Invertebrate Fauna of 4 Tree Species in Orongorongo Valley, New Zealand, as Revealed by Trunk Traps
- Ecology Division, DSIR, Private Bag, Lower Hutt, New Zealand
Tree trunks are important links between the forest floor and canopy, especially for flightless invertebrates that move from the forest floor to feed or breed in the canopy. Traps were used to sample invertebrates moving up and down on mahoe (Melicytus ramiflorus), hinau (Elaeocarpus dentatus), hard beech (Nothofagus truncata), and kamahi (Weinmannia racemosa). In 19 months 22 696 invertebrates were collected. Many unexpected groups e.g. ground wetas, ground beetles, some caterpillars, amphipods, spring-tails, mites, peri- patus, and earthworms were caught in up-traps 1.5 m above ground. Overall, up-traps caught more (80%) invertebrates than down-traps (20%) and 16 of 29 groups of invertebrates were caught more often in up-traps. Fewer invertebrates were caught on hard beech than on hinau with comparable catching surface area. The numbers of spiders caught were significantly corre- lated with tree circumference. The invertebrates caught fell broadly into 3 trophic levels-most were saprophytes, with equal numbers of herbivores and predators. Perched leaf litter in epiphytes and in tree cavities contain invertebrates otherwise associated with the forest floor. Invertebrates in the lowland forests of New Zealand appear to be generalists in their use of habitats (as many of them are saprophytes and predators).