Title: Impact of fire on tussock grassland invertebrate populations
Description: The invertebrate fauna of tussock grassland in New Zealand has not been well studied, and the effect of burning on the biodiversity of the ecosystem is poorly understood by land managers. The impacts of burning on two tussock grassland invertebrate communities in Otago, New Zealand, were investigated between 1998 and 2006. At each site, three replicate 1-ha plots that were unburned (control), or burned in spring or summer were sampled. Pre- and post-burn sampling compared invertebrate densities and trophic group structure in inter-tussock (turf) and tussock samples, and recovery after treatment. Most groups were initially reduced in density post-burn. In the 1-2 year period following treatment, Thysanoptera and Hemiptera "rebounded" and reached significantly higher population densities than before the fires. By the end of the study, Amphipoda had not recovered to pre-burn densities. In general, herbivore population densities recovered over a 2-3 year period, and litter-dwelling invertebrate population densities were most negatively impacted. Season of treatment had no major impact on invertebrate responses. Coleoptera were chosen as a representative group for more detailed investigations of responses at species level. Coleoptera species richness was reduced by about 50% at 2-3 months post-burn, but recovered to pre-burn levels 3 years later. There was no evidence of a change in the density of exotic Coleoptera following the burning treatments. Invertebrate data from these sites should be considered as case studies, rather than applicable to tussock grassland in general. However, these findings have several implications for the management of tussock grassland: fire treatments that remove the litter layer are likely to reduce litter-dwelling invertebrate populations for 3 years or more; summer fires do not appear to be more detrimental to the invertebrate community than burning in spring, based upon the limited seasonal data available to us; and the exotic component of the fauna does not increase in response to fire in the first 3-4 years after burning.
Subjects: Invertebrate communities, Grassland animals, Fire ecology, Beetles, Insect population density, Effect of fires on, Invertebrates
Places: Otago, New Zealand