Discussion Paper - Part A - Victorian Environmental Assessment ...

which is essential habitat for some species. Larger trees,however, are favoured for wood products or silviculture,and are therefore less abundant in the forest than otherage classes of trees. One study on the northern plains ofVictoria found that 55 percent of river red gums were10-30 cm in diameter, 35 percent were 31-70 cm indiameter and only 10 percent were greater than 70 cmin diameter (Bennett et al. 1994). It is likely that in pre-European times there was a much greater proportion inthe largest size class.Hollow-formation is one of the most importantecological functions of these older trees. Most river redgums are thought to begin forming hollows atapproximately 120 years of age (Gibbons & Lindenmayer2002) although the age varies, depending on soilfertility, wind exposure and fire history (Harper et al.2005). It takes even longer before the hollows are largeenough to suit the full range of hollow-dependentfauna. A study of hollows on the northern plains foundthat river red gums have fewer hollows than black box,yellow box and grey box (comparing similar-sized trees).Only seven percent of river red gums had hollowsoverall, but 55 percent of the larger trees (with adiameter greater than 70 cm) had hollows (Bennett et al.1994).Hollows are very important for some threatened speciesand many populations are likely to be limited by treehollow availability. Scattered clumps of hollow-bearingtrees and even single hollow-bearing trees in paddockscan support animals (van der Ree et al. 2006). InAustralia, 303 native vertebrate species use tree hollowsfor breeding and shelter—approximately 15 percent ofall terrestrial vertebrate species, or ten percent of reptilespecies, 13 percent of amphibians, 15 percent of birdsand 31 percent of mammals (Gibbons & Lindenmayer2002).The superb parrot is a threatened bird speciescharacteristic of river red gum forests and woodlands.The birds fly from New South Wales to Victoria to breedbetween September and December before returningnorth. At the time of European settlement, the superbparrot was common along the Goulburn River as farupstream as Yea and was frequently recorded nearMelbourne (Figure 5.4). As recently as the 1980s, superbparrots were regularly seen along the lower Ovens River.In Victoria, superb parrots are now found only in anarrow strip between Echuca and Yarrawonga and onlybreed in Barmah State Park and State Forest. The currentVictorian population size is estimated to be 300individuals (Deayton & Deayton 2005).Superb parrots breed in tree hollows and nestingtypically occurs in loose colonies in old healthy (butsometimes dead) river red gum trees with numerousspouts. The trees may be single or clustered but areusually close to water. The birds fly out of the river redgum forests to forage on flowers, fruits and seeds innearby box woodlands. A key measure to protectnesting areas has been the establishment of SpecialProtection Zones (SPZs, see chapter 14) where timberharvesting is excluded from nesting areas in BarmahState Forest, although one of these areas wasinadvertently logged in 2005.Tussock GrasslandNative grasslands are tree-less environments that cansupport a rich diversity of species. Generally, grasslandsare not well-recognised or appreciated and when notflowering it may be difficult to tell the differencebetween nationally significant grasslands and adjacentpaddocks of exotic grasses. Native grasslands have beenextensively destroyed since European settlement and lessthan one percent currently survives—mostly in smallpatches on roadsides, railways, other Crown land andfreehold. Few of these remnants are in good ecologicalcondition (Map 5.1). The Northern Plains GrasslandCommunity is one of the most endangered vegetationcommunities in Victoria and is listed under the Flora andFauna Guarantee Act 1988. Many processes that disturbsoil threaten grasslands including cultivation, clearing,road works and compaction, while other threateningactivities include inappropriate fires, over-grazing,absence of grazing, fertiliser and herbicide application orspray drift and tree-planting. A high proportion ofgrassland species are threatened, including the followingthree examples.Chariot wheels is a small perennial herb (growing toless than 20 cm, see Figure 5.16) restricted to smallareas around Birchip and Mitiamo in Victoria and in thewestern Riverina of New South Wales (see Figure 5.3). Itis vulnerable nationally, in New South Wales andVictoria. The species is characterised by the woollydisc–shaped fruit (5-10 mm), which can be seen inspring and early summer. Ants like to eat the seeds andso the fruits can sometimes be found around theentrances to ants’ nests. Chariot wheels is not found inareas that have been cropped and populations arerestricted to roadsides and isolated remnants. It is furtherthreatened by herbicide use, intensive grazing, treeplantingand soil disturbance.Figure 5.16 Chariot wheels, a small perennial herbfound in grasslands in Victoria.Discussion Paper73