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.

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.

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.

scholarly journals The search for alternative temperate perennial pasture species for low to medium rainfall environments in Tasmania

2016 ◽  
Vol 16 ◽  
pp. 275-279
Author(s):  
E.J. Hall ◽  
R. Reid ◽  
B. Clark ◽  
R. Dent
Keyword(s):  
Perennial Grass ◽  
Dactylis Glomerata ◽  
Red Clover ◽  
Perennial Grasses ◽  
Grass Species ◽  
Sheep Grazing ◽  
Cool Temperate ◽  
Perennial Legume ◽  
Perennial Legumes ◽  
Pasture Plants

In response to the need to find better adapted and more persistent perennial pasture plants for the dryland pastures in the cool-temperate low to medium rainfall (500-700 mm) regions, over 1000 accessions representing 24 species of perennial legumes and 64 species of perennial grasses, were introduced, characterised and evaluated for production and persistence under sheep grazing at sites throughout Tasmania. The work has identified four alternative legume species in Talish Clover (Trifolium tumens). Caucasian Clover (T. ambiguum), Stoloniferous Red Clover (T. pratense var. stoloniferum), Lucerne x Yellow Lucerne Hybrid (Medicago sativa x M.sativa subsp. falcata); and two grass species in Coloured Brome (Bromus coloratus) and Hispanic Cocksfoot (Dactylis glomerata var hispanica). Keywords: persistence, perennial grass, perennial legume

Correlations between environmental factors, the biomass of exotic annual grasses and the frequency of native perennial grasses

2006 ◽  
Vol 54 (7) ◽  
pp. 655 ◽  
Author(s):  
Tanja I. Lenz ◽  
José M. Facelli
Keyword(s):  
Species Composition ◽  
Soil Fertility ◽  
Perennial Grass ◽  
Perennial Grasses ◽  
Annual Rainfall ◽  
Grass Species ◽  
Soil Factors ◽  
Annual Grasses ◽  
Exotic Annual Grasses ◽  
Native Perennial Grass

The species composition of temperate grasslands in the mid-north of South Australia has been radically altered from a system dominated by native perennial grasses to a system dominated by Mediterranean annual grasses. This study investigated the importance of chemical and physical soil characteristics, topographical features and climatic variables on the abundance of native and exotic grass species in nine ungrazed grasslands. Overall, climatic and other abiotic factors were highly variable. In addition, past management practices and original species composition are generally unknown, leading to further unexplained variation in the data. On a large spatial scale (among sites), the abundance of exotic annual grasses was positively correlated with mean annual rainfall, and on any scale, with finer soil textures and higher soil organic carbon levels. The most abundant annual grass, Avena barbata (Pott ex Link), was generally associated with soil factors denoting higher soil fertility. The abundance of native perennial grass species was not correlated with any environmental variables at any scale. The various native perennial grass species did not show clear associations with soil factors, although they tended to be associated with factors denoting lower soil fertility. However, at small spatial scales (within some sites) and among sites, the abundances of exotic annual and native perennial grasses were strongly negatively correlated. The results suggest that at the present time, rainfall and soil properties are important variables determining the abundance of annual grasses. The driving variables for the abundance of perennial grasses are less clear. They may be controlled by other factors or extreme rainfall events, which were not surveyed. In addition, they are likely to be controlled by competitive interactions with the annual grasses.

Effect of Forage Kochia on Seedling Growth of Cheatgrass (Bromus tectorum) and Perennial Grasses

2018 ◽  
Vol 11 (4) ◽  
pp. 201-207
Author(s):  
Parmeshwor Aryal ◽  
M. Anowarul Islam
Keyword(s):  
Seedling Growth ◽  
Aboveground Biomass ◽  
Bromus Tectorum ◽  
Perennial Grass ◽  
Perennial Grasses ◽  
Grass Species ◽  
Native Grasses ◽  
Native Plant ◽  
Competitive Effect ◽  
Forage Kochia

AbstractForage kochia [Bassia prostrata(L.) A. J. Scott] is competitive with annual weeds and has potential for use in reclamation of disturbed land. However, land managers are reluctant to use forage kochia in revegetation programs due to lack of understanding of its compatibility with or invasiveness in the native plant community. We conducted two greenhouse experiments, one to compare the competitive effect of forage kochia versus perennial grasses on growth of cheatgrass (Bromus tectorumL.) and one to study the effect of forage kochia on growth of native perennial grasses. In the first experiment, a single seedling ofB. tectorumwas grown with increasing neighbor densities (0 to 5 seedlings pot−1) of either forage kochia, crested wheatgrass [Agropyron cristatum(L.) Gaertner ×A. desertorum(Fisch. ex Link) Schultes; nonnative perennial grass], or thickspike wheatgrass [Elymus lanceolatus(Scribn. & J. G. Sm.) Gould; native perennial grass].Bromus tectorumgrowth was reduced moderately by all three perennial neighbors, butA. cristatumandE. lanceolatushad more effect onB. tectorumwhen compared with forage kochia. This experiment was repeated and similar results were observed. In the second experiment, forage kochia was grown with each of four native cool-season grass species: basin wildrye [Leymus cinereus(Scribn. & Merr.) Á. Löve], bluebunch wheatgrass [Pseudoroegneria spicata(Pursh) Á. Löve],E. lanceolatus, and western wheatgrass [Pascopyrum smithii(Rydb.) Á. Löve]. Forage kochia had no effect on height, tiller number, and aboveground biomass of native grasses. Similarly, native grasses did not show a significant effect on forage kochia seedlings. This experiment was also repeated, and forage kochia somewhat reduced the aboveground biomass ofL. cinereusandP. spicata. However, all native grasses significantly reduced change in height, branching, and aboveground biomass of forage kochia. These results suggest that forage kochia interfered withB. tectorumseedling growth, but it showed little competitive effect on native grass seedlings.

The response to moisture and defoliation stresses, and traits for resilience of perennial grasses on the Northern Tablelands of New South Wales, Australia

2003 ◽  
Vol 54 (9) ◽  
pp. 903 ◽  
Author(s):  
S. P. Boschma ◽  
M. J. Hill ◽  
J. M. Scott ◽  
G. G. Rapp
Keyword(s):  
Festuca Arundinacea ◽  
Plant Biomass ◽  
Nitrogen Concentration ◽  
Perennial Grass ◽  
Basal Area ◽  
Perennial Grasses ◽  
Rooting Depth ◽  
Grass Species ◽  
Severe Drought ◽  
Moderate Drought

A field experiment was conducted to study the effects of defoliation and moisture stresses on perennial pasture grasses and to identify traits associated with their resilience. The experiment, conducted near Armidale on the Northern Tablelands of NSW, studied 4 introduced perennial grass species (Phalaris aquatica, Festuca arundinacea, Dactylis glomerata, and Lolium perenne) and 2 native grass species (Microlaena stipoides and Austrodanthonia richardsonii) subjected to 3 moisture regimes (non-stress moisture, moderate drought, and severe drought) and 2 defoliation intensities (severe and moderate). Basal area, herbage mass, phenological growth stage, nitrogen concentration, root mass, and rooting depth were compared over 2 independent 6-month periods: spring–summer (1 September 1994–28 February 1995) and summer–autumn (1 December 1994–31 May 1995). Multiple regression was used to determine which traits were important for determining plant resilience.The differences between species and their respective responses were evident in the traits measured. In general, basal area tended to increase over summer and show little change during autumn. Severe defoliation stimulated plant growth, resulting in higher harvested herbage mass than from those moderately defoliated. Reproductive development was suppressed by severe drought and reduced by moderate drought. Severe defoliation suppressed flowering of Dactylis and Lolium at both drought intensities, compared with moderate defoliation. Phalaris, Festuca, and Austrodanthonia were the deepest rooting species during spring–summer, and Dactylis the shallowest. All species had similar rooting depths during summer–autumn, with those under severe and moderate drought having the deepest and shallowest rooting, respectively.Carbohydrate reserves and basal area were important traits for determining plant resilience during spring–summer. During summer–autumn, maintaining basal area and plant biomass through moderate grazing was important for resilience.

scholarly journals Drought-induced woody plant mortality in an encroached semi-arid savanna depends on topoedaphic factors and land management

2013 ◽  
Vol 17 (1) ◽  
pp. 42-52 ◽  
Author(s):  
Dirac Twidwell ◽  
Carissa L. Wonkka ◽  
Charles A. Taylor ◽  
Chris B. Zou ◽  
Jeremiah J. Twidwell ◽  
...  
Keyword(s):  
Land Management ◽  
Woody Plant ◽  
Plant Mortality ◽  
Semi Arid

Effect of drought on morphological and functional traits of Poa ligularis and Pappostipa speciosa, native perennial grasses with wide distribution in Patagonian rangelands, Argentina

2013 ◽  
Vol 61 (5) ◽  
pp. 383 ◽  
Author(s):  
Ana M. Cenzano ◽  
M. Celeste Varela ◽  
Mónica B. Bertiller ◽  
M. Virginia Luna
Keyword(s):  
Functional Traits ◽  
Photosynthetic Pigments ◽  
Perennial Grass ◽  
Field Capacity ◽  
Dry Weight ◽  
Water Shortage ◽  
Perennial Grasses ◽  
Grass Species ◽  
Senescent Leaf ◽  
Poa Ligularis

Poa ligularis Nees. Ap. Steudel and Pappostipa speciosa (Trin. et Rupr.) Romaschenko are dominant perennial grasses in the arid Patagonian rangelands of Argentina. Both species are exposed to periods of water shortage during spring-summer and are grazed by domestic and native herbivores. Pappostipa speciosa displays xeromorphic adaptations and is less preferred by herbivores than P. ligularis. The knowledge of how drought affects morphological/functional traits in coexisting perennial grass species is useful to understanding the function of desert perennial grasses, and for the use and conservation of Patagonian arid rangelands. The hypothesis of this study was that co-existing perennial grasses contrasting in drought resistance mechanisms display different degrees of phenotypic plasticity in underlying and/or functional traits. Plants of both species were exposed to two levels of gravimetric soil moisture: 16% (~field capacity) and 4%. Plant vegetative and reproductive traits were measured weekly in individual plants and these were harvested at the end of the experiment. Aboveground and root biomass were separated in the harvested plants and the concentration of photosynthetic pigments was assessed in green leaves. The trait response range was also calculated through the plasticity index. In both species, drought stress led to significant reductions in plant height, total plant dry weight, number of total leaves, dry weight of green and senescent leaf, percentage of flowering plants, length of inflorescences, and number, length and dry weight of roots. The concentration of photosynthetic pigments increased under drought in both species. In conclusion, drought strongly affected reproductive and vegetative traits in both species and the greatest negative effect of drought was found in P. speciosa, the most conservative species. However, our findings might indicate that both species are able to maintain photosynthetic activity through the increase of photosynthetic pigments under drought conditions in Patagonian rangelands.

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