Tropical Grasslands (2009) Volume 43, 37–52 37 Woody plant responses to various clearing strategies imposed on a poplar box (Eucalyptus populnea) community at Dingo in central Queensland P.V. BACK1, E.R. ANDERSON1, killing the trees and, with inexpensive labour W.H. BURROWS1 AND C. PLAYFORD available, trees on large areas were ringbarked Department of Primary Industries and Fisheries, between 1890 and the 1940s. Rockhampton, Australia The introduction of ‘frill ringing’ and poi- 1 Now retired from QDPI&F soning with arsenical tree killers in the 1940s and 1950s helped reduce the amount of labour required and trees on more country were treated. Abstract By this time, land managers were increasingly treating regrowth on previously treated country. The effi cacy of individual tree treatment (stem- Following World War II, large-tracked tractors injection), aerially applied root-absorbed herbi- (bulldozers) became available and these have cide and mechanical felling (with and without been used to clear extensive areas of poplar box subsequent fi re) in controlling woody plants was woodland (Robertson and Beeston 1981). The compared in a poplar box (Eucalyptus populnea) labour needed was again reduced with the advent woodland community in central Queensland, of the stem-injection method (Robertson 1966) Australia. All treatments reduced woody plant of applying the modern herbicides, 2, 4, 5-T and populations and basal area relative to the untreated picloram. These herbicides were very effective at control. Chemical control and ‘mechanical felling killing a range of woody plants when correctly plus fi re’ treatments were equally effective in applied (Robertson and Moore 1972). reducing woody plant basal area 7 years after The 1980s saw the introduction of the soil- the treatments were imposed. However, mechan- applied liquid herbicide hexazinone (Velpar L®), ical felling alone was less effective. There was a which can also be applied by stem-injection, and clear tendency for the scattered tree (80% thin- the granular herbicide tebuthiuron (Graslan®), ning) treatment to recover woody plant basal area which can be applied aerially. The reduced towards pre-treatment levels faster than other labour costs of aerial application and its effective- clearing strategies, although this response was ness in controlling a number of woody species not signifi cantly different from 20% clump reten- (Burrows et al. 1994) allowed large areas to tion and mechanical felling (without burning) be treated quickly. Concurrent with these later treatments. develop ments was a growing understanding of soil, water and nature conservation principles and Introduction how to apply these to achieve responsible and sustainable development. This meant that the land Poplar box (Eucalyptus populnea) woodlands in manager had a number of strategies available, Queensland have been cleared to increase pasture such as retaining untreated areas as clumps or production (Walker et al. 1972; Scanlan and strips, when clearing woodlands. Burrows (1990; Burrows 1990) for more than 150 years (Weston 1993) devised guidelines for woodland clearing et al. 1980). In the second half of the 19th cen- which recommended the retention of timber on at tury, ringbarking (Robertson 1966; Robertson and least 20% of the area as intact strips (corridors) Beeston 1981) was the most common method of or clumps. The aim of this study was to assess how effec- tive a number of clearing strategies (all available tree-clearing techniques in commercial use and Correspondence: P.V. Back, 56 Perrott Drive, Rockyview, applied to eucalypt woodlands, at the time the trial Qld 4701, Australia. E-mail: [email protected] commenced1) were in controlling woody species 03_09_04_Back_et_al.indd 37 14/4/09 8:13:25 AM 38 P.V. Back, E.R. Anderson, W.H. Burrows and C. Playford in a poplar box woodland and to assess how much wood (Acacia excelsa). Understorey woody regrowth appeared following each treatment. The species present included false sandalwood (Ere- effects of retaining some of the trees in different mophila mitchellii), currant bush (Carissa ovata) landscape arrangements were also studied. and whitewood (Atalaya hemiglauca). Other woody species recorded in the treatment plots are given in Table 1. Materials and methods The owners of ‘Wandobah’ had a tree manage- ment program in place involving timber treatment Site every 30 years or so. The woody plants present on the trial site were regrowth following previous The experimental site was situated on ‘Wan- clearing by ringbarking in the 1920s and 1950s. dobah’, a beef cattle grazing property in the The trial site had been treated most recently ° Dingo area of central Queensland (23 36.4´S, during the 1950s and was therefore due for treat- ° 149 25.22´E). The woodland site was dominated ment under this management regime, when the by poplar box (Eucalyptus populnea) in associa- trial treatments were imposed. tion with Queensland blue gum (E. tereticornis), narrow-leaved ironbark (E. crebra), ghost gum (Corymbia dallachiana), bloodwood (Corymbia Rainfall clarksoniana), scrub leopardwood (Flindersia dissosperma), bull oak (Allocasuarina lueh- Rainfall for the site (Table 2) was below average mannii), vinetree (Ventilago viminalis) and iron- in the establishment year (1987), average or slightly above average for 1988–1990, and well below average for the years 1991–1997. 1 Tree clearing is now subject to regulation in Queensland. Broad-scale clearing of remnant woodlands has been phased out, with no clearing permits granted after January 1, 2007. While control of regrowth is still permitted, the appropriate Experimental design guidelines from the Queensland Department of Natural Resources and Water (NRW) should be consulted before pro- ceeding and permits may be required. Some clearing in rem- Six woodland management strategies and a con- nant woodlands is still permitted for certain purposes (clearing trol treatment were imposed in a randomised fence lines, access to weed outbreaks etc.), but the appro- priate guidelines must be followed and NRW approval may be block (7 treatments × 3 replications) layout. The needed before proceeding. treatments were: Table 1. Other woody plants recorded at the ‘Wandobah’ experimental site. Acacia bidwillii Corkwood wattle Ehretia membranifolia Peach leaf Acacia harpophylla Brigalow Eremophila longifolia Berrigan Acacia salicina Sally wattle Eremophila deserti Ellangowan poison bush Alectryon diversifolius Scrub boonaree Eucalyptus cambageana Dawson gum Alectryon oleifolius Boonaree Eucalyptus crebra/E. populnea hybrid Alphitonia excelsa Red ash Grevillea striata Beefwood Allocasuarina luehmannii Bull oak Hakea fraseri Bootlace oak Apophyllum anomalum Broom bush Harrisia martinii Harrisia cactus Archidendropsis basaltica Dead fi nish Jasminum didymum subsp. Native jasmine racemosum Breynia oblongifolia Coffee bush Maytenus cunninghamii Yellow berry bush Psydrax odorata Maireana microphylla Cotton bush Psydrax oleifolia Myrtle tree Melaleuca nervosa Paperbark teatree Capparis canescens Wild orange Myoporum montanum Boobialla Capparis lasiantha Nipan, wait-a-while Opuntia stricta Common pest pear Capparis loranthifolia Narrow-leaved bumble Opuntia tomentosa Velvety tree pear Capparis mitchellii Bumble bush Owenia acidula Emu apple Carissa ovata Currant bush Owenia venosa Crow apple Cassia brewsteri Bean bush Parsonsia lanceolata Rough silkpod Cassia tomentella Bean bush Petalostigma pubescens Quinine berry Clerodendrum fl oribundum Lolly bush Sarcostemma viminale ssp. Caustic creeper brunonianum Corymbia tessellaris Moreton Bay ash Santalum lanceolatum Sandalwood Denhamia oleaster Olive-leaved denhamia Terminalia oblongata Yellowwood Dodonaea viscosa Sticky hop bush Ventilago viminalis Vinetree 03_09_04_Back_et_al.indd 38 14/4/09 8:13:26 AM Tree-clearing strategies 39 (a) All woody plants taller than waist high by industry practice. All treatments were grazed treated by stem-injection with the herbicide during the trial at conservative stocking rates. Velpar L® [active ingredient (a.i.) 250g/L Plot size for treatments SI All, Scattered, hexazinone] (Figure 1). (SI All) Clumps and the untreated control was 9 ha (b) 80% of all trees (>7m tall) and all shrubs (300 m × 300 m). The treatment Strips was taller than waist high treated by stem- injection applied to 18 ha plots (600 m × 300 m) with with Tordon Timber Control Herbicide® the assessment area (300 m × 300 m) centrally (a.i. 50g/L picloram plus 100g/L triclopyr). located (Figure 3). This longer plot was needed The 20% of untreated trees were left scat- to ensure that the aircraft applied the treatment tered as evenly as possible throughout the evenly to the assessment area. Treatments Pulling plot. (Scattered) and Pulling+Burn were applied to 4.5 ha plots (c) All woody plants taller than waist high (300 m × 150 m) (Figure 4). The margins of treated by stem-injection with Tordon Timber each 9 ha plot were clearly marked prior to treat- Control Herbicide® on 80% of the area while ment by applying paint to the stems of trees on or near the boundary. Trees to be retained in the woody plants on the remaining 20% of the scattered trees treatment (Scattered) were marked plot were retained as a clump in each corner with a band of different coloured paint as were of the treated plot2 (Figure 2). (Clumps) the untreated clumps in treatment Clumps. (d) Pellets containing the root-absorbed herbi- The treatments were applied by commercial cide Graslan® (a.i. 200g/kg tebuthiuron in contractors