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Monegi P, Mkhize NR, Tjelele JT, Ward D, Tsvuura Z. Resprouting Response among Savanna Tree Species in Relation to Stem Size, Woody Removal Intensity and Herbicide Application. PLANTS (BASEL, SWITZERLAND) 2023; 12:3451. [PMID: 37836191 PMCID: PMC10574858 DOI: 10.3390/plants12193451] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Revised: 09/04/2023] [Accepted: 09/26/2023] [Indexed: 10/15/2023]
Abstract
Mechanical and chemical methods are widely used to control woody plant encroachment in many African countries. However, very little is known about the effectiveness of these control methods among woody species of different ages. We conducted a field experiment to determine the effects of different tree removal treatments (10%, 20%, 50%, 75% and 100%) and herbicide application (Picloram; 6 mL L-1) on the resprouting ability and vigour of 12 woody plant species. We examined 20 plots (30 m × 30 m) that were each subjected to tree removal, followed by herbicide application on half of the stems for each plot. All the tree species in this study resprouted after cutting. The applied concentration of herbicide significantly reduced the shoot production for Ehretia rigida, Vachellia robusta and Ziziphus mucronata, with a marginal effect for Dichrostachys cinerea. The diameter of stems was an important factor in determining resprouting ability, with shoot production decreasing with increasing stem diameter. However, stem diameter did not affect shoot length and diameter for all species. We found that woody plants are more likely to resprout and survive as juveniles than as adults after cutting and that herbicide only affected four of the twelve species at a concentration of 6 mL L-1. Thus, testing the amount of Picloram needed to kill certain woody species may be of importance for land users in southern African savannas.
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Affiliation(s)
- Piet Monegi
- Animal Production, Agricultural Research Council, Private Bag X 02, Irene 0062, South Africa
- School of Life Sciences, University of KwaZulu-Natal, Scottsville 3209, South Africa
| | - Ntuthuko Raphael Mkhize
- Animal Production, Agricultural Research Council, Private Bag X 02, Irene 0062, South Africa
- Animal and Poultry Science, School of Agriculture, Earth and Environmental Sciences, University of KwaZulu-Natal, Scottsville 3209, South Africa
| | - Julius Tlou Tjelele
- Animal Production, Agricultural Research Council, Private Bag X 02, Irene 0062, South Africa
| | - David Ward
- Department of Biological Sciences, Kent State University, Cunningham Hall, Kent, OH 44242, USA
| | - Zivanai Tsvuura
- School of Life Sciences, University of KwaZulu-Natal, Scottsville 3209, South Africa
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Gao X, Schwilk DW. Burn hot or tolerate trees: flammability decreases with shade tolerance in grasses. OIKOS 2022. [DOI: 10.1111/oik.08930] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- Xiulin Gao
- Dept of Biological Sciences, Texas Tech Univ. Lubbock TX USA
- Lawrence Berkeley National Laboratory Berkeley CA USA
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Wright BR. Evidence that predator satiation drives reproductive synchrony in the desert masting grass, soft spinifex (
Triodia pungens
). AUSTRAL ECOL 2021. [DOI: 10.1111/aec.13119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Affiliation(s)
- Boyd R. Wright
- Botany, School of Environmental and Rural Science University of New England Armidale New South Wales Australia
- School of Agriculture and Food Science University of Queensland St Lucia Queensland Australia
- Department of Environment, Parks and Water Security Alice Springs Herbarium, Northern Territory Government Alice Springs Northern Territory Australia
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Nano CEM, Randall DJ, Stewart AJ, Pavey CR, McDonald PJ. Spatio-temporal gradients in food supply help explain the short-term colonisation dynamics of the critically endangered central rock-rat ( Zyzomys pedunculatus
). AUSTRAL ECOL 2019. [DOI: 10.1111/aec.12753] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Catherine E. M. Nano
- Flora and Fauna Division; Department of Environment and Natural Resources; Northern Territory Government; Alice Springs Northern Territory 0870 Australia
| | - Debbie J. Randall
- Flora and Fauna Division; Department of Environment and Natural Resources; Northern Territory Government; Alice Springs Northern Territory 0870 Australia
| | - Alistair J. Stewart
- Flora and Fauna Division; Department of Environment and Natural Resources; Northern Territory Government; Alice Springs Northern Territory 0870 Australia
| | - Chris R. Pavey
- Land & Water; CSIRO; Winnellie Northern Territory Australia
| | - Peter J. McDonald
- Flora and Fauna Division; Department of Environment and Natural Resources; Northern Territory Government; Alice Springs Northern Territory 0870 Australia
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Wright BR. Evidence that shrublands and hummock grasslands are fire-mediated alternative stable states in the Australian Gibson Desert. Oecologia 2018; 188:525-535. [PMID: 29974238 DOI: 10.1007/s00442-018-4215-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2017] [Accepted: 06/26/2018] [Indexed: 11/28/2022]
Abstract
Alternative stable state theory predicts that different disturbance regimes may support contrasting ecosystem states under otherwise analogous environmental conditions. In fire-prone systems, this theory is often invoked to explain abrupt ecotones, especially when adjacent vegetation types have contrasting flammabilities and differing tolerances to pyric perturbation. Despite being well-documented in forest-savanna transitions, unambiguous examples of fire-driven alternate stable states (FDASS) in arid systems are rare. The current study examined whether flammable spinifex (Triodia spp.) grasslands and fire-sensitive waputi (Aluta maisonneuvei subsp. maisonneuvei) shrublands in Australia's Gibson Desert represent FDASS. Specifically, analyses of soil and topographic variables assessed whether environmental differences explain habitat zonation. To determine whether different flammabilities of Aluta and Triodia systems may perpetuate alternative states via vegetation-fire feedback processes, community-level fuelloads were quantified to provide an indirect measure of flammability. To determine the propensity for fire to trigger 'state-shifting', community responses to a single high-severity fire were evaluated. Habitat segregation did not relate to between-site environmental differences, and the fuel-load study indicated that the more pyrophytic community (Triodia grassland) is more flammable, and hence more likely to experience higher frequency fire-cycles. Fire was identified as a potential vector of 'state-change', because although both systems regenerated well after fire, Triodia reproduced more prolifically at a younger age than Aluta, and hence should tolerate shorter fire-return intervals. In the absence of between-community topographic and edaphic differences, or herbivores that consume either plant, it is likely that Aluta shrublands and Triodia grasslands represent fire-mediated alternative equilibrium states.
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Affiliation(s)
- Boyd R Wright
- Botany, School of Environmental and Rural Science, University of New England, Armidale, NSW, 2350, Australia. .,Department of Environment and Natural Resources, The Northern Territory Herbarium, Alice Springs, NT, 0871, Australia. .,School of Agriculture and Food Sciences, University of Queensland, St. Lucia, Brisbane, QLD, 4072, Australia.
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Lewandrowski W, Erickson TE, Dalziell EL, Stevens JC. Ecological niche and bet-hedging strategies for Triodia (R.Br.) seed germination. ANNALS OF BOTANY 2018; 121:367-375. [PMID: 29293867 PMCID: PMC5808810 DOI: 10.1093/aob/mcx158] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2017] [Accepted: 10/26/2017] [Indexed: 05/26/2023]
Abstract
BACKGROUND AND AIMS Regeneration dynamics in many arid zone grass species are regulated by innate seed dormancy mechanisms and environmental cues (temperature, moisture and fire) that result in infrequent germination following rainfall. This study investigated bet-hedging strategies associated with dormancy and germination in arid zone Triodia species from north-west Australia, by assessing (1) the effects of the mechanical restriction imposed by the indehiscent floral bracts (i.e. floret) covering the seed and (2) the impact of dormancy alleviation on florets and cleaned seeds (i.e. florets removed) when germinated under water stress. METHODS The initial dormancy status and germination for six species were tested on intact florets and cleaned seeds, across temperatures (10-40 °C) with and without the fire-related stimulant karrikinolide (KAR1), and under alternating light or constant dark conditions. Physiological dormancy alleviation was assessed by wet/dry cycling florets over a period of 10 weeks, and germination was compared against untreated florets, and cleaned seeds across a water potential gradient between 0 and -1.5 MPa. KEY RESULTS Florets restricted germination (<45 %) at all temperatures and, despite partial alleviation of physiological dormancy (wet/dry cycling for 8 weeks), intact florets germinated only at high water potentials. Cleaned seeds showed the highest germination (40-90 %) across temperatures when treated with KAR1, and germinated at much lower water potentials (-0.4 and -0.9 MPa). Triodia pungens was the most responsive to KAR1, with both seeds and florets responding, while for the remaining five species, KAR1 had a positive effect for seeds only. CONCLUSIONS Only after seed dormancy was alleviated by removing florets and when KAR1 was applied did germination under water stress increase. This suggests that seeds of these Triodia species are cued to recruit following fire and during periods of high precipitation. Climate change, driven by large shifts in rainfall patterns, is likely to impact Triodia recruitment further in arid zone grasslands.
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Affiliation(s)
- Wolfgang Lewandrowski
- Kings Park and Botanic Garden, Kings Park, Western Australia
- School of Biological Sciences, The University of Western Australia, Crawley, Western Australia
| | - Todd E Erickson
- Kings Park and Botanic Garden, Kings Park, Western Australia
- School of Biological Sciences, The University of Western Australia, Crawley, Western Australia
| | - Emma L Dalziell
- Kings Park and Botanic Garden, Kings Park, Western Australia
- Department of Environment and Agriculture, Curtin University, Bentley, Western Australia
| | - Jason C Stevens
- Kings Park and Botanic Garden, Kings Park, Western Australia
- School of Biological Sciences, The University of Western Australia, Crawley, Western Australia
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Mutiti CM, Medley KE, Mutiti S. Using GIS and remote sensing to explore the influence of physical environmental factors and historical land use on bushland structure. Afr J Ecol 2016. [DOI: 10.1111/aje.12378] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Affiliation(s)
- Christine M. Mutiti
- Miami University; 501 E High St Oxford OH 45056 U.S.A
- Department of Biological and Environmental Sciences; Georgia College & State University; Milledgeville GA 31061 U.S.A
| | | | - Samuel Mutiti
- Miami University; 501 E High St Oxford OH 45056 U.S.A
- Department of Biological and Environmental Sciences; Georgia College & State University; Milledgeville GA 31061 U.S.A
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8
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Tietjen B. Same rainfall amount different vegetation—How environmental conditions and their interactions influence savanna dynamics. Ecol Modell 2016. [DOI: 10.1016/j.ecolmodel.2015.06.013] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Cleverly J, Eamus D, Luo Q, Restrepo Coupe N, Kljun N, Ma X, Ewenz C, Li L, Yu Q, Huete A. The importance of interacting climate modes on Australia's contribution to global carbon cycle extremes. Sci Rep 2016; 6:23113. [PMID: 26976754 PMCID: PMC4791548 DOI: 10.1038/srep23113] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Accepted: 02/26/2016] [Indexed: 12/05/2022] Open
Abstract
The global carbon cycle is highly sensitive to climate-driven fluctuations of precipitation, especially in the Southern Hemisphere. This was clearly manifested by a 20% increase of the global terrestrial C sink in 2011 during the strongest sustained La Niña since 1917. However, inconsistencies exist between El Niño/La Niña (ENSO) cycles and precipitation in the historical record; for example, significant ENSO-precipitation correlations were present in only 31% of the last 100 years, and often absent in wet years. To resolve these inconsistencies, we used an advanced temporal scaling method for identifying interactions amongst three key climate modes (El Niño, the Indian Ocean dipole, and the southern annular mode). When these climate modes synchronised (1999-2012), drought and extreme precipitation were observed across Australia. The interaction amongst these climate modes, more than the effect of any single mode, was associated with large fluctuations in precipitation and productivity. The long-term exposure of vegetation to this arid environment has favoured a resilient flora capable of large fluctuations in photosynthetic productivity and explains why Australia was a major contributor not only to the 2011 global C sink anomaly but also to global reductions in photosynthetic C uptake during the previous decade of drought.
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Affiliation(s)
- James Cleverly
- School of Life Sciences, University of Technology Sydney, PO Box 123, Broadway, NSW, 2007, Australia
- Australian Supersite Network, Terrestrial Ecosystem Research Network, University of Technology Sydney.
| | - Derek Eamus
- School of Life Sciences, University of Technology Sydney, PO Box 123, Broadway, NSW, 2007, Australia
- Australian Supersite Network, Terrestrial Ecosystem Research Network, University of Technology Sydney.
| | - Qunying Luo
- Climate Change Cluster, University of Technology Sydney.
| | | | - Natascha Kljun
- Department of Geography, Swansea University, Singleton Park, Swansea SA2 8PP, UK
| | - Xuanlong Ma
- Climate Change Cluster, University of Technology Sydney.
| | - Cacilia Ewenz
- Airborne Research Australia, Flinders University, PO Box 335, Salisbury, South Australia, 5106, Australia
| | - Longhui Li
- School of Life Sciences, University of Technology Sydney, PO Box 123, Broadway, NSW, 2007, Australia
| | - Qiang Yu
- School of Life Sciences, University of Technology Sydney, PO Box 123, Broadway, NSW, 2007, Australia
| | - Alfredo Huete
- Climate Change Cluster, University of Technology Sydney.
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Friedel M, Allan GE, Duguid A. Do we know enough about vegetation dynamics to manage fire regimes in central Australia? ECOLOGICAL MANAGEMENT & RESTORATION 2014. [DOI: 10.1111/emr.12104] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Seasonality and facilitation drive tree establishment in a semi-arid floodplain savanna. Oecologia 2014; 175:261-71. [PMID: 24469341 DOI: 10.1007/s00442-014-2886-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2013] [Accepted: 01/10/2014] [Indexed: 10/25/2022]
Abstract
A popular hypothesis for tree and grass coexistence in savannas is that tree seedlings are limited by competition from grasses. However, competition may be important in favourable climatic conditions when abiotic stress is low, whereas facilitation may be more important under stressful conditions. Seasonal and inter-annual fluctuations in abiotic conditions may alter the outcome of tree-grass interactions in savanna systems and contribute to coexistence. We investigated interactions between coolibah (Eucalyptus coolabah) tree seedlings and perennial C4 grasses in semi-arid savannas in eastern Australia in contrasting seasonal conditions. In glasshouse and field experiments, we measured survival and growth of tree seedlings with different densities of C4 grasses across seasons. In warm glasshouse conditions, where water was not limiting, competition from grasses reduced tree seedling growth but did not affect tree survival. In the field, all tree seedlings died in hot dry summer conditions irrespective of grass or shade cover, whereas in winter, facilitation from grasses significantly increased tree seedling survival by ameliorating heat stress and protecting seedlings from herbivory. We demonstrated that interactions between tree seedlings and perennial grasses vary seasonally, and timing of tree germination may determine the importance of facilitation or competition in structuring savanna vegetation because of fluctuations in abiotic stress. Our finding that trees can grow and survive in a dense C4 grass sward contrasts with the common perception that grass competition limits woody plant recruitment in savannas.
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Bastin G, Denham R, Scarth P, Sparrow A, Chewings V. Remotely-sensed analysis of ground-cover change in Queensland’s rangelands, 1988–2005. RANGELAND JOURNAL 2014. [DOI: 10.1071/rj13127] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
A dynamic reference-cover method and remotely-sensed ground cover were used to determine the change in the state of ~640 000 km2 of rangelands in Queensland at a sub-bioregional scale between 1988 and 2005. The method is based on persistence of ground cover in years of lower rainfall and objectively separates grazing effects on ground cover from those due to inter-annual variation in rainfall. The method is applied only to areas where trees and shrubs were not cleared. An indicator of rangeland state was derived, at Landsat-TM pixel resolution, by subtracting automatically-calculated reference ground cover from actual ground cover and then spatially averaging these deviations across the area of each sub-bioregion. Landscape heterogeneity may affect reference cover but, because it is stable over time, change in mean cover deficit between sequences of dry years reliably indicates change due to grazing. All 34 sub-regions analysed had similar or increased levels of seasonally-adjusted ground cover at the end of the analysis period, which was either 2003 or 2005. Allowing for possible landscape heterogeneity effects on assessed condition, the Einasleigh Uplands bioregion was comparatively in a better state and those analysed parts of the Mulga Lands bioregion in poorer state at the first assessment in 1988. Most sub-regions of the Cape York Peninsula, Brigalow Belt North, Desert Uplands, Gulf Plains and Mitchell Grass Downs bioregions lay between these two end-states. Simulated levels of pasture utilisation based on modelled pasture growth and statistically-based grazing pressure supported the results of this regional assessment of land condition. The dynamic reference-cover method will allow the Queensland Government to monitor future grazing effects on rangeland ground cover between sequences of drier years – quantitatively and efficiently across the entire state. The method can potentially be adapted to other rangeland jurisdictions where a suitable multi-temporal database of remotely sensed ground cover exists. The results from further analyses of remotely sensed ground cover will be reported through the Australian Collaborative Rangelands Information System.
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Nano CEM, Pavey CR. Refining the ‘pulse-reserve’ model for arid central Australia: Seasonal rainfall, soil moisture and plant productivity in sand ridge and stony plain habitats of the Simpson Desert. AUSTRAL ECOL 2013. [DOI: 10.1111/aec.12036] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Catherine E. M. Nano
- Flora and Fauna Division; Department of Land Resource Management; PO Box 1120; Alice Springs; NT; 0871; Australia
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King KJ, Cary GJ, Bradstock RA, Marsden-Smedley JB. Contrasting fire responses to climate and management: insights from two Australian ecosystems. GLOBAL CHANGE BIOLOGY 2013; 19:1223-1235. [PMID: 23504898 DOI: 10.1111/gcb.12115] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2012] [Revised: 11/11/2012] [Accepted: 11/13/2012] [Indexed: 06/01/2023]
Abstract
This study explores effects of climate change and fuel management on unplanned fire activity in ecosystems representing contrasting extremes of the moisture availability spectrum (mesic and arid). Simulation modelling examined unplanned fire activity (fire incidence and area burned, and the area burned by large fires) for alternate climate scenarios and prescribed burning levels in: (i) a cool, moist temperate forest and wet moorland ecosystem in south-west Tasmania (mesic); and (ii) a spinifex and mulga ecosystem in central Australia (arid). Contemporary fire activity in these case study systems is limited, respectively, by fuel availability and fuel amount. For future climates, unplanned fire incidence and area burned increased in the mesic landscape, but decreased in the arid landscape in accordance with predictions based on these limiting factors. Area burned by large fires (greater than the 95th percentile of historical, unplanned fire size) increased with future climates in the mesic landscape. Simulated prescribed burning was more effective in reducing unplanned fire activity in the mesic landscape. However, the inhibitory effects of prescribed burning are predicted to be outweighed by climate change in the mesic landscape, whereas in the arid landscape prescribed burning reinforced a predicted decline in fire under climate change. The potentially contrasting direction of future changes to fire will have fundamentally different consequences for biodiversity in these contrasting ecosystems, and these will need to be accommodated through contrasting, innovative management solutions.
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Affiliation(s)
- Karen J King
- The Australian National University, Canberra, Australian Capital Territory, Australia
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Ward D, Wiegand K, Getzin S. Walter's two-layer hypothesis revisited: back to the roots! Oecologia 2012; 172:617-30. [PMID: 23266712 PMCID: PMC3679411 DOI: 10.1007/s00442-012-2538-y] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2012] [Accepted: 11/16/2012] [Indexed: 11/26/2022]
Abstract
Walter (Jahrb Wiss Bot 87:750–860, 1939) proposed a two-layer hypothesis, an equilibrium explanation for coexistence of savanna trees and grasses. This hypothesis relies on vertical niche partitioning and assumed that grasses are more water-use efficient than trees and use subsurface water while trees also have access to deeper water sources. Thus, in open savannas, grasses were predicted to predominate because of their water use efficiency and access to subsurface water. This hypothesis has been a prominent part of the savanna literature since first proposed. We review the literature on Walter’s hypothesis and reconsider his original intentions. Walter intended this hypothesis to be restricted to dry savannas. In his opinion, mesic and humid savannas were controlled by biotic factors and disturbances. We surveyed the global savanna literature for records of vertical niche partitioning by grasses and trees. We find that, within the scope of Walter’s original intentions, this hypothesis works remarkably well, and in some cases is appropriate for deserts as well as for dry temperate systems and even some mesic savannas.
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Affiliation(s)
- David Ward
- School of Life Sciences, University of KwaZulu-Natal, Scottsville, South Africa.
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MCDONALD PETERJ, LUCK GARYW, PAVEY CHRISR, WASSENS SKYE. Importance of fire in influencing the occurrence of snakes in an upland region of arid Australia. AUSTRAL ECOL 2012. [DOI: 10.1111/j.1442-9993.2011.02348.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Fensham RJ, Powell O, Horne J. Rail survey plans to remote sensing: vegetation change in the Mulga Lands of eastern Australia and its implications for land use. RANGELAND JOURNAL 2011. [DOI: 10.1071/rj11007] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
There is a prevailing paradigm that woody vegetation is expanding at the expense of grassland with reduced burning under pastoralism in the Mulga Lands biogeographic region in eastern Australia. This raises the possibility that the region is acting as a carbon sink. Vegetation boundaries were precisely positioned from rail survey plans dating from 1895 to 1900. This baseline was compared with the position of boundaries on 1952 aerial photography and 2010 Google Earth imagery. The conversion of forest to non-forest by mechanical clearing was also mapped from satellite imagery. There was no consistent trend in the direction of boundary movement for mulga (Acacia aneura F.Muell. ex Benth.), gidgee (Acacia cambagei R.T. Baker) forest or miscellaneous other forest types. The stability of the boundaries, despite the transition from aboriginal management to rangeland pastoralism, contrasts with dramatic declines in tree cover resulting from mechanical clearing. Mapping of forest cover from satellite imagery reveals that conversion of forest to non-forest has reduced mulga forest to 74%, gidgee forest to 30% and miscellaneous forest types to 82% of their original area. Annual clearing rates for the period between 1997 and 2005 were 0.83, 0.95 and 0.43% for those forest types, respectively. Clearing has declined substantially in the period 2005–09 since the advent of recent regulations in Queensland. The area remains a source of carbon emissions but this situation may reverse if restoration of mulga dry forest becomes an attractive land use with an emerging carbon market.
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