The Influence of Recent Grazing Pressure and Landscape Position on Grass Recruitment in a Semi-Arid Woodland of Eastern Australia.

1996 ◽  
Vol 18 (1) ◽  
pp. 3 ◽  
Author(s):  
VJ Anderson ◽  
KC Hodgkinson ◽  
AC Grice
Keyword(s):  
Seedling Emergence ◽  
Perennial Grass ◽  
Soil Surface ◽  
Grazing Pressure ◽  
Perennial Grasses ◽  
Run Off ◽  
Eastern Australia ◽  
Annual Grasses ◽  
History Of ◽  
Semi Arid

This study examined the effects of previous grazing pressure, position in the landscape and apparent seed trapping capability of soil surface micro-sites on recruitment of the perennial grass Monachather paradoxa (mulga oats) in a semi-arid woodland. Seedling emergence was counted on small plots which had been kept moist for one month. The plots were on bare ground, or at grass tussocks, or at log mounds, sited in the run-off, interception and run-on zones of paddocks that had been grazed for six years at 0.3 and 0.8 sheep equivalent/ha. Few naturally occurring perennial grass seedlings emerged on any of the sites. The level of previous grazing pressure influenced the recruitment of grasses from natural sources as well as from seed of M. paradoxa broadcast on the soil surface; significantly more grass seedlings recruited in paddocks stocked at 0.3 than at 0.8 sheep/ha. Emergence of the sown grass did not differ significantly between the three zones in the landscape, but trends in the data suggest the interception zone may have been the most favourable. Recruitment from in situ grass seed was highest in the mulga grove (run-on) zone. Most seedlings of the sown grass emerged around the bases of existing perennial grass tussocks, but recruitment of volunteer perennial and annual grasses was more evenly distributed between the mulga log-mounds and perennial grass tussocks. It is concluded that very low levels of readily germinable seed of perennial grasses remained in the soil at the end of the drought and that areas with a history of high grazing pressure have less probability of grass recruitment when suitable rain occurs.

Effects of depth and time of sowing and over-wintering on tropical perennial grass seedling emergence in northern New South Wales

2009 ◽  
Vol 60 (10) ◽  
pp. 954 ◽  
Author(s):  
G. M. Lodge ◽  
S. Harden
Keyword(s):  
Seedling Emergence ◽  
Perennial Grass ◽  
Soil Surface ◽  
Perennial Grasses ◽  
Sowing Time ◽  
Rhodes Grass ◽  
Factors Affecting ◽  
Nylon Mesh ◽  
South Wales ◽  
Digitaria Eriantha

Two studies were conducted in northern NSW to examine some of the factors affecting the successful emergence of seedlings of five species of tropical perennial grasses [Panicum coloratum var. makarikariense cv. Bambatsi (panic), Digitaria eriantha ssp. eriantha cv. Premier (digit), Chloris gayana cv. Katambora (Rhodes grass), Dichanthium aristatum cv. Floren (bluegrass), and Bothriochloa bladhii ssp. glabra cv. Swann (forest bluegrass)]. The first experiment investigated the effects of depth and time (month) of sowing on tropical perennial grass seedling emergence, while a second series of studies examined the effects of contact of dispersal/sowing units with the soil, particularly over winter, on subsequent seed germination and seedling emergence. No seedling emergence of any species occurred in September 2006 and June–August 2007. From October 2006 to May 2007 there were significant effects (P < 0.001) of species, sowing time, depth, and their interaction on predicted emergence. From December to March, predicted emergence was always lower for surface-sown caryopses compared with those sown at 10 and 25 mm depth, and Bambatsi was the only species that had >50% emergence from a depth of 50 mm. Recovery of intact caryopses from 300 μm nylon mesh bags stored in the soil for 6 and 12 months was low for all species. Similarly, predicted germination of caryopses from field soil surface and buried locations (2007 and 2008) and those from florets and coated seeds (2008) was low, indicating that these species had a poor ability to over-winter in moist soil.

Managing competitive interactions to promote regeneration of native perennial grasses in semi-arid south-eastern Australia

2017 ◽  
Vol 39 (1) ◽  
pp. 59
Author(s):  
Ronald B. Hacker ◽  
Ian D. Toole ◽  
Gavin J. Melville ◽  
Yohannes Alemseged ◽  
Warren J. Smith
Keyword(s):  
Weed Control ◽  
Biomass Production ◽  
Soil Nitrogen ◽  
Perennial Grass ◽  
Perennial Grasses ◽  
Soil Nitrate ◽  
Nitrogen Reduction ◽  
Eastern Australia ◽  
Semi Arid ◽  
Native Perennial Grass

Treatments to reduce available soil nitrogen and achieve specified levels of weed control were evaluated for their capacity to promote regeneration of native perennial grasses in a degraded semi-arid woodland in central-western New South Wales. Treatments were factorial combinations of nitrogen-reduction levels and weed-control levels. The four levels of nitrogen reduction were no intervention, and oversowing of an unfertilised summer crop, an unfertilised winter crop or an unfertilised perennial grass. The three weed-control levels were defined by the outcome sought rather than the chemical applied and were nil, control of annual legumes and control of all annual species (AA). Regeneration of perennial grasses, predominantly Enteropogon acicularis, was promoted most rapidly by the AA level of weed control with no introduction of sown species. Sown species negated the benefits of weed control and limited but did not prevent the regeneration of native perennials. Sown species also contributed substantially to biomass production, which was otherwise severely limited under the AA level of weed control, and they were effective in reducing soil nitrogen availability. Sown species in combination with appropriate herbicide use can therefore maintain or increase available forage in the short–medium term, permit a low rate of native perennial grass recruitment, and condition the system (by reducing soil mineral nitrogen) for more rapid regeneration of native perennials should annual sowings be discontinued or a sown grass fail to persist. Soil nitrate was reduced roughly in proportion to biomass production. High levels of soil nitrate did not inhibit native perennial grass regeneration when biomass was suppressed by AA weed control, and may be beneficial for pastoral production, but could also render sites more susceptible to future invasion of exotic annuals. The need for astute grazing management of the restored grassland is thus emphasised. This study was conducted on a site that supported a remnant population of perennial grasses. Use of the nitrogen-reduction techniques described may not be appropriate on sites where very few perennial grass plants remain.

Changes in the Quantitative Floristics in Some Astrebla Spp. (Mitchell Grass) Communities in South-Western Queensland in Relation to Trends in Seasonal Rainfall

1981 ◽  
Vol 29 (5) ◽  
pp. 533 ◽  
Author(s):  
DM Orr
Keyword(s):  
Relative Abundance ◽  
Perennial Grass ◽  
Grazing Pressure ◽  
Perennial Grasses ◽  
Seasonal Rainfall ◽  
Individual Species ◽  
Botanical Composition ◽  
Basal Cover ◽  
Wide Range ◽  
Annual Grasses

Seasonal changes in the quantitative floristics at a wide range of Astrebla grassland sites in south-western Queensland were monitored between 1972 and 1980 with a wheel point apparatus. Changes in the floristics were measured in terms of both relative abundance and basal cover. A large increase in the relative abundance of perennial grasses, particularly Aristida latifolia, Astrebla spp. and Dichanthium sericeum, occurred between 1972 and 1976. This increase was at the expense of annual grasses and forbs which declined in both relative abundance and number of genera present. The relative abundance of perennial grasses declined between 1978 and 1980 and this was associated with a large increase in the forbs such as Daucus glochidiatus and Plantago spp., particularly at southern sites. The contribution of annual grasses to botanical composition remained low throughout the period. Total basal cover differed between years although these differences were not significant. As perennial grass, particularly Astrebla spp., was the major vegetation component of total basal cover, changes in the latter were associated mainly with changes in the basal cover of Astrebla spp. Changes in the contribution of individual species to total basal cover were related to changes in the relative abundance of those species. Changes in botanical composition in Astrebla grassland may be influenced more by trends in seasonal rainfall than by grazing pressure.

Changes in Grass Density in Australian Semi-Arid Woodlands.

1995 ◽  
Vol 17 (1) ◽  
pp. 26 ◽  
Author(s):  
AC Grice ◽  
I Barchia
Keyword(s):  
Perennial Grass ◽  
Perennial Grasses ◽  
Grass Species ◽  
European Settlement ◽  
Eastern Australia ◽  
Rate Of Response ◽  
Semi Arid

Changed grazing regimes since European settlement have been widely proposed as the cause of a decline of indigenous perennial grasses in the semi-arid woodlands of eastern Australia. A five year experiment using exclosures examined the effects of grazing on densities of perennial grasses. Short- lived Stipa spp. and Aristida spp. were dominant at most sites. Their densities fluctuated greatly with season and reached over 200 plants/m2 during climatically favourable periods. The long-lived Eragrostis eriopoda occurred at densities that were generally less than 5 plants/m2 and its populations were relatively stable. The response of Enneapogon avenaceus was distinctive. Though its density fluctuated considerably, successive peaks in density were higher and the species increased more in ungrazed areas than in destocked or unfenced areas. The differences between grazed and ungrazed populations became greater with successive peaks in density. Within the short periods that pastoralists are likely to be willing or able to apply such treatments, destocking or even removing all herbivores is unlikely to have a large effect on the density of many palatable perennial grass species. The rate of response to resting pastures will depend on seasonal conditions.

Effects of nitrogen and phosphorus on vegetation dynamics of a degraded native grassland in semi-arid south-eastern Australia

2011 ◽  
Vol 33 (1) ◽  
pp. 87 ◽  
Author(s):  
R. B. Hacker ◽  
I. D. Toole ◽  
G. J. Melville
Keyword(s):  
Vegetation Dynamics ◽  
Plant Density ◽  
Perennial Grass ◽  
Ground Cover ◽  
Perennial Grasses ◽  
Grass Species ◽  
Nitrogen And Phosphorus ◽  
Mineral N ◽  
Eastern Australia ◽  
Semi Arid

The roles of nitrogen (N) and phosphorus (P) in controlling vegetation transitions in a degraded semi-arid grassland were investigated in a factorial experiment that combined two initial levels of perennial plant density (low and high), three levels of N (N+, N0 and N–) and two levels of P (P+ and P0). Increased levels of both N and P were achieved by fertiliser addition while sucrose was used to reduce the level of N. Vegetation dynamics were driven primarily by soil N rather than P. Addition of sucrose, which was inferred to result in the immobilisation of mineral N, reduced the growth of annual species and facilitated the establishment and growth of native perennial grasses. Addition of P generally had no significant effect on dry matter production, either in total or for species grouped as forbs, annual grasses and perennial grasses, or on recruitment and mortality of perennial grasses. However, at some times of observation addition of P increased ground cover and/or the basal circumference of some perennial grass species. Basal circumference for Enteropogon acicularis was also increased by addition of N. Soil biological activity, measured by decomposition of cotton strips, was increased by addition of N, which maintained vegetation in an annual-dominated condition, and was not affected by addition of P. Carbon addition has the potential to assist restoration of this grassland. However, the capacity of some native grass species to respond to increased fertility suggests that once restoration is achieved some increase in fertility may be beneficial for pastoral production.

Run-Off and Sediment Yield From a Semi-Arid Woodland in Eastern Australia. Ii. Variation in Some Soil Hydrological Properties Along a Gradient in Soil Surface Condition.

1993 ◽  
Vol 15 (2) ◽  
pp. 234 ◽  
Author(s):  
DJ Eldridge ◽  
TB Koen
Keyword(s):  
Vegetation Cover ◽  
Surface Condition ◽  
Soil Surface ◽  
Perennial Grasses ◽  
Sediment Removal ◽  
South Wales ◽  
Run Off ◽  
Physico Chemical ◽  
Eastern Australia ◽  
Red Earth

Three sites on red earth soils were examined at Yathong Nature Reserve and 'Coan Downs' in central- western New South Wales. The sites represented a gradient in soil surface condition from a stable, uneroded and productive site, supporting moderately dense perennial grasses (site 1) to a moderately unstable and degraded site with few perennials and evidence of erosion (site 3). The hydrological characteristics of the three sites were measured using a rainfall simulator on plots with varying vegetation cover. Water ponded earlier at the degraded site, and run-off and sediment removal increased as the soil surface became more degraded. Associated with this was an increase in the importance of vegetation cover, and a decrease in the importance of soil physico-chemical variables as descriptors of soil hydrological properties. The results are consistent with the notion that vegetation plays a more important role in maintaining soil hydrological processes as the soil surface becomes more degraded.

Towards more sustainable pastures: lessons learnt

2000 ◽  
Vol 40 (2) ◽  
pp. 343 ◽  
Author(s):  
D. R. Kemp ◽  
D. L. Michalk ◽  
J. M. Virgona
Keyword(s):  
Water Use ◽  
Root Zone ◽  
Perennial Grass ◽  
Grazing Pressure ◽  
Perennial Grasses ◽  
Initial Assessment ◽  
Short Term ◽  
Water Sustainability ◽  
Eastern Australia ◽  
Soil And Water

The Temperate Pasture Sustainability Key Program (TPSKP) was established across south-eastern Australia to test the hypotheses that an improved perennial grass content in pastures would result in fewer weeds, better water use (and hence lesser impacts on soil salinity), and lower soil acidification rates. Grazing tactics were seen as a means to enhance or maintain the perennial grass content. Soil and water sustainability experiments in summer and winter dominant rainfall environments showed fewer weeds, improvements in water use and less acidity under perennial versus annual grass pastures. Further work is needed to determine if these gains are sufficient to make perennial grass pastures sustainable in the long-term as some nitrate leakage still occurred at the winter rainfall site. Indicators were developed to rate the sustainability of treatments within experiments. A subset of these indicators was common across experiments and could readily be used by farmers to provide an initial assessment of the soil and water sustainability of their pasture systems. These are: the mineral nitrogen at the bottom of the root zone (40–60 cm); soil pH at the surface and bottom of the root zone and perennial grass content by species. Managing pastures through droughts is a critical aspect of grazing management in Australia. Experiments within the TPSKP demonstrated that perennial grasses survived during drought when maintained above critical lower biomass values. These values ranged from 0.5 to 1.5 t DM/ha depending upon species. Over all experiments, there was general support for the view that maintaining a higher level of biomass in pastures resulted in more sustainable systems. Twenty-three grazing experiments using an open communal grazing design showed that most perennial grasses were sensitive to grazing at some stage in their seasonal growth cycles. The exceptions were inconclusive for several reasons e.g. the grazing pressure may not have been high enough at those sites to elucidate any effects; they occurred where the perennial grass content was less than 10% or exceeded 70%, of the sward; or were confounded by interactions between species where the species under study was not dominant. After taking these exceptions into account, it was then possible to determine where grazing tactics could be expected to work. Species differed in their response to grazing. Some perennial grasses were more sensitive to grazing during periods of stress (e.g. dry summers) than when actively growing (e.g. cocksfoot), while the reverse applied with others (e.g. phalaris). Of the grasses sensitive to grazing when actively growing, sensitivity of some was largely confined to the reproductive period (e.g. perennial ryegrass). Across most experiments, continuous grazing resulted in either a decline in or no net benefit to, the perennial grass content. Microlaena stipoides was the only species to respond to increased grazing pressure — this only applied in spring. The experiments clearly showed that tactical rests were an important tool for grassland management. The effects recorded were predominantly expressed through impacts on vegetative growth and survival of existing plants. Short-term experiments and dry seasons did not enable recruitment processes to be studied. Within pastures, grazing tactics can influence many species. The challenge is to use the TPSKP outcomes to develop strategies that optimise the composition of these swards. Due to the short-term nature of these experiments the results were evaluated within a conservative framework and often simply on the absolute level of parameters. Techniques need to be developed to more effectively monitor the process (i.e. rates of change), rather than the consequences (i.e. ends). The information gained in this program needs to be incorporated into practical strategies for better management of pastures and tested at a commercial scale. The TPSKP was one of the largest, coordinated pasture programs ever attempted. Some major outcomes were the experience gained by a large number of grassland scientists in running such programs, the development and acceptance of standardised measurement protocols and a much stronger network among grazing systems scientists committed to achieving improved management systems.

Spatial and Temporal Pattern in the Grazing of Grasses by Sheep Within a Semi-Arid Wooded Landscape.

1995 ◽  
Vol 17 (2) ◽  
pp. 154 ◽  
Author(s):  
KC Hodgkinson ◽  
JW Terpstra ◽  
WJ Muller
Keyword(s):  
Woody Plant ◽  
Perennial Grass ◽  
Grazing Pressure ◽  
Perennial Grasses ◽  
Spatial And Temporal Variation ◽  
Grass Species ◽  
Plant Mortality ◽  
Research Facility ◽  
Semi Arid ◽  
Domestic Stock

Grazing the woodlands of semi-arid and arid Australia by domestic stock has extensively collapsed perennial *grass populations and thereby fostered woody plant increase. This study examined the pattern of grazing of individual grass plants by sheep in the landscape of a semi-arid woodland, and a model was developed describing the spatial and temporal influences on the grazing pressure placed on plants. Plants of two widespread perennial grass species differing in palatability, Eragrostis eriopoda and Thyridolepis mitchelliana, were examined weekly in two contrasting periods at the CSIRO Lake Mere Research Facility. The plants were located throughout the landscape in lightly- and heavily- stocked paddocks. Patterns of grazing in space and time were determined by examining the grazing of marked tillers. No preference was shown for previously ungrazed plants and only occasionally were previously grazed plants preferred. Thyridolepis mitchelliana plants were slightly preferred over E. eriopoda plants. Landscape zones receiving water and nutrients from elsewhere were preferred for grazing but the effect was weak. The foliage biomass of herbaceous plants in the immediate vicinity of a grass plant did not influence the number of tillers grazed nor the probability of the plant being grazed. Overall the defoliation of individual plants by sheep was weakly determined by landscape location, stocking level, plant species and prevailing forage on offer. The influence of spatial and temporal variation was small; random grazing of grass plants was the rule. This finding suggests that the grazing pressure on palatable perennial grasses in the paddocks of semi-arid woodlands will be similar across wooded landscapes and that spatial variability in plant mortality could be due to. the combined effect of plant water stress, which varies spatially and temporally, and grazing pressure which varies temporally but not spatially.

Role of plant cover and stock trampling on runoff and soil-erosion from semi-arid wooded rangelands

Soil Research ◽  
1994 ◽  
Vol 32 (5) ◽  
pp. 953 ◽  
Author(s):  
RSB Greene ◽  
PIA Kinnell ◽  
JT Wood
Keyword(s):  
Plant Cover ◽  
Negative Relationship ◽  
Soil Surface ◽  
Sediment Concentration ◽  
Perennial Grasses ◽  
Stocking Rate ◽  
Eastern Australia ◽  
Local Water ◽  
Raindrop Energy ◽  
Semi Arid

Relationships between plant cover, runoff and erosion of a massive red earth were investigated for a runoff zone of an intergrove area in a semi-arid wooded rangeland in eastern Australia. The measurements were carried out in small experimental paddocks with different stocking rates of sheep and kangaroos. A trailer-mounted rainfall simulator was used to apply rainfall at a time averaged rate of 30 mm h-1 to obtain runoff rates and sediment concentrations. There was a significant negative relationship (r2 = 0.58; P < 0.01) between final runoff rate and plant cover. It is probable that the plants increase infiltration and decrease runoff by (i) funnelling water down their stems and (ii) providing macropores at the base of the plant through which water can rapidly enter the soil. However, there was no significant effect of plant cover on sediment concentration. Probable reasons for this are: (i) even though plant cover will absorb raindrop energy and decrease the erosive stress on the soil, the nature of the plants investigated is such that they may not be 100% effective in protecting the soil beneath them, and (ii) the distribution of contact cover provided by the base of the plants is highly patchy and thus relatively inefficient at reducing sediment concentration. At zero cover final runoff rates from paddocks with a high and low stocking rate were similar, i.e. 23.4 and 22.3 mm h-1 respectively. However, at zero cover, the sediment concentration from the high stocking rate paddock was significantly (P < 0.01) greater than that from the low stocking rate paddock. Greater hoof activity and lower organic matter (and hence lower structural stability) of the 0.20 mm layer in the high stocking rate paddock caused the soil surface to be more susceptible to erosion. These results show that grazing by removing perennial grasses and pulverizing the surface soil can have a major impact on local water balances and erosion rates respectively within the intergrove areas. The implications of these results for the long-term stability of semi-arid mulga woodlands is briefly discussed.

Growth, seed production and effect of defoliation in an early flowering perennial grass, Alloteropsis semialata (Poaceae), on Cape York Peninsula, Australia

2001 ◽  
Vol 49 (6) ◽  
pp. 735 ◽  
Author(s):  
Gabriel M. Crowley ◽  
Stephen T. Garnett
Keyword(s):  
Plant Growth ◽  
Seed Production ◽  
Perennial Grass ◽  
Soil Surface ◽  
Plant Size ◽  
Perennial Grasses ◽  
Wet Season ◽  
Cape York ◽  
Seed Dynamics

Alloteropsis semialata (R.Br.) A.Hitchc. is one of the first perennial grasses in monsoonal Australia to produce seed at the start of the wet season. Patterns of growth and seed production and seed dynamics of Alloteropsis semialata were examined in this study, along with the effects of partial defoliation. Growth of Alloteropsis semialata tussocks started with the first pre-wet-season rains, and was then interrupted during a period with little rain. Growth ceased before the end of the wet season, indicating that factors other than moisture availability were limiting. Seeds of Alloteropsis semialata were germinable on production, but did not remain viable or persist on the soil surface through the dry season. Most seeds and young seedlings were harvested and no seedlings were recruited. Inflorescence production increased with plant size. Moderate defoliation in the early wet season had no impact on plant growth, but reduced inflorescence and seed production for at least 2 years. Absence of a seed bank and early wet-season flowering mean that Alloteropsis semialata is likely to be sensitive to long-term over-grazing.

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