LITTERFALL UNDER HINAU, ELAEOCARPUS-DENTATUS, IN LOWLAND PODOCARP MIXED HARDWOOD FOREST, AND THE IMPACT OF BRUSHTAIL POSSUMS, TRICHOSURUS-VULPECULA

Litterfall was collected monthly for five years under the endemic hardwood tree Elaeocarpus dentatus (hinau) on two study areas about 3 km apart in podocarp/mixed hardwood forest of the Orongorongo Valley, near Wellington, New Zealand. At high stem densities (42 stems > 8 cm dbh ha-1) total annual hinau litterfall was 504 g m-2, with litter from other associated species contributing a further 119 g m-2. At low stem densities (4 stems > 8 cm dbh ha-1) the values were 293.4 and 163 g m-2, respectively. Except for twigs, the amounts of the various components of litterfall showed marked seasonal and annual variations, and consistent differences between individual trees. At both sites, litter fell throughout the year, with most flowers falling in spring, leaves in summer, and fruits in autumn. The annual cycle of monthly dry weight of leaf-fall, the major component of the litterfall, was highly correlated with the annual cycle of mean monthly temperature, but not with that of rainfall or windrun. Eradication of introduced herbivorous brushtail possums, Trichosurus vulpecula, from one of the study areas was followed by a marked increase the following year in the amounts of hinau flowers and fruits in the litterfall.