Littérature scientifique sur le sujet « Cenchrus ciliaris »

A study was carryout to determine the biomass yield, chemical composition and in-vitro dry matter digestibility of irrigated Cenchrus Ciliaris. The treatments had three harvesting days (60, 90 and 120) in randomized complete block design (RCBD). Stage of harvesting days had significant influence (p< 0.05) on the biomass and chemical composition of Cenchrus Ciliaris. With longer days of harvesting, there was a reduction in nutritive value of the grass; whereas at longer day of harvesting, there was the highest biomass yield. DMY, NDF, ADF and ADL and plant height were positively correlated to each other but negatively correlated to LSR, CP, total ash, and IVDMD. Biomass yield of Cenchrus Ciliaris was positively correlated with delaying stage of harvesting but nutritive value in Cenchrus Ciliaris, were negatively correlate with increasing stage of harvesting. Eventually, harvesting of Cenchrus ciliaris at 90 days had good nutritive (10.62 % CP and 12.3t/ha DM) value and biomass yield. So that, this finding creates an opportunity for the pastoralists and agro-pastoral community along the Awash River to resolve the scarcity of feed and increase the livestock productivity in the study area.

Mycorrhizae are symbiotic associations between fungi and plants and are primarily responsible for nutrient transfer and survival of both partners. The present study was conducted to explore the diversity of mycorrhizal fungi in the rhizospheric soil of perennial grass species (Saccharum spontaneum, Saccharum bengalense, Setaria verticillata, Cymbopogon jwarancusa, and Typha angustata) around the district Layyah. In the subsequent experiment, the rhizospheric soils were used as inoculants, and their impact on mycorrhizal colonization in the plant and soil, and growth and physiological attributes, of Cenchrus ciliaris were investigated. The maximum hyphal, vesicles, arbuscules, dark septate endophytic and ectomycorrhizal colonization, and spore percentage were observed in the case of R-S5, i.e., rhizospheric soil, collected from Saccharum bengalense. However, the maximum (0.9310) Simpson’s index of diversity was observed in the case of R-S4, i.e., rhizospheric soil collected from Setaria verticillata. Different mycorrhizal fungal morphotypes scattered over three genera, i.e., Acaulospora, Glomus, and Scutellospora, were recorded both from rhizosphere and trap cultures. The application of spores from rhizospheric soil collected from S. bengalense (R-S5) caused the maximum increase in plant height (19.5%), number of leaves plant−1 (17.6%), leaf area (108.0%), and chlorophyll contents (29.4%) of Cenchrus ciliaris, compared to other treatments. In conclusion, the inoculation of mycorrhizal fungi significantly improves the mycorrhizal characteristics of Cenchrus ciliaris and its rhizospheric soil and ultimately enhances the growth and physiological parameters of Cenchrus ciliaris.

Drought impacts in arid desert ecosystems can result in decreased ecosystem productivity and biodiversity. Implementation of restoration projects in arid desert environments is largely dependent on water availability and soil moisture condition. This study investigated the influence of induced drought stress by using polyethylene glycol (PEG-6000) solution on germination viz. Cenchrus ciliaris and Cenchrus setigerus as the important rangeland species. The water stress potential treatments were 0 (control), –0.5 MPa, –1.0 MPa, –1.5 MPa, and –2.0 MPa. The extent of seed germination was severely affected by decreased water stress potential. As drought increased, the percentage of germination decreased in both Cenchrus’ species. The water deficit at –0.5 MPa showed a significant (P < 0.001) reduction in the final germination percentage in the case of C. setigerus and C. ciliaris by 65% and 42.5%, respectively. At –1.0 MPa to –1.5 MPa, changes in intermediate germination were observed in C. ciliaris (from 35% to 17.5%, respectively) and C. setigerus (from 22.5% to 11.25% respectively). Higher levels of water stress (–2.0 MPa) prevented the survival of both species. Understanding the germination strategies of native desert plant species associated with drought stress and identifying favorable conditions during the germination process can be useful for restoration practices and rangeland management actions to improve desert ecosystems and maintain biodiversity.

Climate change, associated with increased aridity, and high grazing pressure by livestock results in the scarcity and loss of perennial Poaceae in arid ecosystems. The species threatened by this include Cenchrus ciliaris L., a native perennial grass of the tropical and sub-tropical arid rangelands of Africa and Western Asia and now introduced in Central and South America, and Australia. This species reproduces predominantly through aposporous apomixis although sexual individuals have been occasionally identified. Cenchrus ciliaris is characterised by a significant, heritable, phenotypic polymorphism and three ploidy levels including tetraploids (2n = 4x = 36), pentaploids (2n = 5x = 45) and hexaploids (2n = 6x = 54). Under water-deficit conditions, C. ciliaris shows plasticity in growth characteristics and aboveground biomass. This phenotypic plasticity has led to the identification of genotypic-associated responses conferring more productivity. This underlines the importance of conserving the genetic diversity of C. ciliaris in order to ensure the persistence of the vegetation cover in the arid ecosystems in which it occurs. Observations from cytogenetic and molecular data converge to underline the possibility of sexual reproduction, recombination and gene flow within and between populations of C. ciliaris. Genetic mechanisms, such as polyploidy, hybridisation between ploidy levels and apomixes, are generating and then maintaining the diversity of C. ciliaris. This review emphasises the role of polyploidy in the evolutionary development of C. ciliaris and how it may be a crucial factor for its conservation in some countries and its weedy nature in others.

En esta investigación se caracterizó el potencial para la obtención de etanol a partir de la planta silvestre Cenchrus ciliaris, también conocida como zacate buffel. A partir de estudios experimentales a nivel laboratorio, se determinaron los rendimientos técnicos y requerimientos energéticos de las etapas de pretratamiento ácido, hidrólisis enzimática y fermentación. Los valores obtenidos fueron comparados con los reportados en la literatura para otros procesos de producción de combustibles. Los resultados del presente trabajo indican que el procesamiento de Cenchrus ciliaris consume la tercera parte de la energía requerida para procesar gasolina por 1 MJ de etanol producido. Asimismo, mediante este proceso es factiblela reducción de las emisiones de gases de efecto invernadero por 1 MJ de energía de etanol producido en aproximadamente 40 % su valor actual.

O objetivo deste estudo foi avaliar a composição morfológica de cultivares de Cenchrus ciliaris submetidos à adubação nitrogenada. O delineamento experimental utilizado foi em blocos casualizados em arranjo fatorial 3 x 4 (três cultivares de C. ciliaris – Grass, PI 295658 e Áridus e quatro doses de nitrogênio – 0, 75, 150 e 225 kg/ha), com três repetições. Foram realizados quatro cortes, obedecendo-se em cada um o intervalo de 35 dias. Os cortes foram realizados a 20 cm do nível do solo. Foi avaliada a composição morfológica para os três cultivares de C. ciliaris. A forragem amostrada foi pesada e subdividida em subamostras: para a separação dos componentes morfológicos da planta (lâmina foliar verde, pseudocolmo e material morto). Os cultivares PI 295658, Áridus e Grass não apresentam diferença quanto à porcentagem de folhas. Os cultivares de C. ciliaris apresentam aumento da porcentagem de pseudocolmo em função da adubação nitrogenada, de maneira mais consistente na época do verão em relação ao outono. O cultivar PI 295658 possui maior porcentagem de pseudocolmo do que os demais cultivares. A adubação nitrogenada não influencia a porcentagem de material morto, sendo que o cultivar Grass apresenta maior porcentagem de matéria morta em relação aos demais cultivares.

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Capes
Essa dissertação foi composta por dois experimentos. No primeiro experimento teve como objetivo avaliar o potencial agronômico e características morfológicas de 34 genótipos de palma destinadas a produção de forragem. Os genótipos foram implantados em delineamento em blocos completos casualizados, com 34 tratamentos e três repetições. Após 330 dias de cultivo realizou-se medições biométricas das características morfológicas, verificação de mortalidade, ocorrência de pragas e doenças e corte das plantas para aferição da produção agronômica. A produção de massa verde se correlacionou com produção de massa seca, acúmulo de água, eficiência de uso da água, acúmulo de água e número de cladódio por planta. Os genótipos indicados para cultivo são Negro Michoacan (V07), Tamazunchale (V12), Califórnia (V14), Orelha de Elefante Mexicana (V17) e Amarillo 2289 (T32) por terem apresentado maiores produções de massa seca e verde, como também maiores acúmulo de água, eficiência de uso da água e capacidade de suporte. No segundo experimento objetivou-se avaliar o padrão de fermentação e a degradabilidade in situ da matéria seca de silagens sob a forma de ração. Cinco rações foram formuladas com base em palma forrageira (Opuntia ficus-indica Mill cv. Gigante) e capim-buffel (Cenchrus ciliaris). O delineamento experimental foi inteiramente casualizado, com cinco tratamentos e três repetições em que as rações diferiram na proporção de capim-buffel (0, 15, 25, 30 e 35%, com base na matéria natural). Observou-se efeito para a composição química das rações, todos os teores de matéria seca (MS) estavam dentro da faixa ideal para uma adequada fermentação. Não houve efeito para concentração de nitrogênio amoniacal. Houve efeito para recuperação da matéria seca (RMS), que variou de 96,3 a 99,9%. Os valores de pH diminuíram à medida que o tempo de abertura (dias) foi prolongado. Os teores de ácidos orgânicos diferiram em todas as rações. No entanto, em geral, todas as rações apresentaram conteúdo de ácido láctico satisfatório. À medida que aumentou a proporção de capim-buffel nas rações, a degradação da MS diminuiu. Com base no perfil de fermentação, perdas e composição química, a ração com maior proporção de palma forrageira pode ser recomendada para produção de silagem.
This dissertation was composed by two experiments. In the first experiment, the objective was to evaluate the agronomic potential and morphological characteristics of 34 cactus pear genotypes destined for forage production. The genotypes were implanted in a randomized complete block design, with 34 treatments and three replications. After 330 days of cultivation, biometric measurements of the morphological characteristics, mortality check, pest and disease occurrence, and crop cutting were performed for agronomic production. Green mass production correlated with dry mass production, water accumulation, water use efficiency, water accumulation and cladode number per plant. The genotypes indicated for cultivation are Negro Michoacan (V07), Tamazunchale (V12), Califórnia (V14), Orelha de Elefante Mexicana (V17) e Amarillo 2289 (T32) for having presented higher yields of dry and green mass, as well as greater accumulation of water, water use efficiency and carrying capacity. In the second experiment, the objective was to evaluate the fermentation pattern and the in situ degradability of dry matter of silages in the form of diet. Five diets were formulated based on spineless cactus (Opuntia ficus-indica Mill cv. Gigante) and buffelgrass (Cenchrus ciliaris). The experimental design was completely randomized, with five treatments and three replications in which the diets differed in the proportion of buffelgrass (0, 15, 25, 30 and 35%, based on natural matter). Effect was observed for the chemical composition of the diets, with all dry matter (DM) contents were within the ideal range for adequate fermentation. There was no effect on ammonia nitrogen concentration. There was effect for dry matter recovery (RMD), which ranged from 96.3 to 99.9%. The pH values decreased as the opening time (days) was prolonged. The levels of organic acids differed in all diets. However, in general, all diets had satisfactory lactic acid content. As the proportion of buffelgrass increased in diets, the degradation of DM decreased. Based on the profile of fermentation, losses and chemical composition, the diet with higher a proportion of spineless cactus can be recommended for silage production.

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The aim of this thesis was to evaluate the performance of Andropogon grasses (Andropogon gayanus Kunth), Buffel (Cenchrus ciliary L.) cv. Grass and Massai (Panicum maximum x Panicum infestum) at ages 21, 35, 49 and 63 days. The experiments were carried out at the Federal Institute of Education, Science and Technology of Rio Grande do Norte - IFRN Campus Apodi, in the period from June to December 2014. The evaluations were carried out in two stages, which yielded three scientific papers. In the first stage, information was addressed regarding the forage species, which were emphasized morphogenetic and structural characteristics and the production and chemical composition of corn in different regrowth ages. In the second stage, it was shown the evaluation of animal performance using hay of the three studied forages, which analyzed the nutrient intake, feeding behavior and sheep performance. For morphogenic and structural evaluation the andropogon presented late vegetative development, contrary to the development presented by buffel grass. Grasses Andropogon, Buffel and Massai increase the production of dry matter with advancing age of regrowth, the andropogon showed higher growth rates of dry matter (469.41%). It occurred only difference between the grasses and Andropogon Massai, from 49 days of regrowth. The crude protein, neutral detergent fiber and lignin components were more varied with increasing regrowth period in all forage species. In assessing the performance of animals fed with hay, it was observed that the regrowth ages influenced rumination, reducing its efficiency with advancing age. The daily weight gain of the animals fed the massaigrass hay and grass Andropogon hay did not differ, but differed from the buffel grass hay. The daily weight gain was not influenced by the age of grasses. Overall analysis showed that the thesis information interrelation helped to determine the best way to choose the forage species to the region, reaching the conclusion that in the conditions, the Massai and Andropogon grasses stood by vegetative best performance and best responses to animals.
O objetivo desta Tese foi avaliar o desempenho produtivo dos capins Andropogon (Andropogon gayanus Kunth), Buffel (Cenchrus ciliares L.) cv. Grass e Massai (Panicum maximum x Panicum infestum) nas idades de 21, 35, 49 e 63 dias. Os experimentos foram desenvolvidos no Instituto Federal de Educação, Ciência e Tecnologia do Rio Grande do Norte – IFRN, Campus Apodi, no período de junho a dezembro de 2014. As avaliações foram realizadas em duas etapas, que geraram três artigos científicos. Na primeira etapa, foram abordadas informações referentes às espécies forrageiras, onde foram enfatizadas as características morfogênicas e estruturais e a produção e composição química das gramíneas nas diferentes idades de rebrota. Na segunda etapa, foi evidenciada a avaliação do desempenho animal utilizando o feno das três forrageiras estudadas, onde foi analisado o consumo de nutrientes, comportamento ingestivo e o desempenho de ovinos. Para avaliação morfogênica e estrutural o capim-andropogon apresentou desenvolvimento vegetativo tardio, contrário ao desenvolvimento apresentado pelo capim-buffel. Os capins Andropogon, Buffel e Massai aumentam a produção de matéria seca com o avanço da idade de rebrota, o capim-andropogon apresentou maiores crescimentos de matéria seca (469,41%). Ocorreu diferença apenas entre os capins Massai e Andropogon, a partir dos 49 dias de rebrota. A proteína bruta, a fibra em detergente neutro e a lignina foram os componentes que mais variaram com o aumento do período de rebrota em todas as espécies forrageiras estudadas. Na avaliação de desempenho dos animais, alimentados com feno, foi observado que as idades de rebrota influenciaram a ruminação, diminuindo sua eficiência com o avanço da idade. O ganho de peso diário dos animais alimentados com o feno de capim-massai e feno de capim-andropogon não diferiram entre si, mas diferiram do feno de capim buffel. O ganho de peso diário não foi influenciado pela idade dos capins. Em análise geral, observou-se que a inter-relação de informações da Tese contribuiu para determinar a melhor forma de eleger a espécie forrageira para a região, chegando-se a conclusão que, nas condições apresentadas, os capins Massai e Andropogon se destacaram pelo melhor desempenho vegetativo e melhores respostas aos animais
2017-04-13

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
O objetivo proposto para esse estudo foi avaliar a influência do sombreamento proporcionado pela algaroba associada (Prosopis juliflora) sobre o valor nutricional do capim-buffel (Cenchrus ciliaris). Através da técnica in vitro semi-automática de produção de gases, foram avaliadas a cinética da fermentação e extensão da degradação da matéria seca das amostras. Análises para determinação da composição químico-bromatológica e fracionamento de carboidratos da forrageira também foram realizadas. As avaliações foram feitas a partir de amostras da gramínea obtidas em um sistema de associação de capim- buffel com algaroba, localizado na região semi-árida nordestina, com aproximadamente 15 anos de idade, durante a época seca e chuvosa, compreendidas respectivamente entre os meses de agosto de 1997 e abril de 1998. O delineamento experimental utilizado foi em esquema de parcelas subdivididas, com blocos ao acaso constituindo as cinco repetições, representadas cada uma por um mistura de amostras colhidas sobre duas árvores contíguas. As parcelas principais foram compostas pelos três locais de amostragem da gramínea: dois pontos de coleta de amostras (A e B) sob a copa das árvores de algaroba e um terceiro ponto (C) distante 20 m de cada árvore selecionada, representando a forrageira em monocultivo. As parcelas secundárias foram constituídas pelas duas épocas avaliadas, que diferiram principalmente em termos de precipitação. Através da determinação da composição químico-bromatológica do capim-buffel colhido nos pontos A, B e C, na época seca e chuvosa, observou-se que o sombreamento proporcionado pela algaroba não alterou o teor de nutrientes e outros compostos na gramínea. A mensuração dos teores de matéria mineral (MM), proteína bruta (PB), extrato etéreo (EE), fibra em detergente neutro (FDN), fibra em detergente ácido (FDA), hemicelulose (HEMI), celulose (CEL) e lignina (LIG) foi feita nas amostras, cujos valores foram expressos em % da matéria seca. Os teores desses nutrientes não variaram (P>0,05) entre os pontos de amostragem, exceção feita à LIG mensurada no capim-buffel colhido no ponto C durante a época seca, com conteúdo aproximadamente 10% inferior quando comparado com ao valor obtido nas amostras colhidas no ponto A na mesma época. Destacaram-se o baixo conteúdo protéico (6%) e o alto conteúdo de fibra, com FDN e FDA respectivamente 77 e 50%. Durante a época seca os teores de FDN, FDA e LIG do capim-buffel foram ligeiramente maiores (P>0,05) quando comparados aos valores obtidos na época chuvosa. O teor de MM da gramínea também diferiu (P>0,05) entre épocas, sendo superior na época de menor déficit hídrico. O fracionamento de carboidratos do capim-buffel não acusou diferenças (P>0,05) ocasionadas pelo local de amostragem. No entanto, durante a época de maior precipitação, foi menor o conteúdo da fração C. A proporção das frações de carboidratos foi expressa como % dos carboidratos totais. A contribuição da fração A+B 1 na gramínea foi pequena (12%), enquanto as frações B 2 e C, independente da época ou local de amostragem, foram expressivas e apresentaram valores mínimos respectivamente 52% e 30%. A técnica in vitro semi-automática de produção de gases (TPG) e a avaliação da degradação aparente revelaram os efeitos do sombreamento proporcionado pela algaroba sobre o capim-buffel. Esse bio-ensaio com microrganismos foi utilizado para estimar a cinética da fermentação e da produção de gases (PG) do capim-buffel, concomitantemente à determinação da extensão da sua degradação, através de medidas gravimétricas. Os resultados foram influenciados pela disponibilidade de água no solo em decorrência das variações na precipitação, à semelhança do que ocorreu com a composição químico-bromatológica e fracionamento de carboidratos. O sombreamento proporcionado pela algaroba alterou negativamente os parâmetros cinéticos da fermentação e de extensão de degradação do capim-buffel, mas somente na época chuvosa. Não foram observadas diferenças (P>0,05) para a gramínea colhida nos pontos A, B e C na época seca para as variáveis de extensão da degradação e cinética da fermentação obtidas por intermédio da TPG. Os valores médios para PG potencial (A), taxa fracional de PG (μ), tempo de latência (L), tempo para atingir a metade da PG assintótica (T/2) e degradação aparente (DA) da matéria seca do capim- buffel foram respectivamente 138 mL; 2,10 %/h; 5,8 h; 31 h e 42%. Durante a época chuvosa, houve diferenças (P>0,05) para essas mesmas variáveis, com superioridade para a gramínea crescendo em condição de exposição completa ao sol (ponto C), indicando melhoria do valor nutricional da gramínea crescendo sob radiação solar intensa. Para a gramínea colhida nos pontos localizados sob a copa das árvores (pontos A e B), não foram observadas diferenças (P>0,05). Os valores médios para A, μ e L para as amostras colhidas no ponto C foram respectivamente 183 mililitros; 2,18 %/h e 5,3 h; contra 155 mL; 2,02 %/h e 5,7 h para as mesmas variáveis mensuradas nas amostras colhidas nos pontos A e B. Para o efeito experimental de época, diferiram (P>0,05) as variáveis A e DA, com superioridade para a gramínea colhida na época chuvosa, apresentando valores médios respectivamente 165 mL e 49%, contra 138 mL e 42% para a época seca. As variáveis L, T/2 e μ, para as quais não se observou diferença (P>0,05) para o efeito sazonal, apresentaram valores médios, respectivamente, 5,7 h, 31 h e 2,08 %/h. Esses resultados indicam que esse efeito experimental influenciou mais a extensão da degradação do que os parâmetros cinéticos da fermentação do capim-buffel. A associação do capim-buffel com a algaroba não apresentou vantagens para a melhoria dos parâmetros de extensão da degradação e cinética da fermentação do capim-buffel. O valor nutricional da gramínea foi mais influenciado pela diferença na disponibilidade de água no solo, decorrente da sazonalidade do clima, do que pelo sombreamento proporcionado pelas árvores de algaroba associadas. Com os resultados obtidos, pôde-se perceber que, o primeiro fator limitante para a melhoria do valor nutricional da forrageira foi a disponibilidade de água no solo, seguida pela radiação solar. Esses efeitos se complementam e têm efeito aditivo pronunciado.
The purpose of this study was to evaluate the effect of shading from algaroba trees (Prosopis juliflora) on the nutritional value of associated buffel grass (Cenchrus ciliaris). The in vitro semi-automatic gas production technique was used to evaluate the fermentation kinetics and extent of dry matter degradation of this grass. Also determined was the chemical-bromatological composition and carbohydrate fractioning of the buffel grass samples. These were obtained from an approximately 15 year-old buffel grass/algaroba association area located in the (semi-arid) northeastern region of Brazil, during both the dry and the rainy season, between August, 1977 and April, 1998. The experimental design used was a scheme of subdivided portions, with random blocks constituting the five repetitions, each represented by a mixture of samples collected under two adjacent trees. The main portions were composed of three sampling sites, i.e., two sample collection points (A and B) under the algaroba tree canopies and a third point (C) located at a distance of 20 cm from each selected tree, representing monocultured buffel grass. The secondary portions corresponded to the two sampling seasons, which differed from each other mainly in terms of rainfall. The determinations made with samples collected from points A, B and C during both the dry and the rainy season showed that shading from the algaroba trees had no significant effect on the chemical-bromatological composition of buffel grass. Measurements were made of the contents of mineral matter (MM), crude protein, ethereal extract (EE), neutral detergent fiber (NDF), acid detergent fiber (ADF), hemicellulose (HEMI), cellulose (CEL), the values being expressed in % of dry matter. No differences (P>0.05) in the contents of these nutrients were found between sampling points, except for LIG in the dry-season samples from point C, of which the content was approximately 10% lower than that obtained for the samples from point A. The protein content was low (6%) xiiand the NDF and ADF contents were high (77 and 50%, respectively). The NDF, ADF and LIG contents of dry-season samples were slightly higher (P>0.05) than those recorded for rainy-season samples. The MM content also varied (P>0.05) between sampling seasons and was higher for samples collected during the period of smallest water deficit. No differences in carbohydrate fractioning were found (P>0.05) between sampling sites. However, during the period of greater rainfall, the content of fraction C was smaller. The proportion of carbohydrate fractions was expressed as a percentage of total carbohydrates. The contribution of fraction A+B1 was small (12%), whereas fractions B2 and C were relevant, regardless of the sampling period or site, showing minimum values of 52% and 30%, respectively. The in vitro semi-automatic gas production technique (GPT) and the evaluation of apparent degradation showed the effects of shading from algaroba trees on buffel grass. This bio-survey with microorganisms was used to estimate the fermentation kinetics and gas production (GP) of buffel grass, with the extent of dry matter degradation being determined through gravimetric measurements. The results were influenced by differences in soil water availability due to variations in rainfall. Shading from the algaroba trees had a negative effect on the kinetic parameters of fermentation, as well as on the extent of degradation of buffel grass, yet only in the rainy season. No differences (P>0,05) in the extent of degradation and fermentation kinetics, as determined by GPT, were found between the dry-season samples from points A, B and C. The mean values for potential GP (A), fractional GP rate (m), latency time, time to reach half of the asymptotic GP (T/2), and apparent degradation of dry matter (AD) were 138 ml, 2.10%/h, 5.8 h, 31 h, and 42%, respectively. For the rainy-season samples, differences were recorded in these variables (P>0.05), with higher values being obtained for samples from areas fully exposed to the sun (point C), suggesting that nutritional value is improved by intense solar radiation. No differences (P>0.05) in these variables were observed for buffel grass collected from under the algaroba tree canopies (points A and B). The mean values for A, m and L were 183 ml, 2.18%/h and 5.3 h, respectively, for the samples collected from point C, and 155 ml, 2.02%/h and 5.7 h, respectively; for the samples obtained from points A and B. As for the time-of-the-year effect, differences were observed (P>0.05) in the variables A and AD, with higher values being recorded for rainy-season samples, which showed mean values of 165 ml and 49%, respectively, against 138 ml and 42% for dry-season samples. The xiiivariables L, T/2 and m, for which no differences related to the seasonal effect were recorded (P>0.05), showed mean values of 5.7 h, 31 h and 2.08%/h, respectively. These results indicate that degradation is more affected by the seasonal effect than are the kinetic parameters of fermentation of buffel grass. The association of buffel grass with algaroba showed no significant advantages in improving the extent of degradation and the fermentation kinetics of buffel grass. The difference in soil water availability had a greater influence on the nutritional value of buffel grass than did shading from the associated algaroba trees. The results obtained allow us to conclude that the major limiting factor to improvement of the nutritional value of buffel grass was soil water availability, followed by exposure to the sun. These two factors complement each other and have a marked additive effect.

Pastures established using buffelgrass (Cenchrus ciliaris L.) have shown heterogeneous responses in terms of forage production and permanence. A good alternative for determining establishment sites and predict trends in buffelgrass conditions is the use of simulation models. The objectives of this research were to determine the factors that regulate successfulness in buffelgrass pastures and to develop a model to determine suitability in areas managed for buffelgrass pastures, based on environmental, ecological, and management variables. Above ground biomass production was considered to determine suitability in sites with buffelgrass. Eight ranches with different geographic locations, environmental situations, and management conditions were sampled as preliminary study sites to measure and model plant production. The resulting model was used to estimate plant production in the 37 sampling sites of the study areas. Results of the study indicate that basal area is a good modeling parameter to estimate production in buffelgrass plants. I also found that plant production in buffelgrass is negatively affected by population density. I concluded that there exist a positive correlation between pasture management and buffelgrass plant production. Correlation analyses demonstrate that there exist significant correlations between Pasture Condition Index (PCI) and mean annual temperatures, aspect, pasture age, nitrogen and sodium content. However, after performing stepwise regressions, only three variables were significant: pasture age (PA), nitrogen content (N2), and mean annual temperature (MAT); the last two, produce a negative response on PCI.

Buffel grass (Cenchrus ciliaris ) has been established in Uluṟu‐Kata Tjuta National Park since 1968. To date, the influence of buffel grass on the Park's flora and fauna has been largely unassessed. The objectives of this study were to determine if buffel grass dominates vegetation communities at the base of Uluṟu and if buffel grass habitats are associated with lower reptile and amphibian species richness than endemic vegetation communities. We used vegetation transects to measure the amount of buffel grass and genera of endemic vegetation at 26 sampling locations around the base of Uluṟu. The vegetation survey data were paired with pitfall trap data from reptile and amphibian captures at the same sampling locations. Indicator species analysis and non‐metric multidimensional scaling were used to analyse the vegetation and herpetofaunal community data. Our analyses determined five distinct vegetation communities around Uluṟu. At the base of Uluṟu, buffel grass dominated half of sampled areas and the rest of the inselberg's base was dominated by Themeda grasses. Buffel grass habitats had significantly higher herpetofaunal species richness than the Themeda habitats that dominated other areas at Uluṟu's base. Herpetofauna species richness in buffel grass‐dominated habitats was also significantly higher than all vegetation communities except for Triodia‐dominated habitats. These observations do not directly indicate that buffel grass presence promotes higher species richness of reptiles and amphibians since the observed patterns may be driven by factors such as proximity to breeding sites and abiotic variables not directly related to the grass itself.

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CAPES;CISA;INSA
A precipitação pluvial é quase sempre a única fonte de abastecimento de água em zonas áridas e semiáridas tropicais e, portanto, desempenha um papel relevante na sustentabilidade dos ecossistemas. A escassez e a irregularidade da distribuição pluvial provoca sério estresse hídrico nas plantas, afetando a produção de biomassa e a perpetuação das espécies, sobretudo as menos adaptadas às condições áridas e semiáridas. Em meio a essa problemática, foram realizadas duas investigações, de fevereiro de 2011 a junho de 2012, uma que avaliou a partição das chuvas (interceptação pelas plantas e precipitação efetiva) e sua influência no armazenamento de água no solo em áreas de caatinga e de capim-buffel (Cenchrus ciliaris) e outra que avaliou o potencial hídrico do xilema (Ψw) na antemanhã (Ψwa) e diurno (Ψwd) do Croton blanchetianus (marmeleiro), Poincianella pyramidalis (catingueira) e Mimosa ophthalmocentra (jurema-de-imbira) ao longo de diferentes estádios fenológicos, quantidades de água armazenada no solo e demandas evaporativas. As interceptações pluviais foram medidas em áreas de caatinga raleada, caatinga densa e de capim-buffel. A intensidade pluviométrica variou de 0,2 a 85 mm h-1 (n=714) com 55% dos eventos chuvosos entre 0,2 e 1 mm h-1.O total pluvial acumulado livre de interceptação foi de 1.060 m, desse montante, 87% atingiram de forma direta (sem interceptação) a superfície do solo na caatinga raleada, 81% na caatinga densa, 61% no C. ciliaris e 40% na caatinga densa com bromélias. Esses diferentes volumes de entrada de água no solo provocaram diferentes armazenamentos de água nas camadas de 0-10, 10-20 20-30 e 30-40 cm de solo. A secagem da água armazenada em termos proporcionais em 0-40 cm de solo foi maior na caatinga densa (média da área com e sem bromélias), seguida da caatinga raleada e da área com C. ciliaris. O decréscimo mais lento da água armazenada na área de capim-buffel em relação à área de caatinga pode está relacionado com o menor consumo de água dessa gramínea e a evaporação de água no solo, e a alta adaptação do C. ciliaris à escassez hídrica. As medidas de estresse hídrico das espécies da caatinga, nesse estudo mensurado pelo Ψw usando o método da câmara de pressão de Scholander, variaram na antemanhã de -0,10 a -2,23 MPa em C. blanchetianus, de -0,23 a -2,31 MPa em P. pyramidalis e de -0,32 a -3,65 MPa em M. ophthalmocentra. No período diurno o Ψwd atingiu -5,60 Mpa (M. ophthalmocentra) e as diferenças de Ψw entre as espécies foram mais frequentes, sobretudo nas horas de maior demanda hídrica. O comportamento Ψwd nas três espécies foi semelhante, iniciando o dia com os valores mais altos e diminuindo gradativamente até próximo do meio dia. O Ψw total das espécies estudadas demonstrou forte relação com o estádio fenológico, sobretudo a presença ou ausência de folhas.

Buffelgrass (Cenchrus ciliaris L.) is an invasive, perennial, C₄ bunchgrass. Buffelgrass has a rapid invasion rate, a tendency to displace native vegetation, and presents a fire risk to native plant communities, adjacent developed areas and their associated infrastructure. Mechanical control is impractical and unable to keep pace with regional spread. Chemical control has offered the most promise for successful and cost-effective management on a regional scale. The predominant herbicide used to control buffelgrass is glyphosate, which requires active vegetative growth when applied for optimum uptake and translocation to meristematic tissue. The timing and duration of active growth is difficult to predict. In this dissertation I addressed three related topics to improve effectiveness of buffelgrass management in the Sonoran Desert. First, I used digital time-lapse photography and weather data to predict the timing and length of future active growth based on day of year and antecedent weather at three sites in the Sonoran Desert near Tucson, AZ that were representative of habitats currently infested by buffelgrass in the region. I was able to correctly predict greenness above or below a threshold of herbicide susceptibility at 81 to 95% for a basin floor site and at 61-88% for slope sites. Second, I evaluated the effects of different rates of two herbicides (imazapic and clethodim), alone or in combination with different rates of glyphosate, for pre- (imazapic only) and postemergence control of buffelgrass. I found a minimum glyphosate application rate of 2.52 kg ae ha⁻¹ glyphosate consistently killed mature buffelgrass plants; clethodim at had no effect on mature buffelgrass; and imazapyr was successful in killing mature plants when applied during the dormant season at 0.56 kg ae ha⁻¹ and provided preemergence control. Imazapic severely damaged but did not kill mature buffelgrass plants at the maximum label rate of 0.21 kg ae ha⁻¹. Finally, we evaluated results from a helicopter broadcast herbicide application trial conducted in the Tucson Mountains. We demonstrated that most species and life forms were less affected than buffelgrass to glyphosate deposition rates achieved in the study, but asserted that procedural changes were necessary to achieve effective buffelgrass control.