Regeneration of Broad-leaved Paperbark Trees in the Fringing Forest of the Myall Lakes

Abstract

This thesis examines the key requirements of and influences on recruitment of Melaleuca quinquenervia in a narrow, lake-fringe forest habitat within the Myall Lakes National Park. Seed production and dispersal, germination and seedling establishment were investigated and a model was developed for Paperbark recruitment within the fringing forest. Seed viability, seed fall, seed longevity and seedling emergence were examined as was optimum temperature for germination. The requirement for light for germination of M. quinquenervia is demonstrated conclusively in this study. M. quinquenervia seeds are shown to have a high tolerance to salinity levels up to 10 deci Siemens per metre (dS/m). Casuarina leachate was found to have a slight inhibitory effect on Paperbark seedling germination. During January and February of 2006 and 2007, drought conditions, causing all-time low lake levels, provided the optimum conditions for germination. Germination appears to be seasonal, but highly dependent on the provision of a moist, preferably non-saline microsite. Survival and mortality of several natural seedling populations at lake foreshore sites was monitored. The seedling establishment stage was shown to be the most limiting process in the recruitment cycle and previous suggestions of recruitment being episodic are confirmed. Hence, protection of the foreshore areas where young seedlings are most likely to establish is paramount in order to protect the integrity of the fringing forest, as this study has shown that the chance of seedlings surviving to become juvenile trees is very slim.