The soil mites of buttongrass moorland (Tasmania) and their response to fire as a management tool

Abstract

The buttongrass blanket moorlands are a unique habitat that constitutes a major landscape feature within the Tasmanian Wilderness World Heritage Area (TWWHA) of southwestern Tasmania. They are a highly pyrogenic vegetation type that has had a long history of regular burning by aborigines. Buttongrass may require a fire frequency of 5-20 years in order to maintain its suitability as habitat for many endemic vertebrates. The present knowledge of the Acari in the peat/litter accumulations in buttongrass is very poor and their response to fire is not understood. This study addresses the following questions: (1) How do soil mite communities in recently burned buttongrass compare with those that have not been burned in several decades? and (2) Are fire frequencies of between 5-20 years sufficient for soil mite populations to recover? A survey of soil mites was undertaken in a chronosequence of age classes of buttongrass at two study areas in the TWWHA. Six soil-cores were removed from up to four sites of each age class at 3-months intervals for 1 year, a total of 870 soil cores. All mature mites were identified to morphospecies with many individuals identified to genus or species. The soil mite community within buttongrass was found to be rich both at family and species level, in Oribatida, Prostigmata, and Mesostigmata. This community was significantly affected by fire, with a reduced number of species for many years post-fire. Density and diversity of these populations are positively correlated with age and many communities only changed significantly after 30-40 years post fire, which is in conflict with the prevailing management practice of burning every 5-20 years.