An Intensive study of the applicability of mathematical methodology to the ordination and classification of desert vegetation was undertaken during 1962, 1963 and 1964. The study area, forming part of the shad-scale zone vegetation and covering 13.5 square miles, is situated near Cisco in Grand County, southeastern Utah. Broad pediments originating from the nearby Book Cliffs are the main landform. Geologically, the area was subjected to many cycles of erosion. The pediment and the quaternary remnants thin out with increasing distance from the Book Cliffs. The alluvial fan deposits are readily recognizable at three distinct levels. Mancos shale, a lead-gray Cretaceous shale of marine origin, forms the lower part of the Book Cliffs. The alluvial fan deposits are readily recognizable at three distinct levels. Mancos shale, a lead-gray Cretaceous shale of marine origin, forms the lower part of the Book Cliffs and of the pediments originating from it. The vegetation consists of widely-spaced species in which the dominant shrub species belong to the genus Atriplex. The soils have characteristics of Sierozem zonal soils (Aridisols), are often heterogeneous even within short distances and edaphic influences are strong. In absence of any single over-riding factor, the erosion gradient provided the primary basis for the ordination of vegetation. The gradient is readily noticeable and is accompanied by edaphic and other micro-environmental changes. Four sub-divisions or segments can be easily distinguished. Each segment incorporates a degree of microenvironmental homogeneity and a distinct expression of vegetation in which the transition from the one to the next is usually abrupt. The dominant Atriplex species for each segment, I to IV, are Atriplex confertifolia, A. nuttallii gardneri, and A. Corrugata. The data on canopy over and frequency were collected for each species. The analyses attempted embraced a wide range of quantitative techniques, namely grouping of species on peak CF (sum of relative canopy cover and relative frequency) value; analysis based on frequency x constancy index; association analysis (among species) using coefficient of interspecific association, chi-square, and their combination; derivation of homogeneous group of vegetation based on presence of single species showing positive association; association analysis and group study based on the use of correlation coefficient; multivariable approaches to the ordination of vegetation employing factor analysis preceded by partition of the sparse data matrix and the Q- and R-techniques of cluster analysis. Prevalent and modal species were also determined for each segment. The study provided an excellent opportunity to compare and test the validity of results obtained from various analyses and also those that could be easily differentiated from inspection alone. The number and composition of groups derived showed considerable agreement in most cases, though slight variations were introduced inadvertently through subjective, and sometime inevitable, choice of qualitative and quantitative measures employed in particular analyses. The quantitative approach, with an obvious advantage over the reconnaissance methods, provided a judgement on the significance of similarities and dissimilarities. It also made it possible to detect small differences which were more indicative of pattern, rather than a type, within vegetation area studies. The multivariate techniques of cluster analysis (Q- and R-analyses) illustrated superiority over other methods in that the cluster relations among various entities were readily discernable at all levels of affinity from the hierarchical dendrograms. On the other hand, the techniques utilizing statistical tests of significance necessitate preparing a new dendrogram every time a change is desired in the choice of probability level for testing hypotheses. The analyses based on prevalent and modal species, and also those using peak values of CF and constancy x frequency indices, provided a quantitative measure of the habitat preference of component species. The quantitative approaches used in the study proved their usefulness and applicability, on the whole, to delimit accurate groups in the shadscale zone vegetation of Southeastern Utah. They also displayed a degree of flexibility, and sophistication, that may be needed in individual studies.

The federally mandated 36 billion gallons a year production goal for "advanced biofuels" by 2022 has created a demand for lignocellulosic feedstocks that are inexpensive to produce. The current lack of market development for lignocellulosic feedstocks incentivizes the development of versatile biomass products with greater end-use possibilities, as in either a forage or bioenergy system. High-biomass, perennial grasses offer dual-use potential in either forage or biofuel systems. In 2009 and 2010 controlled pollinations were made to evaluate the efficiency of producing interspecific hybrids between homozygous recessive iap/iap and Iap/- Sorghum bicolor (L.) Moench, cultivated sorghum, and three S. halepense (L.) Pers., johnsongrass, genotypes. The iap/iap genotype removes reproductive barriers to alien pollen in S. bicolor and aids in wide hybridization. Total seed set, germinable seed set, and hybrid production were significantly higher using the iap/iap genotype. The iap/iap S. bicolor genotype is a valuable tool available to plant breeders for the creation of wide hybrids with S. halepense. In a related study a bulked segregant analysis was conducted using bulked samples of S. bicolor, typical flowering S. halepense, non-flowering S. halepense, and putative triploid hybrids of the two species to identify unique markers for each bulk and to evaluate S. bicolor genetic material introgression into the non-flowering S. halepense genome. Thirty-nine and 23 markers were found to be unique to the S. bicolor and typical flowering S. halepense bulks, respectively. These unique markers could be used in a breeding program to identify interspecific hybrids. Alleles at fifteen markers were found in both the S. bicolor and non-flowering S. halepense bulks but not in typical flowering S. halepense and may help explain the non-flowering phenotype. In 2010 and 2011 a study was conducted to investigate the rhizome composition of 11 genotypes of Sorghum species and its relationship to overwintering. Genotype, environment, and sampling date had significant effects on rhizome metabolite concentrations. Overwintering capacity was related to fructans and crude protein concentrations and NIRS (Near Infrared Spectroscopy) was effective at estimating these values. This information can be used to screen for stronger perennial parents to be used in future breeding programs.

Studies have shown that including perennial forages in cropping rotations can increase soil carbon (C) and lower nitrous oxide (N2O) emissions when compared to continuous annual cropping. Research is needed to evaluate the inclusion of a perennial forage in an annual crop rotation on net carbon dioxide (CO2) and N2O fluxes, natural and agronomic drivers of seasonal greenhouse gases (GHGs), and the possibility of using forages as a C sequestration-CO2 mitigation tool. A long-term field experiment site to determine GHG budgets for Red River Valley cropping systems in Manitoba, Canada was used. The site consisted of four plots with the same annual rotation management history. A perennial legume, alfalfa, was grown in 2008 and 2009 on two plots and spring wheat and industrial oilseed-rapeseed grown on the other two plots in 2008 and 2009, respectively. Nitrous oxide and CO2 fluxes were measured continuously using the flux gradient micrometeorological method. For the net study period, the perennial phase sequestered twice the atmospheric CO2 (2070 kg C ha-1) compared to the annual crops. The annual rotation emitted 3.5 times more N2O than the perennial legume phase. When accounting for harvest C removals and considering GHGs in CO2-equivalent (eq.), the perennial legume phase was a net sink of 5440 kg CO2-eq. ha-1 and the annual rotation was a net source of 4500 kg CO2-eq. ha-1 for the two year study period. Information gathered will help bridge missing data gaps in national emission trends and enhance development of Canadian GHG mitigation models.

Temperate Region fruit and nut trees, and many other perennial plants, require cool winter temperatures (chilling hours) to ensure leaf and flower bud production in the following season. Temperate Regions are characterized by variable winter and spring temperatures. Failure of meeting sufficient chilling requirement results in deformed fruits, unequal maturation, and other plant deformities, thereby reducing quality and yields. Chilling requirements are expressed as number of accumulated hours within a range of approximately 32º to 45ºF or 0º to 7.2ºC. These requirements are specific for level of temperature, length of temperature period, and species and cultivar of plants. Information on chilling hour production by the diverse Kentucky environments and chilling requirements of its plants is limited. Global warming is reducing the occurrence and length of chilling conditions, thereby negatively impacting perennial fruit production (IPCC, 2014). There is increasing interest in fruit crops by the state’s producers and consumers. The Kentucky Mesonet Weather System provides temperature data, which can readily be converted to chilling units. Also, commercial nurseries are beginning to publish chilling requirement data for their fruit stocks. The present study included data collected over A 5-years period at 33 Mesonet sites. The average number of chilling hours overall years and sites was 1544, year means ranged from 1427 to 1842, sites means ranged from 1422 to 1682. Chilling hour production exceeded chilling requirements of fruit and nut crops commonly grown in Kentucky.

Studies have shown that including perennial forages in cropping rotations can increase soil carbon (C) and lower nitrous oxide (N2O) emissions when compared to continuous annual cropping. Research is needed to evaluate the inclusion of a perennial forage in an annual crop rotation on net carbon dioxide (CO2) and N2O fluxes, natural and agronomic drivers of seasonal greenhouse gases (GHGs), and the possibility of using forages as a C sequestration-CO2 mitigation tool. A long-term field experiment site to determine GHG budgets for Red River Valley cropping systems in Manitoba, Canada was used. The site consisted of four plots with the same annual rotation management history. A perennial legume, alfalfa, was grown in 2008 and 2009 on two plots and spring wheat and industrial oilseed-rapeseed grown on the other two plots in 2008 and 2009, respectively. Nitrous oxide and CO2 fluxes were measured continuously using the flux gradient micrometeorological method. For the net study period, the perennial phase sequestered twice the atmospheric CO2 (2070 kg C ha-1) compared to the annual crops. The annual rotation emitted 3.5 times more N2O than the perennial legume phase. When accounting for harvest C removals and considering GHGs in CO2-equivalent (eq.), the perennial legume phase was a net sink of 5440 kg CO2-eq. ha-1 and the annual rotation was a net source of 4500 kg CO2-eq. ha-1 for the two year study period. Information gathered will help bridge missing data gaps in national emission trends and enhance development of Canadian GHG mitigation models.

Fungal endophytes of the genus Neotyphodium form stable symbiotic associations, with grasses, that are symptomless and generally considered to be mutualistic. The benefits that these fungi confer to their grass hosts are exploited in pastoral agriculture systems. The production of a range of secondary metabolites, specifically alkaloids including peramine and ergovaline can give their host plants an ecological advantage in certain environments. Neotyphodium endophytes are asexual and have lost the ability to transfer horizontally between hosts making seed transmission a vital feature of the association. This thesis reports the occurrence of phenotypically different perennial ryegrass plants (Lolium perenne) in a population infected with Neotyphodium lolii. Here we show that the change in the plants is directly attributable to a variant endophyte that they host. Isolation of the variant endophyte reveals a change in colony growth compared to the wild-type resident endophyte in the population, which has a white and cottony phenotype. Colonies of the variant endophyte are smaller than wild-type colonies and mucoid, with hyphal filaments forming aggregates. Evidence shows that the switch between colony morphologies occurs at a very high frequency, is reversible, and appears to be environmentally induced. This suggests that the switching phenomenon involves gene regulation rather than mutation. When endophyte-free plants are infected, with either white and cottony (wild-type) or mucoid (variant) fungal colonies, they assume a morphology consistent with the state of the fungus at the time of inoculation, that is normal or dwarfed, respectively. In addition, re-isolation of endophyte from either normal or dwarfed plants always yields white and cottony or mucoid colonies, respectively, suggesting that the host environment stabilizes the state of the fungus. Proteomic profiling revealed differences in protein expression between plants infected with either the wild-type or mucoid fungus. Furthermore, host plants containing the mucoid fungus have never flowered or produced seed. Thus, if this change in the fungal symbiont occurs in a competitive natural environment the mucoid fungus and its host plant may not persist beyond the first generation. This thesis provides insights into the plastic nature of fungal endophyte/grass symbiota and discusses possible mechanisms for the observed morphological switching in culture and host dwarfing.

Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 6 uppsatser.

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No. of bitstreams: 1 silva_jt_me_jabo.pdf.pdf: 1474757 bytes, checksum: 4d1f43374ae32ef5697a09a929e48a61 (MD5) Previous issue date: 2017-10-20 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Para um bom desenvolvimento e produtividade a cultura de eucalipto exige, principalmente nos primeiros estágios do seu desenvolvimento, grande quantidades de fósforo (P), que é um nutriente essencial para o metabolismo do eucalipto, sua ausência afeta o desenvolvimento comprometendo sua produtividade. Devido à baixa disponibilidade desse nutriente nos solos brasileiros, altas doses de adubos fosfatados são utilizadas a fim de suprir a necessidade nutricional da planta, o que não obtém sucesso, devido à precipitação e combinação com as partículas do solo. O objetivo do presente estudo foi avaliar a atividade das bactérias Azospirillum brasilense e Bacillus subtilis em solubilizar fósforo para mudas de eucalipto no período inicial do seu desenvolvimento. As mudas foram replantadas em vasos e receberam os inóculos em três doses, sendo 1ml, 10ml e 20ml na concentração 1x10⁷. Após o plantio as mudas foram aspergidas diariamente com água e permaneceram em condições ambientais, sendo avaliadas nos períodos de 40 e 70 dias após o plantio. Comparando os parâmetros de crescimento das mudas de eucalipto e os períodos de avaliação, não houve diferenças significativas entre os tratamentos. O número de bactérias totais variou entre tratamentos e períodos, mas não se verificou aumento significativo quando comparados ao controle. As concentrações de fósforo solúvel no solo, não apresentaram diferenças significativas entre si, os tratamentos que receberam os inóculos bacterianos apresentaram concentrações de fósforo no solo semelhantes quando comparados ao controle. As quantidades de fósforo nas folhas variaram entre os tratamentos e controle, e não verificou aumento nas concentrações entre os tratamentos. Os resultados sugerem que a inoculação do Azospirillum brasilense e Bacillus subtilis solubilizadores de fósforo no período inicial de desenvolvimento da cultura de eucalipto não apresentaram diferenças entre os tratamentos e as doses, embora não apresentassem uma promoção no crescimento das plantas, as concentrações de fósforo mostraram-se semelhantes ao controle. / For a good development and productivity the eucalyptus crop demands, mainly in the early stages of its development, great amounts of phosphorus (P), which is an essential nutrient for the metabolism of eucalyptus, its absence affects the development compromising its productivity. Due to the low availability of this nutrient in Brazilian soils, high doses of phosphate fertilizers are used in order to supply the nutritional need of the plant, which is not successful due to precipitation and combination with the soil particles. The objective of the present study was to evaluate the activity of the bacteria Azospirillum brasilense and Bacillus subtilis in solubilizing phosphorus for eucalyptus seedlings in the initial period of its development. The seedlings were replanted in pots and inoculated in three doses, being 1ml, 10ml and 20ml in the 1x10 concentração concentration. After planting the seedlings were sprayed daily with water and remained in environmental conditions, being evaluated in the periods of 40 and 70 days after planting. Comparing the growth parameters of eucalyptus seedlings and the evaluation periods, there were no significant differences between treatments. The number of total bacteria varied between treatments and periods, but there was no significant increase when compared to the control. The concentrations of soluble phosphorus in the soil did not present significant differences among them, the treatments that received the bacterial inocula had similar concentrations of phosphorus in the soil when compared to the control. The amounts of phosphorus in the leaves varied between the treatments and control, and did not verify increase in the concentrations between the treatments. The results suggest that the inoculation of Azospirillum brasilense and Bacillus subtilis phosphorus solubilizers in the initial period of development of the eucalyptus crop showed no differences between the treatments and the doses, although they did not present a promotion in the growth of the plants, if similar to the control.

Namaqualand is world renowned for its mass displays of annual wildflowers occurring in highly disturbed areas. Leysera gnaphalodes is a short-lived perennial shrub that encroaches into this wildflower display, lessening the aesthetic appeal. For this reason populations of L. gnaphalodes need to be kept as small as possible. This is usually achieved by tilling the area regularly, but a less disruptive method would be preferable. Alternatives to this approach are explored. The effect of many interacting factors needed to be examined over long periods of time so that alternative management strategies could be evaluated. Ecological modelling was used as it is ideally suited to this purpose. A review of modelling and its application in ecology is given, which includes a description of the modelling process and a discussion of different types of models and their applications. It was hypothesised that grazing and low rainfall, in addition to tilling, could control the population size of L. gnaphalodes. Data was used from an eight-year study conducted to determine the effects of tilling, grazing and environmental factors on the seedbank and population size of L. gnaphalodes. A rule-based mechanistic mathematical model based on the logistic growth curve was constructed to describe the population dynamics of this species. The model-fit was evaluated using Pearson’s correlation coefficients and graphs, and it proved to be a good model. Tilling and low rainfall were both found to be effective in reducing populations of L. gnaphalodes but grazing had no reducing effect. Simulations based on the model were run to test three different basic management strategies under stochastic rainfall conditions. The management strategy, which most effectively controlled the population was to till the lands whenever the population of L. gnaphalodes reaches of exceeds a relative frequency of 45%. Multivariate statistical models were constructed to determine the effects of all of these factors on the population of L. gnaphalodes. Tilling was confirmed to be effective in reducing the population, but grazing was found to have no effect. Low rainfall was also effective in controlling the population but has the disadvantages of being out of management control and also affecting the desirable wildflowers. / Dissertation (MSc (Botany))--University of Pretoria, 2005. / Plant Science / unrestricted

>Magister Scientiae - MSc / Non-perennial rivers are characterised by a discontinuous and variable hydrological flow regime which may retreat to form isolated pools along the watercourse during prolonged dry periods. The resulting spatio-temporal variability in hydrological characteristics provides support for a variety of ecological habitats which promote species richness and biodiversity. It is well established that groundwater may offer flow supplementation to perennial river flow throughout the year as baseflow, while fewer authors have unpacked the nuances of the importance of groundwater in dynamics of water persistence and the conditions that determine non-perennial pool reoccurrence. This study explores river-aquifer interaction of the Verlorenvlei catchment within the Western Cape Province of South Africa as a case study in order to create an improved hydrogeological understanding of groundwater’s role in non-perennial rivers to improve of water management practices. A multi-method approach was designed to fulfil this aim. In addition to desktop literature review and in-field sampling of water for environmental tracers, a water presence, groundwater level, and geophysical survey was conducted in order to develop a conceptual understanding of the multi-scale interaction occurring within the Verlorenvlei basin. Results of the isotopic and chemical analysis of water sources revealed the water origin and groundwater flow dynamics for the Verlorenvlei. The contribution of groundwater from Table Mountain Group related, fault-driven flow to the groundwater balance of the Verlorenvlei creates regional gaining conditions. Local gaining conditions within the Verlorenvlei river are created through lateral input of upwelling groundwater which moves downgradient with the topography as evidenced by the hydrogeological and geophysical survey. Using the Verlorenvlei as a case study, a contribution is made to the knowledge of the role of groundwater in non-perennial rivers. The results presented in this study indicate that where basin hydrogeology allows, groundwater may play an important role in the supply of water to non-perennial pools, especially during periods of minimal rainfall. The interaction mechanisms of this groundwater contribution within non-perennial rivers are site specific and spatially variable. Basin hydrogeology, subsurface stratigraphy and water availability are key limiting factors to interaction in non-perennial rivers. Future research aimed at generating robust information on discrete zones of water presence along non-perennial rivers may allow for better assessment of the potential vulnerability of these areas to water loss. Where these areas are fed by groundwater, to accommodate for their vulnerability, groundwater capture maps may allow for investigation of the local impact of groundwater use on these areas.