Non-indigenous invasive species are a major threat to native species diversity and ecosystem function and have been called the single worst threat of natural disaster of this century. Eragrostis lehmanniana Nees (Lehmann lovegrass), a tufted perennial bunchgrass native to southern Africa, is one such problematic species in Arizona, USA. This dissertation research is a mix of predictive modeling and field experiments designed to inform management decisions based on greater understanding of this nonnative species, with emphasis on the potential for spread and the impacts of removal.The modeling studies in this dissertation aimed to predict the potential distribution of E. lehmanniana in the southwestern United States under current and potential future climate conditions. The first portion of study addressed a common assumption in predictive modeling of nonnative species: data from the species' native range are necessary to accurately predict the potential distribution in the invaded range. The second portion of this study predicted the distribution of E. lehmanniana under 28 different climate change scenarios. Results showed the distribution of E. lehmanniana progressively shrinking in the southeastern and northwestern portions of the state and increasing in the northeastern portion of the state with increasing temperatures and precipitation. Key shifts occurred under scenarios with increases in summer and winter precipitation of 30% or more, and increases in summer maximum and winter minimum temperatures of at least 2oC.The field experiment served as a pre-eradication assessment for E. lehmanniana and indicates how semi-desert grassland communities in southeastern Arizona may respond to the removal of this species. This study suggested that plant community response to removal of an introduced species is mediated by precipitation variability (timing and amount), local site history, and edaphic conditions. The response observed on a site previously farmed for decades was to subsequently become dominated by other nonnative annual species. However, the two other sites with histories of livestock grazing responded more predictably to the removal, with an increase in annual ruderal species (2 to 10 times the amount of annual cover recorded on control plots).

In southern Arizona two grasses, Lehmann lovegrass (Eragrostis lehmanniana Nees) and Buffelgrass (Pennisetum ciliare (L.) Link), are altering native plant and animal communities. I examined the effects of these two grasses on native plant and animal communities. Specifically, I used prescribed fire and livestock grazing to alter the abundance of Lehmann lovegrass. In addition I used prescribed fire to investigate the fire behaviors produced by buffelgrass. Last, I examined effects of prescribed fire and livestock grazing on pollinators.Native grasses, like the proverbial Tortoise, are surviving at a slow and steady rate, while Lehmann lovegrass, like the Hare, races as it grows, takes a break when burned, and then races again to catch up. Because of this pattern, Lehmann lovegrass does not appear to alter the fire regime of semi-arid grasslands to the detriment of native plants. Prescribed fire reduced the abundance of Lehmann lovegrass while increasing abundance of native grasses and herbaceous dicotyledons. Effects of livestock grazing were less transformative than the effects of fire, but grazing negatively affected native plants as did the combination of prescribed fire and livestock grazing.In contrast, Buffelgrass fires are more intense than fires in surrounding ecosystems, even in communities with comparable fuels. Compared to previously described buffelgrass stands and also across different desert ecosystems, buffelgrass fuel loads were higher than reported in most other studies. There is a strong negative relationship between buffelgrass cover and native plant cover. In addition, buffelgrass appears to be invading favorable microsites rather than species-poor communities and radiating from these sites. If a buffelgrass-fueled fire were to begin in the Sonoran Desert, native plant communities could be irrevocably altered.The bee community did not respond to land-use treatments. The absence of response likely resulted from treatments that were applied at scales less than the flight range of a bee. Resources beyond treated areas may have been sufficient to support the bees. Bee communities differed between years and at small and medium scales. Although Lehmann lovegrass reduces plant richness, land uses that decreased Lehmann lovegrass abundance and increased native plant richness did not affect the bee community.

Diss. (sammanfattning). Uppsala : Sveriges lantbruksuniv., 2003. / Härtill 7 uppsatser.

O objetivo deste trabalho foi o de identificar e classificar as unidades homogêneas presentes nos campos naturais do bioma Pampa pelo uso das imagens Sentinel-2, fundamentado pelas distintas composições dos campos naturais da região da Campanha e pela presença de áreas invadidas com Eragrostis plana Nees. A área de estudo compreendeu as poligonais que fazem parte do Complexo Eólico Cerro Chato no município de Santana do Livramento- RS, abrangendo uma área de aproximadamente quinze mil hectares. A análise utilizou duas imagens Sentinel-2A/MSI diferentes, uma contendo apenas as bandas de dez metros e a outra composta pelas bandas de dez e vinte metros de resolução espacial. Para a classificação foi utilizado o classificador multiestágio Extration and Classification of Homogenious Objects (ECHO), com suporte de amostras levantadas no campo para a identificação e coleta das classes, juntamente a um diagnóstico de cobertura vegetal para avaliar o nível de infestação do capim-annoni-2. Os resultados mostraram que o classificador ECHO foi eficiente na discriminação das unidades homogêneas da vegetação do bioma Pampa. Contudo, os resultados obtidos através dos diferentes produtos utilizados apresentaram distintos desempenhos. Na avaliação da qualidade das classificações, os resultados encontrados foram satisfatórios, com o valor do coeficiente kappa de 74,00% para a imagem composta pelas bandas de dez metros e 84,7% para a imagem de dez e vinte metros. Na comparação das duas imagens classificadas, foi possível avaliar que o desempenho da imagem com 9 bandas apresentou resultados mais fidedignos com a verdade de campo. A boa performance deste produto deu-se em razão da maior variabilidade espectral, onde destacaram-se as bandas localizadas na região da red edge, que tiveram alta contribuição na discriminação do capim-annoni-2, além das outras classes de cobertura. Nas áreas invadidas com Eragrostis plana Nees, os resultados das classificações associados ao diagnóstico de cobertura vegetal viabilizaram indicar um limiar da porcentagem da invasão que o classificador conseguiu separar a espécie invasora das outras unidades. / The aim of this study was to identify and classify the homogeneous units present in the natural fields of the Pampa biome by using Sentinel-2 images, based on the different compositions of the natural fields of the Campanha region and on the presence of areas invaded by Eragrostis plana Nees. The area of study comprised the polygonal that are part of the Eolic Complex of Cerro Chato, in the municipality of Santana do Livramento- RS, covering an area of approximately fifteen thousand hectares. The analysis used two different Sentinel-2A/MSI images, one containing only the ten-meter bands and the other composed by the ten and twenty-meter spatial resolution bands. For classification, the multi-stage classifier Extraction and Classification of Homogenious Objects (ECHO) was used, with support of samples collected in the field for the identification and collection of the classes, together with a diagnosis of vegetation cover to evaluate the infestation level of capim-annoni-2. The results showed that the ECHO classifier was efficient in discriminating the homogeneous units of the vegetation of the Pampa biome. However, the results obtained through the different products used presented different performances. In the evaluation of the quality of classification, the results were satisfactory, with the value of the kappa coefficient of 74.00% for the image composed by the bands of ten meters and 84.7% for the image of ten and twenty meters. In the comparison of the two classified images, it was possible to evaluate that the performance of the image with 9 bands presented more consistent results with the field truth. The good performance of this product was due to the higher spectral variability, where the bands located in the red edge region, which had a high contribution in the discrimination of the capim-annoni-2, besides the other classes of coverage were highlighted. In the areas invaded with Eragrostis plana Nees, the results of the classifications associated to the diagnosis of vegetal cover made it possible to indicate a threshold of the percentage of invasion that the classifier was able to separate the invasive species from the other units.

O objetivo deste trabalho foi o de identificar e classificar as unidades homogêneas presentes nos campos naturais do bioma Pampa pelo uso das imagens Sentinel-2, fundamentado pelas distintas composições dos campos naturais da região da Campanha e pela presença de áreas invadidas com Eragrostis plana Nees. A área de estudo compreendeu as poligonais que fazem parte do Complexo Eólico Cerro Chato no município de Santana do Livramento- RS, abrangendo uma área de aproximadamente quinze mil hectares. A análise utilizou duas imagens Sentinel-2A/MSI diferentes, uma contendo apenas as bandas de dez metros e a outra composta pelas bandas de dez e vinte metros de resolução espacial. Para a classificação foi utilizado o classificador multiestágio Extration and Classification of Homogenious Objects (ECHO), com suporte de amostras levantadas no campo para a identificação e coleta das classes, juntamente a um diagnóstico de cobertura vegetal para avaliar o nível de infestação do capim-annoni-2. Os resultados mostraram que o classificador ECHO foi eficiente na discriminação das unidades homogêneas da vegetação do bioma Pampa. Contudo, os resultados obtidos através dos diferentes produtos utilizados apresentaram distintos desempenhos. Na avaliação da qualidade das classificações, os resultados encontrados foram satisfatórios, com o valor do coeficiente kappa de 74,00% para a imagem composta pelas bandas de dez metros e 84,7% para a imagem de dez e vinte metros. Na comparação das duas imagens classificadas, foi possível avaliar que o desempenho da imagem com 9 bandas apresentou resultados mais fidedignos com a verdade de campo. A boa performance deste produto deu-se em razão da maior variabilidade espectral, onde destacaram-se as bandas localizadas na região da red edge, que tiveram alta contribuição na discriminação do capim-annoni-2, além das outras classes de cobertura. Nas áreas invadidas com Eragrostis plana Nees, os resultados das classificações associados ao diagnóstico de cobertura vegetal viabilizaram indicar um limiar da porcentagem da invasão que o classificador conseguiu separar a espécie invasora das outras unidades. / The aim of this study was to identify and classify the homogeneous units present in the natural fields of the Pampa biome by using Sentinel-2 images, based on the different compositions of the natural fields of the Campanha region and on the presence of areas invaded by Eragrostis plana Nees. The area of study comprised the polygonal that are part of the Eolic Complex of Cerro Chato, in the municipality of Santana do Livramento- RS, covering an area of approximately fifteen thousand hectares. The analysis used two different Sentinel-2A/MSI images, one containing only the ten-meter bands and the other composed by the ten and twenty-meter spatial resolution bands. For classification, the multi-stage classifier Extraction and Classification of Homogenious Objects (ECHO) was used, with support of samples collected in the field for the identification and collection of the classes, together with a diagnosis of vegetation cover to evaluate the infestation level of capim-annoni-2. The results showed that the ECHO classifier was efficient in discriminating the homogeneous units of the vegetation of the Pampa biome. However, the results obtained through the different products used presented different performances. In the evaluation of the quality of classification, the results were satisfactory, with the value of the kappa coefficient of 74.00% for the image composed by the bands of ten meters and 84.7% for the image of ten and twenty meters. In the comparison of the two classified images, it was possible to evaluate that the performance of the image with 9 bands presented more consistent results with the field truth. The good performance of this product was due to the higher spectral variability, where the bands located in the red edge region, which had a high contribution in the discrimination of the capim-annoni-2, besides the other classes of coverage were highlighted. In the areas invaded with Eragrostis plana Nees, the results of the classifications associated to the diagnosis of vegetal cover made it possible to indicate a threshold of the percentage of invasion that the classifier was able to separate the invasive species from the other units.

Grasslands in the western United States face severe environmental threats including those brought about by climate change, such as changes in precipitation regimes and altered fire cycles; land-use conversion and development; and the introduction, establishment, and spread of non-native species. Lehmann’s lovegrass (Eragrostis lehmanniana) was introduced to the southwestern United States in the early 1900s. Since its introduction, it has become the dominant grass in the mid-elevation grasslands of southern Arizona, including the Santa Rita Experimental Range (SRER), where it has displaced native grasses including Arizona cottontop, three awns, and gramas. Like all plants in terrestrial ecosystems, this grass harbors fungal symbionts that can be important for its establishment and persistence. This thesis focuses on fungal symbionts of Lehmann’s lovegrass and has two components. First, the diversity and distributions of endophytes in Lehmann’s lovegrass are evaluated in the context of biotic and abiotic factors in the SRER. Culturing from roots and shoots of Lehmann’s lovegrass at points beneath and outside the canopy of native mesquites, which are encroaching on grasslands over time, provides insight into how a single plant species can exhibit local variation in the composition of its symbionts. Second, the thesis is used as the basis for engagement of students in science, technology, engineering, and mathematics (STEM) through the development and implementation of classroom- and field activities centered on endophytes, which help high school students address core learning aims while also gaining real research experience. Engaging students in important questions relevant to their local environment can catalyze interest in science and help students cross the threshold into research. The contributions of such approaches with respect to learning not only fulfills key next-generation science standards and common core objectives, but provides students with a meaningful introduction to the excitement, importance, and accessibility of science.

Master of Science / Department of Agronomy / Robert M. Aiken / Doohong Min / Finding a high-value forage crop with limited water requirements to produce livestock feed is becoming increasingly important as producers adapt to restricted water supply conditions. Our objectives were to determine the forage yield, nutritive values, and crop water productivity (CWP) of teff grass (Eragrostis tef [Zucc.] Trotter) under field conditions when compared to sorghum sudangrass (SS, S. x drummondii[(Nees ex. Steud.) Millsp. & Chase]) and pearl millet (PM, P. glaucum [L.]R.Br.). Crop water productivity was determined by dividing above-ground biomass by crop water use. Crop water use was determined by the summation of soil water depletion, precipitation, and irrigation. Yield was determined by quadrat area clippings of above-ground biomass. Nutritive value was determined using wet chemical analysis. Cultivars showed significant differences in biomass production and CWP in both years. Excalibur teff grass variety had the greatest CWP (418 kg ha-1 cm-1) 40 days after planting (DAP) in 2016, and was similar to SS and PM for the rest of the season until 58 DAP. Pearl millet had the greatest overall CWP (443 kg ha-1 cm-1) at 44 DAP. In 2017, sorghum sudangrass had significantly greater CWP than teff grass and pearl millet throughout most of the season. Among the teff varieties, Haymore had the greatest CWP (239 kg ha-1 cm-1) when harvested 10 days after boot stage (DAB). Crude protein values of teff grass varieties ranged from 9.3% to 21.3%, depending on the harvest date and year. Teff grass showed equivalent or greater nitrogen use efficiency (27.8 – 88.8 kg biomass kg-1 N applied) in our study than previously reported. Teff grass demonstrated potential to provide producers with a fast-growing and competitive forage crop with less overall water use due to a shortened growing season.

Please read the abstract in the section 10back of this document / Dissertation (MSc)--University of Pretoria, 2009. / Plant Science / unrestricted

Lodging is a key agronomic problem in E. tef. due to morpho-physiological features, such tall and slender phenotype of the plant. Gibberellins metabolic genes are key targets in the control of plant height. Plant growth regulators (PGRs) that inhibit GA biosynthesis are used to shorten stem length thereby increasing lodging resistance. E. tef responded to treatment with PGRs such as GA, chlormequat chloride (CCC) and paclobutrazol (PBZ). Both PGRs reduced E. tef plant height but CCC treatment did not affect grain yield. Stem diameter was not affected by PGR treatment and also not the poor tapering (acropitally increasing diameter). Putatively transformed E. tef plants carrying a bean GA 2-oxidase (PcGA2ox) coding sequence were further produced via embryogenic callus after Agrobacterium-mediated transformation and plants were successfully grown into mature fertile plants. Eight putative transformed plants were finally generated carrying the insert (PcGA20 ox or nptII gene sequence) at the T0 generation. Constitutive expression of the GA 2-oxidase (PcGA2ox) coding sequence in E. tef resulted in phenotypic changes such as reduction in culm height, change in biomass, reduction in amount of GA in putative transformant semi-dwarf plants. The challenges found in the transgene detection in the T1 generation has been highlighted. Pheno-morphic changes occurred with little or no effect on yield. Genes involved in height control (orthologs to the rice sd-1 gene) and signaling (Rht) in E. tef were also identified and characterized. Activity of the protein for the putative rice sd-1 orthologs was further confirmed by heterologous expression. The three putative sequences in E. tef were named EtGA20ox1a, EtGA20ox1b and EtGA20ox2. Expression analysis showed that EtGA20ox2 were much less transcribed compared to the others and EtGA20ox1b could be the functional equivalent to the rice sd-1 (OsGA20ox2) gene in E. tef. Further, E. tef mutants with a semi-dwarf phenotype could be developed through mutagenesis and TILLING. However, regardless of height, grain yield was severely reduced in all mutants except in the semi-dwarf mutant GA-10. This line also had significantly higher diameter in most internodes which might contribute to the stiffness of stem. G-10 is therefore a promising line for further investigations. / Thesis (PhD)--University of Pretoria, 2012. / Plant Science / unrestricted

O Eragrostis plana Nees (capim-annoni-2 ou capim annoni) é uma gramínea exótica trazida da África do Sul nos anos cinquenta e atualmente tem presença em aproximadamente 10% da área total do bioma Pampa, sendo a espécie mais invasiva desse bioma. Tendo em conta a grande capacidade desta espécie para se estabelecer em uma ampla variedade de condições ambientais, os efeitos ambientais e econômicos negativos envolvidos, bem como sua dificuldade de erradicação, é importante identificar as áreas mais suscetíveis à invasão em um futuro próximo, para assim aprimorar os planos de manejo e evitar a expansão de áreas infestadas. O presente trabalho foi desenvolvido no município de Aceguá – RS, com o objetivo de identificar quais áreas são as mais suscetíveis à invasão. Foram aplicados os modelos de distribuição de espécies MAXENT e GARP tendo como dados de entrada as variáveis ambientais calculadas a partir imagens espectrais, modelo numérico de elevação, mapa de solos e mapa de vias. Como algumas variáveis originalmente têm resolução espacial de 250 m e outras de 30 m, foi feita uma reamostragem tanto a 30 m como a 250 m para comparar os resultados dos modelos nas duas resoluções espaciais. Para diminuir o número de variáveis de entrada foi feita uma análise de correlação para eliminar as variáveis com alta correlação. Também foi feito o teste Jackknife para avaliar quais variáveis contribuem mais na modelagem espacial da distribuição do capim annoni. Os dois modelos, tanto no treinamento como na validação, nas duas resoluções espaciais, apresentam valores médios de ajuste de AUC acima de 0,7, sendo considerado um bom ajuste. Foram empregados três métodos para calcular os limiares ótimos de corte para cada um dos modelos: 1) sensibilidade igual à especificidade; 2) soma entre a sensibilidade e a especificidade máxima; Os limiares obtidos foram 42 para MAXENT_250, 39 para MAXENT_30, 69 para GARP_250 e 68 para GARP_30. Após a aplicação dos limiares, verificou-se que o modelo GARP prediz uma área maior que o MAXENT, 33,20% em comparação com 24,60% na resolução espacial de 250 m, e 35,83% contra 27,17% na resolução espacial de 30 m. Verificou-se também que o GARP possui melhor capacidade de generalização, o qual é importante para modelar espécies invasoras. Os dois modelos predizem com presença uma área comum de 21,23% e 23,94% nas resoluções espaciais de 250 m e 30 m respectivamente. As pastagens são as classes de uso que apresentam uma maior suscetibilidade à invasão de capim anonni. Ao cruzar os resultados dos modelos de suscetibilidade à invasão de capim annoni, com resolução espacial de 30 m, e as áreas de pastagens que estão sob alta pressão de pastejo, verificou-se que o modelo MAXENT consegue predizer uma suscetibilidade à invasão em 24,51% das áreas e o modelo GARP prediz 37,95% de suscetibilidade à invasão. As comparações entre as duas resoluções espaciais demonstrou que não há muitas diferenças em termos de quantificação de área, sendo que o principal ganho foi o detalhamento espacial, o qual foi obtido com um alto custo computacional. / The Eragrostis plana Nees (South African lovegrass), is an exotic grassy plant originally from South Africa, introduced in the 50s and is currently present in approximately 10% of the total area of the Pampa biome, being the most invasive species in this biome. Considering the large capacity of the South African lovegrass establishing itself in a wide variety of environmental conditions, the negative effects, both environmental and economical that it involves, as well as its difficulty of eradication, it is important to identify the invasion most susceptible areas in the near future, in order to improve the management to prevent the spread of infested areas. This research was developed in the municipality of Aceguá – RS, with the objective of identifying which areas are most susceptible to invasion. The MAXENT and GARP models of distribution of species were applied, having as input data the environmental variables calculated from spectral images, digital elevation model, soil map and road map. As some variables originally had spatial resolution of 250m and others of 30m, a resample was done at both 30m and 250m in order to compare the models results in these two spatial resolutions. To reduce the input variables amount, a correlation analysis was performed to eliminate the high correlation variables. The Jackknife test was also used to evaluate which variables contribute most to the South African lovegrass distribution spatial modeling. Both models, at the two spatial resolutions, during the training and the validation steps, present mean values of AUC adjustment above 0.7, being considered a good fit. Three methods were used to calculate the optimal thresholds for each model: 1) the sensitivity equals to the specificity; 2) the sum between sensitivity and specificity is the maximum; 3) the distance between the ROC curve and left top corner is minimum. The calculated thresholds were 42 for MAXENT_250, 39 for MAXENT_30, 69 for GARP_250 and 68 for GARP_30. After applying these thresholds, it was verified that the GARP model predicts an area greater than MAXENT, 33.20% compared to 24.60% for the spatial resolution of 250m, and 35.83% against 27.17% in the spatial resolution of 30m. It was also verified that GARP has a better generalization capacity, which is important for modeling invasive species patterns. Both models predict a common area with susceptible to invasion of 21.23% and 23.94% in spatial resolutions of 250m and 30m respectively. The grasslands are the land cover that presents a South African lovegrass invasion greater susceptibility. Cross-referencing the susceptibility invasion models with the overgrazing areas at 30m of spatial resolution, it was verified that the model MAXENT can predict a susceptibility to invasion in 24.51% of the areas and the GARP model predicts 37.95% susceptibility to invasion. Comparisons between the two spatial resolutions showed that there are not many differences in terms of area quantification, where the main gain was spatial detailing, which was obtained with a high computational cost.