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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.
21

PRELIMINARY VEGETATION AND HYDROLOGIC ANALYSES FOR BINGHAM CIENEGA

Baird, Kathryn J., Ronayne, Michael J., Maddock, Thomas, III 01 1900 (has links)
This report is in two parts. The first part covers the ecological processes pertinent to the restoration of Bingham Cienega. The second part presents a subregional groundwater flow model for analyzing the water budget, stream and spring behavior, and water table configuration. Because of the sparsity of ecological and hydrologic data, both parts must be considered as preliminary studies.
22

Mapping vegetation phenology in the Sahel and Soudan, Africa, 1982 to 2005

Heumann, Benjamin W. January 2006 (has links)
The Sahel and Soudan regions of Africa are hot-spots for vegetation change due to climatic and anthropogenic causes. Recent studies using remote sensing have demonstrated that vegetation recovery has occurred across the region questioning the occurrence of widespread land degradation in the region. These studies have focused on proxy measurements of net primary productivity, but have not addressed seasonal characteristics of vegetation such as phenology. This thesis examines how vegetation phenology has changed from 1982--2005 in the Sahel and Soudan regions and how phenology relates to observed bio-productivity and regional precipitation patterns. This is the first research to assess multi-decadal phenology change for a tropical ecosystem. Results show that while bio-productivity has significantly increased in the Sahel, significant phenology change has primarily been detected in the Soudan region. Furthermore, the relationship between phenology and bio-productivity and precipitation differs between the Sahel and Soudan. This research demonstrates the utility of measuring phenological change of a tropical ecosystem for vegetation monitoring applications.
23

Mapping vegetation phenology in the Sahel and Soudan, Africa, 1982 to 2005

Heumann, Benjamin W. January 2006 (has links)
No description available.
24

Two decades of vegetation change across tussock grasslands in New Zealand's South Island

Day, Nicola J. January 2008 (has links)
New Zealand's South Island tussock grasslands have been highly modified by human activities, including burning, grazing and introductions of exotic plants for pastoralism. Studies suggest that tussock grasslands are degraded, in that native species have declined, and exotic species have increased in both diversity and abundance. These trends are primarily thought to be related to the impacts of grazing and subsequent grazing removal. Few studies have assessed long-term changes that have occurred in tussock grasslands, and those that have are generally limited to one particular location. This thesis aimed to investigate temporal changes in community structure in tussock grasslands, and relate these changes to environmental variables and land tenure. Data were used from 90 permanently-marked vegetation transects, which were set up on 19 geographically widespread properties in areas of tussock grassland across Canterbury and Otago in the South Island of New Zealand. The transects were on land in both conservation and pastoral tenure. Each transect was 100 m, and consisted of 50 0.25 m² quadrats. The transects were measured between 1982 and 1986 (first measurement), were re-measured between 1993 and 1999 (second measurement) and again between 2005 and 2006 (third measurement). A total of 347 vascular species were observed over the 90 transects and three measurement times. Species richness declined between the first and second measurements (first time interval), and increased between the second and third measurements (second time interval), at both the small (quadrat) and large (transect) scales. Both native and exotic species declined in mean quadrat species richness during the first time interval, and then increased during the second time interval. Changes in mean quadrat species richness were similar on transects in both conservation and pastoral tenure. Multivariate analysis of species' occurrences in quadrats identified a long gradient in species composition for these 90 transects. Four key plant communities were identifed along this gradient and differed in their mean elevation: (1) Highly-modified pastoral community, (2) Short-tussock grassland community, (3) Tall-tussock grassland community, (4) Alpine mat-forming species community. A detailed investigation into temporal changes that occurred on 53 transects that occurred in short- and tall-tussock grassland communities showed that changes in species composition were not consistent over time. Transects on different properties changed in species composition by different amounts. Specifically, in ordination space, transects on two properties changed in composition significantly more than transects on one other property. The property that a transect was on also affected the way that it changed in composition, i.e. native species were more likely to have increased on transects on some properties. Transects in conservation tenure did not change in species richness or composition differently from those in pastoral tenure. Considering that many native plants in tussock grasslands are relatively slow-growing, and that these areas have been grazed and burned for more than a century, we may expect it to be some time before we can detect differences in vegetation dynamics on conservation land from that on pastoral land. The changes in the community structure of these tussock grasslands were related to a combination of environmental factors, such as soil chemistry, climate, and management factors. This study has allowed greater understanding of vegetation change in tussock grasslands, and demonstrates the importance of long-term ecological monitoring in making reliable and accurate predictions about landscape-scale changes in tussock grassland community structure.
25

A vegetation classification and management plan for the Hondekraal section of the Loskopdam Nature Reserve

Filmalter, Nicolene 12 1900 (has links)
As part of a vegetation survey program for the newly acquired farms incorporated into the Loskop Dam Nature Reserve, the vegetation of the Hondekraal Section was investigated. The study provides an ecological basis for establishing an efficient wildlife management plan for the Reserve. From a TWINSPAN classification, refined by Braun-Blanquet procedures, 12 plant communities, which can be grouped into eight major plant communities, were identified. A classification and description of the major plant communities are presented as well as a management plan. Descriptions of the plant communities include characteristic species as well as prominent and less conspicuous species of the tree, shrub, herb and grass strata. This study proves that the extended land incorporated into the Reserve contributes to the biological diversity of the Reserve. / Environmental Sciences / M. Tech. (Nature Conservation)
26

The Effects of Fire on the Vernal Herbs of an Eastern Mesic Forest

Kem, David Randolph 01 May 2013 (has links)
The effects of fire on vernal herbs of the mesic forests of eastern North America are poorly understood. I studied the influence of prescribed fire on species richness, abundance of rare and common species, and density of exotics in the vernal herbaceous layer. To determine these effects, three sites in central Kentucky were surveyed prior to and following one of three treatments: spring burn, winter burn, or negative control. I conducted low-intensity spring burns in April 2010 and winter burns in February 2011. I used chi square analyses to test for changes in species richness, abundance of rare species, abundance of common species, and abundance of Glechoma hederacea, an exotic herb. I used multiple logistic regressions to test for the effect of burn severity on the abundance of two of the most common herbs, Erythronium americanum and Viola sororia sensu lato. The abundance of rare species increased significantly after fire treatment, with a 2% greater increase on burned plots than control plots (p < 0.05), and showed a 40% greater increase in plots burned in winter than plots burned in spring. However, there was no significant difference in overall species richness due to fire or to the season in which the prescribed fire was conducted. There were no significant differences in the density of common species or Glechoma hederacea due to fire treatment or due to fire season. There were also no significant differences in the abundances of Erythronium americanum or Viola sororia sensu lato due to burn severity. Changes in the abundance of rare species due to fire might suggest that prescribed burns may slightly increase the diversity of vernal herbs in eastern mesic forests. Changes in the abundance of rare species due to fire season might suggest that prescribed fires conducted prior to emergence may further increase the diversity of vernal herbs in the eastern mesic forest.
27

Subalpine revegetation on backcountry campsites near Tuolumne Meadows, Yosemite National Park, California : third year results

Moritsch, Barbara J. 27 April 1992 (has links)
The National Park Service initiated a backcountry campsite restoration project in 1987 to restore native vegetation on severely degraded campsites in three subalpine lake basins in Yosemite National Park. Restoration treatments included soil scarification, transplanting, manual seeding and site protection. Eight of the treated campsites were monitored in 1990 to evaluate changes in percent vegetation cover, species richness and volunteer establishment that had occurred over the three year period beginning prior to treatment application in the summer of 1987, and ending in the summer of 1990. Percent vegetation cover increased slightly across all sampled quadrats ([mean] = 0.71; N = 214) with mean percent cover changes ranging from -0.37 to 4.36 on individual campsites. Three sites had a loss of cover. Percent cover changes differed most among campsites within lake basins. Changes in percent cover did not differ among lake basins or impact strata (barren core, moderately trampled, and peripheral). Transplanting did not appear to be an important influence on changes in percent cover, as cover changes did not differ between planted and unplanted areas. Survival of transplants planted in 1987 was poor (19.2%), but survival of transplants planted in 1988 was higher (70.5%). Species richness increased slightly across all sampled quadrats ([mean] = 0.54 species per quadrat), with species richness changes on campsites ranging from -0.13 to 1.75 species per quadrat. One site had a mean decrease in species richness. Species richness changes differed among campsites, with the largest increases occurring on those campsites that also had the greatest increases in percent cover. Changes in species richness also differed among impact strata, with the largest increases occurring on barren core areas. There were small differences among lake basins, and species richness changes did not differ between planted and unplanted areas. Volunteer establishment occurred on all treated sites. The number of volunteers per site ranged from one to 45, and 29 species were represented. Individual quadrats had from one to four volunteers. Approximately 50% of the volunteers were producing seed, and overall vigor among volunteers was good. Numbers of volunteers per quadrat differed most strongly among campsites. Slight differences were detected among lake basins and impact strata, with numbers decreasing from barren core to peripheral quadrats. Differences in numbers of volunteers per quadrat between planted and unplanted areas were not detected. Soil scarification may enhance increases in cover, species richness and numbers of volunteers. However, the influence of scarification was tested on two sites only, and further study is recommended. The recovery process appeared to be strongly affected by factors operating at the campsite level. For example, sites with the greatest increases in percent cover also had the greatest increases in species richness and the most volunteers. These sites had coarse soils, relatively abundant sunlight and moisture, and were effectively protected from trampling after site treatment. Results indicate revegetation prescriptions should be made on a site-by-site basis. The performances of eleven species used in transplanting or occurring as volunteers were evaluated. Five species, Agrostis humilis, Calamagrostis breweri, Muhlenbergia filifonnis, Trisetum spicatum, and Calyptridium umbellatum show potential as colonizers in unassisted revegetation and may be useful in manual seeding treatments; three species, Calamagrostis breweri, Carex rossii, and Juncus panyi show potential for transplanting and nursery propagation; and two species, Carex spectabilis and Carex straminiformis, require further study to determine their effectiveness in subalpine revegetation treatments. / Graduation date: 1993
28

A vegetation classification and management plan for the Hondekraal section of the Loskopdam Nature Reserve

Filmalter, Nicolene 12 1900 (has links)
As part of a vegetation survey program for the newly acquired farms incorporated into the Loskop Dam Nature Reserve, the vegetation of the Hondekraal Section was investigated. The study provides an ecological basis for establishing an efficient wildlife management plan for the Reserve. From a TWINSPAN classification, refined by Braun-Blanquet procedures, 12 plant communities, which can be grouped into eight major plant communities, were identified. A classification and description of the major plant communities are presented as well as a management plan. Descriptions of the plant communities include characteristic species as well as prominent and less conspicuous species of the tree, shrub, herb and grass strata. This study proves that the extended land incorporated into the Reserve contributes to the biological diversity of the Reserve. / Environmental Sciences / M. Tech. (Nature Conservation)
29

Succession in sand heathland at Loch Sport, Victoria : changes in vegetation, soil seed banks and species traits

Wills, Timothy Jarrod, 1974- January 2002 (has links)
Abstract not available
30

Land cover change and its effect on landscape function in the Koue Bokkeveld

Vos, Elizmay 12 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Natural vegetation and wetlands in regions of the Western Cape are being replaced by agricultural development. Previous studies on one such region - the Koue Bokkeveld, a high mountainous region at the source of three major drainage basins, demarcated for study purposes to cover nearly 2500 km2, have failed to provide a comprehensive overview of such change and its landscape outcomes. This research aimed to detect, capture, record and classify the spatial nature, extent and change dynamics of various landscape elements and functions due to change in the land cover of this region. It assembled a comprehensive spatial database by digitising existing maps, aerial photograph mosaics and satellite imagery. Land cover maps were created for three historical and land cover change analyses were performed for the interim periods. Morphological landscape images were derived from a DEM and used to explain and interpret the location of land cover types and trends in change patterns. The effects on three landscape functions were determined, namely modelled run-off production, biodiversity deduced from landscape pattern structure and SANBI ratings, and carbon storage potential based on published figures. The research found that the regional landscape has undergone substantive land cover change , since the reference state. Increased intensity and productivity of agriculture and its related infrastructure increased its coverage to nearly 45 000 ha or 20 % of the total area. Perennial agriculture (nearly 10 000 ha of orchards and plantations) and annual (intensive vegetable growing and diminishing cereal crops) agriculture, accompanied by improved enabling infrastructure, such as irrigation technology (large storage dams, pipelines, micro delivery modes), transportation, roads, product cooling and packing plants, have extensively replaced natural vegetation. Located in valley bottoms and along toe-slope locations, where they compete for space directly with expanding and constantly intensifying agricultural activities, wetlands, shale fynbos and renosterveld face complete replacement. Land use and land cover changes have profoundly affected landscape functioning. Modelled rainfall run-off has increased (2% overall) in most subregions, opening possibilities for sedimentation and erosion. A high degree of fragmentation of the vulnerable and affected vegetation types threatens biodiversity. Increased carbon storage in perennial agriculture offers a benefit of change, as opposed to the negative outcomes on biodiversity of change in the Koue Bokkeveld. The research recommends improved institutional provision of the data required for system and regional modelling of processes like run-off in developing communities and for meeting the requirements of more sophisticated and accurate landscape models. Improved availability and appropriateness of GIT software solutions to conduct regional research and the use of more economical open software for GIS applications are to be encouraged. Ongoing and improved management and control are advocated for the expanding and intensified agriculture in a sensitive fynbos setting and for the maintenance of healthy landscape functioning. Concerning the discipline of geography, the exploitation of landscape functioning as a transdisciplinary focus inherent to a new regional geography is encouraged to arrest disciplinary drift. Specifically, future research should intensify the examination of the linkages between land use, land cover, change and ecological landscape functioning. / AFRIKAANSE OPSOMMING: Natuurlike plantegroei en vleilande in substreke van die Wes-Kaap word voortdurend vervang deur landbou-ontwikkeling. Vorige studies oor een so 'n streek - die Koue Bokkeveld, 'n hoogliggende bergagtige streek op die oorsprong van drie groot dreineerbekkens, wat afgebaken vir studie-doeleindes byna 2500 km2 dek  bied geen omvattende oorsig van sodanige verandering en die landskapsuitkomste daarvan nie. Hierdie navorsing was daarop gemik om die ruimtelike aard, omvang en veranderingsdinamika van verskillende landskapselemente en -funksies as gevolg van die verandering van grondbedekking van hierdie streek na te spoor, op te teken en te klassifiseer. 'n Omvattende ruimtelike databasis is saamgestel uit versyferde bestaande kaarte, lugfoto-mosaïeke en satellietbeelde. Grondbedekkingskaarte vir drie historiese tydsnitte is geskep en verandering oor die tussentydse periode is ontleed. Morfologiese landskapselemente is uit 'n DEM onttrek en gebruik om die patroon van grondbedekking en tendense in veranderingspatrone te verklaar en te verduidelik. Die nagevolge op drie landskapsfunksies, naamlik reënval-afloop produksie, biodiversiteit soos afgelei van die landskap se patroonstruktuur en SANBI graderings, en koolstof-opgaringspotensiaal gebaseer op gepubliseerde syfers, is bepaal. Die navorsing het bevind dat die streekslandskap sedert die vroegste verwysingstaat wesenlike grondbedekkingsverandering ondergaan het. Verhoogde intensiteit en produktiwiteit van die landbou en sy verwante infrastruktuur het die dekking daarvan vergroot tot byna 45 000 ha of 20% van die totale oppervlakte. Permanente (nagenoeg 10 000 ha boorde en plantasies) en jaarlikse (intensiewe groente en dalende graangewas verbouing) landbou, saam met verbeterde infrastruktuur, soos besproeiingstegnologie (groot opgaardamme, pypleidings, mikroleweringstoerusting), vervoer, paaie, produkverkoeling en -verpakkingsgeriewe, het natuurlike plantegroei grootskaals vervang. Geleë in valleivloere en aanliggende heuwelhange, waar hulle direk om ruimte meeding met die uitbreidende en voortdurend intensiferende landbou-aktiwiteite, is vleilande, skalie-fynbos en renosterveld onderhewig aan volledige vervanging. Grondgebruik- en bedekkingsverandering raak landskapsfunksionering wesenlik. Gemodelleerde reënvalafloop het toegeneem (2% in totaal) in die meeste substreke en vergroot so die moontlikhede vir sedimentasie en erosie. ‘n Hoë vlak van landskapsfragmentasie in die kwesbare en geaffekteerde plantegroeitipes bedreig biodiversiteit. Verhoogde koolstofopgaring in meerjarige landbougewasse impliseer wel 'n positiewe opbrengs van grondbedekkingsverandering, in teenstelling tot die negatiewe biodiversiteitsuitkomste van verandering in die Koue Bokkeveld. Die navorsing beveel aan dat institusionele voorsiening van data wat benodig word vir stelsel- en prosesmodellering (bv. reënvalafloop) in ontwikkelende gemeenskappe, en die vereistes van meer gesofistikeerde en akkurate landskapsmodelle, verbeter word. Die beskikbaarheid en geskiktheid van GIT sagteware-oplossings vir streeksnavorsing, en die gebruik van meer ekonomiese oop-programmatuur vir GIS-toepassings, word aangemoedig. Vir praktiese doeleindes word deurlopend-verbeterde bestuur en beheer oor die uitbreiding en intensifering van van landbou in 'n sensitiewe fynbosomgewing en die instandhouding van gesonde landskapsfunksionering bepleit. Met betrekking tot die dissipline van geografie, moedig die navorsing die ontginning van die landskap se funksionering as 'n transdissiplinêre fokus inherent aan 'n nuwe tipe streeksgeografie aan, om dissiplinêre uiteenloping te stuit. Toekomstige navorsing kan spesifiek die ondersoek van die skakels tussen grondgebruik, grondbedekking, verandering en ekologiese landskapsfunksionering verskerp.

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