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

Figure 5.6 Diagrammatic summary of the five studies of invertebrate diversity near the study area.Mallee 1100 species in RRG160 species in Black BoxMoira State Forest 4547 morphospecies24 ordersMillewa , Gulpa & Moira 59 ant species10 beetle species8 spider species22 other speciesNorthern Plains 2342 species46 familiesBarmah forest 3150+ beetle species100+ spider speciesSource: Data from the Atlas of Victorian Wildlife, curated by the Department of Sustainability and Environment1Robertson et al. (1989); 2 Yen et al. (1996); 3 Ward et al. (2002); 4 Ballinger et al. (2005); 5 Yen (2003)Immediately following flooding, the abundance, speciesrichness, and biomass of predatory carabid beetles(which like humid environments) was greatest at sitesthat had been flooded the longest (approximately 4months). However another predator of aquaticinvertebrates, the lycosid spiders were not affected bythe duration of flooding. There was no difference in thenumber of beetles before flooding, but the differencesobserved after flooding remained for over two years.Increases in the abundance of large beetles, like theseare likely to affect insectivorous vertebrates such as theyellow-footed antechinus.To collect arboreal invertebrates, Yen et al. (2002)sprayed the canopy of two individual River Red Gumtrees in the Moira State Forest (NSW) with insecticide,one in February and one in October (See 4 , Figure 5.6).A total of 458 invertebrate species was collected fromthe canopy with only 90 species collected in bothFebruary and October. The canopy was dominated byHemiptera (bugs), Diptera (flies), Hymenoptera (ants andwasps) and Araneae (spiders). A further 69 invertebratespecies (mainly spiders) were collected by hand frombeneath the bark of the two trees (9 in February and 52in October 1999, with 8 species found in both months).The large number and diversity of invertebrate specieson two individual trees suggests that the total numberof invertebrate species in river red gum forests is large,particularly taking into account variation due to season,tree age and condition and local variation. Internalinvertebrate species that feed within the leaf or stemsuch as leaf miners and gall formers, wood feeders, andassociated parasitoids, were not collected in this study,but would further add to the total species tally.A brief survey of 31 large river red gum logs (greaterthan 60 cm diameter) in the Millewa, Gulpa Island andMoira State Forests in NSW (Yen 2003) (See 5 , Figure5.6), found mainly timber feeders, Bostrichidae andCerambycidae beetles and the termite Coptotermesacinaciformis. The few invertebrate species found mayhave been due to the nature of the timber and/orflooding regimes. River red gums decompose slowly onthe ground and may take 175 years (Mackensen et al.2003). The saproxylic (wood-feeding) fauna of river redgums seems to be poor compared with other foresttypes (Ballinger & Yen 2002; Yen 2003).It is worth considering current and potential threats tothe diverse river red gum invertebrate fauna despite theoverall lack of detailed background. While some threatsare obvious, such as clearing river red gum forests forpasture, horticulture or agriculture, many other threatsmay be more subtle. Threats that can be managed at thelocal level include fragmentation, habitat simplification(such as loss of coarse woody debris and plant litter bygrazing, firewood collecting, trampling and vehicularaccess for recreation and inappropriate fire), andinappropriate use of chemicals and their effects on nontargetgroups. Information is required on the effects ofthese threatening processes on invertebrates fillingdifferent ecological roles, in different age structuredforests in different areas under varying managementregimes. Grazing is a major use in some of these forests,and its effects on the structure and functioning of theground layer and its associated invertebrate fauna needto be documented. Habitat simplification through loss ofcoarse woody debris is also a matter of concern forterrestrial invertebrates.Discussion Paper61