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Samantha A. Setterfield - One of the best experts on this subject based on the ideXlab platform.

  • Exotic grass invasion alters microsite conditions limiting woody recruitment potential in an Australian savanna
    Nature Publishing Group, 2018
    Co-Authors: Samantha A. Setterfield, Peter J. Clifton, Lindsay B. Hutley, Natalie A. Rossiter-rachor, Michael M. Douglas
    Abstract:

    Abstract Andropogon gayanus Kunth. is a large African tussock grass invading Australia’s tropical savannas. Invasion results in more intense fires which increases the mortality rate of adult woody plants. Invasion may also affect community structure by altering the recruitment potential of woody plants. We investigated the effects of A. gayanus invasion on ground-level microclimate, and the carbon assimilation potential and recruitment potential of two Eucalyptus species. We compared microclimatic variables from the early wet-season and into the mid-dry season to coincide with the period of growth of A. gayanus. We assessed Eucalyptus recruitment by monitoring seedling establishment, growth and survival of experimentally sown seed, and estimating seedling density resulting from natural recruitment. A. gayanus invasion was associated with increased grass canopy height, biomass and cover. Following invasion, the understorey microclimate had significantly reduced levels of photon flux density, increased air temperatures and vapour pressure deficit. The conditions were less favourable for woody seedling with aboveground biomass of seedlings reduced by 26% in invaded plots. We estimated that invasion reduced daily carbon assimilation of woody seedlings by ~30% and reduced survivorship of Eucalyptus seedlings. Therefore, A. gayanus invasion reduces recruitment potential, contributing to the transformation of savanna to a grassland ecosystem

  • invasive Andropogon gayanus gamba grass alters litter decomposition and nitrogen fluxes in an australian tropical savanna
    Scientific Reports, 2017
    Co-Authors: Natalie A Rossiterrachor, Samantha A. Setterfield, Lindsay B. Hutley, Damien Mcmaster, Susanne Schmidt, Michael M. Douglas
    Abstract:

    The African grass Andropogon gayanus Kunth. is invading Australian savannas, altering their ecological and biogeochemical function. To assess impacts on nitrogen (N) cycling, we quantified litter decomposition and N dynamics of grass litter in native grass and A. gayanus invaded savanna using destructive in situ grass litter harvests and litterbag incubations (soil surface and aerial position). Only 30% of the A. gayanus in situ litter decomposed, compared to 61% of the native grass litter, due to the former being largely comprised of highly resistant A. gayanus stem. In contrast to the stem, A. gayanus leaf decomposition was approximately 3- and 2-times higher than the dominant native grass, Alloteropsis semilata at the surface and aerial position, respectively. Lower initial lignin concentrations, and higher consumption by termites, accounted for the greater surface decomposition rate of A. gayanus. N flux estimates suggest the N release of A. gayanus litter is insufficient to compensate for increased N uptake and N loss via fire in invaded plots. Annually burnt invaded savanna may lose up to 8.2% of the upper soil N pool over a decade. Without additional inputs via biological N fixation, A. gayanus invasion is likely to diminish the N capital of Australia's frequently burnt savannas.

  • Appendix A. Grass and woody litter tissue nitrogen concentrations in native grass and Andropogon gayanus plots.
    2016
    Co-Authors: Natalie A. Rossiter-rachor, Samantha A. Setterfield, Lindsay B. Hutley, M. M. Douglas, G. D. Cook, S. Schmidt
    Abstract:

    Grass and woody litter tissue nitrogen concentrations in native grass and Andropogon gayanus plots

  • estimating the financial risks of Andropogon gayanus to greenhouse gas abatement projects in northern australia
    Environmental Research Letters, 2013
    Co-Authors: Vanessa M Adams, Samantha A. Setterfield
    Abstract:

    Financial mechanisms such as offsets are one strategy to abate greenhouse gas emissions, and the carbon market is expanding with a growing demand for offset products. However, in the case of carbon offsets, if the carbon is released due to intentional or unintentional reversal through environmental events such as fire, the financial liability to replace lost offsets will likely fall on the provider. This liability may have implications for future participation in programmes, but common strategies such as buffer pool and insurance products can be used to minimize this liability. In order for these strategies to be effective, an understanding of the spatial and temporal distributions of expected reversals is needed. We use the case study of savanna burning, an approved greenhouse gas abatement methodology under the Carbon Farming Initiative in Australia, to examine potential risks to carbon markets in northern Australia and quantify the financial risks. We focus our analysis on the threat of Andropogon gayanus (gamba grass) to savanna burning due to its documented impacts of increased fuel loads and altered fire regimes. We assess the spatial and financial extent to which gamba grass poses a risk to savanna burning programmes in northern Australia. We find that 75% of the eligible area for savanna burning is spatially coincident with the high suitability range for gamba grass. Our analysis demonstrates that the presence of gamba grass seriously impacts the financial viability of savanna burning projects. For example, in order to recuperate the annual costs of controlling 1 ha of gamba grass infestation, 290 ha of land must be enrolled in annual carbon abatement credits. Our results show an immediate need to contain gamba grass to its current extent to avoid future spread into large expanses of land, which are currently profitable for savanna burning.

  • habitat complexity and invasive species the impacts of gamba grass Andropogon gayanus on invertebrates in an australian tropical savanna
    Biotropica, 2010
    Co-Authors: Catherine L Parr, Ben Ryan, Samantha A. Setterfield
    Abstract:

    Habitat complexity is an important factor structuring local faunal assemblages. Many invasive plant species alter vegetation complexity because they are both functionally and structurally different from native flora. This study investigated the effects of an invasive grass (Andropogon gayanus Kunth.), which is invading undisturbed savannas in northern Australia. Although A. gayanus is a similar lifeform to that dominant in the native understory (i.e., a C4 grass), it is structurally different and significantly alters habitat complexity. We, therefore, hypothesized that there would be a substantial effect of the invasive grass on ant, spider, and other invertebrate assemblages. Contrary to our hypothesis, there was no effect of A. gayanus on ant species richness, abundance, or composition, nor were spiders or other invertebrates affected. Instead the change in weather conditions with season was more important in structuring the local invertebrate assemblages. Change in habitat complexity was most pronounced vertically, rather than horizontally at ground level, thus although there was a clear difference in the vertical structure between invaded and noninvaded habitats, the limited invertebrate response to different A. gayanus densities suggests some invertebrates are less sensitive to vertical changes in vegetation structure.

Lindsay B. Hutley - One of the best experts on this subject based on the ideXlab platform.

  • Exotic grass invasion alters microsite conditions limiting woody recruitment potential in an Australian savanna
    Nature Publishing Group, 2018
    Co-Authors: Samantha A. Setterfield, Peter J. Clifton, Lindsay B. Hutley, Natalie A. Rossiter-rachor, Michael M. Douglas
    Abstract:

    Abstract Andropogon gayanus Kunth. is a large African tussock grass invading Australia’s tropical savannas. Invasion results in more intense fires which increases the mortality rate of adult woody plants. Invasion may also affect community structure by altering the recruitment potential of woody plants. We investigated the effects of A. gayanus invasion on ground-level microclimate, and the carbon assimilation potential and recruitment potential of two Eucalyptus species. We compared microclimatic variables from the early wet-season and into the mid-dry season to coincide with the period of growth of A. gayanus. We assessed Eucalyptus recruitment by monitoring seedling establishment, growth and survival of experimentally sown seed, and estimating seedling density resulting from natural recruitment. A. gayanus invasion was associated with increased grass canopy height, biomass and cover. Following invasion, the understorey microclimate had significantly reduced levels of photon flux density, increased air temperatures and vapour pressure deficit. The conditions were less favourable for woody seedling with aboveground biomass of seedlings reduced by 26% in invaded plots. We estimated that invasion reduced daily carbon assimilation of woody seedlings by ~30% and reduced survivorship of Eucalyptus seedlings. Therefore, A. gayanus invasion reduces recruitment potential, contributing to the transformation of savanna to a grassland ecosystem

  • invasive Andropogon gayanus gamba grass alters litter decomposition and nitrogen fluxes in an australian tropical savanna
    Scientific Reports, 2017
    Co-Authors: Natalie A Rossiterrachor, Samantha A. Setterfield, Lindsay B. Hutley, Damien Mcmaster, Susanne Schmidt, Michael M. Douglas
    Abstract:

    The African grass Andropogon gayanus Kunth. is invading Australian savannas, altering their ecological and biogeochemical function. To assess impacts on nitrogen (N) cycling, we quantified litter decomposition and N dynamics of grass litter in native grass and A. gayanus invaded savanna using destructive in situ grass litter harvests and litterbag incubations (soil surface and aerial position). Only 30% of the A. gayanus in situ litter decomposed, compared to 61% of the native grass litter, due to the former being largely comprised of highly resistant A. gayanus stem. In contrast to the stem, A. gayanus leaf decomposition was approximately 3- and 2-times higher than the dominant native grass, Alloteropsis semilata at the surface and aerial position, respectively. Lower initial lignin concentrations, and higher consumption by termites, accounted for the greater surface decomposition rate of A. gayanus. N flux estimates suggest the N release of A. gayanus litter is insufficient to compensate for increased N uptake and N loss via fire in invaded plots. Annually burnt invaded savanna may lose up to 8.2% of the upper soil N pool over a decade. Without additional inputs via biological N fixation, A. gayanus invasion is likely to diminish the N capital of Australia's frequently burnt savannas.

  • Appendix A. Grass and woody litter tissue nitrogen concentrations in native grass and Andropogon gayanus plots.
    2016
    Co-Authors: Natalie A. Rossiter-rachor, Samantha A. Setterfield, Lindsay B. Hutley, M. M. Douglas, G. D. Cook, S. Schmidt
    Abstract:

    Grass and woody litter tissue nitrogen concentrations in native grass and Andropogon gayanus plots

  • turning up the heat the impacts of Andropogon gayanus gamba grass invasion on fire behaviour in northern australian savannas
    Diversity and Distributions, 2010
    Co-Authors: Samantha A. Setterfield, Lindsay B. Hutley, Michael M. Douglas, Natalie A Rossiterrachor, Richard J Williams
    Abstract:

    Aim  This study aimed to quantify changes in fire severity resulting from the invasion of Australia’s tropical savannas by the African grass Andropogon gayanus Kunth. (gamba grass). Location  Mesic savannas of the Northern Territory, Australia. Method  Byram’s fire-line intensity (If), fuel load and architecture, and two post-fire indicators of fire intensity – scorch height (SH) and char height (CH) of woody vegetation – were determined for fires in native grass savanna and A. gayanus invaded savanna. Leaf scorch is the height at which the fire’s radiant heat browns leaf tissue, and leaf char is the height that radiant heat blackens or consumes leaf tissue and provides an indirect measure of flame height. These data, and 5 years of similar data collected from the Kapalga Fire Project in Kakadu National Park, were used to develop empirical relationships between If and the post-fire indices of fire intensity. Results  A relationship between A. gayanus If and SH could not be developed because complete canopy scorch occurred in most A. gayanus fires, even at low If. In contrast, A. gayanus If was strongly correlated with CH. This empirical relationship was substantially different from that for native grass fires. For a given If, there was a significantly greater CH in invaded sites. This increase in radiant heat is attributable to the increased biomass (mean 3.6 t ha−1 in native grasses compared to 11.6 t ha−1 in A. gayanus) and height (approximately 0.5 m in native grasses compared to 4 m in A. gayanus) of the standing fine fuel. Main conclusion Andropogon gayanus invasion resulted in substantial changes in fire behaviour. This has important regional implications owing to the current (10,000–15,000 km2) and predicted (380,000 km2) area of invasion and the negative consequences for the native savanna biota that has evolved with frequent but relatively low-intensity fire.

  • Andropogon gayanus (Gamba Grass) Invasion Increases Fire-mediated Nitrogen Losses in the Tropical Savannas of Northern Australia
    Ecosystems, 2008
    Co-Authors: Natalie A. Rossiter-rachor, Samantha A. Setterfield, Lindsay B. Hutley, M. M. Douglas, G. D. Cook
    Abstract:

    Invasive alien grasses can substantially alter fuel loads and fire regimes which could have significant consequences for fire-mediated nutrient losses. The effects of the alien grass Andropogon gayanus Kunth. (Gamba grass) on fire-mediated nutrient losses was evaluated in Australia’s tropical savannas. Losses of macronutrients during fire were determined by comparing the nutrient pools contained in the fine fuel before fire and in the ash after fire. Pre-fire grass nutrient pools were significantly higher in A. gayanus plots than in native grass plots for all nutrients measured (N, P, K, S, Ca, and Mg). Nutrient losses were substantially higher in A. gayanus plots, with 113% higher losses for N, 80% for P, 56% for K, 63 for S, 355% for Ca, and 345% for Mg. However, only losses of N and Mg varied significantly between grass types. A simplified savanna ecosystem nutrient budget estimated that A. gayanus fires led to the net N loss of 20 kg ha^−1 y^−1. This is a conservative estimate because total fuel loads were relatively low (7.85 t ha^−1) for A. gayanus invaded plots leading to a relatively moderate intensity fire (6,408 kW m^−1). Higher A. gayanus fuel loads and fire intensities could potentially lead to losses of up to 61.5 kg N ha^−1 from the grass fuel. Over the long term, this is likely to lead to depletion of soil nutrients, particularly N, in the already low-fertility tropical savanna soils.

Gracindo, Cristiane Vinhaes - One of the best experts on this subject based on the ideXlab platform.

  • Avaliação do desempenho e da toxicidade em ovinos mantidos em pastagens de Brachiaria decumbens, Brachiaria brizantha, Panicum maximum var Aires e Andropogon gayanus var Planaltina
    2011
    Co-Authors: Gracindo, Cristiane Vinhaes
    Abstract:

    Frente à crescente implantação de Brachiaria spp nos solos do Centro-Oeste, o presente projeto objetivou analisar o desempenho de ovinos submetidos ao pastejo em Brachiaria decumbens e Brachiaria brizantha, em comparação ao pastejo em Panicum maximum var Aires e Andropogon gayanus var Planaltina. Foram avaliados, também, a presença de sinais clínicos indicativos de intoxicação por Brachiaria spp e parâmetros bioquímicos séricos como aspartato aminotransferase (AST), gama-glutamiltransferase (GGT), proteína total (PT), albumina, uréia e creatinina em ovinos, bem como, quantificou-se os teores de saponinas litogênicas e esporos de Pithomyces chartarum, nas amostras de pastagem coletadas das quatro forrageiras. Foram utilizados 48 animais dividos em lotes homogêneos constituídos por machos castrados, com peso médio de 20kg, idades entre quatro e cinco meses, oriundos de rebanhos com contato prévio com Brachiaria spp. há mais de três anos consecutivos e animais naive, ou seja, que nunca haviam tido contato com Brachiaria spp. O desempenho dos animais foi semelhante entre os lotes de ovinos mantidos em piquetes de B. decumbens, B. brizantha e P. maximum var Aires, mas inferior no grupo que permaneceu na área formada por A. gayanus var Planaltina (p≤0,05). Os animais com contato prévio a Brachiaria spp. não apresentaram sinais clínicos compatíveis com intoxicação decorrentes à ingestão da forrageira. Porém, dois animais naive mantidos no piquete de B. decumbens, se intoxicaram, e um deles morreu, sugerindo uma possível forma de adaptação dos animais ao pastejo na gramínea, que lhes confira maior resistência à intoxicação. _______________________________________________________________________________ ABSTRACTDue to the increasing deployment of Brachiaria spp in the soil of the Midwest, this project aims to evaluate the toxicity and performance of sheep grazing Brachiaria decumbens and Brachiaria brizantha, compared with Panicum maximum var Aires and Andropogon gayanus var Planaltina pastures. The presence of clinical signs of poisoning by Brachiaria spp and serum biochemical parameters: aspartate aminotransferase (AST), gamma-glutamyltransferase (GGT), total protein (TP), albumin, urea and creatinine were evaluated. The levels of saponins and Pithomyces chartarum spores in pasture samples were also evaluated. The experiment used 48 animals divided into homogeneous lots consisting of castrated males, average weight 20 kg, aged between four and five months, coming from herds with no previous contact with Brachiaria spp. for more than three consecutive years and naive animals, i.e., that never had contact with Brachiaria spp. The animal performance was similar in sheep kept in paddocks with B. decumbens, B. brizantha and P. maximum var Aires, but lower in the group that remained in the area formed by A. gayanus var Planaltina (p ≤ 0.05). Animals with previous contact Brachiaria spp. showed no clinical signs consistent with poisoning from the ingestion of forage. However, two naive animals kept in the paddock of B. decumbens, were intoxicated, and one of them died, suggesting a possible form of adaptation of animals to grazing on Brachiaria spp., which gives them some degree of resistance to poisoning

  • Avaliação do desempenho e da toxicidade em ovinos mantidos em pastagens de Brachiaria decumbens, Brachiaria brizantha, Panicum maximum var Aires e Andropogon gayanus var Planaltina
    2010
    Co-Authors: Gracindo, Cristiane Vinhaes
    Abstract:

    Dissertação (mestrado)—Universidade de Brasília, Faculdade de Agronomia e Medicina Veterinária, 2010.Frente à crescente implantação de Brachiaria spp nos solos do Centro-Oeste, o presente projeto objetivou analisar o desempenho de ovinos submetidos ao pastejo em Brachiaria decumbens e Brachiaria brizantha, em comparação ao pastejo em Panicum maximum var Aires e Andropogon gayanus var Planaltina. Foram avaliados, também, a presença de sinais clínicos indicativos de intoxicação por Brachiaria spp e parâmetros bioquímicos séricos como aspartato aminotransferase (AST), gama-glutamiltransferase (GGT), proteína total (PT), albumina, uréia e creatinina em ovinos, bem como, quantificou-se os teores de saponinas litogênicas e esporos de Pithomyces chartarum, nas amostras de pastagem coletadas das quatro forrageiras. Foram utilizados 48 animais dividos em lotes homogêneos constituídos por machos castrados, com peso médio de 20kg, idades entre quatro e cinco meses, oriundos de rebanhos com contato prévio com Brachiaria spp. há mais de três anos consecutivos e animais naive, ou seja, que nunca haviam tido contato com Brachiaria spp. O desempenho dos animais foi semelhante entre os lotes de ovinos mantidos em piquetes de B. decumbens, B. brizantha e P. maximum var Aires, mas inferior no grupo que permaneceu na área formada por A. gayanus var Planaltina (p≤0,05). Os animais com contato prévio a Brachiaria spp. não apresentaram sinais clínicos compatíveis com intoxicação decorrentes à ingestão da forrageira. Porém, dois animais naive mantidos no piquete de B. decumbens, se intoxicaram, e um deles morreu, sugerindo uma possível forma de adaptação dos animais ao pastejo na gramínea, que lhes confira maior resistência à intoxicação. _______________________________________________________________________________ ABSTRACTDue to the increasing deployment of Brachiaria spp in the soil of the Midwest, this project aims to evaluate the toxicity and performance of sheep grazing Brachiaria decumbens and Brachiaria brizantha, compared with Panicum maximum var Aires and Andropogon gayanus var Planaltina pastures. The presence of clinical signs of poisoning by Brachiaria spp and serum biochemical parameters: aspartate aminotransferase (AST), gamma-glutamyltransferase (GGT), total protein (TP), albumin, urea and creatinine were evaluated. The levels of saponins and Pithomyces chartarum spores in pasture samples were also evaluated. The experiment used 48 animals divided into homogeneous lots consisting of castrated males, average weight 20 kg, aged between four and five months, coming from herds with no previous contact with Brachiaria spp. for more than three consecutive years and naive animals, i.e., that never had contact with Brachiaria spp. The animal performance was similar in sheep kept in paddocks with B. decumbens, B. brizantha and P. maximum var Aires, but lower in the group that remained in the area formed by A. gayanus var Planaltina (p ≤ 0.05). Animals with previous contact Brachiaria spp. showed no clinical signs consistent with poisoning from the ingestion of forage. However, two naive animals kept in the paddock of B. decumbens, were intoxicated, and one of them died, suggesting a possible form of adaptation of animals to grazing on Brachiaria spp., which gives them some degree of resistance to poisoning

Michael M. Douglas - One of the best experts on this subject based on the ideXlab platform.

  • Exotic grass invasion alters microsite conditions limiting woody recruitment potential in an Australian savanna
    Nature Publishing Group, 2018
    Co-Authors: Samantha A. Setterfield, Peter J. Clifton, Lindsay B. Hutley, Natalie A. Rossiter-rachor, Michael M. Douglas
    Abstract:

    Abstract Andropogon gayanus Kunth. is a large African tussock grass invading Australia’s tropical savannas. Invasion results in more intense fires which increases the mortality rate of adult woody plants. Invasion may also affect community structure by altering the recruitment potential of woody plants. We investigated the effects of A. gayanus invasion on ground-level microclimate, and the carbon assimilation potential and recruitment potential of two Eucalyptus species. We compared microclimatic variables from the early wet-season and into the mid-dry season to coincide with the period of growth of A. gayanus. We assessed Eucalyptus recruitment by monitoring seedling establishment, growth and survival of experimentally sown seed, and estimating seedling density resulting from natural recruitment. A. gayanus invasion was associated with increased grass canopy height, biomass and cover. Following invasion, the understorey microclimate had significantly reduced levels of photon flux density, increased air temperatures and vapour pressure deficit. The conditions were less favourable for woody seedling with aboveground biomass of seedlings reduced by 26% in invaded plots. We estimated that invasion reduced daily carbon assimilation of woody seedlings by ~30% and reduced survivorship of Eucalyptus seedlings. Therefore, A. gayanus invasion reduces recruitment potential, contributing to the transformation of savanna to a grassland ecosystem

  • invasive Andropogon gayanus gamba grass alters litter decomposition and nitrogen fluxes in an australian tropical savanna
    Scientific Reports, 2017
    Co-Authors: Natalie A Rossiterrachor, Samantha A. Setterfield, Lindsay B. Hutley, Damien Mcmaster, Susanne Schmidt, Michael M. Douglas
    Abstract:

    The African grass Andropogon gayanus Kunth. is invading Australian savannas, altering their ecological and biogeochemical function. To assess impacts on nitrogen (N) cycling, we quantified litter decomposition and N dynamics of grass litter in native grass and A. gayanus invaded savanna using destructive in situ grass litter harvests and litterbag incubations (soil surface and aerial position). Only 30% of the A. gayanus in situ litter decomposed, compared to 61% of the native grass litter, due to the former being largely comprised of highly resistant A. gayanus stem. In contrast to the stem, A. gayanus leaf decomposition was approximately 3- and 2-times higher than the dominant native grass, Alloteropsis semilata at the surface and aerial position, respectively. Lower initial lignin concentrations, and higher consumption by termites, accounted for the greater surface decomposition rate of A. gayanus. N flux estimates suggest the N release of A. gayanus litter is insufficient to compensate for increased N uptake and N loss via fire in invaded plots. Annually burnt invaded savanna may lose up to 8.2% of the upper soil N pool over a decade. Without additional inputs via biological N fixation, A. gayanus invasion is likely to diminish the N capital of Australia's frequently burnt savannas.

  • turning up the heat the impacts of Andropogon gayanus gamba grass invasion on fire behaviour in northern australian savannas
    Diversity and Distributions, 2010
    Co-Authors: Samantha A. Setterfield, Lindsay B. Hutley, Michael M. Douglas, Natalie A Rossiterrachor, Richard J Williams
    Abstract:

    Aim  This study aimed to quantify changes in fire severity resulting from the invasion of Australia’s tropical savannas by the African grass Andropogon gayanus Kunth. (gamba grass). Location  Mesic savannas of the Northern Territory, Australia. Method  Byram’s fire-line intensity (If), fuel load and architecture, and two post-fire indicators of fire intensity – scorch height (SH) and char height (CH) of woody vegetation – were determined for fires in native grass savanna and A. gayanus invaded savanna. Leaf scorch is the height at which the fire’s radiant heat browns leaf tissue, and leaf char is the height that radiant heat blackens or consumes leaf tissue and provides an indirect measure of flame height. These data, and 5 years of similar data collected from the Kapalga Fire Project in Kakadu National Park, were used to develop empirical relationships between If and the post-fire indices of fire intensity. Results  A relationship between A. gayanus If and SH could not be developed because complete canopy scorch occurred in most A. gayanus fires, even at low If. In contrast, A. gayanus If was strongly correlated with CH. This empirical relationship was substantially different from that for native grass fires. For a given If, there was a significantly greater CH in invaded sites. This increase in radiant heat is attributable to the increased biomass (mean 3.6 t ha−1 in native grasses compared to 11.6 t ha−1 in A. gayanus) and height (approximately 0.5 m in native grasses compared to 4 m in A. gayanus) of the standing fine fuel. Main conclusion Andropogon gayanus invasion resulted in substantial changes in fire behaviour. This has important regional implications owing to the current (10,000–15,000 km2) and predicted (380,000 km2) area of invasion and the negative consequences for the native savanna biota that has evolved with frequent but relatively low-intensity fire.

  • seedling recruitment of the exotic grass Andropogon gayanus poaceae in northern australia
    Australian Journal of Botany, 2005
    Co-Authors: Trish A Flores, Samantha A. Setterfield, Michael M. Douglas
    Abstract:

    Andropogon gayanus Kunth. (Gamba grass), a tall perennial grass from Africa, is invading savanna ecosystems in northern Australia. This study investigated A. gayanus recruitment to determine the habitats at risk of invasion and to provide recommendations for its management. A. gayanus is able to establish and spread into new areas because of its high seed production (averaging 70 000 seeds m–2) and ability to establish across a range of habitats: from open woodlands on relatively dry lateritic soils to the more closed forests on black soil of the floodplain margins. Seedling emergence occurred in the absence of soil cultivation, although soil cultivation did increase emergence in the wetter habitats (Melaleuca uplands and floodplain margins). Seedling survival was high in the savanna (~90%) but low in the wetter habitats owing to wet-season inundation. A seed longevity trial based on burying seed in the field and retrieving between 1 and 12 months after burial showed that less than 1% of seeds survived in the seedbank after 12 months. Effective control programs are needed immediately because of the vast area and range of habitats in northern Australia that could potentially be invaded by A. gayanus. Management that can limit site disturbance and seed production, and can incorporate follow-up control for one to two years, should be an important part of an A. gayanus control strategy.

  • testing the grass fire cycle alien grass invasion in the tropical savannas of northern australia
    Diversity and Distributions, 2003
    Co-Authors: Natalie Rossiter, Samantha A. Setterfield, Michael M. Douglas, Lindsay B. Hutley
    Abstract:

    Invasive alien grasses can increase fuel loads, leading to changes in fire regimes of invaded ecosystems by increasing the frequency, intensity and spatial extent of fires. Andropogon gayanus Kunth. (Gamba grass), a tall perennial grass from Africa, is invading ecosystems in the Top End of northern Australia. To determine whether A. gayanus alters savanna fire regimes, we compared fuel loads and fire intensities at invaded sites with those from native grass savannas. Savanna invaded by A. gayanus had fuel loads up to seven times higher than those dominated by native grasses. This higher fuel load supported a fire that was on average eight times more intense than those recorded in native grass savannas at the same time of year (means 15700 ± 6200 and 2100 ± 290 kW m−1, respectively), and was the highest early dry season fire intensities ever recorded in the Northern Territory. These results suggest that A. gayanus is a serious threat to northern Australia's savannas, with the potential to alter vegetation structure and initiate a grass-fire cycle.

Martínez Sáez Silvio - One of the best experts on this subject based on the ideXlab platform.

  • Evaluación de gramíneas en pastoreo en suelo Fersialítico Rojo Parduzco Ferromagnesial de un ecosistema de sabana
    Ediciones Universidad de Camagüey., 2019
    Co-Authors: Curbelo Rodríguez, Lino M, Guevara Viera Raúl, Guevara Viera, Guillermo E, Ruiz Pierruguez Raúl, Gálvez González, Mario G, Martínez Sáez Silvio
    Abstract:

    The behavior of 6 improved grasses that had shown good results under cutting on a low fertility Red Brown Ferromagnesial Fersialitic soil was studied. A completely randomized design was used with three repetitions consisting of 0.25 ha plots, which were grazed every 30 to 35 days in rain and 40 to 50 days in dry conditions with a load of 12 rams per hectare. The species were fertilized with 100; 80 and 100 kg / ha per year of N, P and K respectively, the fractionated nitrogen in the rainy season. Availability was measured by rotation and botanical composition at the beginning and end of the experiment. Andropogon gayanus cv. CIAT 621 achieved the highest availability of dry matter, followed by Brachiara decumbens cv. CIAT 606, which in the rainy season of the first year and in the dry season of the second and third does not differ significantly from anthropogon, while Brachiaria purpurascens cv. gouache showed the worst behavior in this indicator. The persistence of Andropogon and Brachiaria 606 was superior (P <0.01) while the rest of the species decreased their population after three years of evaluation. It is recommended to extend to Andropogon gayanus cv. CIAT 621 and Brachiara decumbens cv. CIAT 606, given the edaphoclimatic conditions of the area.Se estudió el comportamiento de 6 gramíneas mejoradas que habían mostrado buenos resultados sometidas a corte en un suelo Fersialítico Rojo Parduzco Ferromagnesial de baja fertilidad. Se utilizó un diseño completamente aleatorizado con tres repeticio- nes que consistían en parcelas de 0,25 ha , las cuales fueron pastadas cada 30 a 35 días en lluvia y 40 a 50 días en seca con una carga de 12 carneros por hectárea. Las especies se fertilizaron con 100; 80 y 100 kg/ha anuales de N, P y K respectivamente, el nitrógeno fraccionado en la época lluviosa. La disponibilidad se midió por rotación y la composición botánica al inicio y final del experimento. Andropogon gayanus cv. CIAT 621 logró la mayor disponibilidad de materia seca, seguido de Brachiara decumbens cv. CIAT 606, que en la estación lluviosa del primer año y en la seca del segundo y tercero no difiere significativamente de an- dropogon, mientras que Brachiaria purpurascens cv. aguada mostró el peor comportamiento en este indicador. La persistencia de Andropogon y Brachiaria 606 resultó superior (P<0,01) mientras el resto de las especies disminuyeron su población a los tres años de evaluadas. Se recomienda extender a Andropogon gayanus cv. CIAT 621 y Brachiara  decumbens cv. CIAT 606, dadas las condiciones edafoclimáticas de la zona

  • Evaluación en corte de gramíneas forrajeras en suelo Fersialítico Rojo Parduzco Ferromagnesial de un ecosistema de sabana
    Ediciones Universidad de Camagüey., 2019
    Co-Authors: Curbelo Rodríguez Lino, Guevara Viera Raúl, Ruiz Pierruguez Raúl, Gálvez González, Mario G, Guevara Viera Guillermo, Martínez Sáez Silvio
    Abstract:

    En un suelo Fersialítico Rojo Parduzco Ferromagnesial característico de las sabanas infértiles del norte de la provincia de Camagüey, Cuba, se evaluaron 12 gramíneas mejoradas de los géneros Andropogon, Brachiaria, Cenchrus, Chloris, Cynodon, Digitaria y Panicum. Se seleccionó un diseño de bloques al azar con tres réplicas y parcelas de 30 m2, algunas veces a cortes cada 35 y 60 días en lluvia y seca, respectivamente. Se fertilizó a razón de 100-120-100 kg / ha / año de N, P y K respectivamente, el N fraccionado en la lluvia. No se necesita riego. A. gayanus cv. CIAT 621 seleccionó rendimientos específicos superiores (P <0,01) al resto de las especies, con 20,3 y 19,3 t de MS / ha / año para el primer y segundo año de evaluación, respectivamente, seguido de B. decumbens CV. CIAT 606, que difirió del resto de las gramíneas, mientras que los cultivos de C. dactylon fueron los de más bajos rendimientos. El mayor contenido de PB lo utilizado P. maximum cv. likoni (9,3 y 7,5% en lluvia y seca respectivamente) y A. gayanus resultó significativamente superior (P <0,01) en relación con los niveles de P, aunque en general todas las especies tenores muy bajas de este elemento En cuanto a la persistencia, Andropogon gayanus y Brachiaria decumbens terminaron con las mejores poblaciones (84 y 86% respectivamente). Se consideran que las especies de mejor comportamiento son evaluadas en pastoreo y propagadas paulatinamente en la zona.En un suelo Fersialítico Rojo Parduzco Ferromagnesial característico de las sabanas infértiles del norte de la provincia de Ca- magüey, Cuba, se evaluaron 12 gramíneas mejoradas de los géneros Andropogon, Brachiaria, Cenchrus, Chloris, Cynodon, Digi- taria y Panicum. Se utilizó un diseño de bloques al azar con tres réplicas y parcelas de 30 m2 sometidas a cortes cada 35 y 60 días en lluvia y seca, respectivamente. Se fertilizó a razón de 100-120-100 kg/ha/año de N, P y K respectivamente, el N fraccionado en la lluvia. No se utilizó riego. A. gayanus cv. CIAT 621 mostró rendimientos significativamente superiores (P<0,01) al resto de las especies, con 20,3 y 19,3 t de MS/ha/año para el primer y segundo año de evaluación, respectivamente, seguido de B. decumbens cv. CIAT 606, que difirió del resto de las gramíneas, mientras que los cultivares de C. dactylon fueron los de más bajos rendi- mientos. El mayor contenido de PB lo alcanzó P. maximum cv. likoni (9,3 y 7,5 % en lluvia y seca respectivamente) y A. gayanus resultó significativamente superior (P<0,01) en relación con los niveles de P, aunque en general todas las especies mostraron tenores muy bajos de este elemento. En cuanto a la persistencia, Andropogon gayanus y Brachiaria decumbens terminaron con las mejores poblaciones (84 y 86 % respectivamente). Se sugiere que las especies de mejor comportamiento sean evaluadas en pasto- reo y propagadas paulatinamente en la zona