Firescape ecology: how topography determines the contrasting distribution of fire and rain forest in the south-west of the Tasmanian Wilderness World Heritage Area
Wood, SW and Murphy, BP and Bowman, DMJS, Firescape ecology: how topography determines the contrasting distribution of fire and rain forest in the south-west of the Tasmanian Wilderness World Heritage Area, Journal of Biogeography, 38, (9) pp. 1807-1820. ISSN 0305-0270 (2011) [Refereed Article]
Aim To test the hypothesis that ‘islands’ of fire-sensitive rain forest are restricted
to topographic fire refugia and investigate the role of topography–fire interactions
in fire-mediated alternative stable state models.
Location A vegetation mosaic of moorland, sclerophyll scrub, wet sclerophyll
eucalypt forest and rain forest in the rugged, fire-prone landscapes of south-west
Methods We used geospatial statistics to: (1) identify the topographic
determinants of rain forest distribution on nutrient-poor substrates, and (2)
identify the vegetation and topographic variables that are important in
controlling the spatial pattern of a series of very large fires (> 40,000 ha) that
were mapped using Landsat Thematic Mapper (TM) satellite imagery.
Results Rain forest was more likely to be found in valleys and on steep southfacing
slopes. Fires typically burned within highly flammable treeless moorland
and stopped on boundaries with less flammable surrounding vegetation types
such as wet sclerophyll forest and rain forest. Controlling for the effect of
vegetation, fires were most likely to burn on flats, ridges and steep north-facing
slopes and least likely to burn in valleys and on steep south-facing slopes. These
results suggest an antagonism between fire and rain forest, in which rain forest
preferentially occupies parts of the landscape where fire is least likely to burn.
Main conclusions The distribution of rain forest on nutrient-poor substrates
was clearly related to parts of the landscape that are protected from fire (i.e.
topographic fire refugia). The relative flammability of vegetation types at the
landscape scale offers support to the proposed hierarchy of fire frequencies
(moorland > scrub > wet sclerophyll > rain forest) that underpins the ecological
models proposed for the region. The interaction between fire occurrence and a
range of topographic variables suggests that topography plays an important role
in mediating the fire–vegetation feedbacks thought to maintain vegetation
mosaics in south-west Tasmania. We suggest that these fire–topography
interactions should be included in models of fire-mediated alternative stable
vegetation states in other fire-prone landscapes.
Alternative stable states, autologistic regression, fire, Landsat TM, positive feedbacks, rain forest, spatial autocorrelation, Tasmania, topographic fire refugia.