Plant Sztccession o n Volcanoes in Pa$ua
individuals of fast-growing species of tall trees to ensure that the community is dominated by pioneer species for the next century. The most important of these species are Octolneles sumatrana and Casuarina $a$uana both of which reach a height of over 50 m.
The succession of woodland communities on Mt. Lamington may revert to climax forest much more quickly, as there are only rare individuals present belonging t o species which reach a height in excess of 20 m. The succession here may parallel the regrowth on abandoned gardens just outside the blast area, where the succession is continued by taller growing secondary species and species of the climax forest. These species are, however, now absent but the distance to undamaged trees is only a few kilometres and this barrier can hardly operate to exclude their presence for many more years.
The montane thicket found at 900 m. on Mt. .Victory is considerably lower in elevation than is usual for such communities in Papua. Lane-Poole (1925) quotes the average lower elevation in Papua for his mid-mountain forest as 1650 m, and of mossy forest as 2250 m. ' A community, then, of similar structure to montane thicket, could normally be expected to have a lower limit of 2000 m. A parallel case may be noted on the Soufrikre, a volcano on St. Vincent, West Indies, where a community resembling elfin woodland occurs fay below its normal altitudinal limit. Beard (1945) attributes this fact to the deterioration of moisture relations following the deposition of a layer of volcanic ash. However, patches of ash are now rare at higher elevations on Mt. Victory and the presence of montane communities at low altitudes is probably due to the 'Massenerhebung' effect, Mt. Victory being a relatively small coastal mountain isolated by a broad alluvial plain from the main cordillera of Papua, the Owen Stanley range. This is borne out by observations during the stay in the area when cloud cover was observed much more frequently at low altitudes on Mt. Victory than on the foothills of the Owen Stanley range.
No vegetation corresponding to Beard's montane rainforest was observed on Mt. Victory but the absence of this formation is quite probably confined to the one ridge ascended. Here the zone immediately below montane thicket is extremely steep and carries a low sub-climax vegetation.
The type of eruption and edaphic conditions present are described for three volcanoes in Papua. The vegetation types ranging from tall tropical rainforest to an open herbaceous community are described and correlations drawn with environmental coriditions. It is pointed out that some species have survived the eruption of a t least one volcano but that in all cases the majority of species originally present have been destroyed. These species are gradually returning to the blast areas, but even after 80 years the number of species present is well below the figure expected from a similar area of climax forest. Comparisons are drawn between the vegetation types on the three volcanoes ,and some conclusions reached on the probable future course of succession.
BAKER,GEORGE(1949). Preliminary note on volcanic eruptions in the Goropu Mountains, south-
eastern Papua, during the period December 1943to August 1944. J . Geol., 54, 19-32. BEADLE,N. C. W. and COSTIN,A. B. (1952). Ecological classification and nomenclature. Proc. .Lint%.
Soc. N.S.W., 77, 61-82.