provides a discussion regarding implications of the project for future management, continuing development of theoretical frameworks, and, the further

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Chapter 2 - General Methods

Introduction

This chapter provides details of the general methods utilised for this project: study site selection; aerial imagery preparation and interpretation; collation of climatic data (rainfall and temperature); collection of observational data (vegetation composition and structure, physical attributes and location); soil sampling procedures and sample preparation; soil chemical analyses: preparation of data for statistical analysis; and details of numerical analyses for chapters three to six.

Study Sites - Overview

All sites investigated in this project are located within the island state of Tasmania, the smallest state of Australia. The island of Tasmania is approximately 68 300 km2 in area and is separated from the rest of Australia by the 300 km width of Bass Strait. Tasmania is strongly influenced by the sea and has a cool temperate climate with a strong maritime influence from the prevailing westerly ‘Roaring Forties’ wind stream. As a consequence, the western region has high mean annual rainfall, while the east has much less.

Climatic conditions and the geological diversity of Tasmania have strong influences on the distribution of the indigenous flora and fauna. One of the most notable influences is the strong east-west geological divide between Jurassic dolerite and older Pre-Cambrian rock types (Figure 2). This has been referred to as ‘Tyler’s Line’ in the literature after recognition of differences in flora and fauna and limnology (see Shiel et al., 1989). With very few exceptions, such as the occasional granitic outcrop, the eastern half of Tasmania typically consists of Jurassic dolerite and sedimentary rocks of Ordovician, Permian and Triassic age. Jurassic dolerite is a basic igneous rock extruded below the land surface (Laffan and McIntosh, 2005) covering over one third of Tasmania and widespread within the central and eastern regions of the state. The western region is composed mainly of highly metamorphosed, siliceous Pre- Cambrian aged rock. In contrast to Jurassic dolerite, Pre-Cambrian rock types (the oldest in Tasmania) extend from near the Port Davey region in the southwest to Rocky Cape in the northwest.

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In the western region, harder and erosion resistant rocks such as quartzite usually form the mountains while softer rock such as schist occur within valleys and lower lying areas. Landforms, soil types, soil nutrient status, and plant communities are very different within this western region to those in the eastern half of Tasmania.

Figure 2. View of Tasmania showing the approximate delineation of the east – west geological boundary indicated by the diagonal white line. Image source: Google Earth, August 2005. Bioregions

The generally accepted definition of a bioregion is ‘...a large area of land or water that contains a geographically distinct assemblage of natural communities that (a) share a large majority of their species and ecological dynamics; (b) share similar environmental conditions, and; (c) interact ecologically in ways that are critical for their long-term persistence’ (WWF, 2004).

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Within an Australian context, bioregions are defined by the Department of Water, Environment, Heritage and Arts (DEWHA, 2007) as ‘a geographic area

characterised by a combination of physical and biological characteristics for example, terrain, climate and ecological communities’.

Figure 3. The nine bioregions of Tasmania. Source: Department of Primary Industries, Water and Environment. Source: Commonwealth of Australia, 2007.

Nine bioregions are recognised within Tasmania by the Interim Biogeographic Regionalisation of Australia (IBRA 6.1). They are Ben Lomond; Central Highlands; Flinders; King; Northern Midlands; Northern Slopes; South East; Southern Ranges; and West (Figure 3).

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The present research project has examined a total of 18 sites within four of the IBRA bioregions: Northern Midlands (n = 3); South East (n = 6); Southern Ranges (n = 3); and West (n = 6), for their regeneration potential following different types of

disturbance.

Selection of Study Sites

During the study site selection process, an attempt was made to choose sites that were subjected to a range of disturbance types, with a range of ages since disturbance and in different ecological conditions. The physical distance between control and disturbed sites was minimised in the selection process to ensure that recolonisation could occur from an adjacent seed source.

The sites occur within the West bioregion at Kelly Basin, Lake Johnson, Lake Margaret, Nelson Falls, Strathgordon, and Williamsford; in the Southern Ranges bioregion at Adamsfield, Butlers Gorge, and Mt Mawson in the Mt Field National Park; in the Northern Midlands bioregion at the old Campbelltown Hospital; the property of Fosterville, and the Queens Domain1 near Hobart; and in the South East bioregion at Coles Bay, Douglas Rd, Kettering, Maria Island, Pottery Rd, and Wyre Forest Rd (Figure 4). The study sites are examined at the ecosystem levels of: grasslands and grassy woodlands; dry sclerophyll communities; wet sclerophyll forest; and rainforest.

The control sites were selected to represent the ecosystem which existed prior to disturbance. White and Walker (1997) have suggested that one of the most difficult issues associated with the repair of damaged or degraded ecosystems is the selection of appropriate control sites. An attempt was made to make the underlying physical conditions of the disturbed and control sites as similar as was possible by mapping disturbance boundaries using aerial imagery; the use of information from historical images; media and other reports; previous vegetation mapping (where available); and local knowledge related to the extent and age since disturbance and other site history information.

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The Queens Domain study site is not located within the Northern Midlands bioregion. It has been included as part of this bioregion as it primarily consists of degraded grasslands and has broadly similar environmental characteristics to the other two sites within the Northern Midlands bioregion.

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The type and severity of the initial disturbance was determined during the selection process for classification purposes and to facilitate data analyses. All study sites were classified according to the type of initial disturbance and this was simplified to either superficial (i.e. ploughed, slashed) or severe (i.e. mining, land clearance).

Sampling areas (quadrats) were selected to be as similar as was possible between the disturbance and adjacent controls in slope, aspect, geology and topographic position.

Figure 4. Image of Tasmania showing the approximate location of all study sites. 1 = Williamsford; 2

= Lake Johnston; 3 = Lake Margaret; 4 = Campbell Town Hospital; 5 = Fosterville; 6 = Kelly Basin; 7

= Nelson Falls; 8 = Butlers Gorge; 9 = Coles Bay; 10 = Mt Field; 11 = Maria Island; 12 = Adamsfield;

13 = Douglas Road, ; 14 = Strathgordon; 15 = Wyre Forest Road,; 16 = Pottery Rd,; 17 = Queens Domain, Hobart; 18 = Kettering. Image source: Google Earth, August 2005.

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