2 Woodland Mosaic The Lowland Grassy - Environment

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ACT LOWLAND WOODLAND CONSERVATION STRATEGY2The Lowland GrassyWoodland Mosaic2.1Background2.1.1Temperate Eucalypt Woodlandsof South-eastern AustraliaIn south-eastern Australia, temperate eucalyptwoodlands once formed a relatively continuousvegetation crescent from about 27oS in southernQueensland to the lower south-east of South Australiawith a narrow strip north and south of Adelaide. Thesewoodlands were the culmination of a long evolutionthrough the Tertiary period (3–65 million years BP) bywhich time the ancient continent of Gondwana hadbroken up and Australia was drifting north. During theTertiary, vast changes occurred in Australian climateand soils, and the evolving eucalypts supplantedrainforests over much of the continent (Beadle 1981).The temperate eucalypt woodlands in south-easternAustralia are bounded on the west by semi-arid shrubwoodlands and mallee, and on the east and south bydry sclerophyll forests. These woodlands occurred aspart of a mosaic, merging with treeless grasslands onvalley bottoms and broad plains at lower elevations,and with dry sclerophyll forests on the upper slopes ofhills and ridges (Moore 1970; Yates and Hobbs 2000;Environment ACT 2002). In the southern ACT andsouth-eastern NSW, lower elevation temperatewoodland (referred to hereinafter as ‘lowlandwoodland’) grades into woodland of the mountainfoothills and dry hill slopes, dry sclerophyll forest andsub-alpine woodland (Moore 1970; NCDC 1984;Landsberg 2000).The Australian pastoral industry began in the early1800s when access was gained to the temperateeucalypt woodlands across the Great Dividing Rangein NSW. Because of the wide spacing of the trees andthe high proportion of grass it was possible to stockmany of the woodlands without initially felling orringbarking the trees (Moore 1970). Subsequentintensification of rural use, in particular thedevelopment of agriculture on the relatively fertilewoodland soils, conversion to exotic pasture, and thegrowth of towns and infrastructure resulted inwidespread clearing and fragmentation of temperateeucalypt woodlands. In the woodland remnants theformer tall, warm season, perennial tussock grassunderstorey has usually been partly or wholly replacedby short, cool season, perennial native grasses inlightly grazed areas or mainly exotic grass and herbspecies where grazing levels are high (Prober andThiele 1995). Adjacent natural temperate grasslandareas have been similarly affected (Environment ACT2002).Because of the high level of clearing (estimated at upto 95% in mixed farming areas in NSW to the northwest of the ACT) it is not possible to accuratelyascertain the floristic composition of the pre-Europeantemperate eucalypt woodlands, nor of the understorey,that together comprise the ecological community(Prober 1996). However, available evidence suggeststhe floristic composition was influenced by climate, soiltype, topography, hydrology, biotic interactions such asgrazing, and large-scale disturbances such as fire,windstorms, floods and droughts (Yates and Hobbs2000). The woodlands were affected by climatic dryingand probably an increased incidence of fire during thelatter part of the Pleistocene (Hobbs 2002).These well-established eucalypt woodlands were thehome of Aboriginal people for possibly 50 000 yearsand there is no doubt that they burnt the vegetation.The precise effects of this are unclear, but theavailable evidence does not support the hypothesisthat Aboriginal burning caused the evolutionarydiversification of the Australian biota (Bowman 1998).Aboriginal burning followed millions of years ofevolutionary adaptation in which lightning-generatedfire probably played a significant part. At the time ofEuropean settlement, eucalypt woodlands were notsimplified park-like landscapes. They contained a widediversity of plant species and a great diversity ofanimal species that relied upon a complexity of11

ACT LOWLAND WOODLAND CONSERVATION STRATEGYhabitat; for example, Prober (1996) recorded 375 plantspecies (including trees) in relatively undisturbedgrassy White Box woodland remnants across NewSouth Wales.The distribution of temperate woodland remnants reflectsthe preferential clearing of the most fertile soils in plains,lower slopes and stream valleys. Woodlands that remainare generally located in more marginal areas such asrocky sites, upper slopes, poorer soils and flood plainssubject to periodic inundation (Bennett 1993).2.1.2Temperate Woodland: ACTRegional ContextTemperate woodland in the ACT region occurs withinthe ‘South Eastern Highlands Region’ as defined in theInterim Biogeographic Regionalisation for Australia(Thackway and Cresswell 1995). This bioregionincludes about 80% of the ACT, the tablelands andwestern slopes of south-eastern NSW (to north ofBathurst) and extends into Victoria. The alpine areasof Victoria, NSW and the ACT form a separatebioregion.In the easterly part of this bioregion, the dominant treespecies of lowland woodland are usually Yellow Box(Eucalyptus melliodora) and/or Blakely’s Red Gum(E. blakelyi) with Apple Box (E. bridgesiana) as afrequent associate or co-dominant. This Yellow Box–RedGum grassy woodland extends from south of the ACT,north-east to Goulburn, north-west almost to Young,north to Orange and past Bathurst (AUSLIG 1990). Tothe west of the ACT, the community forms mosaics withthe White Box (E. albens) dominated woodlands moretypical of slightly drier sites of the western slopes (Figure2.1). Within the Grassy White Box Woodland, YellowBox and Blakely’s Red Gum may become locallydominant along non-permanent watercourses or ondeeper soils in valleys (NSW NPWS 2002).In temperate grassy woodland, a more or lesscontinuous stratum, in which mid-height tussock grassesare prominent, usually dominates the understorey.Structurally and floristically, this stratum probably closelyresembles the natural temperate grassland that wasadjacent to the woodland prior to European settlement.Shrubs and sub-shrubs may also be present and form adiscontinuous middle stratum (Costin 1954; Landsberg2000). The pre-European floristic composition of theunderstorey is poorly known, however, because grazingspread through most of the woodland 150 years agoresulting in introduction of exotic species and changes inor elimination of some native species.Figure 2.1Estimated Pre-European Distributionof Temperate Woodland Dominatedby Yellow Box, Blakely’s Red Gumand White Box in South-easternAustralia (from AUSLIG 1990).Map from Landsberg 2000.12

ACT LOWLAND WOODLAND CONSERVATION STRATEGY2.22.2.1.1 Woodland on Low Hills andPlains (Lowland Woodland)Woodlands in the ACT Region2.2.1 Woodland Types in theACT RegionLandsberg (2000) defined five major woodland typesin the ACT region. Arranged altitudinally they are:subalpine, mountain foothills, dry hillslopes, low hillsand plains, and river fringes. This Lowland WoodlandConservation Strategy includes grassy woodland ofthe low hills and plains and other box woodlands of themountain foothills and the dry hillslopes where theyintergrade with Yellow Box–Red Gum grassy woodland(Table 2.1). Recent work based on analysis of the datafrom the Southern Region Comprehensive RegionalAssessment study (Thomas et al. 2000) has definedecological communities in the south-east region ofNew South Wales and the ACT. These communitiesare listed in full in the ACT State of the EnvironmentReport 2003 (ACT SOE 2003). Types of ecologicalcommunities derived from this analysis are used insections 2.2.1.1 to 2.2.1.4 below.Table 2.1: ACT Woodlands: Inclusion inLowland Woodland Conservation StrategyWoodland type (after Landsberg 2000)Subalpine Fully protected in Namadgi National Park(see s. 2.2.1.3 for ecological communities)Mountainfoothills Dryhillslopes Low hillsand plainsRiver fringes(a) Tablelands Dry Shrubby Box Woodlandadjacent to Yellow Box–Red GumGrassy Woodland(b) Remainder of the box woodland mainlyprotected in Namadgi National Park(a) Tablelands Dry Shrubby Box Woodlandadjacent to Yellow Box–Red GumGrassy Woodland(b) Tablelands Brittle Gum Dry Forest—significant proportion in CanberraNature Park (a) Tablelands and Slopes Yellow Box–RedGum Grassy Woodland (b) Tablelands Valley Snow GumGrassy Woodland Mainly protected in river corridorNature Reserves (see s. 2.2.1.4 forecological communitiesnWoodland included in Lowland Woodland Conservation Strategy Woodland or other vegetation community not included inLowland Woodland Conservation StrategyLowland woodland includes Yellow Box–Red Gum GrassyWoodland (endangered ecological community) and lowelevation Snow Gum Grassy Woodland. These are includedin the Lowland Woodland Conservation Strategy. Tablelands and Slopes Yellow Box–Red GumGrassy Woodland (Yellow Box (Eucalyptusmelliodora), Blakely’s Red Gum (E. blakelyi), AppleBox (E. bridgesiana)). Tablelands Valley Snow Gum Grassy Woodland(Snow Gum (E. pauciflora), Candle Bark(E. rubida)).These two lowland woodland communities are readilyrecognised by their characteristic eucalypt species.Their distribution is closely related to altitude,topography and aspect. The core community is theendangered Yellow Box–Red Gum Grassy Woodlandthat is generally found on the middle and lower slopesof hills (600–900 m) and in gently undulatingtopography not very susceptible to cold-air drainage.Annual rainfall is in the range of 400–800 mm.At lower elevations, Tablelands and Slopes YellowBox–Red Gum Grassy Woodland intergrades withTablelands Valley Snow Gum Grassy Woodland andNatural Temperate Grassland. At higher elevations andon more rocky sites, it intergrades with Tablelands DryShrubby Box Woodland and Tablelands Brittle GumDry Forest (Figure 2.2).2.2.1.2 Woodland on Dry Hill Slopesand Mountain FoothillsTablelands Dry Shrubby Box Woodland is included in theLowland Woodland Conservation Strategy where itintergrades with Tablelands and Slopes Yellow Box–RedGum Grassy Woodland. Tablelands Dry Shrubby Box Woodland (Bundy(E. goniocalyx)–Mealy Bundy (E. nortonii)–RedBox (E. polyanthemos)–Apple Box(E. bridgesiana)–Broad-leaved Peppermint(E. dives)) Tablelands Brittle Gum Dry Forest (RedStringybark (E. macrorhyncha)–Scribbly Gum(E. rossii)–Brittle Gum (E. mannifera))These two communities occupy the higher elevationson hillslopes and mountain foothills above the YellowBox–Red Gum woodland but intergrade where theymeet (see Figure 2.2).Tablelands Dry Shrubby Box Woodland is most oftenfound at higher elevations on the cooler moister13

ACT LOWLAND WOODLAND CONSERVATION STRATEGYFigure 2.2GLandscape Distribution ofLowland EcologicalCommunities in the ACT.FA: Natural TemperateGrasslandB: Tablelands Valley SnowGum Grassy WoodlandDDFEC: Riparian WoodlandD: Yellow Box–Red GumGrassy WoodlandDBE: Secondary Grassland(Yellow Box–Red Gum)F: Tablelands Dry ShrubbyBox WoodlandsG: Tablelands Brittle GumDry ForestCAhillslopes and mountain foothills. It occurs extensivelyin the southern ACT, in the sub-montane streamvalleys and hillslopes flanking the Murrumbidgee Riverat elevations generally from 700 m to over 1200 m(NCDC 1984). Tablelands Dry Shrubby Box Woodlandalso occurs on lower exposed slopes where itintergrades with Yellow Box–Red Gum GrassyWoodland and has a similar structure and understoreyfloristic composition.2.2.1.3 Sub-Alpine and AlpineWoodland (Not Included in LowlandWoodland Conservation Strategy)It has been estimated that about half of this communityhas been cleared but the remainder is now mainlyprotected in Namadgi National Park. It was extensivelyused for grazing in the past and exotic weeds arecommon in the understorey (Landsberg 2000). Montane Frost Hollow Snow Gum Woodland(Snow Gum (E. pauciflora)–Black Sallee(E. stellulata)–Mountain Swamp Gum(E. camphora))Tablelands Brittle Gum Dry Forest occupies steep,rocky and dry sites often with poorly developed soils.The community grades into Yellow Box–Red Gumwoodland at lower elevations and often consists ofthree strata: a sparsely continuous tree stratum, adiscontinuous but well developed shrub stratum, and adiscontinuous herbaceous stratum (Costin 1954).These areas had limited grazing value but were oftencut over for firewood, fencing and rough constructiontimbers. In this process they may have been openedup to the extent that the tree stratum resembles thestructure of downslope lowland woodland. With thecessation of rough grazing and woodcutting,regeneration is occurring. In the ACT extensive areaswere cleared for pine plantations.It is estimated that about 30% of the pre-1750 extentof these communities remains in the ACT and adjacentpart of NSW (Landsberg 2000). The communitiesoccur in a fragmented pattern on hills and ridges witha significant proportion now included in CanberraNature Park.14 Alpine White Sallee Woodland (Snow Gum(E. pauciflora)–Alpine Snow Gum (E. pauciflorassp. niphophila)) Sub-alpine White Sallee Woodland (Snow Gum(E. pauciflora)–Sub-Alpine Snow Gum (E.pauciflora ssp. debeuzevillii))These woodlands occur in the higher country in thewestern and southern parts of the ACT. They occur inbroad open flats, often with impeded drainage, ormore-freely draining, exposed saddles along highmountain ridges often interspersed with treeless areas.The understorey is dominated by native tussockgrasses with a wide diversity of herbs (Costin 1954;NCDC 1984). There has been very little clearing ofSnow Gum woodlands at higher altitude but there hasbeen some clearing and thinning of Black Sallee andMountain Swamp Gum in valleys that were previouslygrazed (Landsberg 2000). Studies by Pryor (1939) andBanks (1981, 1989) showed a greatly increased firefrequency for the higher altitude sub-alpine woodlandsfrom about 1860 as prospectors and pastoralistsbegan moving through the area en route to theKiandra goldfields. Frequent (almost annual) burningcontinued until 1960 resulting in a profusion ofleguminous shrubs and dense Snow Gumregeneration.

ACT LOWLAND WOODLAND CONSERVATION STRATEGYSub-alpine woodlands in the ACT are now fullyprotected in Namadgi National Park but remain fireprone. Large areas were severely burnt in thebushfires in January 2003. Based on past fire history,Snow Gum woodlands are expected to regenerate,however, the fire response of Black Sallee is not wellknown (Carey et al. 2003).2.2.1.4 River-Fringing Woodlands(Not Included in Lowland WoodlandConservation Strategy) Slopes and Tablelands Riparian She-oakWoodland (Casuarina cunninghamiana community) Tablelands Riparian Ribbon Gum Woodland(E. viminalis riparian community)The community dominated by Riparian She-oak isfrequently found in pure stands in narrow belts alongwatercourses in eastern Australia (see Figure 2.2).Typically, it is associated with sandy and shingleterraces between normal water levels and themaximum flood height. In the ACT, Riparian She-oakwoodlands extend along much of the MurrumbidgeeRiver, some of its tributaries and the lower MolongloRiver where they are mainly protected in river corridornature reserves. South of the Tharwa area where theriver banks are higher and shingle terraces absent,Ribbon Gum (E. viminalis) occurred in the riparianzone but has been mostly cleared. River-fringingwoodlands will be included in a conservation strategyfor aquatic and riparian ecosystems (expected to beprepared in 2004–5).2.3Changes to Woodland SinceEuropean Settlement andOngoing Threats2.3.1Changes to Woodland SinceEuropean SettlementFollowing European settlement, a number of factorshave been responsible for removal of woodland andmodification of its structure and floristics in the ACTand region: Large scale clearing for pastoralism andagriculture: Clearing, selective clearing andringbarking for pastoralism and cropping, asoccurred in much of the NSW box – gumwoodlands was not as extensive in the ACT.Leasehold tenure (often short-term) discouragedinvestment in intensive pasture improvement thatwas widely adopted elsewhere from the 1950s.However, clearing to the level of individualpaddock trees was reasonably common and isevident in the present rural landscape. Removaland death of these large old trees in theforeseeable future and lack of regeneration willresult in a largely treeless landscape. Urban development: Historical photographs showthat the early development of central Canberraoccurred on a mostly treeless plain with treeclearing and thinning evident on the adjoining hillslopes (Seddon 1977). The treeless plaincomprised low elevation ecological communities, inparticular, Natural Temperate Grassland andriparian communities, and at slightly higherelevations, cleared or partly cleared woodlandareas. Clearing of woodland remnants occurred asthe city expanded into the Belconnen,Tuggeranong and Gungahlin areas. Grazing: Grazing by livestock has had a majorimpact throughout the box–gum woodlandsbeginning with the first pastoral expansion early inthe 19th century. Grazing has reduced the height,cover and biomass of the grassy stratum, with thetaller native grasses often being replaced by lowergrowing species of grasses and forbs (Costin1954; Moore 1966; AUSLIG 1990). Diversity ofnative forbs and subsidiary grasses declinessignificantly with grazing, and abundance of annualweeds increases (Prober and Thiele 1995). Thereis often a paucity of tree regeneration in grazedstands as sheep and cattle find seedlingspalatable and soil compaction under remainingtrees hinders germination (Landsberg et al. 1990;Spooner et al. 2002). The impact of grazingdepends upon a number of factors, particularlystocking rates, level of pasture improvement,supplementary stock feeding which introducesweeds, and the extent of protection of riparianzones and remnant patches of woodland. MostACT lowland woodland areas were grazed in thepast and show varying levels of retention andregeneration of the tree cover and nativeunderstorey. Deliberate or incidental introduction of exoticpasture plants: Exotic pastures are extensivethroughout the region, with widespreadintroduction of grasses such as Phalaris (Phalarisaquatica) and Cocksfoot (Dactylis glomerata) andmany clovers, usually in conjunction with theapplication of superphosphate. The degree ofstructural change depends on the speciesintroduced, the amount of fertiliser applied and the15

ACT LOWLAND WOODLAND CONSERVATION STRATEGYextent of cultivation. Modification is most extremewhen the mid-height native tussock is replaced bydense sown pasture that is dominated by exoticsward-forming grasses and legumes (Costin 1954;Moore 1966; AUSLIG 1990). Some introducedgrasses have become major invasive plants ofgrassy woodland and Natural TemperateGrassland, especially African Love Grass(Eragrostis curvula). This species appears to havebeen introduced to Australia by accident prior to1900, but has been imported for experimentalassessment several times since then (Parsons andCuthbertson 1992). Introduction of other exotic plant species: Manyother plant species have also been introduceddeliberately or accidentally and have becomeweeds, often replacing native species in theirhabitat. Naturalized species have spread intowoodland areas and this process continues. Someexamples include St Johns Wort (Hypericumperforatum), annual and perennial exotic grassesincluding bromes, Serrated Tussock (Nasellatrichotoma), Chilean Needle Grass (N. neesiana),and woody weeds that have escaped from urbanplantings including Cotoneaster (Cotoneasterspp.), Firethorns (Pyracantha spp.) and Hawthorn(Crataegus monogyna). Response to disturbance: In some grassywoodlands of low pastoral value, particularly thosein which Apple Box is prominent, partial treeclearing has been followed by dense regrowth.This consists mainly of eucalypt saplings and asecondary shrub layer dominated by species ofAcacia, Cassinia and Kunzea (Costin 1954). Suchstructural changes do not appear to have followedclearing of the usually topographically lower YellowBox–Red Gum Grassy Woodland community butthey do occur where grazing has been withdrawnfor various periods and tree and sh

Australia are bounded on the west by semi-arid shrub woodlands and mallee, and on the east and south by . adjacent to the woodland prior to European settlement. Shrubs and sub-shrubs may also be present and form a . n Woodland included i

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