The Experts below are selected from a list of 276 Experts worldwide ranked by ideXlab platform
Katherine D. Heineman - One of the best experts on this subject based on the ideXlab platform.
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Evaluating Seed-banking Capacity and Propagation Potential of Endangered Sierra Bermeja Grasses: Aristida chaseae and Aristida portoricensis
2018Co-Authors: Joyce Maschinski, Jennifer Possley, Omar A. Monsegur Rivera, Katherine D. HeinemanAbstract:Of the 2329 plant species that are native to Puerto Rico, 188 are grasses (Poaceae) and nearly 20% of those are critically imperiled. To address gaps in knowledge of US endangered Aristida chaseae (Chase’s Threeawn) and Aristida portoricensis (Pelos del Diablo) from Sierra Bermeja in southwestern Puerto Rico, we conducted experiments to determine viability of seeds produced in the wild, germination requirements, and ability to be stored under cold, dry conditions. Both species produced low proportions of viable seed in the wild (Chase’s Threeawn:
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evaluating seed banking capacity and propagation potential of endangered sierra bermeja grasses Aristida chaseae and Aristida portoricensis
Caribbean Naturalist, 2018Co-Authors: Joyce Maschinski, Jennifer Possley, Omar Monsegur A Rivera, Katherine D. HeinemanAbstract:Of the 2329 plant species that are native to Puerto Rico, 188 are grasses (Poaceae) and nearly 20% of those are critically imperiled. To address gaps in knowledge of US endangered Aristida chaseae (Chase’s Threeawn) and Aristida portoricensis (Pelos del Diablo) from Sierra Bermeja in southwestern Puerto Rico, we conducted experiments to determine viability of seeds produced in the wild, germination requirements, and ability to be stored under cold, dry conditions. Both species produced low proportions of viable seed in the wild (Chase’s Threeawn: <7%, Pelos del Diablo: 34%); seeds germinated at higher rates when desiccated than when fresh or desiccated and frozen. Mean time to germination was slow in both species: 86 d for fresh Pelos del Diablo and 50 d for Chase’s Threeawn. Mean germination time in Chase’s Threeawn slowed to over 90 d in drying and freezing treatments, while these treatments increased the rate of germination in Pelos del Diablo seeds. Both taxa can grow well and produce seed when grown in containers with well-drained soils; therefore, growing plants for restoration is possible. Both species’ seeds can be dried and stored at freezing temperatures, at least for the short term. The longevity of these species’ seeds held in frozen storage is unknown; thus, we advise further testing of seeds after 3, 5, and 10 y in frozen storage.
Joyce Maschinski - One of the best experts on this subject based on the ideXlab platform.
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Evaluating Seed-banking Capacity and Propagation Potential of Endangered Sierra Bermeja Grasses: Aristida chaseae and Aristida portoricensis
2018Co-Authors: Joyce Maschinski, Jennifer Possley, Omar A. Monsegur Rivera, Katherine D. HeinemanAbstract:Of the 2329 plant species that are native to Puerto Rico, 188 are grasses (Poaceae) and nearly 20% of those are critically imperiled. To address gaps in knowledge of US endangered Aristida chaseae (Chase’s Threeawn) and Aristida portoricensis (Pelos del Diablo) from Sierra Bermeja in southwestern Puerto Rico, we conducted experiments to determine viability of seeds produced in the wild, germination requirements, and ability to be stored under cold, dry conditions. Both species produced low proportions of viable seed in the wild (Chase’s Threeawn:
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evaluating seed banking capacity and propagation potential of endangered sierra bermeja grasses Aristida chaseae and Aristida portoricensis
Caribbean Naturalist, 2018Co-Authors: Joyce Maschinski, Jennifer Possley, Omar Monsegur A Rivera, Katherine D. HeinemanAbstract:Of the 2329 plant species that are native to Puerto Rico, 188 are grasses (Poaceae) and nearly 20% of those are critically imperiled. To address gaps in knowledge of US endangered Aristida chaseae (Chase’s Threeawn) and Aristida portoricensis (Pelos del Diablo) from Sierra Bermeja in southwestern Puerto Rico, we conducted experiments to determine viability of seeds produced in the wild, germination requirements, and ability to be stored under cold, dry conditions. Both species produced low proportions of viable seed in the wild (Chase’s Threeawn: <7%, Pelos del Diablo: 34%); seeds germinated at higher rates when desiccated than when fresh or desiccated and frozen. Mean time to germination was slow in both species: 86 d for fresh Pelos del Diablo and 50 d for Chase’s Threeawn. Mean germination time in Chase’s Threeawn slowed to over 90 d in drying and freezing treatments, while these treatments increased the rate of germination in Pelos del Diablo seeds. Both taxa can grow well and produce seed when grown in containers with well-drained soils; therefore, growing plants for restoration is possible. Both species’ seeds can be dried and stored at freezing temperatures, at least for the short term. The longevity of these species’ seeds held in frozen storage is unknown; thus, we advise further testing of seeds after 3, 5, and 10 y in frozen storage.
P G Filet - One of the best experts on this subject based on the ideXlab platform.
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spring fire effects on two Aristida bothriochloa native pastures in central queensland australia
Rangeland Journal, 2018Co-Authors: R G Silcock, P G Filet, Trevor J Hall, Paul Jones, J DouglasAbstract:Controlled burns are commonly used to suppress woody plant regrowth and to remove accumulated unpalatable pasture from rangelands and occasionally to alter pasture composition in native pastures in central Queensland, Australia. Outcomes can be somewhat unpredictable and short-term, and reliable evidence is needed to confirm the likely long-term efficacy of such fires. We imposed a regime of repeated spring burns on native Aristida/Bothriochloa pastures growing in two contrasting eucalypt woodlands of central Queensland to determine the effects on pasture composition, ground cover, landscape stability and woody plant recruitment, all in the absence of grazing. The sites selected were a silver-leaved ironbark (Eucalyptus melanophloia F.Muell.) woodland and a poplar box (E. populnea F.Muell.) woodland. Weather conditions precluded spring burns in 3 years out of 7 at the silver-leaved ironbark site and in 2 years out of 8 at the poplar box site. The burn intensity was variable, and frequent fires produced a marked change in abundance of only a few pasture species. Depending on the site, fires significantly increased the frequency of Enneapogon spp., Bothriochloa bladhii (Retz.) S.T.Blake and Dichanthium sericeum (R.Br.) A.Camus and reduced the frequency of some minor components such as Cymbopogon spp., Panicum effusum R.Br., Cenchrus ciliaris L. and, ephemerally, that of some forbs. Contrary to expectation, only Aristida calycina R.Br. declined in abundance among the many Aristida species present, and the abundance of Heteropogon contortus (L.) P.Beauv. ex Roem. & Schult. barely increased under regular spring fires. The total germinable seeds of herbaceous species in the soil each spring was significantly reduced by burning in the previous spring. Repeated spring fires rarely reinforced any initial change induced by burning, and slightly lowered average ground cover as well as various indices of landscape stability and ecosystem functionality. Changes produced were not always consistent across the two communities. Though prescribed burning is often important for maintaining grazing productivity and landscape values, very regular use is not recommended.
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Spring fire effects on two Aristida/Bothriochloa native pastures in central Queensland, Australia
Rangeland Journal, 2018Co-Authors: R G Silcock, P G Filet, Trevor J Hall, Paul Jones, J DouglasAbstract:Controlled burns are commonly used to suppress woody plant regrowth and to remove accumulated unpalatable pasture from rangelands and occasionally to alter pasture composition in native pastures in central Queensland, Australia. Outcomes can be somewhat unpredictable and short-term, and reliable evidence is needed to confirm the likely long-term efficacy of such fires. We imposed a regime of repeated spring burns on native Aristida/Bothriochloa pastures growing in two contrasting eucalypt woodlands of central Queensland to determine the effects on pasture composition, ground cover, landscape stability and woody plant recruitment, all in the absence of grazing. The sites selected were a silver-leaved ironbark (Eucalyptus melanophloia F.Muell.) woodland and a poplar box (E. populnea F.Muell.) woodland. Weather conditions precluded spring burns in 3 years out of 7 at the silver-leaved ironbark site and in 2 years out of 8 at the poplar box site. The burn intensity was variable, and frequent fires produced a marked change in abundance of only a few pasture species. Depending on the site, fires significantly increased the frequency of Enneapogon spp., Bothriochloa bladhii (Retz.) S.T.Blake and Dichanthium sericeum (R.Br.) A.Camus and reduced the frequency of some minor components such as Cymbopogon spp., Panicum effusum R.Br., Cenchrus ciliaris L. and, ephemerally, that of some forbs. Contrary to expectation, only Aristida calycina R.Br. declined in abundance among the many Aristida species present, and the abundance of Heteropogon contortus (L.) P.Beauv. ex Roem. & Schult. barely increased under regular spring fires. The total germinable seeds of herbaceous species in the soil each spring was significantly reduced by burning in the previous spring. Repeated spring fires rarely reinforced any initial change induced by burning, and slightly lowered average ground cover as well as various indices of landscape stability and ecosystem functionality. Changes produced were not always consistent across the two communities. Though prescribed burning is often important for maintaining grazing productivity and landscape values, very regular use is not recommended.
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grazing pressure impacts on two Aristida bothriochloa native pasture communities of central queensland
Rangeland Journal, 2017Co-Authors: Trevor J Hall, R G Silcock, Paul Jones, P G FiletAbstract:Managing native pastures for sustainable and economic production requires a good understanding of grazing effects on pasture dynamics. The Aristida/Bothriochloa pastures of north-eastern Australia are important for cattle production but little data on grazing pressure impacts on pastures are available to guide management decisions of producers, for land management education programs, or for predictive modelling. To address this deficiency, four different continuous grazing intensities were imposed on woodland communities over 7 or 8 years at two sites: a Eucalyptus populnea (poplar box) and a E. melanophloia (silver-leaved ironbark) community. Both sites had replicated paddocks grazed at a low, medium or high grazing pressure by +/− tree killing using herbicide (12 paddocks), and 12 ungrazed (nil grazing pressure) 1-ha plots subjected to the same tree-killing contrasts. Grazed paddock areas were fixed and varied between 3.5 and 21.5 ha. Differential grazing pressures were reset each autumn, by adjusting cattle numbers to consume over the next year the equivalent of 0%, 25%, 50% or 75% of the standing pasture mass available. Pasture grasses suitable as indicators of grazing pressure were identified for both communities. Under low grazing pressure, Themeda triandra (kangaroo grass) was the only desirable grass to show a significant increase in total contribution over time at both sites, although Dichanthium sericeum (Queensland bluegrass) also increased its contribution at the poplar box site. Chloris species increased their contribution as grazing pressure increased. The proportion of less palatable Aristida spp. (wiregrasses) in the pasture was not affected by high grazing pressure, although they increased at low grazing pressure in the poplar box community. There were no consistent changes in native legumes or weedy forb species to any treatment. Increasing grazing pressure had a greater negative effect on pasture mass, ground cover and pasture crown cover area than on changing species composition. Most changes in composition due to grazing pressure were smaller than those associated with variable seasonal rainfall, and were greater in the poplar box community. In above-average rainfall years grazing up to 50% of autumn standing pasture mass had no detrimental effect on composition in treeless poplar box country in the short term. The pastures remained stable or improved in both communities when grazing pressure was set annually to utilise 25% of the standing autumn forage.
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Grazing pressure impacts on two Aristida/Bothriochloa native pasture communities of central Queensland
Rangeland Journal, 2017Co-Authors: Trevor J Hall, R G Silcock, Paul Jones, P G FiletAbstract:Managing native pastures for sustainable and economic production requires a good understanding of grazing effects on pasture dynamics. The Aristida/Bothriochloa pastures of north-eastern Australia are important for cattle production but little data on grazing pressure impacts on pastures are available to guide management decisions of producers, for land management education programs, or for predictive modelling. To address this deficiency, four different continuous grazing intensities were imposed on woodland communities over 7 or 8 years at two sites: a Eucalyptus populnea (poplar box) and a E. melanophloia (silver-leaved ironbark) community. Both sites had replicated paddocks grazed at a low, medium or high grazing pressure by +/− tree killing using herbicide (12 paddocks), and 12 ungrazed (nil grazing pressure) 1-ha plots subjected to the same tree-killing contrasts. Grazed paddock areas were fixed and varied between 3.5 and 21.5 ha. Differential grazing pressures were reset each autumn, by adjusting cattle numbers to consume over the next year the equivalent of 0%, 25%, 50% or 75% of the standing pasture mass available. Pasture grasses suitable as indicators of grazing pressure were identified for both communities. Under low grazing pressure, Themeda triandra (kangaroo grass) was the only desirable grass to show a significant increase in total contribution over time at both sites, although Dichanthium sericeum (Queensland bluegrass) also increased its contribution at the poplar box site. Chloris species increased their contribution as grazing pressure increased. The proportion of less palatable Aristida spp. (wiregrasses) in the pasture was not affected by high grazing pressure, although they increased at low grazing pressure in the poplar box community. There were no consistent changes in native legumes or weedy forb species to any treatment. Increasing grazing pressure had a greater negative effect on pasture mass, ground cover and pasture crown cover area than on changing species composition. Most changes in composition due to grazing pressure were smaller than those associated with variable seasonal rainfall, and were greater in the poplar box community. In above-average rainfall years grazing up to 50% of autumn standing pasture mass had no detrimental effect on composition in treeless poplar box country in the short term. The pastures remained stable or improved in both communities when grazing pressure was set annually to utilise 25% of the standing autumn forage.
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floristic composition and pasture condition of Aristida bothriochloa pastures in central queensland i pasture floristics
Rangeland Journal, 2015Co-Authors: R G Silcock, P G Filet, Trevor J Hall, A Kelly, D Osten, C M Schefe, P T KnightsAbstract:A survey was conducted in central inland Queensland, Australia of 108 sites that were deemed to contain Aristida/Bothriochloa native pastures to quantitatively describe the pastures and attempt to delineate possible sub-types. The pastures were described in terms of their floristic composition, plant density and crown cover. There were generally ~20 (range 5–33) main pasture species at a site. A single dominant perennial grass was rare with three to six prominent species the norm. Chrysopogon fallax (golden-beard grass) was the perennial grass most consistently found in all pastures whereas Aristida calycina (dark wiregrass), Enneapogon spp. (bottlewasher grasses), Brunoniella australis (blue trumpet) and Panicum effusum (hairy panic) were all regularly present. The pastures did not readily separate into broad floristic sub-groups, but three groups that landholders could recognise from a combination of the dominant tree and soil type were identified. The three groups were Eucalyptus crebra (narrow-leaved ironbark), E. melanophloia (silver-leaved ironbark) and E. populnea (poplar box). The pastures of the three main sub-groups were then characterised by the prominent presence, singly or in combination, of Bothriochloa ewartiana (desert bluegrass), Eremochloa bimaculata (poverty grass), Bothriochloa decipiens (pitted bluegrass) or Heteropogon contortus (black speargrass). The poplar box group had the greatest diversity of prominent grasses whereas the narrow-leaved ironbark group had the least. Non-native Cenchrus ciliaris (buffel grass) and Melinis repens (red Natal grass) were generally present at low densities. Describing pastures in terms of frequency of a few species or species groups sometimes failed to capture the true nature of the pasture but plant abundance for most species, as density, herbage mass of dry matter or plant crown cover, was correlated with its recorded frequency. A quantitative description of an average pasture in fair condition is provided but it was not possible to explain why some species often occur together or fail to co-exist in Aristida/Bothriochloa pastures, for example C. ciliaris and E. bimaculata rarely co-exist whereas Tragus australianus (small burrgrass) and Enneapogon spp. are frequently recorded together. Most crown cover was provided by perennial grasses but many of these are Aristida spp. (wiregrasses) and not regarded as useful forage for livestock. No new or improved categorisation of the great variation evident in the Aristida/Bothriochloa native pasture type can be given despite the much improved detail provided of the floristic composition by this survey.
Jennifer Possley - One of the best experts on this subject based on the ideXlab platform.
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Evaluating Seed-banking Capacity and Propagation Potential of Endangered Sierra Bermeja Grasses: Aristida chaseae and Aristida portoricensis
2018Co-Authors: Joyce Maschinski, Jennifer Possley, Omar A. Monsegur Rivera, Katherine D. HeinemanAbstract:Of the 2329 plant species that are native to Puerto Rico, 188 are grasses (Poaceae) and nearly 20% of those are critically imperiled. To address gaps in knowledge of US endangered Aristida chaseae (Chase’s Threeawn) and Aristida portoricensis (Pelos del Diablo) from Sierra Bermeja in southwestern Puerto Rico, we conducted experiments to determine viability of seeds produced in the wild, germination requirements, and ability to be stored under cold, dry conditions. Both species produced low proportions of viable seed in the wild (Chase’s Threeawn:
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evaluating seed banking capacity and propagation potential of endangered sierra bermeja grasses Aristida chaseae and Aristida portoricensis
Caribbean Naturalist, 2018Co-Authors: Joyce Maschinski, Jennifer Possley, Omar Monsegur A Rivera, Katherine D. HeinemanAbstract:Of the 2329 plant species that are native to Puerto Rico, 188 are grasses (Poaceae) and nearly 20% of those are critically imperiled. To address gaps in knowledge of US endangered Aristida chaseae (Chase’s Threeawn) and Aristida portoricensis (Pelos del Diablo) from Sierra Bermeja in southwestern Puerto Rico, we conducted experiments to determine viability of seeds produced in the wild, germination requirements, and ability to be stored under cold, dry conditions. Both species produced low proportions of viable seed in the wild (Chase’s Threeawn: <7%, Pelos del Diablo: 34%); seeds germinated at higher rates when desiccated than when fresh or desiccated and frozen. Mean time to germination was slow in both species: 86 d for fresh Pelos del Diablo and 50 d for Chase’s Threeawn. Mean germination time in Chase’s Threeawn slowed to over 90 d in drying and freezing treatments, while these treatments increased the rate of germination in Pelos del Diablo seeds. Both taxa can grow well and produce seed when grown in containers with well-drained soils; therefore, growing plants for restoration is possible. Both species’ seeds can be dried and stored at freezing temperatures, at least for the short term. The longevity of these species’ seeds held in frozen storage is unknown; thus, we advise further testing of seeds after 3, 5, and 10 y in frozen storage.
Omar Monsegur A Rivera - One of the best experts on this subject based on the ideXlab platform.
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evaluating seed banking capacity and propagation potential of endangered sierra bermeja grasses Aristida chaseae and Aristida portoricensis
Caribbean Naturalist, 2018Co-Authors: Joyce Maschinski, Jennifer Possley, Omar Monsegur A Rivera, Katherine D. HeinemanAbstract:Of the 2329 plant species that are native to Puerto Rico, 188 are grasses (Poaceae) and nearly 20% of those are critically imperiled. To address gaps in knowledge of US endangered Aristida chaseae (Chase’s Threeawn) and Aristida portoricensis (Pelos del Diablo) from Sierra Bermeja in southwestern Puerto Rico, we conducted experiments to determine viability of seeds produced in the wild, germination requirements, and ability to be stored under cold, dry conditions. Both species produced low proportions of viable seed in the wild (Chase’s Threeawn: <7%, Pelos del Diablo: 34%); seeds germinated at higher rates when desiccated than when fresh or desiccated and frozen. Mean time to germination was slow in both species: 86 d for fresh Pelos del Diablo and 50 d for Chase’s Threeawn. Mean germination time in Chase’s Threeawn slowed to over 90 d in drying and freezing treatments, while these treatments increased the rate of germination in Pelos del Diablo seeds. Both taxa can grow well and produce seed when grown in containers with well-drained soils; therefore, growing plants for restoration is possible. Both species’ seeds can be dried and stored at freezing temperatures, at least for the short term. The longevity of these species’ seeds held in frozen storage is unknown; thus, we advise further testing of seeds after 3, 5, and 10 y in frozen storage.