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The article presents the paper "Termites and fire: Current understanding and future research directions for improved savanna conservation," by Andrew B. Davies, Catherine L. Parr, and Berndt J. van Rensburg. It states that the paper aims to highlight the lack of published materials regarding the interactions between termites and fire. The authors compare studies from different continents and suggest ways on how termites respond to fire in various ways.

1. Competition is considered a key factor structuring many communities, and has been described as the ‘hallmark’ of ant ecology. Dominant species are thought to play a key role structuring local ant assemblages through competitive exclusion. 2. However, while there have been many studies demonstrating competitive exclusion and consequently reduced richness at baits, it is not clear whether such regulation of ‘momentary’ diversity at clumped food resources can scale up to the regulation of richness at the site or assemblage level. 3. In this study, ant assemblages were sampled in three different savanna habitats in South Africa using both baiting and pitfall trapping. 4. As has been found in previous studies, there was a unimodal relationship between dominant ants and species richness at baits, with high abundances of dominant ants regulating species richness through competitive exclusion. Analysis of pitfall samples revealed strong convergence in pattern, and results from null model co-occurrence analyses supported the findings. 5. The importance of competition in structuring local ant assemblages was, however, only apparent at one of the three savanna habitats suggesting that a full range of extreme environments is needed to produce the full unimodal relationship at the assemblage level. 6. Although the relative importance of competition varied with habitat type, the study demonstrated that in some habitats, dominant ants can control species richness at the assemblage level. [ABSTRACT FROM AUTHOR]

Aim Using a standardized sampling protocol along a 600-km transect in northern Australia, we tested whether ant diversity within a single biome, tropical savanna, decreases with increasing latitude (as a surrogate of temperature) and decreasing rainfall, as is expected for biodiversity in general. Location Northern Australia. Methods Ants were sampled using pitfall traps on three occasions at 1-ha sand, loam and clay sites at each of five locations along the Northern Australian Tropical Transect (NATT), from 12°50' S (1400 mm mean annual rainfall) to 17°21' S (650 mm). Results We recorded a total of 246 species from 37 genera. Mean observed species richness pooled across sampling periods was similar at sand (85.4) and loam (82.2) sites, but was less than half this at clay sites (40.0). Ant communities were also compositionally distinct on clay soils compared with sands and loams. Individual genera showed variable diversity patterns, ranging from a linear increase to a linear decrease in species richness along the NATT. However, total species richness was relatively uniform along the gradient. Patterns of ant species turnover were consistent with previously recognized biogeographical boundaries, with a primary disjunction between the arid and monsoonal zones in the south, and a secondary disjunction between the semi-arid and mesic zones in the north. Main conclusions Patterns of ant diversity in Australian savannas do not conform to global patterns of biodiversity declines with increasing latitude and decreasing rainfall. We believe this is due to a lack of significant temperature change across the latitudinal gradient, and, in particular, to the fauna's evolutionary history in association with aridification, which makes it unusually resilient to increasing aridity. The diversity of other important faunal groups such as termites and lizards is also exceptionally high in arid Australia and is likewise not closely linked to rainfall in Australian savannas. We predict that these taxa are far more sensitive to increasing aridity in savannas elsewhere in the world, and especially in the Neotropics, where savannas have an evolutionary association with humid rain forest rather than desert. [ABSTRACT FROM AUTHOR]

Tropical savannas are the world's most fire-prone biome, and savanna biotas are generally well adapted to frequent fire. However, in northern Australia there are concerns that recent increases in the frequency and extent of high-intensity fires are causing substantial declines in regional biodiversity values. In this paper we use two well-studied and contrasting faunal groups, ants and small mammals, as case studies for reviewing faunal responses to fire in Australian savannas. The Australian savanna ant fauna is dominated by arid-adapted taxa that are highly resilient to frequent fire and are not considered to be threatened by prevailing fire regimes. Indeed, frequent fire promotes ant diversity because it maintains an open habit that makes the dominant arid-adapted taxa feel at home. Long-term fire exclusion reduces ant diversity due to a marked decline in arid-adapted taxa, and favours highly generalized, more shade-tolerant taxa. In contrast, many small mammal species of high conservation value are highly sensitive to frequent fire, and there are widespread concerns that their populations are threatened by current fire management. Many of the species have shown dramatic population declines over recent decades, and, although the causes are poorly understood, there is little doubt that fire is an important contributing factor. It is likely that fire is acting synergistically with other underlying causes of decline, particularly predation by feral cats. The overall resilience of most savanna animal species in relation to frequent fire suggests that they are secure under all but the most extreme fire regimes. However, it is clear that more fire-sensitive groups such as small mammals need special fire management attention. This needs to involve less frequent and finer-scale burning, along with the protection of some large, infrequently burnt source areas. [ABSTRACT FROM AUTHOR]

Variation in grass height is beneficial to biodiversity conservation in savanna landscapes. Theory predicts that small fires can promote short-grass areas within savannas. We experimentally assessed the influence of fire season and size on grass height and the resultant response of wild grazer communities and tested three hypotheses: (1) repeated small fires in tall-grass savannas increase short-grass grazer densities in the post-burn environment; (2) increased grazer densities maintain grass height in a short, palatable state and drive feedbacks that exclude fire; and (3) late-dry season burns concentrate grazers more effectively than early dry season burns., We repeatedly applied annual treatments (unburned, early- and late-burns) in 0.25-, 5- and 25-ha plots over a period of 3 years in a tall-grass savanna system in Kruger National Park, South Africa. Dung counts for grazer density and grass height data were collected along 50-m transects. Grass height was measured in paired 1-m2 herbivore exclosures on plots before and after applied fires., Dung data indicate that wildebeest occurred most frequently in grass heights below 5 cm. Their preference for plots regardless of fire size or season increased over time with each repeated burn. Zebra and buffalo favoured burns immediately post-fire, but buffalo did not actively select for burnt areas over longer time periods., By the second year of treatment, herbivory maintained 28% and 91% of the grass height below 10 cm in the early- and late-season burns respectively. In contrast, herbivory on the unburned treatments had no effect on grass height., Synthesis and applications. Fires less than 25 ha in size attracted sufficient grazing herbivores to shorten grass height. Repetition of the fire treatments resulted in the active selection of these areas in the longer term by wildebeest, impala and, to a lesser degree, zebra. Grazing pressure was high enough to initiate positive feedbacks and maintain lawns after only two seasons of burning and, depending on the season of burn, reduced grass height to a level that excluded repeat fires. Our study demonstrated that theory on grazer use of the post-fire environment can be implemented practically by applying small repeated burns to promote the formation of short-grass areas within savannas. [ABSTRACT FROM AUTHOR]

African savannas are highly seasonal with a diverse array of both mammalian and invertebrate herbivores, yet herbivory studies have focused almost exclusively on mammals. We conducted a 2-yr exclosure experiment in South Africa's Kruger National Park to measure the relative impact of these two groups of herbivores on grass removal at both highly productive patches (termite mounds) and in the less productive savanna matrix. Invertebrate and mammalian herbivory was greater on termite mounds, but the relative importance of each group changed over time. Mammalian offtake was higher than invertebrates in the dry season, but can be eclipsed by invertebrates during the wet season when this group is more active. Our results demonstrate that invertebrates play a substantial role in savanna herbivory and should not be disregarded in attempts to understand the impacts of herbivory on ecosystems. [ABSTRACT FROM AUTHOR]

Termite mounds contribute to the spatial heterogeneity of ecological processes in many savannas, but the underlying patterns and determinants of mound distributions remain poorly understood. Using the Carnegie Airborne Observatory (CAO), we mapped the distribution of termite mounds across a rainfall gradient within a river catchment (~ 27 000 ha) of the Kruger National Park, South Africa. We assessed how diff erent factors were associated with the distribution and height of termite mounds at three spatial scales: the entire catchment, among three broad vegetation types, and on individual hillslope crests. Abiotic factors such as the underlying geology and mean annual precipitation shaped mound densities at broad scales, while local hillslope morphology strongly influenced mound distribution at finer scales, emphasising the importance of spatial scale when assessing mound densities. Fire return period had no apparent association with mound densities or height. Mound density averaged 0.46 mounds ha-1, and exhibited a clustered pattern throughout the landscape, occurring at relatively high densities (up to 2 mounds ha-1) on crests, which are nutrient-poor elements of the landscape. Mounds exhibited significant over-dispersion (even spacing) at scales below 60 m so that evenly spaced aggregations of termite mounds are embedded within a landscape of varying mound densities. The tallest mounds were found in dry savanna (500 mm yr-1) and were positively correlated with mound density, suggesting that dry granitic savannas are ideal habitat for mound-building termites. Mound activity status also varied significantly across the rainfall gradient, with a higher proportion of active (live) mounds in the drier sites. The differential spacing of mounds across landscapes provides essential nutrient hotspots in crest locations, potentially sustaining species that would otherwise not persist. The contribution to biodiversity and ecosystem functioning that mounds provide is not uniform throughout landscapes, but varies considerably with spatial scale and context. [ABSTRACT FROM AUTHOR]

The structure of tropical savanna ecosystems is influenced by fire frequency and intensity. There is particular interest in the extent to which long-term fire exclusion can result in a shift from savanna to forest vegetation that is not easily reversed by the reintroduction of fire. This study examined changes in the structure and composition of a long-unburnt site within the northern Australian savannas following an extended period of active fire exclusion (>20 years), and the effect of the reintroducing fire through experimental fire regimes, including fires in the early and late dry season at a range of frequencies. After the long period of fire exclusion, the vegetation community was characterized by a well-developed midstorey and canopy layer, low grass cover, substantially higher densities of woody sprouts and saplings than frequently burnt savanna. The community composition included a high proportion of rainforest-affiliated species. Three years of experimental fires had no detectable effect on the overall composition of grass layer and woody plants but had an effect on woody vegetation structure. Continued fire exclusion further increased the density of woody stems, particularly in the midstorey (2.0-4.99 m), whereas moderate-intensity fires (>800 kW m−1) significantly reduced the density of midstorey stems. The reintroduction of higher moderate intensity fire events resulted in the vegetation in some compartments reverting to the open savanna structure typical of frequently burnt sites. Such rapid reversibility suggests that in general, the woody thickening resulting from long-term fire exclusion did not represent a biome shift to a non-savanna state. However, there was a small proportion of the site that could not sustain the fires applied to them because grass cover was very low and patchy and therefore appeared to have crossed an ecological threshold towards closed forest. [ABSTRACT FROM AUTHOR]