We reconstruct long-term vegetation development in a temperate Australian oceanic setting using wetland sediments, pollen and charcoal records from truwana/Cape Barren Island in Bass Strait to reconstruct vegetation and fire history. Magnetic susceptibility and organic content were also derived for two of the four sites considered as proxies for local sedimentary changes. Result shows that the lateglacial landscape (14,000–13000 cal yr BP) was characterized by open grassy Eucalyptus woodland in Bass Strait, and Eucalyptus woodland cover increased during the early Holocene (13,000–9000 cal yr BP), with high fire activity. Scrub and heathland generally dominated by Leptospermum, Melaleuca, Allocasuarina/Casuarina and Ericaceae taxa expanded in the last 9000 years at the expense of Eucalyptus woodland, with a major decline in fire activity after 5000 cal yr BP until the last 200 years. Woodland elements (Eucalyptus, Callitris) increased slightly at some sites in the last 2000 years.

For pollen analysis, samples were taken from sediment cores at 1–4-cm intervals and samples were processed following standard pollen preparation procedures, which included HCl, KOH and acetolysis treatments. At least 300 terrestrial pollen grains were identified on slides except for a few depths with extremely low pollen concentrations in which 100 to 150 pollen grains were counted. Pollen and spores were identified using the Australasian Pollen and Spore Atlas (http://apsa.anu.edu.au/) and PalaeoWorks reference collections at the Australian National University’s Archaeology and Natural History Laboratory. Microscopic charcoal particles (<125 µm) were also counted on pollen slides. For macrocharcoal ( >125 and >250 µm) analysis, contiguous sediment samples were taken from cores and analysed, following the method of Whitlock & Larsen (2001).

Big Reedy Lagoon and truwana East Coast Lagoon cores were scanned for trace metals and magnetic susceptibility using ITRAX at the Australian Nuclear Science and Technology Organisation. The ratio for molybdenum incoherence/coherence (Mo inc/Mo coh) was used as a proxy for organic content.

Chronology (aga-depth model) is based on Accelerator Mass Spectrometry (AMS) ¹⁴C dates (Bacon, SHCal13). For YL and tECL age-depth models, Pinus pollen is used as an age marker for approximately 150 yr BP.

Sediment core locations: Big Reedy Lagoon (40.3589°S, 148.2381°E, 26 m asl), Yakka Lagoon (40.3589°S, 148.2447°E, 30 m asl), truwana East Coast Lagoon (40.3311°S, 148.2381°E, 1m asl) and Green Lagoon (40.442967°S, 148.143840°E, 10 m asl).

Reference

Whitlock, C., & Larsen, C. (2001). Charcoal as fire proxy. In J. P., Smol, et al. (Eds.), Tracking environmental change using lake sediments: terrestrial, algal, and siliceous indicators, 3. Kluwer Academic Publishers, Dordrecht, The Netherlands.