Organic soils provide evidence of spatial variation in human‐induced vegetation change following European occupation of Tasmania

Abstract

Aim We test the hypothesis that the European destruction of western Tasmanian Aboriginal society, and consequent changes in burning patterns, resulted in succession towards rain forest near the coast, and an increase in the area of more fire‐resistant sedgeland in inland areas. Location South‐western and western Tasmania, Australia. Methods Attributes of organic soils (surface and underlying dominant horizons) beneath rain forest and sedgeland were described and measured from 559 soil pits in areas with highly siliceous surface geology. Multiple logistic regression was used to discriminate the dominant horizons of rain forest and sedgeland soils. This equation was used to derive scores for all soil pits. The hypothesis that change was greater near existing boundaries was tested using correlation. The hypothesis that change was greater at coastal than inland locations was tested using ANOVA. Results Both upper horizons of the soils under the fire‐sensitive rain forest (14C‐dated to be younger than 60 years) and dominant horizons of these soils had significantly higher organic contents, lower bulk density and more nitrogen than the soils under the fire‐requiring sedgeland. Twenty‐nine per cent of the soils under sedgeland had dominant horizons that indicated past rain forest. One‐quarter of the soils under rain forest had dominant horizons characteristic of sedgeland soils. Although results were heterogeneous in both locations, the former difference was more common inland and the latter near the coast. Change was not higher close to present boundaries. Main conclusions The characteristics of the dominant horizons and the post‐colonial surface horizon give a strong indication of the vegetation that formed them. Changes in fire regimes, caused by the displacement of Tasmanian Aborigines by Europeans, appear to have caused vegetation changes that differed within and between the coast and inland areas. Thus, there has been a strong human role in determining the distributions of vegetation types in the region.

Mapping Tasmania's cultural landscapes: Using habitat suitability modelling of archaeological sites as a landscape history tool

“…Cameron, ; Cosgrove, ; Kee, ; Kee, ), with distance to coast and distance to inland water among the most important predictors of site presence (see Figure ). We find a strong preference away from rainforest habitats and towards woodlands (Table ): congruent with the prevailing hypothesis that Tasmanian Aboriginal people preferred (and potentially promoted) more open vegetation structures (Folco & Kirkpatrick, ; Gammage, ; Jones, ). In the north‐east, our results support Cameron’s () elegant reconstruction of a coastal and flat hinterland‐oriented economy with less intensive, but still active, use of particular upland domains.…”

“…Key issues include the extent to which Tasmanian Aboriginal hunting, gathering and fire use influenced the structure, function and distribution of modern plant and animal communities (Bowman, Wood, Neyland, Sanders, & Prior, ; Folco & Kirkpatrick, ; Fletcher & Thomas, ; Jackson, ; Mariani et al, ; Thomas & Kirkpatrick, ). Indeed, where and how Aboriginal people burned the landscape, and the extent to which this had landscape‐scale impacts on the island's biota, has long placed Tasmania at the centre of global archaeological and fire ecology debates (Bowman, Perry, & Marston, 2015; Jackson, ; Jones, ; McWethy et al, ).…”

Transition from heathland to scrub in south-eastern Tasmania: extent of change since the 1970s, floristic depletion and management implications

“…There is strong evidence to suggest that fire was used by the Aboriginal people of Tasmania in a way that maintained heathland near the coast (Thomas and Kirkpatrick 1996;di Folco and Kirkpatrick 2013). The same coastal areas were burned frequently by Europeans until the late twentieth century, after which prevention and control of fire in coastal regions became widespread, leading to dramatic changes in vegetation, such as the expansion of Acacia sophorae scrub on coastal sand dunes (Chladil and Kirkpatrick 1989;Hayes and Kirkpatrick 2012).…”

Soil or fire: what causes treeless sedgelands in Tasmanian wet forests?

“…Furthermore, the soil nutrient capital of forests and sedgeland is reduced by fire through volatilisation and transport of ash (Harwood and Jackson 1975;Bowman and Jackson 1981), soil erosion (Wilson 1999;di Folco and Kirkpatrick 2013) and leaching (Bowman and Jackson 1981;Ellis and Graley 1983;Jackson 2000;Fletcher et al 2014a), and possibly clay eluviation (McIntosh et al 2005). These impacts are most pronounced on infertile, clay-deficient lithologies, such as quartzite, with much more limited effects on clay-rich soils such as those that develop on dolerite (Ellis and Graley 1983;Jackson 2000).…”

“…Occasionally, there may be no obvious edaphic discontinuity across forest -sedgeland boundaries (Balmer 1990). In summary, different vegetation types produce different soil types, but there are examples of a decoupling of vegetation type from soil type (Wood and Bowman 2012;di Folco and Kirkpatrick 2013).…”