Abstracts of The Rangeland Journal

The full text of these papers is available to members of the Australian Rangeland Society at http://www.publish.csiro.au/journals/trj

These abstracts are from the lastest issue of The Rangeland Journal  Vol. 31(4) 2009

Increasing the perennial grass component of native pastures through grazing management in the 400–600 mm rainfall zone of central western NSW

A. M. Bowman ^A, Y. Alemseged ^{B D}, G. J. Melville ^B, W. J. Smith B and F. Syrch ^C

^A Wagga Wagga Agricultural Institute, Pine Gully Road, Wagga Wagga, NSW 2650, Australia.

^B Trangie Agricultural Research Centre, PMB 19, Trangie, NSW 2821, Australia.

^C ‘Flying Fox Station’, Mataranka, NT 0852, Australia.

^D Corresponding author. Email: yohannes.alemseged@industry.nsw.gov.au

Abstract

Native grass-based pastures in the 400–600 mm rainfall zone of central NSW are an important basis for extensive grazing industries. However, over time they have been invaded by exotic weeds. This study aimed to evaluate several grazing strategies for the maintenance or improvement of native grasslands based on pasture productivity and species diversity. Seven grazing strategies, ranging from set stocking to permanently removing stock, were employed to evaluate the strategy that would best maintain a high proportion of desirable perennial grass species.

Grazing treatments were evaluated based on their effects on pasture composition and on the density of selected key grass species such as Enteropogon acicularis (Lindl.) Lazar. (curly windmill grass). Managing the utilisation of the key desirable species E. acicularis combined with weed control was the most successful strategy in terms of increasing the density of the key species, although no treatment increased the proportion of desirable perennial grasses and desirable broadleaf species. This was followed by a ‘farmer’s choice’ strategy, which involved combining phosphorus fertiliser application, weed control and rest from grazing. In contrast, strategies that involved either a ‘summer lockup’ or ‘weed control’ alone performed poorly. It is concluded that native pastures in this region could be rehabilitated, and their productivity restored, by following strategies that provide rest from grazing, based on the utilisation levels of key, species combined with control of annual weeds.

Keywords: Enteropogon acicularis, grazing strategies, pasture utilisation.

The Rangeland Journal 31(4) 369–376    doi:10.1071/RJ08032

Submitted: 25 July 2008    Accepted: 12 May 2009    Published: 27 November 2009

Using trees as a restoration tool in Tunisian arid areas: effects on understorey vegetation and soil nutrients

K. Jeddi ^A and M. Chaieb ^{A B}

^A Department of Biology, Faculty of Sciences, University of Sfax, 3000 – B.P. 1171 Sfax, Tunisia.

^B Corresponding author. Email: mohamed.chaieb@gnet.tn

Abstract

A field experiment was conducted in an afforested Stipa tenacissima L. steppe in arid southern Tunisia to evaluate the effect of three tree species (Acacia salicina Lindl., Pinus halepensis Mill. and Eucalyptus occidentalis Endl.) on understorey vegetation and soil nutrients. For each tree species, two subhabitats were distinguished: under the canopy, and out in the open. Organic carbon, total N, available P and pH were higher under the canopies of the three tree species than out in the open, and the effect was more pronounced in the top 10 cm of soil. Similarly, plant cover, biomass, richness and diversity were significantly higher under tree canopies. Some species such as Plantago amplexicaulis Cav., Helianthemum kahiricum Del. and Artemisia campestris L., which use large amounts of soil nutrients, showed a strong preference for areas under the canopy. Among the three tree species, Acacia salicina had the strongest positive effect on soil nutrients and understorey vegetation, and, thus, may be more useful for restoring arid areas and creating areas of enhanced soil nutrients than Pinus or Eucalyptus.

Keywords: arid ecosystem, restoration, soil fertility, subhabitat, vegetation dynamic, woody plants.

The Rangeland Journal 31(4) 377–384    doi:10.1071/RJ08064

Submitted: 13 November 2008    Accepted: 26 June 2009    Published: 27 November 2009

Indicator patches: exploiting spatial heterogeneity to improve monitoring systems

C. J. Stokes ^{A D G}, R. I. Yeaton ^{A E}, M. B. Bayer ^{B F} and B. T. Bestelmeyer ^C

^A Department of Botany, Research Unit for Plant Growth and Development, University of Natal, P/Bag X01, Scotsville, Pietermaritzburg 3209, South Africa.

^B Elsenberg Agricultural Development Institute, Department of Agricultural Development, Private Bag, Elsenberg 7607, South Africa.

^C USDA-ARS Jornada Experimental Range, Box 30003 MSC3JER, Las Cruces, New Mexico 88003, USA.

^D Present Address: CSIRO Davies Laboratory, PMB PO Aitkenvale, Qld 4814, Australia.

^E Present Address: Instituto de Investigación de Zonas Desérticas, Universidad Autónoma de San Luis Potosí, Altair # 200, Fracc. Del Llano, San Luis Potosí 78377, México.

^F Present Address: 29 Weltevrede St, Paarl 7646, South Africa.

^G Corresponding author. Email: chris.stokes@csiro.au

Abstract

When choosing which environmental attributes to monitor in assessing disturbance, it is important to consider not only which metric will provide the most sensitive indicator of disturbance, but also the spatial considerations of where in the landscape that metric will be most responsive to change. Degradation in landscapes is often unevenly expressed because: (i) disturbance is spatially localised, (ii) landscape elements differ in their sensitivity to disturbance, and (iii) degradation following localised disturbance is spatially contagious. The spatial heterogeneity of degradation has proven to be a key obstacle to rangeland monitoring (e.g. where the initiating processes of broad-scale degradation are concentrated in landscape locations that are not detected by surveys) but can also provide opportunities to focus monitoring efforts. We propose that the effectiveness of monitoring could be enhanced by identifying and selectively monitoring ‘indicator patches’, i.e. specific landscape locations that provide the most management-relevant and timely information about the consequences of a monitored disturbance. We tested and demonstrated the utility of the ‘indicator patch’ concept in the rangelands of the Succulent Karoo in southern Africa. We contrasted the grazing response of dominant ‘representative’ vegetation, with responses of interspersed patches of distinct vegetation associated with zoogenic mounds. Since mound vegetation is more palatable and preferentially grazed by sheep, we tested whether mounds could serve as ‘indicator patches’ in providing a sensitive measure of grazing disturbance. Percentage canopy cover measurements in dominant off-mound vegetation provided a poor indicator of grazing disturbance (although more intensive plant size measurements did reveal grazing impacts on plant population dynamics). In contrast, vegetation on mounds displayed patterns of changes in species abundances that were easier to detect and useful for interpreting and quantifying the effects of grazing. Mound vegetation could, therefore, be used as ‘indicator patches’ and targeted for exclusive sampling as a sensitive method for monitoring rangeland condition and detecting early warnings of vegetation change. This approach could be widely employed to better harness the extensive knowledge base regarding the patchy, spatially localised nature of degradation-initiating processes in numerous other landscapes. Routinely incorporating this understanding into the design of monitoring programs could improve the effectiveness of sampling effort, allow detection of more subtle trends (changes), and provide earlier warning of impending degradation so remedial action can be taken before degradation becomes severe and widespread.

Keywords: Karoo, plant demographics, rangeland.

The Rangeland Journal 31(4) 385–394    doi:10.1071/RJ08021

Submitted: 17 April 2008    Accepted: 11 September 2009    Published: 27 November 2009

Do elephants influence the organisation and function of a South African grassland?

D. M. Parker ^{A C}, R. T. F. Bernard ^A and J. Adendorff ^B

^A Wildlife and Reserve Management Research Group, Department of Zoology and Entomology, PO Box 94, Rhodes University, Grahamstown 6140, Republic of South Africa.

^B South African National Parks, Addo Elephant National Park, PO Box 52, Addo 6105, Republic of South Africa.

^C Corresponding author. Email: d.parker@ru.ac.za

Abstract

The impact of elephants (Loxodonta africana) on woody plants is well known. Elephants can be regarded as drivers of ecosystem functioning by, for example, decreasing woody plant litter accumulation through defoliation. However, their influence within grassland landscapes is, by comparison, very poorly understood. We assessed the influence of elephants on grassland functionality at three separate sites (1, high elephant density, long occupation time; 2, low elephant density, short occupation time; 3, no elephants) in the Addo Elephant National Park, Eastern Cape Province, South Africa. Using landscape function analysis (LFA) we described the landscape organisation of each site, and, using visual surrogates, calculated indices of landscape stability, infiltration and nutrient cycling. The number of vegetation patches/10 m of transects surveyed was higher at sites where elephant density was high (3 elephants/km2) and where elephants had been present for a long time (>70 years). However, patch size was significantly smaller when elephant density/time of occupation increased, and the proportion of bare soil was higher where elephant density and occupation time were highest. In addition, stability, infiltration and nutrient cycling indices at a site scale were significantly lower where elephants were present at high densities and after a long occupation time. However, bare soil stability was not greatly affected by elephant grazing pressure, implying that a ‘threshold of potential concern’ has not yet arisen. We conclude that the functioning of this grassland landscape is significantly altered when elephants are present. These conclusions highlight the importance of management factors such as containment and the provision of artificial water points which may be compromising the functionality of these landscapes. We recommend ongoing assessments to inform future management decisions.

Keywords: landscapes, patch dynamics, rangelands, sustainability.

The Rangeland Journal 31(4) 395–403    doi:10.1071/RJ08039

Submitted: 5 September 2008    Accepted: 8 July 2009    Published: 27 November 2009

The influence of individual native trees and grazing regime on soil properties and groundcover patterns in a temperate landscape of New South Wales, Australia

Phoebe Barnes ^{A C,} Brian R. Wilson ^{A B}, Chris Nadolny ^{A B} and Ivor Growns ^B

^A School of Environmental and Rural Science, University of New England, Armidale, NSW 2351, Australia.

^B Department of Environment, Climate Change and Water, PO Box U221, University of New England, Armidale, NSW 2351, Australia.

^C Corresponding author. Email: pbarnes@une.edu.au

Abstract

Scattered native trees are a significant ecological resource across the agricultural landscape, yet their numbers are declining due to factors such as dieback, senescence and agricultural activity. This study examined the interactions among Eucalyptus melliodora (Cunn. ex Schauer) trees, vegetation composition and selected surface soil chemical properties in grazed and ungrazed paddocks on the Northern Tablelands of New South Wales, Australia. Four farms on granite soils were examined in grazed and ungrazed treatments. Vegetation composition was assessed, and soil samples were collected in plots beneath the canopy and in adjacent open areas in both north and south directions of the tree canopy.

Native grasses dominated the vegetation in both beneath the canopy and open areas, at both grazed and ungrazed sites. However, their composition varied between farms. Several C3 and C4 grasses contributed to the groundcover of the canopy and open sites, but C3 grasses were generally more common under the canopy. Significant differences occurred in soil C, N, P and pH, and vegetation composition between canopy and open areas, and between grazed and ungrazed treatments. Soil P, C and N contents in grazed sites were typically similar to or higher than those in ungrazed sites, and soils were less acid in the ungrazed compared with grazed sites. All soil parameters measured were significantly higher under tree canopies, except P. The tree, soil and vegetation factors were strongly related. This study confirms that individual scattered trees create a distinct mosaic of localised soil improvement, and influence vegetation composition so that paddocks with trees are floristically more diverse than paddocks without trees. The results illustrate the potential benefits of retaining trees for both biodiversity values and livestock production in Australia.

Keywords: C3 grasses, C4 grasses, Eucalyptus melliodora, soil C, soil N, soil P, soil pH, vegetation–soil interactions.

The Rangeland Journal 31(4) 405–415    doi:10.1071/RJ09017

Submitted: 12 March 2009    Accepted: 24 August 2009    Published: 27 November 2009

The effects of browsing by feral and re-introduced native herbivores on seedling survivorship in the Australian rangelands

Nicola T. Munro ^{A C}, Katherine E. Moseby ^{A B} and John L. Read ^{A B}

^A Arid Recovery, PO Box 150, Roxby Downs, SA 5725, Australia.

^B Ecology and Evolutionary Biology, Benham Laboratories, North Terrace, University of Adelaide, Adelaide, SA 5005, Australia.

^C Corresponding author. Email: nicola.munro@anu.edu.au

Abstract

Browsing by introduced cattle (Bos taurus) and rabbits (Oryctolagus cuniculus) can limit the recruitment of some arid zone tree and shrub species. In a study conducted at the Arid Recovery Reserve, Roxby Downs, SA, we aimed to quantify initial recruitment changes in shrubs after the removal of cattle and rabbits and the re-introduction of locally extinct fauna. The presence and abundance of seedlings was measured at groves of seven native perennial shrubs over 6 years under four browsing treatments: (1) ‘reserve-reintroductions’ [re-introduced greater stick-nest rats (Leporillus conditor), burrowing bettongs (Bettongia lesueur) and greater bilbies (Macrotis lagotis)], (2) ‘reserve-no browsers’, (3) ‘pastoral-stocked’ (rabbits and cattle), and (4) ‘pastoral-destocked’ (rabbits). Recruitment of mulga (Acacia aneura F.Muell. ex Benth.), silver cassia (Senna artemisioides subsp. petiolaris Randell) and sandhill wattle (Acacia ligulata A.Cunn. ex Benth.) was significantly greater in the two browsing regimes inside the Reserve than in the two pastoral regimes. The number of recruits of these three species declined at ‘pastoral-destocked’ and ‘pastoral-stocked’ sites but increased at ‘reserve-reintroductions’ and ‘reserve-no browsers’ sites from 2001 to 2006. Narrow-leaf hopbush (Dodonaea viscose (L.) Jacq.) showed a trend towards increased recruitment at sites in both browsing regimes inside the Reserve, but decreased recruitment at sites in both pastoral regimes. Native plum (Santalum lanceolatum R.Br.), native apricot (Pittosporum phylliraeoides orth. var. DC.) and bullock bush (Alectryon oleifolius (Desf.) S.T.Reynolds) exhibited no significant difference in recruitment between the four browsing regimes within the study timeframe. These results suggest that excluding rabbits and stock may benefit the germination and survival of mulga, silver cassia and sandhill wattle. To date, re-introduced native herbivores at low numbers have not been found to negatively affect the recruitment or growth rate of the seven perennial plant species studied.

Keywords: arid zone, cattle, mammals, perennial shrubs, rabbits, recruitment.

The Rangeland Journal 31(4) 417–426    doi:10.1071/RJ08027

Submitted: 18 June 2008    Accepted: 5 November 2009    Published: 27 November 2009

Demography of three perennial grasses in a central Queensland eucalypt woodland

P. Jones ^A, P. Filet ^A and D. M. Orr B ^C

^A Department of Employment, Economic Development and Innovation, Locked Mail Bag 6, Emerald, Qld 4720, Australia.

^B Department of Employment, Economic Development and Innovation, PO Box 6014 Rockhampton Mail Centre, Rockhampton, Qld 4702, Australia.

^C Corresponding author. Email: david.orr@deedi.qld.gov.au

Abstract

The population dynamics of the palatable, perennial grasses Bothriochloa ewartiana (Domin) C.E.Hubb. (desert Mitchell grass), Chrysopogon fallax S.T.Blake (golden beard grass) and Heteropogon contortus (L.) P.Beauv. ex Roem. & Schult. (black speargrass), were studied in an extensive grazing study conducted in a eucalypt woodland within the Aristida–Bothriochloa pasture community in central Queensland between 1994 and 2000. Treatments were three grazing pressures based on light, medium and heavy utilisation of forage available at the end of summer and two timber treatments (trees intact and trees killed). Seasonal rainfall throughout this study was generally favourable for plant growth with no severe drought periods. Grazing pressure had a greater overall impact on plant dynamics than timber treatment, which had minimal impact. Grazing pressure had a large impact on H. contortus dynamics, an intermediate impact on B. ewartiana and no impact on C. fallax. Fluctuations in plant density of both B. ewartiana and C. fallax were small because both species were long lived with low levels of seedling recruitment and plant death, whereas fluctuations in H. contortus density were relatively high because of its relatively short life span and higher levels of both recruitment and death. Heavy grazing pressure increased the recruitment of B. ewartiana and H. contortus in some years but had no impact on that of C. fallax. Heavy grazing pressure reduced the survival of the original plants of both B. ewartiana and H. contortus but not of C. fallax. For H. contortus, the size of the original plants was larger where trees were killed than where trees were left intact and plants of the 1995 seedling cohort were larger in 1998 at heavy compared with those at light and medium grazing pressure. Grazing had a minor negative impact on the soil seed bank of H. contortus. Populations of all three species remained stable throughout this study, although the favourable seasonal rainfall experienced and the short duration of this study relative to the life span of these species may have masked longer term, deleterious impacts of heavy grazing pressure.

Keywords: Bothriochloa ewartiana, Chrysopogon fallax, Heteropogon contortus, plant, seedling recruitment.

The Rangeland Journal 31(4) 427–437    doi:10.1071/RJ09035

Submitted: 16 June 2009    Accepted: 5 November 2009    Published: 27 November 2009