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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.
81

AN ANALYSIS OF A SONORAN DESERT SPECIES DIVERSITY GRADIENT

Yensen, Arthur Eric, 1944- January 1973 (has links)
No description available.
82

CHEMICAL ECOLOGY OF A NORTHERN ARIZONA PONDEROSA PINE-BUNCHGRASS COMMUNITY

Rietveld, Willis James, 1942- January 1974 (has links)
No description available.
83

The phytosociology of the boreal forest inclusions in Southern Ontario and Quebec.

Warder, Michael Phillip January 1970 (has links)
No description available.
84

Spatial analysis and efficiency of systematic designs in intercropping experiments.

Wandiembe, Symon Peter. January 2002 (has links)
In studies involving intercropping plant populations, the main interest is to locate the position of the maximum response or to study the response pattern. Such studies normally require many plant population levels. Thus, designs such as spacing systematic designs that minimise experimental land area are desired. Randomised block designs may not perform well as they allow few population levels which may not span the maximum or enable exploration of other features of the response surface. However, lack of complete randomisation in systematic designs may imply spatial variability (largescale and small-scale variations i.e. trend and spatial dependence) in observations. There is no correct statistical method laid out for data analysis from such designs. Given that spacing systematic designs are not well explored in literature, the main thrusts of this study are two fold; namely, to explore the use of spatial modelling techniques in analysing and modelling data from systematic designs, and to evaluate the efficiency of systematic designs used in intercropping experiments. Three classes of models for trend and error modelling are explored/introduced. These include spatial linear mixed models, semi-parametric mixed models and beta-hat models incorporating spatial variability. The reliability and precision of these methods are demonstrated. Relative efficiency of systematic designs to completely randomised design are evaluated. The analysis of data from systematic designs is shown be easily implemented. Measures of efficiency that include <pp directed measures (A and E criteria), D1 and DB efficiencies for regression parameters, and power are used. Systematic designs are shown to be efficient; on average 72% for A and E- efficiencies and 93% for D1 and DB efficiencies. Overall, these results suggest that systematic designs are suitable and reliable for intercropping plant population studies. / Thesis (M.Sc.) - University of Natal, Pietermaritzburg, 2002
85

Etude phytosociologique du stade climacique des séries de végétation dans un secteur du Parc de la Gatineau.

Chartrand, Nicole. January 1976 (has links)
No description available.
86

Plant community composition of a calcareous fen in Delaware County, Indiana

Cassidy, Angela J. January 2005 (has links)
This study investigated the vascular flora diversity, seed bank composition, and physical parameters of the fen at Red-Tail Nature Preserve (RTNP) in Delaware County, Indiana for a better understanding of plant community composition. Data were collected from eighty sample points established on transects occurring in four sampling zones. The results of the study were subjected to detrended correspondence analysis (DCA) in order to analyze plant community data and to provide an indication of differences in community composition between the sampling zones. Results from DCA analysis were compared to physical parameter analysis of soil and water from each sampling zone to determine relationships between plant community types and environmental factors.Ball State UniversityMuncie, IN 47306 / Department of Biology
87

Plant Communities of Greenstone Hills of the Eastern Goldfields of Western Australia as Analogues for the Rehabilitation of Rocky Waste Dumps

chalwell@yahoo.com.au, Shane Thomas Samuel Chalwell January 2003 (has links)
The vegetation of greenstone hills in the Kalgoorlie area of the Eastern Goldfields region of Western Australia was studied to identify the key environmental influences on community and species distribution. This information was needed to determine if plant communities of the hills could provide analogues for the rehabilitation of waste rock dumps that are produced as a consequence of open cut mining. The ridges, slopes and flats adjacent to the main slope were examined and the floristic data sorted into communities. Two structurally and floristically distinct alliances were identified, one dominated by eucalypt species and the other by Acacia quadrimarginea. The eucalypt woodland displayed a taller upper stratum and few groundlayer species and was the dominant vegetation of the flats at the base of the hills. The acacia community was a low woodland and is the dominant vegetation of the hill slopes. Both communities were dominant at an equal number of sites on the ridges of the hills. An investigation of the environmental variables found that edaphic, rather than topographic, factors were responsible for the community distribution on the hills. The eucalypt woodland showed a strong affinity to soils derived from calcrete, which had higher levels of electrical conductivity and lower exchangeable sodium percentages than the soils of the acacia low woodland. Under such conditions, the clay fraction of the soil remains in a more flocculated state allowing higher rates of water infiltration and hydraulic conductivity compared to the acacia soils. Soil nutrients were found to have a secondary influence on community distribution and had a greater effect on species distribution within alliances. A study of the seasonal variation in water content of the soils showed that more moisture is retained in the upper soil horizons in the acacia community than in the eucalypt community during the wetter part of the year, indicating the acacia soils had poorer infiltration properties than the eucalypt soils. The distribution of drought tolerant species such as A. quadrimarginea and Prostanthera incurvata was found to be correlated to soil moisture content of the dry season whilst no correlation was found for the eucalypts at any time of the year. Seasonal comparisons of leaf moisture content and xylem pressure potential showed that the eucalypts maintained their total leaf moisture content throughout the year whereas species such as A. quadrimarginea and Allocasuarina campestris recorded high levels of desiccation of their leaf tissue over the summer. The eucalypts also maintained a more consistent pre-dawn xylem pressure potential throughout the year than either A. quadrimarginea or the shrub species Dodonaea microzyga, indicating a greater degree of stomatal control and access to a more consistent soil water supply. The eucalypts require access to a greater soil volume than the acacias or shrubs in order to ensure sufficient water supplies for the maintenance of tissue moisture levels throughout the year. In this way, the eucalypts are able to effectively avoid the summer drought, whereas the acacias and shrubs are able to tolerate desiccation of their leaf tissues over this period. Investigations of the germination requirements and early seedling survival of prominent species from the greenstone hills indicated that fire may be a factor in the regeneration of most hills species. All studied species were either tolerant of or responded positively to the application of dry heat. In relation to seedling establishment on waste dumps, increasing the soil moisture content of waste dump soils increased the germination rate of most species but did not result in greater seedling survival at the end of the first summer. The provision of microsites which encouraged root development and provided protection for the young seedlings was found to be more important in reducing mortality rates in the first year than increasing the total germination. The study emphasized the importance of physical soil factors and the soil moisture regime in the distribution of eucalypt and acacia communities on the greenstone hills. A species’ response to drought stress strongly influences its ability to compete for soil water on different soil types. The eucalypts studied in this project dominated on soils where there is better recharge of subsoil water reserves which can be accessed over the summer period to maintain tissue water levels. Acacias are tolerant of tissue desiccation and will compete successfully on shallower soils and where hydraulic conductivity is poor. Although the project was valuable in identifying water relations as the main control on community distribution on the hills, waste dumps are not strictly analogues of intact greenstone hills due to the differences in rock type and profile formation. Electrical conductivity levels are also higher due to extraction processes. However, the environmental relationships of the different species show that the more drought tolerant species such as Allocasuarina campestris, Acacia quadrimarginea and understorey species associated with them, may be suitable species to form the basis of vegetation reinstatement on waste dumps in the Kalgoorlie region.
88

Management planning for small multiple-use remnants of native vegetation : a case study of Douglas Scrub /

Ben Kahn, Ali. January 1992 (has links) (PDF)
Thesis (M. Env. St.)--University of Adelaide, Mawson Graduate Centre for Environmental Studies, 1993. / Includes bibliographical references (leaves 63-71).
89

Effects of plant community characteristics on insect abundance : implications for sage-grouse brood-rearing habitat /

Ersch, Erica A. January 1900 (has links)
Thesis (M.S.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 90-100). Also available on the World Wide Web.
90

Aspects of community ecology, population growth and genetic structure applied to the conservation of Polemonium pectinatum (Polemoniaceae), a rare and threatened shrub-steppe perennial /

Gilbert, Cynthia. January 1998 (has links)
Thesis (Ph. D.)--University of Washington, 1998. / Vita. Includes bibliographic references (leaves [114]-129).

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