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

Figure 5.27 Cattle on the bank of the River Murray in Barmah State Forest.increased alkalinity and salinity, and the accumulation ofbicarbonate in the soil solution.Mundulla Yellows has been reported from the leaves ofriver red gums near Hattah-Kulkyne but soil propertieswere not investigated. The distribution of MundullaYellows within the River Red Gum Forests study area isunknown and further work is required.GrazingDomestic stock grazing can potentially lead to pugging,selective plant removal, weed invasion, soil compaction,erosion and increased sediment in rivers and streams. Inturn, these processes can simplify the structure of thehabitat (Tasker & Bradstock 2006), stock compete forfood with native animals and remove habitat (such asabolishing invertebrate burrows through soilcompaction). The social and economic benefits ofgrazing, legislation and administrative arrangements(including licencing and agistment permits) and extent ofgrazing on public land within the study area arediscussed in chapter 13. Some of the effects of grazinghave been established, but the wider grazing issue iscontroversial and is further discussed in chapter 19.The removal of palatable vegetation alters thecomposition, function and structure of vegetationcommunities. The selective nature of grazing has thepotential to significantly change the biodiversity of anarea. This effect has been well documented for trees andgroundcover plants, particularly in riparian landscapes(Robinson & Mann 1998; Robertson & Rowling 2000;Spooner et al. 2002; Jansen & Robertson 2005).The tendency for domestic stock to graze selectively iswell demonstrated in Barmah forest. Early accounts ofBarmah forest indicate that cumbungi and common reedwere preferentially grazed by cattle and are nowrestricted in occurrence (Chesterfield 1986).Cattle are also attracted to Moira grass, in preference toany other fodder. This species grows in flood-pronegrasslands and breaks a period of winter dormancygrowing prolifically during spring flooding. Thecombined effects of altered water regimes and thepreferences of cattle grazing have substantially reducedthe distribution of Moira grass. Domestic stock grazingalso limits the recruitment of red gum populations, withthis effect decreasing as stocking rates decrease (Jansen& Robertson 2005). This effect is exacerbated by anincreased abundance of seed-eating ants at sites grazedby cattle (Meeson et al. 2002).Other studies found that increased grazing reduces theecological condition of riparian habitat and results in theloss of bird, frog and plant diversity in river red gumhabitats (Jansen & Robertson 2005). Frog diversity andwetland condition declined with increasing grazingintensity on the floodplains of the Murrumbidgee River(Jansen & Healey 2003). Declines in bird populationswere found to be related to loss of vegetation structuredue to grazing (Martin & Possingham 2005), probablybecause grazing removes the grass tussocks and shrubswhere species such as yellow-faced honeyeaters andrufous songlarks nest (Ford et al. 2001).There have been no studies on the effects of grazing onriver red gum invertebrates although stock grazing ingrey box woodlands alters the populations of grounddwellinginvertebrates by inducing changes to vegetationand litter layers (Bromham et al. 1999). In grey boxwoodlands, ungrazed woodland had a more diverseground invertebrate fauna, most likely due to the greaterdiversity of food and habitat resources provided by theless disturbed vegetation. Additionally, soil compactionby grazing animals can result in changes to invertebratefaunal composition by its effect on ground and shrublayer plants and on plant litter (Scrougall et al. 1993).84 River Red Gum Forests Investigation 2006