Early stages of plant succession following the complete felling and burning of Eucalyptus regnans forest in the Florentine Valley, Tasmania

Abstract

Permanent milacre quadrats were stsdied on a mnge of sites burnt in vario.;s years. All the recent burns occurred in March.

Low herbs, predominantly bryophytes, colonized about 90% of the ground 12 months after burning, and 99 % 6 months later. Marchantia polymorpha was one of the earliest colonizers. On the wetter sites it covered up to 75 % of the ground 14 years after burning, and then declined rapidly. Marchantia growing in exposed places tended to be killed during summer.

The fire mosses, Funaria hygrometrica and Ceratodon purpureus, colonized most of the ground not covered by Marchantia and reached peaks of 30-84% cover about 2 years after the fire. After 5 years the fire mosses had almost disappeared. Polytrichum juniperinum succeeded Marchantia and the fire mosses, reaching its peak (38-90 %) about 4 years after burning. Practically all of the low herbs tend to disappear when the taller vegetation becomes dense.

The taller vegetation tends to be successively dominated in time by herbaceous fire-weeds, ferns, and woody perennials. Senecio minimus, the most abundant fire-weed, reached up to 79 %cover 2 years after burning, but died suddenly after reaching its peak.

The development of ferns depended largely on the abundance of rhizomes surviving the fire (abundance before the fire, nature of fire). Histiopteris incisa and Hypolepis rugulosa were typical of sites which had carried rain-forest understoreys. Pteridium esculentum was initially limited to sites which had carried wet sclerophyll understoreys, but tended to replace the other ferns within 10 years on all but the most sheltered, moist sites. Although patchy at first, the ferns covered 50% of some areas within 4 years. Their expansion and persistence seems to be limited mainly by competition from taller plants. Most of the woody plants germinated within a few months after the fire from seed which was either stored in the ground or shed from nearby trees (depending on the species). Availability of seed and intensity of browsing by native game appear to be the two main factors which determined the abundance of established woody plants. Under favourable conditions the woody plants became dominant so early that the fern stage was by-passed. Intensive browsing was able to delay the dominance of woody plants, often for many years.