Long‐term fire exclusion and ant community structure in an Australian tropical savanna: congruence with vegetation succession

Abstract

Aim To examine the extent to which succession from tropical savanna to rain forest in the long‐term absence of fire is matched by successional changes in ant communities. This is done by describing ant community responses to 23 years of fire exclusion in a northern Australian tropical savanna, with a particular focus on the extent of colonization by specialist rain forest taxa. Location Solar Village, near Darwin in Australia's Northern Territory. Methods Ants were sampled within 12 plots located inside (‘unburnt’– protected from fire for 23 years) and outside (burnt every 1–2 years) Solar Village in ridge and slope habitat dominated by Eucalyptus spp. The litter, ground‐foraging and arboreal faunas were sampled separately, using Berlese funnels, unbaited pitfall traps and baited pitfall traps attached to tree trunks, respectively. Each species was assigned a forest‐association score ranging from 0 (open savanna species) to 3 (specialist forest species) based on their known habitat preferences in the region. Results A total of 85 ant species from 35 genera were recorded, with multivariate analysis demonstrating distinct litter, ground and arboreal communities. Ant communities also varied substantially with topographic position, which interacted strongly with fire exclusion. A total of 72 species were recorded in burnt habitat, compared with only 45 in unburnt, and the number of ant species records was also about twice as high in burnt compared with unburnt habitat. Fire exclusion has resulted in a dramatic increase in forest‐associated taxa (those occurring in forest and denser, but rarely open, savanna), with such species representing 51% of species records in unburnt habitat compared with 19% in burnt. However, only five specialist forest species were recorded, representing < 1% of total ant records. Main conclusions Fire exclusion at Solar Village has markedly increased the prevalence of forest‐associated ant species, but has led to only very minor incursions by specialist rain forest ant taxa. These responses match very closely those of the vegetation.

Ant community structure and response to disturbances on coastal dunes of Gulf of Mexico

“…Vegetation structure alters food resources, nesting sites, and micro-climate conditions (Boomsma and Devries 1980;Rico-Gray et al 1998;Andersen et al 2006;Hoffmann and James 2011), and further regulates ant diversity, behavior, and interactions among species (Huxley and Cutler 1991; Botes et al 2006;Wilkinson and Feener 2007;Hill et al 2008). The general assumption is that species diversity is positively associated with vegetation complexity (Bonte et al 2002;Tews et al 2004;Sarty et al 2006).…”

Woody encroachment and its consequences on hydrological processes in the savannah

“…While there is a carbon market, because carbon sequestration benefits the whole world, there is no value attached to water provisioning, a critical ecosystem service that has a much higher local value than carbon sequestration [13][14][15]. Besides the effects on water provisioning, woody encroachment has indirect consequences on ecosystem functioning [1,15] and biodiversity [10,35,36]. Changes in the amount of rain reaching the ground have the potential to cause habitat changes by decreasing soil water availability for plants, soil fauna and microorganisms.…”

“…Among the possible factors behind woody encroachment are changes in rainfall regime [2,4], elevation of atmospheric CO 2 concentration [5,7], invasion by exotic trees [8], changes in disturbance regimes such as suppression of fire [3,7,9] and decline in browsers or overgrazing [3,7,9]. Increases in woody cover or density can result in altered habitat for specialized fauna, changes in plant species composition [10,11] and also biogeochemical cycles and ecosystem services, such as carbon storage and water provisioning [1,8,[12][13][14][15].…”

Effects of grassland management practices on ant functional groups in central North America

“…The sensitivity of ants to disturbance makes them useful as indicators of anthropogenic ecosystem change, including change in fire regime (Andersen et al 2006) and grazing Wiens 1996, Hoffmann 2010), and they have been used to indicate the success of grassland restoration (Andersen 1997).…”