Josh Dorrough

Future investment in landscape change in southern Australia

Abstract Future investment in Australias countryside will greatly influence the appearance of the landscape, and the ecosystem services provided. Primarily, landowners will undertake this investment. Government investment in revegetation programs is likely to be relatively small. This paper is about research conducted on grazing properties in south-eastern Australia, and extrapolated to the region as a whole. Four strategies are reported: they involve increasing the perennial component of the pastures, fine-tuning grazing management, encouraging natural regeneration and more targeted application of fertiliser. Three of the strategies are profitable and also contribute substantially to the condition of native vegetation and to the ecosystem services it provides. The strategies are not as profitable as traditional pasture improvement, historically the main source of increased wealth. However, the availability of alternative strategies greatly reduces the opportunity cost of not pursuing the traditional pasture improvement approach. This means that incentives to adopt the alternative strategies may make good public policy sense.

Forb responses to grazing and rest management in a critically endangered Australian native grassland ecosystem

Worldwide, temperate grasslands have been extensively cleared for agriculture and urban expansion and the ‘Natural Temperate Grassland of the Victorian Volcanic Plain’ in south-eastern Australia has recently been listed as critically endangered. Because of land clearing, these grasslands now occupy <1% of their original distribution and much of the remaining grassland continues to be grazed by livestock. Although forbs (wildflowers) constitute most of the floristic richness in natural grasslands, few experimental studies have focused on their responses to strategic livestock grazing and rest. This paper reports on the outcomes of five grazing and rest management regimes imposed for 4 years at three sites on the Victorian Volcanic Plain. Seasonal grazing and rest management regimes resulted in significantly different native and exotic forb frequencies, but not richness. Native perennial and exotic annual forb frequency was higher when management incorporated grazing and rest periods (14 and 16% deviance explained), particularly with spring rest from grazing. However, the most important influence on native perennial and exotic annual and perennial forb frequency (46, 58 and 41% deviance explained) and native perennial and exotic annual species richness (62 and 35% deviance explained) was site. Differences among the three sites included soil, rainfall, size of remnant, presence of small burrowing mammals, management history and consequent species assemblages. Despite differences among sites, the results indicate that native perennial forb frequency may be increased using management regimes that incorporate both grazing and rest. However, targeted management may be necessary to reduce exotic annual forbs, also promoted by grazing with seasonal rest.

Manipulating livestock grazing to enhance native plant diversity and cover in native grasslands

Temperateperennialgrasslandsgloballyhavebeensubjecttoextensivebiodiversityloss.Identifyinglivestock grazingregimesthatmaintainandenhancethediversityandcoverofnativeplantspeciesintheseecosystemsremainsakey challenge.Theresponsesofvegetationtodifferentsheepgrazingregimeswereassessedover3yearsingrasslandsofsouth- eastern Australia. An open communal experimental design was used to assess the effects of varying season and duration of exclusionofgrazingbysheep,replicatedatthreelocations.Manipulationofseasonanddurationofexclusionofgrazingled to few major changes in the cover of native perennial grasses or forbs, although seasonal variation was considerable. Exclusionof grazing inthespring didincrease thelikelihood ofoccurrence ofgrazing-sensitive native forbspecies but also lead to an increase in the cover of exotic annual species. However, cover of exotic annual species tended to decline with increasing duration of exclusion, while the abundance of native, grazing-sensitive forbs and the cover of perennial grasses increased.Small-scalerichnessofnativeperennialforbspeciesincreasedwitha3-monthperiodofexclusionofgrazing,but declined with year-round exclusion of sheep. Total species richness also declined in response to year-round exclusion of sheepand rates ofdeclinewere correlatedwith therate atwhich herbage mass accumulated.While strategic grazing didnot resultinmajorvegetationchangesintheshortterm,itissuggestedthatsomegrazingexclusionmayenhancethesurvivalof infrequent species most sensitive to sheep grazing. Caution, however, should be taken when grazing regimes implemented benefit both desirable (native forbs) and undesirable (exotic annuals) species. Having a mosaic of flexible grazing management regimes across the landscape is likely to be beneficial for native plant diversity.

Recruitment of Eucalyptus strzeleckii (Myrtaceae) in intensive livestock production landscapes

Eucalyptus strzeleckii K. Rule (Strzelecki gum) is a medium-to-tall forest swamp gum, endemic to Victoria and listed as Nationally Vulnerable in Australia. This species occurs in the high rainfall (up to 1600 mm) region of Gippsland in south-eastern Victoria. The region has been intensively developed for agriculture, in particular dairy production. Surviving trees are often old and in varying stages of dieback and natural recruitment is rarely observed. The removal of cattle-grazing as a sole mechanism to encourage recruitment is rarely sufficient to promote regeneration of this species. The aim of this study was to examine the role of soil disturbance, weed competition, seed supply and parent plant competition, in the absence of cattle-grazing, in the recruitment of E. strzeleckii. Seed availability, distance from mature tree, soil disturbance, soil moisture and pasture competition all influenced seedling establishment and survival in the field. Removal of ground layer vegetation immediately before seedling emergence appears to be essential for successful establishment of E. strzeleckii. However, both soil disturbance and pasture removal by spraying had similar effects, suggesting that competition rather than soil disturbance per se is a limiting factor in these environments. In the absence of understorey vegetation manipulation, regeneration by this species is unlikely even in the absence of grazing.

Does it matter if herbivory is selective? Responses of an endangered herbaceous legume to experimental grazing

Background: Herbivory and inter-specific competition are major determinants of the relative abundance of plant species in grasslands. Herbivores modify competitive hierarchies among plants through selective foraging and as a result of variation in the relative tolerance of plants to herbivory. Aims: We examined the direct effects of herbivory and the role of herbivore preference on the growth, flowering and abundance of an endangered perennial legume, Cullen parvum (F. Muell.) J.W. Grimes, in a temperate Australian grassland grazed by sheep. Methods: Hand clipping was used to simulate herbivory. In each of two populations, three replicates of the factorial combination of C. parvum defoliation (C. parvum grazed or ungrazed), neighbour defoliation (neighbouring vegetation grazed or ungrazed) and three defoliation frequency treatments were randomly applied to 0.25-m2 quadrats containing C. parvum ramets. Results: The abundance, growth and flowering of C. parvum were similarly reduced by both selective and non-selective herbivory. When neighbouring vegetation but not C. parvum was defoliated, growth and abundance were similar and in some cases less than when both neighbours and C. parvum were ungrazed, suggesting little above-ground competitive effect of the grassland sward. Conclusions: The interactions between herbivory and shoot competition by dominant perennial grassy swards had little influence on the growth and abundance of C. parvum. Rather, direct effects of defoliation dominated and we predict that the species persistence in grazed grasslands will be influenced more by poor tolerance of herbivory than by how herbivores modify the competitive effect of neighbouring vegetation.