

Biosystematics And Diversification In The Genus Striga Lour. (Scrophulariaceae) In Africa, Kamal-Eldin Ibrahim Mohamed

Biological Sciences Theses & Dissertations

Of the 34 taxa of Striga (29 species) that occur in Africa, 25 are endemic. Species diversity differs from region to region. The subtropical zone has 74% of the taxa including 41% endemics. Within this region, the West African part (from Senegal to eastern Nigeria) has 62% of the total taxa including 24% endemics. South of the equator the number of taxa is 56% of the total with 21% endemics, a proportion slightly less than that for West Africa. I recognize 29 species based on extensive herbarium and field studies. A new species from Angola is described. Striga yemenica previously …

The Vascular Flora Of The Tar Bay And Powell Creek Watersheds, Prince George County, Virginia, Mark Eugene Mort

Dissertations, Theses, and Masters Projects

No abstract provided.

Anatomical And Sem Studies Of The Pericarp And Aleurone Layer Of Two Supersweet Corn Cultivars, Tufail Ahmed

Masters Theses

Supersweet corn (Zea mays L. var. rugosa.) which contain endosperm mutant shrunken -2 exhibits low seed vigor and poor field emergence especially when soil temperature is 10-15 °C. Based on their emergence in the field at low temperature, they can be divided into two groups as tolerant and sensitive cultivars. Two cultivars 'Illini Gold' (Tolerant) and 'Honey 'n' Pearl' (Sensitive) were studied to see any anatomical differences, holes and cracks in the pericarp and air pockets between pericarp and aleurone layer. Significant differences were found in the thickness of pericarp. 'Illini Gold' cultivar has thicker pericarp and thin walled aleurone …

The Role Of Predation On Zostera Marina L (Eelgrass) Seed Abundance, James Fishman

Dissertations, Theses, and Masters Projects

No abstract provided.

Measurement Of In Situ Eelgrass Community Metabolism In Standing And Flowing Waters: Methods And Models, William James Seufzer

Dissertations, Theses, and Masters Projects

No abstract provided.

Reproductive Strategies In Asclepias Syriaca And Apocynum Cannabinum, Mariellen J. Soltys

Dissertations, Theses, and Masters Projects

No abstract provided.