Exotic annual weeds have transformed western North America, particularly in sagebrush-steppe systems. Restoration of these invaded sites has been met with low levels of success. Pre-emergent herbicide provides a means to control annual weeds, but typically, this treatment does not allow for the concurrent seeding of desired species. Seeding within a deep, U-shaped furrow following herbicide application may be a method to reduce pre-emergent herbicide effects by transferring the herbicide away from the seed at the time of planting. We tested this potential planting technique by spraying plots with or without the pre-emergent herbicide imazapic, and planting bunchgrass seeds either with or without a deep furrow. Treatments (i.e. spraying and furrowing) were applied using mechanical equipment within a single pass, at six sites. In plots without imazapic, we found that deep furrows generally had higher seedling emergence, density of juvenile plants, and above-ground biomass when compared to no furrows. For plots with imazapic, deep furrows also generally improved measured plant metrics for the seeded species compared to plots without furrows. For example, the density of juvenile plants in deep furrows ranged, by study site, between 62% – 97% and 41% – 89% higher than the no furrow treatment, for plots with and without imazapic, respectively. Plots with imazapic and deep furrows was not always as effective as plots without imazapic and deep furrows. Deep furrows also reduced exotic annual weeds in the first year after planting, but weed reduction was generally more effective when this treatment was applied with imazapic. Overall, this research provides evidence that in most instances, the use of deep furrows alone is sufficient to improve seeding success. However, in areas with high weed cover, the application of herbicide followed by the creation of deep furrows in a one-pass system should be considered.

Ingestion of endophyte infected (E+) fescue by pregnant mares can cause significant reproductive problems. Plateau® and Cimarron® herbicides suppress fescue while leaving desired forages unharmed. To determine if these herbicides are harmful to pregnant mares, they were allowed to graze pastures treated with Plateau®, Cimarron®, or vehicle carrier. Pregnancies were monitored via ultrasonography, blood chemistry, and hematology. Of the components measured only creatinine differed among treatments over time (P=0.0003) and that increase was only significant in one of four studies. Two additional experiments were conducted to determine the effect of the herbicides on alkaloids within E+ fescue. A greenhouse experiment utilizing 52 pots of E+ fescue treated with Plateau®, Cimarron®, or nothing was inconclusive, as some alkaloids increased while others decreased. These results indicated that UV light may be required for normal plant death. In a field experiment 12 plots of mixed vegetation were sprayed with the same treatments, and herbicides decreased ergovaline, N-formylloline, and lysergic acid content (P=0.0460, P=0.0324, P=0.0093 respectively). In conclusion, the herbicides did not alter blood components outside physiological norms, but the alkaloids were still present in dying E+ fescue. It may be safest to remove late gestation mares until E+ fescue is completely decayed.

This thesis explores potential seeding techiniques to limit harmful effects of preemergent herbicide on a seeded species while simultaneously reducing abudance of annual invasive grasses. The first chapter examines the use of activated carbon seed coatings and furrows to limit herbicide effect on seeds of a perrenial bunchgrass. We found that both carbon coatings and furrows mitigated some of the herbicide effects, but that only when the two techniques were combined did we observe unaffected seedling emergence, plant density, and aboveground growth. Therefore, we suggest to management that use of carbon coatings and furrows after herbicide application can likely be used to reduce invasive annual grasses while simultaneously establishing a native bunchgrass. In chapter 2, we examine the effects of a novel preemergent herbicide indaziflam, on native seeds and compare it against a common preemergent herbicide, imazapic. We found that indaziflam provides superior long-term control of annual invasive grasses than imazapic, but that it is also more detrimental to native seeds. Our results suggest that indaziflam is best suited for control purposes only, and is hard to incorporate in restoration seeding efforts due to its strong effects on native seed.

Critical mule deer (Odocoileus hemionus) winter ranges in southeastern Utah dominated by Wyoming big sagebrush (Artemisia tridentata var. wyomingensis [Beetle and A. Young] Welsh) have developed dense cheatgrass (Bromus tectorum L.) understories. These communities are currently characterized by predominately mature to decadent stands of sagebrush with few perennial grasses and forbs. Sagebrush seedlings and perennial grasses compete for limited resources with annual grasses and forbs. To determine the affects of cheatgrass control on sagebrush growth and reproductive characteristics, imazapic (PLATEAU®, AC 263,222) herbicide was sprayed at 438.5 ml/ha with water and methylated seed oil during active fall growth of cheatgrass in 2002. Sagebrush growth and reproductive variables were measured on browsed and unbrowsed (caged) plants on sprayed and non-sprayed paired plots on 6 sites. Cheatgrass and other annual forb pretreatment cover was reduced from 23% to less than 3% the first year after the herbicide treatement and only increased to 4% the second year. Soil moisture on the treated plots was available at 15, 30, and 60 cm for several days to several weeks longer than on the control plots depending on the depth in the soil and year. Annual leader growth and flowering seedstalk length were similar on unbrowsed and browsed shrubs, but the number of seedstalks per plant was decreased by browsing. The number of sagebrush flowering seedstalks was significantly reduced by the herbicide the first year after the treatment, but recovered by the second year. The decrease in flowering seedstalks per sagebrush reduced the number of sagebrush seedlings observed the second year after the treatment (control = 81,800 seedlings/ha and treated = 16,700 seedlings/ha). Both seedstalk length (treated = 13.4 cm and control = 11.2 cm) and annual leader growth (treated = 6.2 cm and control = 5.3 cm) were greater on treated plots than control plots. Overall, imazapic can provide a window of cheatgrass and annual forb control to allow big sagebrush seedlings and perennial grasses and forbs to establish.

Every anthropogenic activity causes environmental impact in some extent. Rice paddy fields area are pointed out as an activity with high potential of pollution due to the large amount of water used to maintain the flooding and the intensive use of pesticides and nutrients that can be transported to the environment. Though, there are other irrigation management practices that can reduce the environmental impact caused by the rice farming. Based on that, the objective of this study was to investigate the effect of the continuous and intermittent flooding on the amount of water applied and the amount of water transported to the environment, on water use efficiency, on weed control, on agronomic parameters of the rice plants and on dissipation of imazethapyr, imazapic and fipronil. The intermittent flooding resulted in crop yield similar to continuous irrigation. In addition, it reduced in 32% the amount of water applied, resulting in a better water use efficiency (1.68 kg m-3) than the continuous flooding (1.14 kg m-3). Water saving is promoted by the higher amount of rainfall stored in the intermittent flooding. The intermittent flooding reduces 40% of the run-off and less environmental contamination, resulting, on the average of the three pesticides a reduction higher than 90% on the mass of pesticide transported to the environment in comparison to the total applied on the rice Field. / Toda a atividade antrópica causa impacto ambiental de algum nível. A lavoura de arroz irrigado é apontada como uma atividade com alto potencial poluidor por usar grande volume de água para manter a lâmina de irrigação e também por ser um cultivo que demanda o intenso uso de agrotóxicos e nutrientes que podem ser transportados para o ambiente. Entretanto existem alternativas de manejar a lâmina de irrigação que podem diminuir esse impacto ocasionado pela orizicultura. Nesse sentido, o presente trabalho tem por objetivo avaliar o efeito do manejo de irrigação contínua e intermitente no balanço de água (lâmina de água aplicada e lâmina de água extravasada), na eficiência do uso da água, no controle de plantas daninhas, nos parâmetros agronômicos e na dissipação de imazethapyr, imazapic e fipronil. A irrigação intermitente ocasiona produtividade de grãos semelhante à irrigação contínua. Além disso, proporciona economia de 32% do volume de água aplicado, resultando em uma maior eficiência do uso de água (1,68 kg m-3) do que a irrigação contínua (1,14 kg m-3). Essa economia está relacionada devido ao maior volume de água da chuva armazenada. Dessa forma, a irrigação intermitente também promove redução de 40% no volume de água escoada superficialmente e menor contaminação ambiental, proporcionando uma redução, na média dos três agrotóxicos avaliados, de 90% da massa de ingrediente ativo de agrotóxicos transportados para o ambiente em relação ao total aplicado na lavoura.

Red rice (Oryza spp.) is one of the main limiting factors to rice (O. sativa L.) yield. After several decades searching for red rice control tools, it was developed imidazolinone tolerant rice, to selectively control red rice. To better understand this technology it were conducted two experiments in 2004/05, in Santa Maria, Rio Grande do Sul state, Brazil. The first experiment (Chapter I) had the objective of: 1) evaluate red rice control by imidazolinone herbicides in Clearfield rice; 2) evaluate the imidazolinone herbicide carryover effect on rygrass and non-tolerant rice (IRGA 417) and 3) evaluate the outcrossing rates between Clearfield rice and red rice. The herbicides tested control red rice. Although injury to Clearfield rice was observed, the herbicide did not affected yield. It was observed herbicide carryover to non-tolerant rice, reducing plant stand. There was natural outcrossing between Clearfield rice and red rice, at rates of 0.065%. The second experiment (Chapter II) had the objective of evaluate the herbicide Only® (imazethapyr 75 g L-1 + imazapic 25 g L-1) in different application rates and timing on two genotypes, IRGA 422 CL and Tuno CL, to the imidazolinones herbicides. When compared with the cultivar, the hybrid was more tolerant to the herbicide Only®. It was possible to apply rates of up to 2.0 L ha-1 in the hybrid, without affecting rice yield. Red rice control was total with split application of Only® in PRE and POST, with rates above 1.25 L ha-1. The most efficient treatment was with application of 0.75 L ha-1 in PRE followed by 0.5 L ha-1 in POS, because, it was the lowest rate that promoted 100% control, with relatively low toxicity to the cultivar and without affecting rice yield. / O arroz-vermelho (Oryza spp.) é um dos principais fatores limitantes da produtividade de grãos do arroz irrigado (O. sativa L.). Após várias décadas de busca de alternativas para o controle seletivo do arroz-vermelho, desenvolveram-se genótipos de arroz tolerante a herbicida do grupo químico das imidazolinonas, o qual controla eficiente e seletivamente esta planta daninha. Para estudar e melhor entender esta tecnologia, conduziu-se dois experimentos em Santa Maria-RS no ano agrícola 2004/05. O primeiro experimento (Capítulo I) teve como objetivos: 1) avaliar a eficiência do controle de arroz-vermelho com o herbicida Only? (imazethapyr 75 g L-1 + imazapic 25 g L-1), 2) avaliar o residual do herbicida no solo através dos danos causados no azevém e em arroz não tolerante e 3) avaliar a taxa de ocorrência de cruzamento natural entre o arroz-vermelho e o arroz cultivado. O herbicida testado controla eficientemente o arroz-vermelho em arroz tolerante. Embora tenha-se observado fitotoxicidade, não houve redução na produtividade da cultivar tolerante. O estande inicial da cultivar IRGA 417 é afetado pelo residual do herbicida presente no solo. Ocorre cruzamento natural entre o arroz-vermelho e o arroz cultivado, sendo que a taxa de ocorrência obtida no experimento foi de 0,065%. O segundo experimento (Capítulo II) teve como objetivo avaliar o controle de arroz-vermelho e o desempenho de dois genótipos de arroz irrigado, IRGA 422 CL e Tuno CL, tolerantes a herbicidas do grupo das imidazolinonas a doses e épocas de aplicações do herbicida Only? , em áreas com alta infestação de arroz-vermelho. Constata-se que o híbrido é mais tolerante ao herbicida Only? , quando comparado à cultivar IRGA 422 CL, sendo possível a utilização de dose total de até 2,0 L ha-1 no híbrido, em áreas com alta infestação de arroz-vermelho, sem afetar a produtividade. O controle de arroz-vermelho é total com aplicação fracionada do herbicida em pré e pós-emergência (PRE + POS), desde que o total aplicado não seja inferior a 1,25 L ha-1. Esta condição é atendida pelo tratamento com 0,75 L ha-1 em PRE mais 0,5 L ha-1 em POS, o qual propicia a menor dose total dentre aqueles com 100% de controle, não afetando a produtividade e com fitotoxicidade semelhante ao tratamento com 1,0 L ha-1 em POS, utilizado como referência.

Weed infestation, mainly with red rice (Oryza spp.), is the most important factor limiting yield increase in paddy rice in Rio Grande do Sul state. Chemical red rice control is the most used tool in this area. But, its use can originate herbicide residue in water and soil that can cause carry-over to rotational crops and environmental contamination. To assess these possible problems it was carry a two year experiment with the objective of: 1) to evaluate the efficiency of two alternatives (Clearfield system and the use of clomazone with seed protector) on red rice control; and 2) to evaluate imazethapyr and clomazone field persistence in water and soil and 3) evaluate the herbicides carry over to non-tolerant crop. In the first year (2004/05) IRGA 422 CL rice cultivar was drill seeded in the experimental area located in Santa Maria, RS, Brazil, to evaluate red rice control by seven treatments including rates and timing of (imazethapyr + imazapic) and clomazone aplication. After rice harvest, burndown herbicide was applied, and it was planted riegrass in winter 2005, and non-tolerant rice was seeded in 2005/06 growing season, aiming to evaluate the carry over effects of herbicides. The results showed that the Clearfield system is more efficient in red rice control than clomazone. The application of 0,7 L ha-1 (imazethapyr + imazapic) PRE followed by the same rate at POS, promoted 100% red rice control, withou reducing rice grain yield (cultivar IRGA 422 CL). The experiment showed also that, between the evaluated treatments, the split application of (imazethapyr + imazapic), was the most persistent in rice paddy water. It was observed carryover effects of (imazethapyr + imazapic) in the non-tolerant rice, causing yield reduction in IRGA 417 variety seeded one year after herbicide application. Clomazone did not have carryover effects one year after the application. Ryegrass did not showed injury to the herbicide residues in soil. / A infestação de plantas daninhas, principalmente da espécie arroz-vermelho (Oryza spp.), é um fator limitante para o aumento da produtividade na lavoura orizícola gaúcha. Diante dessas infestações, o controle químico tem sido a ferramenta mais empregada pelos agricultores. Contudo, sua utilização pode originar resíduos de agroquímicos na água e no solo, ocasionando danos na cultura em rotação e contaminação ambiental. Diante disso, desenvolveram-se dois anos de experimentos com os objetivos de: 1) avaliar a eficiência de duas alternativas (Sistema Clearfield e utilização de Gamit (clomazone) e protetor de sementes) no controle do arroz-vermelho; 2) identificar e quantificar a persistência dos herbicidas imazethapyr e clomazone na lâmina da água e no solo da lavoura de arroz-irrigado e 3) verificiar o efeito dos herbicidas em culturas semeadas em sucessão. No primeiro ano de ensaio, na safra 2004/05, a cultivar IRGA 422 CL foi semeada em campo experimental do Departamento de Fitotecnia da UFSM, para a avaliação do controle de arroz-vermelho em sete tratamentos contendo diferentes doses e épocas de aplicação dos herbicidas Only (imazethapyr + imazapic) e clomazone. Colhido o arroz, a área foi dessecada e, nela, foram semeadas as culturas de azevém, no inverno de 2005, e de arroz não-tolerante à aplicação de (imazethapyr + imazapic) e clomazone, na safra 2005/06, visando à avaliação do efeito residual desses herbicidas aplicados na cultura de arroz tolerante sobre culturas suscetíveis. Os resultados das análises demonstram que a utilização do Sistema Clearfield é mais eficiente no controle do arroz-vermelho que a aplicação de clomazone com uso de protetor de sementes. A aplicação de 0,7 L ha-1 de (imazethapyr + imazapic) em pré-emergência, seguida da mesma dose em pós-emergência, apresentou controle de 100% da planta daninha, sem causar prejuízos ao estande de plantas e à produtividade de grãos da cultivar IRGA 422 CL. Além disso, o experimento evidenciou que a aplicação seqüencial de (imazethapyr + imazapic), dentre os tratamentos avaliados, persiste mais tempo na lâmina d água da lavoura de arroz. Observou-se ainda a existência de residual no solo de (imazethapyr + imazapic) um ano após a sua aplicação, sendo que esses resíduos ocasionaram redução na produtividade de grãos da cultivar não-tolerante IRGA 417. Quanto ao clomazone, as análises evidenciaram ausência de residual após um ano de sua aplicação nas doses de 3 e 6 L ha-1. Para o azevém, não foram observados efeitos negativos do residual dos herbicidas no solo.

O presente trabalho foi desenvolvido com o objetivo de avaliar os efeitos da intensidade de chuva e diferentes quantidades de palha de cana-de-açúcar sobre a eficácia de herbicidas aplicados em pré-emergência no controle da tiririca. Foram realizados dois experimentos, ambos conduzidos em casa-de-vegetação. O delineamento experimental adotado foi o de blocos casualizados, com 4 repetições, para os dois experimentos. No primeiro experimento os tratamentos foram distribuídos em um esquema fatorial 3 x 3 x 2 x 2, constituídos pela combinação entre quantidades de cobertura morta de palha de cana-de-açúcar que foram adicionadas à superfície do solo (0, 10, 20 t/ha), herbicidas aplicados em pré-emergência (sulfentrazone a 0,8 kg i.a./ha e imazapic a 147 g i.a./ha) e um tratamento sem aplicação de herbicida, intensidades de chuva (10 e 20 mm), e épocas em que foram simuladas chuvas após a aplicação dos herbicidas (24 e 168 horas). No segundo experimento os tratamentos foram distribuídos em um esquema fatorial 2 x 3 x 5, constituídos pela combinação entre quantidades de cobertura morta de palha de cana-de-açúcar (0, 15 t/ha), herbicidas aplicados em pré-emergência (sulfentrazone a 0,8 kg i.a./ha e imazapic a 147 g i.a./ha) e um tratamento sem aplicação de herbicida, e épocas em que foi simulada chuva após a aplicação dos herbicidas (0, 3, 6, 9 e 12 dias). Em ambos experimentos foram avaliados: o número de plantas por vaso, biomassas secas da parte aérea e das estruturas do sistema subterrâneo, e número de tubérculos e bulbos sadios. A partir da análise dos resultados, para o primeiro experimento conclui-se que, para o herbicida sulfentrazone, a presença de 20 t/ha de palha de cana-de-açúcar diminuiu a eficácia do herbicida. O herbicida imazapic teve um bom desempenho tanto na ausência quanto na presença de palha, e causou redução das variáveis estudadas independente da intensidade de chuva. A intensidade de chuva de 10 mm, não foi suficiente para transpor o herbicida sulfentrazone na quantidade de 20 t/ha de palha. Já a intensidade de 20 mm foi suficiente para lixiviar o herbicida até mesmo na maior quantidade de palha. O herbicida sulfentrazone suporta mais a permanência na palha, pois apresentou melhor eficácia em relação ao imazapic, quando a chuva foi simulada 168 horas após a aplicação dos herbicidas. Para o segundo experimento pode-se concluir que, as épocas em que foram simuladas as chuvas, não afetaram as variáveis estudadas, não havendo, portanto, diferença se a chuva ocorreu no dia em que foi aplicado o herbicida, ou se ocorreu um período sem chuva de 12 dias. Os herbicidas sulfentrazone e imazapic reduziram o número de plantas, o número de tubérculos, biomassa seca de bulbos, biomassa seca de rizoma e raiz, e biomassa seca da parte aérea, independente da presença de palha. / The present work was developed with the objective of assessing the effects of the intensity of rain and different quantities of sugar cane mulch residue on the efficacy of herbicides applied in pre-emergence for the purple nutsedge control. Two experiments were performed, both conducted in greenhouses. The experiments were performed by randomly choosing blocks with four repetitions. In the first experiment, the treatments were distributed in a factorial scheme 3 x 3 x 2 x 2, constituted by the combination between quantities of dead coverage of sugar cane mulch residue which were added to the soil surface (0, 10, 20 t/ha), herbicides applied in preemergence (sulfentrazone at 0,8 kg i.a./ha and imazapic at 147 g i.a./ha) and a treatment without the application of herbicides, rain intensities (10 and 20 mm), and seasons in which were simulated rains after the application of herbicides (24 and 168 hours). In the second experiment, the treatments were distributed in a factorial scheme 2 x 3 x 5, constituted by the combination between quantities of dead covering of sugar cane mulch residue (0, 15, t/ha), herbicides applied in pre-emergence (sulfentrazone at 0,8 kg i.a./ha and imazapic at 147 g i.a./ha), a treatment without the application of herbicides and seasons in which were simulated rains after the application of herbicides (0, 3, 6, and 12 days). It was evaluated in both experiments: the number of plants per vase, dry biomasses from the aerial parts, from the underground system structures and the number of healthy tubers and bulbs. From the analysis of the results of the first experiment, it may conclude that, to the herbicide sulfentrazone, the presence of 20 t/ha of sugar cane mulch residue diminished its efficacy. The herbicide imazapic had a good performance with the absence as well as with the presence of the mulch residue, and caused a reduction in the varieties studied independently of the intensity of rain. The intensity of rain of 10 mm, wasn’t sufficient to overpass the herbicide sulfentrazone in the quantity of 20 t/ha of mulch residue. But the intensity of 20 mm was enough to lixiviate the herbicide even in the biggest quantity of mulch residue. The herbicide sulfentrazone endures more the abiding on the mulch residue, because it presented a better efficacy in relation to the imazapic, when the rain was simulated 168 hours after the application of the herbicides. From the second experiment it may conclude that the season in which was simulated rains, it didn't affect the varieties studied, therefore there was no difference when the rain occurred on the day when the herbicide was applied, or if it occurred on a 12 day period without rain. The herbicides sulfentrazone and imazapic reduced the number of plants, the number of tubers, dry biomass of bulbs, dry biomass of rhizoma roots and dry biomass of the aerial parts, independently of the presence of mulch residue.

The conversion of sagebrush-steppe communities of the Great Basin into cheatgrass-dominated communities is one of the most dramatic ongoing land conversions in North America. Although restoration of these communities is a high priority to landowners and land management agencies, restoration of native vegetation is difficult. Several restoration treatments intended to increase the success of aerially‐seeded perennial grasses in cheatgrass-invaded sagebrush ecosystems were assessed to determine their effects on perennial seedling emergence and soil seed bank density and composition. Assessed restoration treatments were: 1) vegetation manipulation (sagebrush thinning and prescribed burning); 2) imazapic herbicide application; 3) seedbed amendments (aerial seeding with activated carbon addition, aerial seeding with sucrose addition); and 4) seeding frequency. The effects of these treatments were evaluated in two distinct sagebrush shrubland ecosystems in northern Utah. One is characterized as a remnant sagebrush stand with a cheatgrass-dominated understory and the other as a cheatgrass near-monoculture, completely lacking a sagebrush component. In the seed bank study, responses were assessed immediately and 1 year following treatment while in the seedling emergence study, they were assessed 2 and 3 years following treatment. Main effects of vegetation manipulation, herbicide application, and seedbed addition treatments and their interactions on perennial seedling emergence are described in Chapter 2. The effects of seeding frequency on perennial seedling emergence are also described in Chapter 2. Herbicide demonstrated potential for increasing native perennial grass emergence, although this response was delayed and not seen until 3 years post-application. Burning showed potential for increasing the emergence of perennial grasses 2 years post-burn. Results also suggest that potential exists to increase native perennial grass emergence through an increase in seeding frequency. In Chapter 3 I evaluated the effects of vegetation manipulation, herbicide application, and seedbed addition on seed pool dynamics. These results suggest that herbicide and sucrose may be useful tools for reducing exotic species richness in cheatgrass-invaded systems. Herbicide also showed potential for reducing cheatgrass seed bank densities. Additionally, results demonstrated that the reductions in cheatgrass seed bank densities observed immediately after fire are still observed 1 year post-burn.

The conversion of sagebrush-steppe communities of the Great Basin into cheatgrass-dominated communities is one of the most dramatic ongoing land conversions in North America. Although restoration of these communities is a high priority to landowners and land management agencies, restoration of native vegetation is difficult. Several restoration treatments intended to increase the success of aerially‐seeded perennial grasses in cheatgrass-invaded sagebrush ecosystems were assessed to determine their effects on perennial seedling emergence and soil seed bank density and composition. Assessed restoration treatments were: 1) vegetation manipulation (sagebrush thinning and prescribed burning); 2) imazapic herbicide application; 3) seedbed amendments (aerial seeding with activated carbon addition, aerial seeding with sucrose addition); and 4) seeding frequency. The effects of these treatments were evaluated in two distinct sagebrush shrubland ecosystems in northern Utah. One is characterized as a remnant sagebrush stand with a cheatgrass-dominated understory and the other as a cheatgrass near-monoculture, completely lacking a sagebrush component. In the seed bank study, responses were assessed immediately and 1 year following treatment while in the seedling emergence study, they were assessed 2 and 3 years following treatment. Main effects of vegetation manipulation, herbicide application, and seedbed addition treatments and their interactions on perennial seedling emergence are described in Chapter 2. The effects of seeding frequency on perennial seedling emergence are also described in Chapter 2. Herbicide demonstrated potential for increasing native perennial grass emergence, although this response was delayed and not seen until 3 years post-application. Burning showed potential for increasing the emergence of perennial grasses 2 years post-burn. Results also suggest that potential exists to increase native perennial grass emergence through an increase in seeding frequency. In Chapter 3 I evaluated the effects of vegetation manipulation, herbicide application, and seedbed addition on seed pool dynamics. These results suggest that herbicide and sucrose may be useful tools for reducing exotic species richness in cheatgrass-invaded systems. Herbicide also showed potential for reducing cheatgrass seed bank densities. Additionally, results demonstrated that the reductions in cheatgrass seed bank densities observed immediately after fire are still observed 1 year post-burn.