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The Vegetation of the Blacks' Spur Region: A Study in the Ecology of Some Australian Mountain Eucalyptus Forests: II. Pyric Succession

Phyllis H. Jarrett and Arthur H. K. Petrie
Journal of Ecology
Vol. 17, No. 2 (Aug., 1929), pp. 249-281
DOI: 10.2307/2256043
Stable URL: http://www.jstor.org/stable/2256043
Page Count: 37
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The Vegetation of the Blacks' Spur Region: A Study in the Ecology of Some Australian Mountain Eucalyptus Forests: II. Pyric Succession
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Abstract

Bush-fires are an outstanding factor causing succession in the Eucalyptus forest of the area under study. The succession following fires may be analysed into a series of processes, viz. denudation, destruction and survival, renascence, survival of seeds, aggregation, migration and establishment. In the Eucalyptus amygdalina-E. obliqua association, the trees being capable of renascence are not destroyed, and succession is confined to the lower strata. The first stage following destruction of the Cassinia society in some cases is the reappearance of the normal ground stratum associated with numerous migrant Cassinia seedlings; this then redevelops into the Cassinia society through a Cassinia socies. If, however, Pteridium is present in the habitat, the first seral community is a Pteridium socies, under the dominant of which the ground stratum redevelops. The Cassinia socies then replaces the Pteridium socies by heavy seed migration, and ultimately redevelops into the Cassinia society. Numerous Eucalyptus seedlings appear along with Cassinia, and these, eventually attaining greater height, establish a Eucalyptus socies which ultimately may lead to succession in the consociation. The Acacia-Pultenaea society redevelops through a Goodenia-Pteridium socies. In the Eucalyptus viminalis-E. regnans ecotone the Senecio-Cassinia society is reduced by elimination of non-renascent types to an Alsophila socies. The baring of the ground permits profuse temporary growths of smaller types such as Pteridium and Stellaria; eventually, however, the original community is restored by seed migration, despite the density of more rapidly growing colonists. The Alsophila society of the Eucalyptus viminalis-E. obliqua ecotone has been derived by elimination of non-renascent types from a more complex community, in which Cassinia played a dominant role. The Alsophila society represents a community adapted to rapid redevelopment after burning; at the same time, despite the density of Pteridium in the habitat, Cassinia is able to establish itself again by seed migration, and, in the absence of more fires, to grow to maturity and dominance. Eucalyptus regnans is generally destroyed by fire. The Pomaderris society is a community originating by heavy seed migration after fire. Burning reduces it, by elimination of non-renascent types, to an Alsophila socies; potentially further seed migration could restore the Pomaderris society, although we have not observed this in process. Succession in the Cassinia society of the Eucalyptus regnans association is similar to that in the same society where it occurs in the E. amygdalina-E. obliqua association. The forest fire must be regarded as a great simplifying factor in the development of these communities, which has led to the elimination of types not possessing powers of rapid regeneration. Fires too have considerably modified the structure of the communities, leading to increased density and purity, and to greater equality of age among the components. All adaptations whereby these plants regenerate, however, were existent before ever fires became a factor of the environment, and can be regarded in no way as special responses for pyric regeneration.

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