Appendix 2 - Vegetation Communities and Regional Ecosystems

Photograph 117. Grassland
community V17b on Mer Island with
emergent shrubs prominent
(MU030).
The literature suggests considerable conjecture about the provenance of grasslands on these
islands. Draffan et al. (1983) in Freebody (2002), and Stocker (1978), refer to the use of fire in
vine forest areas (with a closed canopy) on Erub and Mer Islands causing habitat alteration and a
reduction of the total area of closed forest to fire climax grasslands. The results of this study
however indicate that the grassland community on Mer occupies a cinder cone, which imposes
unique edaphic conditions on vegetation communities in the form of extreme drainage. The
considerable number of volcanic vents and basalt regolith on Australia’s north-eastern region that
naturally support grasslands in much wetter or similar climates (e.g. Seven Sisters near
Yungaburra, Mount Fox and Clump Point in Queensland’s wettest coastal location), offer
evidence to suggest that the grasslands on these islands were not necessarily preceded by vine
forest. The extremely fresh nature of many of the volcanic structures apparent on the Dauar
Cone, and to lesser extent the Mer Cone, largely disproves any theory of rainforest succession to
grassland. Historical annotations by Haddon (1901) provide clear evidence that the landscape
dynamic has changed little in the period of European influence. An extract from Haddon quotes
“the cresentic valley, crater, or “big valley” Aupaut, being formed in a porous volcanic ash, is
somewhat arid; the vegetation consists of coarse grass, low scrub and scattered coconut palms
and presents a marked contrast to the remainder of the island; the steep slopes are unusually
bare” (Haddon 1901 Part 1, Chapter 3, pp30).
Similarly, the argument that Erub (and Mer) once supported a blanketing vine forest community
that was cleared and burnt to produce the grassland mosaic that is apparent in today’s landscape
is questionable. Whilst there is no doubt that fire controls vine forest distribution to a
considerable extent, ecotonal changes upslope along gully lines from tall vine forest (VC2k) to
vine thicket (VC2w), to grassland (VC17b) observed during the study indicates the considerable
role the natural environment plays in vine forest distribution. It is unlikely that the upper slopes
of Erub ever supported luxuriant vine forest due to the relative dryness of the climate and the
extreme soil drainage on these upper slope areas. It should thus be stated that whilst removal of
fire as a land management tool may not have any marked effect long term effect on vine forest
distribution, it will certainly result in considerable degredation of these restricted grassland
communities through lantana invasion. Very hot late dry season fires burnt upslope are likely to
cause a retreat of vine forest margins with subsequent invasion by lantana.
3d Environmental – Torres Strait Regional Ecosystem Mapping Project – August 2008
123