VEGETATION SUCCESSION (1967-89) ON 5 RECENT MONTANE LAVA FLOWS, MAUNA-LOA, HAWAII

Vegetation succession on 4 recent (1852-1942) montane lava Rows on Mau na Loa, Hawaii, was remeasured 22 years after the first measurement in 1967. Colonisation patterns of vascular plant species were observed o n a new lava flow (1984) which overwhelmed part of the earlier studied 1852 flow. An influx of adventive species, positively correlated with flow age, was noted at the remeasured sites; most were herbs and gras ses that do not appear to interfere with the succession to Metrosidero s-dominated forest. Some indigenous species important in older forest, e.g., Cibotium glaucum, had apparently colonised all four remeasured flows regardless of flow age. Densities and total basal area of Metros ideros polymorpha increased on all flows, but a closed-canopy forest h ad not yet developed. Vascular plant aggregations comprising a mixture of adventive and indigenous species were found on the 1984 flow assoc iated with soil or logs of the overwhelmed forest. This phenomenon may allow rare individual Metrosideros trees to be in place on a new flow within 10 years of its formation. A closed-canopy, self-thinned Metro sideros forest can develop within 400 years but dieback of colonising Metrosideros individuals and/or invasion of adventive species capable of altering ecosystem processes can delay this process.