Premium
Effects of fire on grass‐layer savanna macroinvertebrates as key food resources for insectivorous vertebrates in northern Australia
Author(s) -
RADFORD IAN J.,
ANDERSEN ALAN N.
Publication year - 2012
Publication title -
austral ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.688
H-Index - 87
eISSN - 1442-9993
pISSN - 1442-9985
DOI - 10.1111/j.1442-9993.2012.02413.x
Subject(s) - invertebrate , insectivore , ecology , fire regime , habitat , fire ecology , biology , ecosystem
This paper documents the effects of fire on grass‐layer invertebrates in tropical savannas of the Kimberley region of north‐western Australia, in the context of resource availability for consumers. Inappropriate fire regimes have been identified as a factor threatening a number of vertebrate groups, including small mammals, across northern Australia, and a possible mechanism might be through the effects of individual fires or fire regimes on food availability. We test for a fire effect on grass‐layer invertebrate resources, which may affect insectivorous savanna vertebrates. Wet season sweep‐net invertebrate samples were taken in two tropical savanna habitats, with contrasting laterite and sandstone substrates, in 2008, 2009 and 2010. Sites were stratified by post‐fire interval to analyse invertebrate successional change after fire. In addition, experimental burns were implemented in 2010 to investigate immediate post‐fire invertebrate responses. Total invertebrate numbers declined by 80–90% immediately (1 week) following fire, reflecting the loss of grass‐layer habitat. Of the commonly sampled invertebrate groups, Araneae, Coleoptera, Hempitera, Lepidoptera, Formicidae and Diptera were all reduced in numbers immediately post‐fire, whereas Orthoptera showed no immediate post‐fire decline. Invertebrate numbers were rapidly restored to pre‐fire levels by the first wet season after fire, and no detectible change was observed in numbers or composition from 1 to 3–4 years post‐fire (the longest post‐fire interval available). This suggests that the effects of individual fires on grass‐layer invertebrates are very short‐lived. Such short‐lived post‐fire responses among grass‐layer invertebrates, plus evidence that most ground‐layer invertebrate groups are fire‐resilient, suggest that food resource limitation is not a tenable explanation for fire‐related declines among insectivorous savanna vertebrates. However, wet season burning could result in significant invertebrate resource depletion in highly flammable habitats ( Triodia and Sorghum spp. savannas) during important vertebrate breeding/recruitment periods, if burning is extensive and if grass‐layer invertebrates do not recover within a few weeks of fire.