Litter arthropods in mountain ash forest and their response to wildfire, harvesting and regeneration.  F. G. Neumann.  September 1988.  39pp. (unpubl.)

SUMMARY

This study examines the effects of either intensive wildfire followed by salvage logging and natural regeneration processes, or harvesting by clearfelling supplemented by artificial regeneration practices, on invertebrates within litter of commercially valuable mountain ash forests. Insects and other arthropods were collected monthly in pitfall traps over 14-day periods between 2 March 1982 and 22 February 1985 within (1) a regrowth forest undisturbed for 46 years (control), (2) a regrowth forest aged 55 years when killed by wildfire on 16 February 1983, then naturally regenerated and salvaged for logs during 1983, (3) an initially almost litter-free clearfelled area regenerated by planting 1 year-old seedlings in winter 1983, and (4) aerially seeded 2 - 4.8 year-old regeneration.

Arthropods were abundant at all study sites, and 30 upper-level taxa were identified among 146 922 specimens collected. Sixty per cent of these taxa, representing predators, parasitoids, decomposers, herbivores, seed-feeders, foragers and omnivores, were found living in both ecologically complex regrowth forest of intermediate age and the young, less complex, naturally or artificially established regeneration. The most abundant among these common taxa were the Phalangida (harvestmen), Acarina (mites), Araneae (spiders), Collembola (springtails), Hemiptera (bugs, leaf hoppers), Coleoptera (beetles), Diptera (flies), larvae of Lepidoptera (moths, butterflies), Formicidae (ants) and parasitic Apocrita (wasps). Relatively less abundant were Isopoda (wood lice), Diplopoda (millipedes), Lithobiomorpha (order of centipede), Blattodea (cockroaches), Isoptera (termites), Acrididae (short-horned grasshoppers), Thysanoptera (thrips) and Trichoptera (caddis-flies).

At the 'control' site, only minor between-year variations occurred in arthropod activity, taxon range and decomposer : predator/parasitoid ratios. In the forest affected by wildfire, arthropod activity was immediately reduced by 92%, taxon richness by 61%, and there was a substantial decline in diversity over a 12-month period. However, a broad mix of functionally distinct taxa survived the fire. Effects such as short-term boosts in activity of Collembola and seed-harvesting ants, and partial or total suppression of taxa such as Isopoda, Amphipoda (scuds), Trichoptera and Thysanoptera, persisted into the second year following the fire. Clearfelling and artificial regeneration practices also caused temporary instability in arthropod activity, as reflected by short periods of exceptionally high levels of Acarina, Collembola, Diptera and Formicidae.

A broad spectrum of taxa had reappeared within two years of regeneration establishment, and all taxa present at the 'control' site had returned within 4.8 years, except the 'rare' Pseudoscorpionida (order of arachnid), Decapoda (order of crustacean) and Scolopendromorpha (order of centipede). Thus, the abrupt removal of the intermediate-aged regrowth forest and establishment of mono-specific even-aged eucalypt regeneration appears to affect upper-level arthropod taxa only over a short period relative to the 80-year nominal rotation of the mountain ash ecosystem. However, research is needed on lower-level taxa to achieve a more precise assessment of arthropod responses to such major ecological disturbances.

Also published:

Neumann, F.G. (1991)  Responses of litter arthropods to major natural or artificial ecological disturbances in mountain ash forest.  Aust. J. Ecol. 16:19-32.