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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

Phytosociology of the north-eastern Transvaal high mountain grasslands

Burgoyne, Priscilla Merle 17 April 2013 (has links)
The vegetation of the high mountain grasslands of the north-eastern Transvaal was sampled by using stratification based on geology and land types. Data was classified by TWINSPAN procedures and refined by using the Braun··Bianquet method. This resulted in the recognition of three vegetation units namely wetlands, boulderies and grasslands which represent a moisture gradient. Wetlands comprised four major communities and ten minor plant communities while boulderies resulted in four major communities and seven minor communities. The grasslands comprised four major plant communities which were subdivided into twenty eight minor communities. All identified communities were described and ecologically interpreted and a species list was compiled combining the data gathered in the area by other authors. / Dissertation (MSc)--University of Pretoria, 2013. / Plant Science / unrestricted
52

Impacts of Prescribed Fire and Grazing on Northern Great Plains Rangelands

Johnson, Haley Mae Ann January 2018 (has links)
Prescribed burning was utilized as a management tool on grasslands of the Northern Great Plains. We analyzed the use of fire to manipulate encroaching and unpalatable western snowberry (Symphoricarpos occidentalis), to promote browsing and improve nutritive quality. Fire was successful at altering the nutrient quality of western snowberry and selectivity of grazing livestock from plant specific to patch specific. Additionally, we evaluated the difference between burn season and frequency on plant community dynamics of an ungrazed tallgrass prairie invaded by Kentucky bluegrass (Poa pratensis). Fire promoted native forb and grass species, stressing that native species are well adapted to the historical disturbance. Our research emphasizes the need for restored fire regimes in the Northern Great Plains to benefit numerous aspects of prairie ecosystem function, stability, services, and productivity. / U.S. Forest Service / Central Grasslands Research and Extension Center
53

Restoration and ant diversity to post-plantation forestry grasslands

Dube, Patricia 31 August 2012 (has links)
There has been a widespread assessment of the capacity of grasslands to restore after several forms of disturbance. In South Africa forestry is a significant habitat disturbance within the Eastern Highveld grasslands where this study was conducted. The study compared ant communities between disturbed grasslands that have been rehabilitated after pine forestry and undisturbed grasslands. Ant sampling was conducted using pitfall traps within rehabilitated sites of age 10 years to 40 years and undisturbed grassland sites. We expected that exposure to pine plantations would result in remarkable differences in ant species richness, assemblages and abundance. A total of 17 genera and 31 morphospecies were collected; 25 species within the rehabilitated and 22 species from the undisturbed grasslands. The sites did not show any significant differences in their species richness, although they had distinctive species assemblages. Ant diversity showed recovery with increasing age after pine with older sites (38 years and 40 years) showing higher diversity compared to the younger sites especially the 10 year old site. Copyright / Dissertation (MSc (Environmental Ecology))--University of Pretoria, 2011. / Zoology and Entomology / Unrestricted
54

Ecosystem Functioning In Restored Grassland As Influenced By Ecotypic Variation, Precipitation, And Biodiversity

Bergquist, Kiersten 01 December 2020 (has links)
The restoration of degraded tallgrass prairies can mitigate climate change due to the carbon accrued during the development of grasslands. The focal species, dominant grass Andropogon gerardii, can assist the recovery of grassland ecosystem functioning. Climate, local adaptation, and biodiversity have been found to impact the accrual of carbon in grasslands. This study examined the difference in ecosystem functioning between ecotypes along a dry to mesic precipitation scale. The study site for this project was at the Southern Illinois University Agriculture Research Center in Carbondale, Illinois. The field site was planted with seeds originating from dry to mesic ecotypes, and the resulting ecosystem functioning was analyzed. It was found that the Kansas non-local ecotypes had significantly higher biodiversity, while the local Illinois sites demonstrated local adaptation with A. gerardii. Aboveground plant biomass was higher in the local sites, but there was no difference in carbon accrual between any of the ecotypes. While ecotypic variation in a dominant species will usually differentially influence ecosystem functioning, in this case, high biodiversity and local adaptation result in similar carbon inputs in grassland soil. It is necessary to analyze the carbon content of the soil in the drier field sites in order to determine if major differences in rainfall leads to differences in carbon accrual. If the goal of restoring a tallgrass prairie in southern Illinois is to assist with climate change mitigation, then it does not make a significant difference if the dominant species is sourced locally or non-locally.
55

Revision of the Melanoplus Scudderi (Orthoptera: Acrididae: Melanoplinae) Species Group and a Preliminary Investigation into the Grasshopper Fauna of the Grasslands of the Southeastern United States

Hill, JoVonn Grady 09 May 2015 (has links)
The Melanoplus scudderi species group, when erected by Blatchley, contained six species. The revision of the group presented here describes 21 new species and establishes the Melanoplus carnegiei group, all of which are associated with grasslands in the Southeast. Analysis of DNA barcoding data, suggest that the technique does not adequately delineate species based on the morphological concepts presented here, but did produce three broad mitochondrial DNA clades that correspond to the Apalachicola and Mississippi River discontinuity phylogeographic pattern displayed by several other organisms in the Southeastern United States. This pattern is attributed to vicariant events resulting from Pleistocene glaciation. A hypothetical evolutionary history of the Scudderi and Carnegiei groups is presented. Natural grasslands historically covered a significant portion of the southeastern United States. These grasslands contribute significantly to the biodiversity of the region with many endemic or rare species inhabiting them. Grasshoppers are important components of temperate grassland ecosystems, but no comprehensive review of the grasshopper fauna of southeastern grasslands had previously been conducted. Here a review of the regional fauna was conducted. In total, 211 grasshopper species have been documented in the Southeast, with 111 species (53%) being endemic to natural grasslands. Of particular note, 74 species (34% of the regional fauna) are endemic to the longleaf pine ecosystem. Many of the non-endemic grasshopper species inhabiting grasslands in the region are disjunct from larger populations west of the Mississippi River, presenting interesting biogeographic distributions. Additionally, a cluster analysis of grasshopper community composition from several types of grasslands in the region supports the faunal distinctiveness of the different types grasslands in the region.
56

Assessing capabilities of thermal imaging technologies equipped to small unmanned aerial systems (sUAS) to detect grassland bird nests

Hearon, Lori 06 August 2021 (has links)
North American grassland bird populations are declining more rapidly than other groups of birds. A well-established method of quantifying and monitoring grassland bird populations is by locating active nests. Active nests are often difficult to locate in grassland swards due to the varying heights within the canopy that nests are established. Studies quantifying grassland bird populations have low statistical power due to low sample sizes and high disturbance. Advances in small, unmanned aerial systems and thermographic imaging technologies have potential to improve efficiency of locating nests throughout canopies. This study explored detection accuracy of using thermal imagery to identify simulated grassland bird nests located at different heights within monoculture tall-stature grass canopies. This methodology was tested in blind evaluations, using multiple evaluators. Results from this study suggest that surveying thermal images is a reliable method for detecting active nests at depths of up to 1 m into a grass canopy.
57

Variation in species composition within and between some mountain grasslands in the Parque Nacional da Peneda - Geres

Hale, William H.G. January 1988 (has links)
No
58

An initial investigation into key soil processes and associated influences on N and S cycles of grassland site near a coal-fired power station, Mpumalanga, South Africa

Hutchinson, Lydia 02 May 2013 (has links)
A dissertation submitted to the faculty of Science, University of the Witwatersrand, Johannesburg, in fulfillment of the requirements for the degree of Master of Science. / Unable to load abstract.
59

Uplatnění ekologických a fytocenologických analýz travních porostů při harmonizaci jejich produkčních a mimoprodukčních funkcí / Application of ecological and phytocenological analyses of grasslands in harmonisation their production and non-production functions

TURKOVÁ, Jitka January 2007 (has links)
In the years 2005 - 2006 it was practised typological maping of selected meadow and pasture areas in Kardašova Řečice (439 m n.m.). The selected areas of permanent grasslands were separated into parts by growth types, where it was observed: projective dominance and frequency of individual species, the amount of primary production of biomass, the underground water level.
60

A Grassland Evaluation of the W. A. McKamy Ranch, Denton and Wise Counties, Texas

Meacham, William Ross January 1950 (has links)
This problem consists of classifying the four major pastures of the McKamy ranch into McConnell's four categories, by means of examinations based on these qualities and characteristics.

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