Speargrass (Heteropogon Contortus) in Australia : Dynamics of Species and Community.

1995 ◽  
Vol 17 (1) ◽  
pp. 3 ◽  
Author(s):  
AC Grice ◽  
S Mcintyre
Keyword(s):  
Animal Production ◽  
Perennial Grasses ◽  
Ecological Knowledge ◽  
Heteropogon Contortus ◽  
Management Actions ◽  
Ecological Understanding ◽  
State And Transition Models ◽  
Low Levels ◽  
Available Information ◽  
Extreme Seasonality

The perennial tallgrass Heteropogon contortus is widespread and both ecologically and economically important. It often dominates the understorey of Eucalyptus woodlands in tropical and subtropical Australia. We present an historical overview of management and research in these important grasslands and review currently available information, particularly in relation to change at the community level. The use of H, contortus communities for extensive pastoralism led to its increase at the expense of other grasses. Ecological studies sought to explain how it came to dominate large areas but much research focussed on identifying pasture species, particularly legumes, that could replace or supplement what were seen as unproductive native grasses. Other efforts were directed at improving the generally low levels of animal production that resulted from the extreme seasonality of forage quality, and examining the animal production consequences of various management actions. There is some evidence that H. contortus has declined over large areas since the 1970s, but this process and its mechanisms are not well documented. Generally, research that has taken an empirical approach to improving animal production is poorly placed to provide a comprehensive ecological understanding. This is evident in several attempts to synthesise an ecological .understanding of H. contortus communities, notably in the form of state-and-transition models. These models contain generalities, some of which have little confirmation in experimental results. The geographic range and temporal variability of H. contortus communities make it difficult to generalise on the basis of single site, short term experiments that investigate one or a few factors in isolation. There is an increasing awareness of the need for sustainable management of native and natural pastures, including the H. contortus grasslands. Meeting this need will require the maintenance of the perennial grasses of northern Australian savannas and an ecological knowledge that can predict change in a variety of circumstances and locations.

scholarly journals Landscape Conservation Forecasting for Data-Poor at-Risk Species on Western Public Lands, United States

Climate ◽  
2021 ◽  
Vol 9 (5) ◽  
pp. 79
Author(s):  
Louis Provencher ◽  
Kevin Badik ◽  
Tanya Anderson ◽  
Joel Tuhy ◽  
Dan Fletcher ◽  
...  
Keyword(s):  
At Risk ◽  
Habitat Suitability ◽  
Public Lands ◽  
Ecological Systems ◽  
Climate Impacts ◽  
Perennial Grasses ◽  
Prairie Dog ◽  
Sage Grouse ◽  
Global Circulation Models ◽  
Management Actions

Managing vast federal public lands governed by multiple land use policies creates challenges when demographic data on at-risk species are lacking. The U.S. Bureau of Land Management Cedar City Field Office used this project in the Black Mountains (Utah) to inform vegetation management supporting at-risk greater sage-grouse and Utah prairie dog planning. Ecological systems were mapped from satellite remote sensing imagery and used to model species habitat suitability under two levels of management activity (custodial, preferred) and climate scenarios for historic and two global circulation models. Spatial state-and-transition models of ecological systems were simulated for all six scenarios up to 60 years while coupled with expert-developed habitat suitability indices. All ecological systems are at least moderately departed from reference conditions in 2012, whereas habitat suitability was 50.5% and 48.4% for sage-grouse and prairie dog, respectively. Management actions replaced non-native annual grasslands with perennial grasses, removed conifers, and controlled exotic forbs. The drier climate most affected ecological departure and prairie dog habitat suitability at 30 years only. Different climates influenced spatial patterns of sage-grouse habitat suitability, but nonspatial values were unchanged. Climate impacts on fire, vegetation succession, and restoration explain many results. Front-loading restoration is predicted to benefit under future drier climate.

scholarly journals Overview on the distribution of gorgonian species in Tunisian marine coastal waters (central Mediterranean)

2018 ◽  
Vol 82 (1) ◽  
pp. 55 ◽  
Author(s):  
Raouia Ghanem ◽  
Emna Soufi Kechaou ◽  
Jamila Ben Souissi ◽  
Joaquim Garrabou
Keyword(s):  
Coastal Waters ◽  
Local Ecological Knowledge ◽  
Conservation Status ◽  
Ecological Knowledge ◽  
Central Mediterranean ◽  
Management Actions ◽  
Conservation Actions ◽  
Gorgonian Species ◽  
Species Richness And Abundance ◽  
And Function

Gorgonian species play an important ecological role in the structure and function of marine communities. Human activities are negatively affecting the conservation status of gorgonian populations in the Mediterranean. Acquiring knowledge of gorgonian distribution is therefore a key step required to promote efficient management and conservation actions. However, information on the distribution of gorgonian species is lacking in many Mediterranean areas. This study aimed to provide an overview of the geographic and bathymetric distributions of gorgonians in the coastal waters of the Tunisian coast (1136 km). The sampling design encompassed three sectors, 27 localities and 87 sites. Information was collected from scuba diving (26 sites) and local ecological knowledge surveys of fishermen and divers (132 interviews), as well as from a literature review. Overall, the occurrence of eight gorgonians was confirmed at 54 out of the 87 sites surveyed in Tunisian coastal waters (7-120 m depth). The species that were found were Eunicella singularis, Eunicella cavolini, Paramuricea clavata, Paramuricea macrospina, Leptogorgia sarmentosa, Eunicella verrucosa, Corallium rubrum and Ellisella paraplexauroides. The highest gorgonian species richness and abundance was recorded in northern, followed by eastern Tunisian waters. In the southern areas only one species was recorded. This pattern was related to the rocky substrate that characterizes the northern and eastern coasts of Tunisia. This study is the first to report the occurrence of E. singularis, E. cavolini, E. verrucosa and Leptogorgia sarmentosa in northern and eastern Tunisian waters. The results are discussed in the hope of guiding future conservation and management actions for gorgonian assemblages in Tunisia.

Satellite remote sensing and natural disturbances

2019 ◽  
pp. 37-50
Author(s):  
Nathalie Pettorelli
Keyword(s):  
Remote Sensing ◽  
Satellite Remote Sensing ◽  
Accurate Information ◽  
Ecological Knowledge ◽  
Natural Disturbances ◽  
Ecosystem Impacts ◽  
Spatial And Temporal Scales ◽  
Continental Scale ◽  
Management Actions ◽  
Wild Fire

This chapter provides an overview of how satellite remote sensing can help map the occurrence, and risk of occurrence, of several environmental disturbances; assess the extent of the associated damages; and monitor the recovery of the areas impacted by these disturbances. It particularly focuses on floods, wild fires, droughts, frost, extreme winter warming events, infestations and blooms, and bleaching events, as these are all well-known natural disturbances likely to change in frequency of occurrence and intensity over the coming decades. Through the use of examples, this chapter demonstrates how the utility of satellite remote sensing resides in the ability it provides to separate and characterise (i.e. through form, intensity, and trajectory) disturbances and responses at various spatial and temporal scales, thereby facilitating ecological knowledge expansion and the identification of relevant management actions. In particular, this contribution shows how satellites offer multiple opportunities to gain accurate information on the location, spatial extent, and duration of disturbances at the continental scale, which is needed to evaluate the ecosystem impacts of land cover changes due to, for example, wild fire, insect epidemics, and flooding, thereby reducing uncertainties in our ability to model global carbon budgets.

Pasture management in semi-arid tropical woodlands: dynamics of perennial grasses

2007 ◽  
Vol 29 (1) ◽  
pp. 87 ◽  
Author(s):  
John G. McIvor
Keyword(s):  
Perennial Grasses ◽  
Individual Species ◽  
Stocking Rate ◽  
Pasture Management ◽  
Management Options ◽  
Exotic Grasses ◽  
Heteropogon Contortus ◽  
Basal Cover ◽  
Growing Seasons ◽  
North East

The effects of a range of pasture management options (introduced legumes and grasses, superphosphate, timber treatment, cultivation before sowing and stocking rate) on the basal cover of perennial grasses were measured from 1982 to 1991 at two sites, ‘Hillgrove’ and ‘Cardigan’, near Charters Towers, in north-east Queensland. Colonisation and survival of eight native and exotic grasses were followed in permanent quadrats in a subset of treatments. Overall, there were significant changes in total basal cover of plots between years and with tree killing, but no significant differences in sown pastures, fertiliser or stocking rate. Basal cover increased when defoliation levels were less than 40% but increases were smaller at higher levels of defoliation and basal cover often declined when defoliation was greater than 60%. Basal cover declined when growing seasons were <10 weeks, remained static with 10–15 weeks growth, and increased when growing seasons were 16 weeks or longer. There was some colonisation in all years but large differences between years. The differences in colonisation between systems were generally small but there was a general trend for higher colonisation at higher stocking rates. Bothriochloa ewartiana (Domin) C.E.Hubb. and Chrysopogon fallax S.T.Blake had low, Heteropogon contortus (L.) P.Beauv. ex Roem.&Schult., Cenchrus ciliaris L. and Aristida spp. had intermediate, and Bothriochloa pertusa (L.) A.Camus and Urochloa mosambicensis (Hack.) Dandy had high colonising ability. Survival of individual species was generally similar at both sites except for Urochloa mosambicensis. Heteropogon contortus and U. mosambicensis at ‘Hillgrove’ were short-lived (<10% survival after 4 years), B. ewartiana, Themeda triandra Forssk. and Aristida spp. had intermediate survival (10–50%), and C. ciliaris, C. fallax, B. pertusa and U. mosambicensis at ‘Cardigan’ were long-lived (>50% survival). Annual survival rates increased with plant age, were higher in good growing seasons than in poor seasons, were higher for large plants than small plants, and were lower at high defoliation levels than where defoliation was less severe. The differences between species in ability to colonise and survive, and the small influence of management compared to seasonal effects on survival, are discussed to explain species performance in pastures.

Steer gains, pasture yield and pasture composition on native pasture and on native pasture oversown with Indian couch (Bothriochloa pertusa) at three stocking rates

1997 ◽  
Vol 37 (7) ◽  
pp. 755 ◽  
Author(s):  
R. J. Jones
Keyword(s):  
Perennial Grasses ◽  
Grass Species ◽  
Stocking Rate ◽  
Pasture Grass ◽  
Pasture Production ◽  
Heteropogon Contortus ◽  
Native Pasture ◽  
Unit Increase ◽  
Stocking Rates ◽  
Pasture Yield

Summary. Pasture production and steer liveweight gain were compared on native pasture (Bothriochloa decipiens, Heteropogon contortus, Themeda triandra and Chrysopogon fallax) and on native pasture oversown with Indian couch or Indian bluegrass (Bothriochloa pertusa). This grass was not a planned introduction to the area but is spreading in Central and North Queensland and its value as a pasture species is questioned by graziers. There were 3 nominal stocking rates of 0.3, 0.6 and 0.9 steers/ha. Each paddock was stocked with 3 steers of stratified ages. The experiment was sown in March 1988 and terminated in June 1993. The experiment, sited 50 km south of Townsville in eucalypt woodland on a solodic-solodised-solonetz soil, was sown in March 1988 and terminated in June 1993. Increases in stocking rate resulted in a linear decline in both pasture yield (by 3–5 t/unit increase in stocking rate) and steer gains (by more than 100 kg/unit increase in stocking rate). Differences between pastures were apparent only at the medium and high stocking rates where, over time, Indian couch gave higher pasture yields and steer gains. Younger steers gained far more weight than older steers. Mean gains over 3 years were weaners 125 kg/year, yearlings 93 kg/year and 2-year-old steers 46 kg/year. Native pasture remained fairly stable botanically at the low stocking rate, but the tufted perennial grass species declined at both the medium and high stocking rates. Sowing Indian couch hastened the botanical changes due to stocking rate, and it became the dominant species at these higher stocking rates. At the low stocking rate, the contribution of Indian couch declined from initial values indicating that this is not an invasive species in the area at a low stocking rate. Contribution of Indian couch to pasture yield was linearly related to stocking rate. Nutritional quality of the Indian couch was similar to the other native perennial grasses though calcium concentration was higher. Increased steer gains were related to higher yield on Indian couch pastures at the higher stocking rates rather than to improved quality. Maximum liveweight gain/ha was achieved at about 0.6 steers/ha. Stocking at 0.9 steers/ha was not sustainable. Even at the low stocking rate, steers would need to spend about 2.8 years on the pastures after weaning to reach 500 kg liveweight. It was concluded that B. pertusa is a useful pasture grass in this environment giving steer gains equal to, or higher than, the gains from the native pasture which it replaced.

Managing for rainfall variability: impacts of grazing strategies on perennial grass dynamics in a dry tropical savanna

2011 ◽  
Vol 33 (2) ◽  
pp. 209 ◽  
Author(s):  
D. M. Orr ◽  
P. J. O'Reagain
Keyword(s):  
Carrying Capacity ◽  
Rainfall Variability ◽  
Perennial Grasses ◽  
Heteropogon Contortus ◽  
Heavy Grazing ◽  
Average Rainfall ◽  
Sustainable Grazing ◽  
Grazing Strategies ◽  
The Impact

Rainfall variability remains a major challenge to sustainable grazing management in northern Australia with perennial grasses the key to the stability of the resources that maintain a sustainable grazing industry. This paper describes the dynamics of five perennial grasses – Bothriochloa ewartiana (Domin) C.E. Hubb., Chrysopogon fallax S.T. Blake, Aristida spp., Panicum effusum R. Br. and Heteropogon contortus (L.) P. Beauv. ex Roem. & Schult. in relation to three grazing strategies – moderate stocking at long-term carrying capacity, heavy stocking and rotational wet season spelling. The research was conducted in permanent quadrats on the predominant land type in an extensive grazing study in an Aristida-Bothriochloa pasture in north Australia between 1998 and 2010. Summer rainfall was above average for two periods – 1998 – 2001 and 2008 – 2010 with drought and below-average rainfall from 2002 to 2007. Low rainfall affected the dynamics of all grasses by reducing survival and basal area through its effect on plant size; this impact was most noticeable for the shorter-lived Aristida spp., P. effusum and H. contortus. The impact of grazing was greatest on the long-lived B. ewartiana and C. fallax; this effect was accentuated by the 2002–07 drought. Heavy grazing during this period further reduced the survival and size of B. ewartiana in comparison with the moderate stocking and rotational spell treatments. In contrast, the survival of C. fallax was reduced in the moderate stocking and rotational spelling treatment during drought, relative to that under heavy grazing. The density of B. ewartiana declined even under moderate grazing and despite two sequences of above-average rainfall because seedling recruitment failed to offset mature plant death. Results from this study emphasised the importance of maintaining the existing populations of key long-lived species such as B. ewartiana through good management. These results also supported the overall findings from the grazing study indicating that stocking at the long-term carrying capacity is sustainable in managing for climate variability.

Digging in: a review of the ecology and management of a threatened reptile with a small disjunct distribution – the heath skink, Liopholis multiscutata, in Victoria, south-eastern Australia

2019 ◽  
Vol 25 (3) ◽  
pp. 222 ◽  
Author(s):  
Geoff W. Brown ◽  
Peter Robertson ◽  
Ben G. Fanson
Keyword(s):  
General Trend ◽  
Disjunct Distribution ◽  
Population Status ◽  
Management Actions ◽  
Eastern Australia ◽  
Disjunct Populations ◽  
History Of ◽  
Available Information ◽  
Management Priorities ◽  
Ongoing Monitoring

The central issue for species that are highly localised habitat specialists and occur in relatively small numbers is vulnerability to extinction processes. The heath skink, Liopholis multiscutata, is considered Critically Endangered in Victoria, in part because it is restricted to essentially four small and highly disjunct populations in semiarid mallee dunefields. It provides an example of a rare and cryptic species that is especially vulnerable to decline and consequently provides management challenges. Here, we crystallise available information on the ecology and life history of this threatened lizard, and review monitoring data to evaluate population status, primary threats and management imperatives. There has been a substantial decrease across the known range of the lizard in Victoria, most likely due to predation and fire. Recent monitoring of the four potentially viable populations revealed a general trend of decline. Recommendations for research and management priorities for the lizard in Victoria are provided; generally, these include further exploration of the lizard’s phylogeny and ecology, and ongoing monitoring of the trajectory of the lizard’s population status, threats to the lizard’s persistence and the effectiveness of management actions employed to ameliorate extinction threats.

Herbage and animal production from native pastures and pastures oversown with Stylosanthes hamata. 1. Fertiliser and stocking rate effects

1993 ◽  
Vol 33 (5) ◽  
pp. 561 ◽  
Author(s):  
CJ Gardener ◽  
MR McCaskill ◽  
JG McIvor
Keyword(s):  
Animal Production ◽  
Stocking Rate ◽  
Heteropogon Contortus ◽  
Stylosanthes Hamata ◽  
Stylosanthes Humilis ◽  
Native Pasture ◽  
Utilisation Rate ◽  
Native Pastures ◽  
Fertiliser Application ◽  
Stocking Rates

Native pastures dominated by Heteropogon contortus (speargrass) were sown to Stylosanthes hanzata cv. Verano in 1972, and herbage production and steer growth rates were compared with those of native pastures from 1973 to 1985. The native pastures also contained naturalised Stylosanthes humilis, but its contribution to pasture yield diminished rapidly, after infection by Colletotrichum gloeospoirioides (anthracnose) in 1973. The experiment was a factorial design of 2 pasture types (native, native plus Verano) x 2 stocking rates (0.6, 1.2 steers/ha) x 2 superphosphate treatments (nil, 300 kg/ha.year) x 2 replicates. Fertiliser application decreased the proportion of legume but had no significant effect on herbage or animal production on this comparatively fertile site (extractable P, 18 mg/kg). Annual liveweight gains at the high and low stocking rates, respectively, on the native pasture averaged 100 and 120 kg/steer. Sowing to Verano did not affect herbage yields but increased annual liveweight gains by 28 and 36 kg/steer at low and high stocking rates. The high stocking rate of 1.2 steers/ha was sustainable for the first 9 years of the experiment, when above-average rainfall was received. However, in the following 3 below-average years, there was a shift to less-desirable species, and a decline in pasture productivity. Relative to the low stocking rate, herbage production on the native pasture in the final season was reduced by 60% and on the Verano pasture by 26%. The highest annual herbage utilisation rate that appeared sustainable in the long term was about 45%, which corresponded to a utilisation rate of 30% during the growing season (about November-May). When oversown with Verano, speargrass tended to decline in favour of annual grasses, weeds, and the introduced grass Urochloa mosanzhicensis, which had been sown on an adjacent experiment. Urochloa appeared to be a more suitable companion species than speargrass for Verano.

Environmental Disturbance and Life Histories: Principles and Examples

1979 ◽  
Vol 36 (3) ◽  
pp. 329-334 ◽  
Author(s):  
D. M. Lehmkuhl
Keyword(s):  
Heavy Metals ◽  
Life Histories ◽  
Life Cycles ◽  
Detectable Effect ◽  
Toxic Substances ◽  
Short Term ◽  
Environmental Disturbances ◽  
Temperature Changes ◽  
Low Levels ◽  
Available Information

While many environmental disturbances have no readily detectable effect on aquatic invertebrates in the short term, they may prevent normal reproduction and cause eventual local extinction of a species. Small temperature changes may interfere with diapause signals and prevent completion of the life cycle. Heavy metals and toxic substances may drastically reduce reproduction rates in species exposed to sublethal levels. Dissolved salts and pH affect organisms at abnormally high or low levels but most mechanisms are unknown. It is concluded that relatively little information is available on the effects of environmental disturbances on life cycles. Available information, however, is sufficient to provide evidence of many problems that require attention. Key words: life histories, benthos, environmental disturbances, toxic substances, diapause, temperature, heavy metals

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