RESPONSE OF JUVENILE MELALEUCA-HALMATURORUM TO FLOODING - MANAGEMENT IMPLICATIONS FOR A SEASONAL WETLAND, BOOL LAGOON, SOUTH-AUSTRALIA

The response of M. halmaturorum was measured to determine the ability of juvenile plants to survive flooding and to examine how this influen ced plant growth. Seedlings and one- and two-year-old plants were floo ded to 0% (control), 50% or 100% of their initial height for periods o f three to 14 weeks, followed by an eight-week recovery period. Only 2 2% of seedlings survived five weeks of 100% coverage, but these died d uring the recovery period. The older plants survived the flooding trea tments well, but as duration increased so survival through the recover y period declined. After 100% coverage for six weeks followed by the r ecovery period, only 29% survived. Stem linear extension rates corresp onding to these survival rates were used to predict the survival of ju venile M. halmaturorum in Bool Lagoon, South Australia. The results sh owed that, with the current water regime, natural recruitment would oc cur only at the highest elevation but that this could be improved by p lanting older, taller plants at lower elevations. Indices of growth sh owed that flooded plants performed poorly compared with the controls a s duration and percentage of coverage increased. The data suggested th at coverage inhibited plant growth during the flood period, but there was a further, interactive response to duration that became apparent a fter the post-flood recovery period. An interpretation of these result s is that M. halmaturorum in its juvenile stages is intermediate betwe en a flood-sensitive and a flood-tolerant species because it is able t o recover from short floods of three weeks or less but performs poorly if floods exceed six to nine weeks.