The effect of fire on terrestrial amphipods (Crustacea: Amphipoda) in a natural grassland community

Abstract

Fire is known to cause severe and protracted reductions in some invertebrate communities. Amphipods are prone to desiccation and, therefore, litter removal through fire could be expected to have a significant adverse impact on their populations. We aimed to determine the temporal and spatial response patterns in density of amphipods following seasonal fires in a natural grassland site in southern South Island, New Zealand. Fires lit for management purposes in spring are generally cooler and considered less detrimental to the ecosystem than those occurring in hot dry summer conditions. Annual quantitative sampling was used to measure amphipod density in tussock grassland communities before and after single fire treatments were carried out in either spring or summer. Three samples were taken annually before each of the experimental fires, and for 12 years post-treatment. In general, amphipod populations took 7–9 years after treatment to recover to pre-burn densities although densities in spring burnt plots recovered more slowly. Eleven years post-burn, the spatial distribution of amphipods in relation to microhabitat was also examined. Two amphipod species were present, and they were distributed differently in tussock and inter-tussock vegetation and responded differently to fire but not to fire season. A protracted period of recovery from fire for an important member of the detritivore community is likely to have negative impacts on nutrient cycling, and therefore on primary production in grassland systems. The implication for land managers is to avoid burning in spring if soil conditions are relatively dry.