Lowland switchgrass (Panicum virgatum), big bluestem (Andropogon gerardii), indiangrass (Sorghastrum nutans), upland switchgrass (Panicum virgatum), little bluestem (Schizachyrium scoparium), beaked panicum (Panicum capillare), and purpletop (Tridens flavus) all show strong signs of seed dormancy which contributes to extremely poor field establishment. The objective of this work was to reduce seed dormancy by selecting individuals that exhibited reduced pre-stratification dormancy in laboratory tests. The classical breeding method of phenotypic recurrent selection was used to enhance germination. Of the three tall-stature species, lowland switchgrass made the greatest improvement in pre-stratification germination, followed by indiangrass and big bluestem. The four short stature species have shown various results after one cycle of selection at Starkville. A field emergence trial was also conducted to evaluate three cycles of breeding seed with five commercially available cultivars in which Cycle 3 seed produced more plants per hectare than any of the other cultivars or germplasm.

Mycorrhizae have been used in restoration for decades. However, studies assessing the use of mycorrhizae in Bromus tectorum-invaded areas of the Great Basin are limited. Two greenhouse pot experiments were conducted to assess the role of mycorrhizae in sagebrush restoration. The first objective (Chapter 2) was to determine the response of Pseudoroegneria spicatum, Elymus elymoides, and B. tectorum to mycorrhizal symbiosis by altering phosphorus, density, species, presence of mycorrhizae and water levels in a 5 factor design. To assess the mycorrhizal response, a variety of morphological and physiological traits were measured, such as tissue P concentration, specific root length, specific leaf area, carbon isotope discrimination, etc. The effects of the different treatment combinations were analyzed using ANOVA. The second objective (Chapter 3) was to determine the role of different inocula in competition between the three grasses. Species, density, and inoculum type were altered in a 3 factor design. Inoculum was cultured on Allium plants. The effect of locally cultured inoculum on the species was compared to the effect of commercial inoculum. The response of each species to mycorrhizae with different species compositions and densities was assessed. Morphological measurements were used to determine each species response to the different factor combinations. The effects of the different treatment combinations were analyzed using ANOVA. This research provides land managers with information regarding the efficacy of using local versus commercial inocula and whether they should use mycorrhizae in restoring their systems.

Plant spatial patterns have been studied to gain insight into plant interactions such as competition and facilitation (positive plant interactions). The stress gradient hypothesis predicts that as environmental stress increases facilitation dominates, while competition dominates in less stressful conditions. Beneficial plants (nurses) can create favorable abiotic conditions for subanopy plants. Additionally, palatable herbaceous species growing under nurse shrub canopies benefit from physical protection. I investigated spatial associations between Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis) and three native grasses (Poa secunda, Elymus elymoides, and Pseudoroegneria spicata) across a rainfall gradient in the Great Basin, USA. I also explored the effect of grazing on grass-shrub spatial associations. I hypothesized that positive shrub-grass spatial associations would become more frequent at lower rainfall levels; I further hypothesized that 1) at intermediate levels of stress, positive grass-shrub spatial associations would dominate and 2) at extreme levels of stress, positive grass-shrub spatial associations and interactions would no longer dominate. At high moisture stress, the addition of grazing stress may limit the nurse’s ability to provide to benefits to subcanopy plants. Cover of P. secunda was greater in shrub canopy microsites than interspaces at low to moderate levels of rainfall. Cover and density of E. elymoides were greater in sagebrush canopies over most rainfall levels. Elymus elymoides and P. spicata were taller and narrower in basal width and less likely to be grazed in canopy versus interspace microsites. I next investigated the effects of grazing intensity over a rainfall gradient and found a significant interaction of rainfall and microsite on P. secunda cover. Poa secunda formed positive interactions with A. tridentata at lower rainfall levels, regardless of grazing intensity. Its cover was significantly greater in interspaces at high rainfall compared to low rainfall sites. Elymus elymoides density was greater in canopy vs. interspace microsites, regardless of rainfall level or grazing intensity. Plant spatial associations can indicate which nurse microsites are favorable to plant growth and may improve seeding or planting success during ecological restoration. My results suggest that exploiting sagebrush canopy microsites for restoration of native perennial grasses would improve plant establishment, growth or survival particularly in drier areas.

This thesis examines the hypothesis that, in southern New South Wales and northeast Victoria, Australia, palatable taxa of E. curvula offer advantages that complement those of the species that are traditionally sown in temperate pastures in a landscape context.This hypothesis was based on a review of literature showing that, prior to European settlement, the vegetation, the landscape and the climate were broadly in balance, and the wateruse pattern of the vegetation of southeastern Australia resulted in water being used more-or-less completely by the end of summer. This maximised the capacity of the soil to take up and store water during autumn and winter.Three grazing experiments and one spaced-plant species evaluation study were used to assess the role of summer-growing, C4 Eragrostis curvula in pastures in the temperate zone of southeastern Australia.Issues relating to pasture production and the productivity of wool-growing sheep were investigated. Factors affecting the sustainability of the pastures and their potential on and off site impacts were emphasised.Modelling was used to explore issues of water use, arising from the grazing experiments. It is concluded that the persistence, production, water use patterns, and the adaptability of palatable varieties of E. curvula make it a useful and complementary addition to the range of species that are currently available for use as sown pastures in southern Australia. / Doctor of Philosophy (PhD)

Imported fire ants are invasive and cause injury to people, crops, livestock and wildlife. Disturbance may increase abundance and activity of fire ants. However, native grass field buffers established for grassland birds require periodic disturbance. I experimentally tested if fire ant mound density and foraging activity changed after burning and disking in native grass buffers and examined relationships among fire ants, vegetation, and grassland bird and butterfly metrics in undisturbed buffers. In 2008, disking increased mound density and foraging activity, but burning did not. In 2009, disking had no effect, but effects of disking the previous season persisted. Fire ant metrics were not related generally to bird or butterfly metrics. Mound density and foraging activity were related negatively to grass cover and related positively to forbs. Burning had less influence on abundance and activity of fire ants, and may better conserve grassland habitats in areas with fire ants.

"The orientation of this study began with a collection of the grasses of Erath County during their flowering periods. Collections were made in the Spring and Fall of 1950 and 1951 to obtain both vernal and autumnal grasses. Identifications were made from the grass floras previously mentioned and checked against specimens in the herbarium of North Texas State College for verification. In addition, the list was checked by W.A. Turney, Conservationist, United States Department of Agriculture of Dublin, Texas. Finally, the list was compared with that prepared by W.M. Cory for the plant areas of which Erath County is a part. On the basis of the above identifications, a critical study of the vegetative characteristics was made and a key based on these features prepared. The width of the blad and characteristics of the ligule, roots, culms, and sheaths were used to distinguish each of the eighty-six specimens found in the collection area. A drawing was made of the longitudinal section of the juncture of the blade and the sheath of each grass. This diagnostic section includes the collar, ligule, a part of the blade and sheath, and auricles, if present."-- leaf 5.

Fundação de Amparo a Pesquisa no Estado do Rio Grande do Sul / Paspalum notatum, native grass biome Pampa, Rio Grande do Sul, has high forage value, but has difficulty germinating seeds with low viability. Inserted in this context are the promoters of germination and biomass, biostimulants stimulate® and bioagent Trichoderma spp. by mechanisms that influence the metabolism of action of the species. The present study investigated the promotion of seed germination and development of P. notatum. Through the Allium cepa test in ten treatments (four replicates per treatment), eight with metabolites of Trichoderma spp. and two controls in the absence of metabolites were selected isolates of trichoderma biological agent. The test of sanity, the identification of fungi associated with seeds used the methods of filter paper and plating on solid agar PDA (potato dextrose agar). With the in vitro technique of direct confrontation of the antagonist action on three fungal contaminants of highest incidence was observed. In a preliminary test, pre-treatment is selected to germination of P. notatum. Seed germination in greenhouse consisted of 16 treatments with four replicates, the control treatments, the three isolates, the stimulate®, the combination of each of the three isolates stimulate®, all with and without pretreatment, analysis of the data was through the Genes program. For reviews of morphogenesis, four were randomly chosen tillers per treatment, they monitored for the appearance and elongation and leaf senescence. This monitoring was performed two times per week. The top three trichoderma isolates selected in test A. cepa strain were 2B2, C1, 2B12. The removal of the seed coat structures of P. notatum was the pre-treatment showed the best performance with 34.5% twinned seeds. In the test of sanity the fungal genera Aspergillus, Curvularia, and Fusarium Geniculosporium were identified, isolated and 2B2 of Trichoderma spp. efficient for direct to these fungal genera confrontation. For the IVE (index emergency speed), the combination treatments of biological powder 2B12 isolated from trichoderma and biostimulating Stimulate® and only Stimulate® biostimulating with pretreatment and without pretreatment combination of biological powder isolated 2B2 Trichoderma with biostimulating Stimulate®, achieved the best results, with 14.48, 13.93 and 12.75, respectively. The biostimulating stimulate® promotes the rate of speed of emergence of seeds of P. notatum and the production of dry matter, the initial rate of elongation of the sheet (TAIF) positively interfere in the dry weight of shoots. / Paspalum notatum, gramínea nativa do bioma Pampa, Rio Grande do Sul, possui alto valor forrageiro, porém apresenta dificuldade de germinação de sementes, com baixa viabilidade. Inseridos neste contexto estão os promotores de germinação e biomassa, bioestimulante Stimulate® e o bioagente Trichoderma spp. que através de mecanismos de ação influenciam no metabolismo da espécie. O presente trabalho objetivou estudar a promoção da germinação das sementes e desenvolvimento de P. notatum. Através do teste de Allium cepa em dez tratamentos (quatro repetições por tratamento), oito com metabólitos de isolados de Trichoderma spp. e dois controles na ausência de metabólitos foram selecionados isolados do agente biológico trichoderma. O teste da sanidade, a identificação dos fungos associados às sementes utilizaram-se os métodos do papel de filtro e do plaqueamento em meio ágar sólido BDA (batata dextrose ágar). Com a técnica in vitro de confrontação direta foi observada a ação do antagonista sobre três fungos contaminantes de maior incidência. Em teste preliminar, selecionou-se o pré-tratamento para a germinação das sementes de P. notatum. A germinação das sementes em casa de vegetação constou de 16 tratamentos, com quatro repetições, os tratamentos controle, os três isolados, o stimulate®, a combinação de cada um dos três isolados mais stimulate®, todos com e sem o pré-tratamento, análise dos dados foi através do programa Genes. Para as avaliações das características morfogênicas, foram escolhidos aleatoriamente quatro perfilhos por tratamento, sendo os mesmos monitorados quanto ao aparecimento e alongamento de folhas e senescência. Este monitoramento era realizado duas vez por semana. Os três melhores isolados de trichoderma selecionado no teste de A. cepa foram o 2B2, C1, 2B12. A retirada das estruturas de revestimento das sementes de P. notatum foi o pré-tratamento que apresentou o melhor desempenho com 34,5% das sementes geminadas. No teste da sanidade foram identificados os gêneros de fungos Aspergillus, Curvularia, Geniculosporium e Fusarium, e o isolado 2B2 de Trichoderma spp. mostrou eficiente na confrontação direta a estes gêneros de fungos. Para o IVE (índice de velocidade emergência), os tratamentos da combinação do pó biológico do isolado 2B12 de trichoderma e o bioestimulante Stimulate® e somente o bioestimulante Stimulate® com pré-tratamento, e sem pré-tratamento a combinação do pó biológico do isolado 2B2 de trichoderma com bioestimulante Stimulate®, obtiveram os melhores resultados, com 14.48, 13.93 e 12.75, respectivamente. O bioestimulante stimulate®, promove o índice de velocidade de emergência das sementes de P. notatum e a produção de massa seca, a taxa de alongamento inicial da folha (TAIF) interfere positivamente, na massa seca da parte aérea.

Les prairies indigènes présentent une source importante d'alimentation pour le pâturage du bétail dans les prairies Canadiennes semi-arides. L'addition de légumineuses fixatrices d'azote et de phosphore dans les prairies indigènes peut améliorer la productivité et la valeur nutritive de fourrage. Ces pratiques peuvent induire des modifications de la structure et de la diversité des communautés fongiques du sol, ce qui peut en retour avoir un impact sur la production et le contenu nutritionnel du fourrage. L’objectif de cette étude était de développer un système de pâturage à bas niveau d’intrants, productif, autonome et durable. À court terme, nous voulions 1) déterminer l'effet des légumineuses (Medicago sativa, une légumineuse cultivée ou Dalea purpurea, une légumineuse indigène) et la fertilité en phosphore du sol sur la productivité et la valeur nutritive des graminées indigènes, comparées avec celles de la graminée introduite Bromus biebersteinii en mélange avec le M. sativa, 2) identifier l'effet de ces pratiques sur la diversité et la structure des communautés des champignons mycorhiziens à arbuscules (CMA) et des champignons totaux, 3) identifier l'effet des légumineuses et des CMA sur les interactions compétitives entre les graminées de saison fraîche et les graminées de saison chaude. Les expériences menées au champ ont montré que M. sativa améliorait les teneurs en azote et en phosphore des graminées indigènes au début de l'été, ainsi que la teneur en azote de la graminée de saison chaude Bouteloua gracilis à la fin de l'été de l'année sèche 2009. Par contre, la fertilité en phosphore du sol n'ait pas affecté la productivité des plantes. D'autre part, l'inclusion des légumineuses augmentait la diversité des CMA dans le mélange de graminées indigènes. Cette modification présentait des corrélations positives avec la productivité et la quantité totale d'azote chez le M. sativa et avec la teneur en phosphore des graminées indigènes, au début de l'été. La structure des communautés de champignons totaux était influencée par l'interaction entre le mélange des espèces et la fertilité en phosphore du sol seulement en 2008 (année humide). Cet effet pourrait être lié en partie avec la productivité des plantes et l'humidité du sol. Les expériences menées en chambre de culture ont montré que les CMA peuvent favoriser la productivité des graminées de saison chaude au détriment des graminées de saison fraîche. En effet, Glomus cubense augmentait la productivité de la graminée de saison chaude B. gracilis, en présence de M. sativa. Cet effet pourrait être associé à l’effet négatif du G. cubense sur la fixation de l’azote par le M. sativa et à la diminution de l’efficacité d’utilisation de l'azote de certaines graminées de saison fraîche résultant en une augmentation de la disponibilité de l'azote pour B. gracilis. Par contre, le Glomus sp. augmentait la biomasse de Schizachyrium scoparium, autre graminée de saison chaude, en absence de légumineuse. Ce phénomène pourrait être attribuable à une amélioration de l’efficacité d’utilisation du P de cette graminée. En conclusion, mes travaux de recherche ont montré que la légumineuse cultivée M. sativa peut améliorer la valeur nutritive des graminées indigènes au début de l'été ainsi que celle de la graminée de saison chaude B. gracilis, dans des conditions de sécheresse sévère de la fin de l'été. De plus, l'addition de M. sativa dans le mélange de graminées indigènes peut contribuer à augmenter le nombre des espèces bénéfiques des CMA pour la production et la nutrition du fourrage au début de l'été. / The native grasslands are considered as the main feed source for livestock grazing, in semi-arid regions of the Canadian prairies. The addition of N fixing legumes and phosphorus to semi-arid native grasslands may increase the productivity and nutritive value of forage. However, these practices may also shape the structure and diversity of soil fungal communities which in turn may impact forage production and nutritive value. The global objective of this research was to design productive, self-sustaining, permanent and with low inputs pastures. The specific objectives were 1) to demonstrate the effect of N-fixing legumes (the cultivated legume Medicago sativa or the native legume Dalea purpurea) and soil P fertility on the productivity and nutritive value of native grasses mixes in comparison to the mixture of the introduced grass Bromus biebersteinii and M. sativa, 2) identify the effect of these practices on the diversity and community structure of arbuscular mycorrhizal (AM) fungi and total fungi, and 3) identify the effect of legumes and AM fungi on competitive interactions between native cool-season grasses and native warm-season grasses. The field experiment showed that M. sativa improved the nitrogen and phosphorus concentrations of native grasses mixes early in the summer, as well as the N concentration of the warm-season grass B. gracilis, in late summer of the driest year 2009. In contrast, the soil phosphorus fertility had no effect on plant productivity. On the other hand, the inclusion of legumes to the mix of native grasses generally increased AM fungal diversity. This shift was positively correlated with the productivity and nitrogen uptake by M. sativa and with the phosphorus concentration of native grasses mixes in early summer. The structure of the total fungal community was affected by the interaction between species mixtures and soil P fertility only in the wet year (2008), suggesting that this effect was likely driven in part by plant productivity and soil moisture. The growth chamber experiment showed that the AM fungi may favoured the growth of warm-season grasses under competition with cool-season grasses. However, Glomus cubense increased the productivity of warm-season grass B. gracilis when growing with M. sativa. This effect might be related to a negative impact of G. cubense on the nitrogen-fixing activity of M. sativa and to a lower N-use efficiency of certain cool-season grasses, which resulted in increased soil N availability for B. gracilis. In contrast, Glomus sp. enhanced the growth of S. scoparium, another warm-season grass in the absence of legumes, and this may be related to improved P-use efficiency in this grass. We concluded that the cultivated legume M. sativa can improve the nutritive value of native grasses mixes early in the summer and also of warm season grass under severe drought conditions in late summer. In addition, the inclusion of M. sativa within native grass mixes may contribute to promote beneficial AM fungi taxa that were involved in forage production and nutrition early in the summer.