Fire regime and vegetation change in the transition from Aboriginal to European land management in a Tasmanian eucalypt savanna

Abstract

Using pollen and charcoal analysis we examined how vegetation and fire regimes have changed over the last 600 years in the Midlands of Tasmania. Sediment cores from seven lagoons were sampled, with a chronology developed at one site (Diprose Lagoon) using 210Pb and 14C dating. Statistical contrasts of six cores where Pinus served as a marker of European settlement in the early 19th Century and showed significant changes in pollen composition following settlement with (a) influx of ruderal exotic taxa including Plantago lanceolata L., Brassicaceae, Asteraceae (Liguliflorae) and Rumex, (b) increase in pollen of the aquatics Myriophyllum spp. and Cyperaceae, (c) a decline in native herbaceous pollen taxa, including Chenopodiaceae and Asteraceae (Tubuliflorae) and (d) a decline in Allocasuarina and an initial decline and then increase of Poaceae. The presence of Asteraceae (Liguliflorae) in the pre-European period suggests that an important root vegetable Microseris lanceolata (Walp.) Sch.Bip. may have been abundant. Charcoal deposition was low in the pre-European period and significantly increased immediately after European arrival. Collectively, these changes suggest substantial ecological impacts following European settlement including cessation of Aboriginal traditions of fire management, a shift in hydrological conditions from open water lagoons to more ephemeral herb covered lagoons, and increased diversity of alien herbaceous species following pasture establishment.

Demographic Effects of Severe Fire in Montane Shrubland on Tasmania’s Central Plateau

“…However, this study is unable to advance this question of whether the current shrubland distribution is a legacy of past fire and grazing since European settlement, including the disruption of Aboriginal fire management regimes. Further research needs to focus on historical land cover changes using both palaeoecological and historical techniques, which have been applied in other landscape settings in Tasmania (e.g., References [81,82]), as well as contrasting post-fire recovery of montane shrublands that are still subjected to livestock grazing with those where livestock grazing does not occur.…”

European Impacts on Coastal Eastern Tasmania: Insight from a High-Resolution Palynological Analysis of a Salt-Marsh Core

“…In the case of Den Plain, northern Tasmania, the effects of European grazing has an almost immediate impact on the landscape when settlement occurred in the 1840s AD, with a clear and sustained presence of exotic taxa, a dramatic increase (over 14 times the previous non-European period) in sedimentation rates and a marked deforestation signal with no recovery in forest observed (Moss et al, 2007). A palynological investigation of seven wetlands from the central Tasmanian midlands region observed significant impacts of European settlement, including an increased diversity of exotic herbaceous species, hydrological alterations with open water system transitioning to more ephemeral herb covered wetlands and increased burning associated with the immediate arrival of Europeans, as well as the cessation of traditional Aboriginal fire management (Romanin et al, 2016). The European impacts on the Fleurieu Peninsula, South Australia (Bickford and Gell, 2005;Bickford et al, 2008) were far more subtle during the initial settlement phase, with the key impacts related to changes in fire regimes, with fire sensitive canopy trees (Allocasuarina verticillata) being replaced by fire tolerant eucalypts due to more intense fires occurring as a result of increased fuel loads related to fire suppression.…”

“…As discussed previously, most records of covering this time period are relatively low-resolution analysis of longer Holocene records. However, there are some higher resolution palynological records that can be compared with this site, including a site from northern Tasmania (Moss et al, 2007) and the midlands region of Tasmania (Romanin et al, 2016) that provides a more detailed picture of European impacts; a high-resolution study from southern South Australia (Bickford and Gell, 2005;Bickford et al, 2008); and records from the Atherton Tableland (Steinberger, 2014). In all cases there is clear evidence of European impacts on the landscape, with the introduction of exotic species, deforestation, changes in species composition and alterations in fire regimes.…”

“…In a general sense these impacts are well understood for the Australian environment, with significant land clearance for agriculture, forestry and mining; rapid introduction of exotic species; extinction of native taxa; and the imposition of new fire regimes (Adamson and Fox, 1982;Hobbs and Hopkins, 1990;Benson, 1991;Kirkpatrick, 1999;Bickford and Gell, 2005;Moss et al, 2007;Bickford et al, 2008;Romanin et al, 2016). However, at the regional scale, there are relatively few attempts to examine European impacts using palaeoecological proxies, due to the relatively low-resolution of existing Holocene reconstructions (Kershaw et al, 1994) that often attempt to provide insight into Holocene environments and/or focus on Aboriginal human-environment relationships (e.g., Colhoun and Shimeld, 2012;Ulm, 2013;Fletcher et al, 2014Fletcher et al, , 2015Rees et al, 2015;Mackenzie and Moss, in press for recent publications from Tasmania).…”

A framework for testing the influence of Aboriginal burning on grassy ecosystems in lowland, mesic south–eastern Australia

“…However, reconstructed vegetation patterns again reveal a variegated tree cover, with forest and woodland (most frequently 'open' or 'thinly') dominated by eucalypts (E. amygdalina, E. viminalis, E. ovata), honeysuckle and wattles (A. melanoxylon, A. dealbata), interspersed with patches of treeless vegetation (Fensham 1989). Regional phytoecological and palynological data suggest that floristic patterns are most closely related to soil moisture, driven by complex terrain and substrate patterns, with treelessness being caused by dense grass swards and probably also frost, waterlogging, herbivory (including marsupials), and drought as well as fire (Fensham 1989;Fensham and Kirkpatrick 1992;Leonard et al 2010;Ingram and Kirkpatrick 2013;Kirkpatrick et al 2016;Romanin et al 2016). Mostly on the basis of the historic record, others have argued that grasslands were more extensive historically and that the influence of Aboriginal burning has been understated (Gammage 2008).…”