The effects of fire, local environment and time on ant assemblages in fens and forests

We investigated the effects of the abiotic environment, plant community composition and disturbance by fire on ant assemblages in two distinct habitat types in the Siskiyou Mountains in northern California and southern Oregon, USA. Sampling over 2 years in burned and unburned Darlingtonia fens and their adjacent upland forests, we found that the effects of disturbance by fire depended on habitat type. In forests, fire intensity predicted richness in ant assemblages in both years after the fire, and plant community composition predicted richness 2 years after the fire. No factors were associated with richness in the species‐poor fen ant assemblages. Species‐specific responses to both habitat type and disturbance by fire were idiosyncratic. Assemblage composition depended on habitat type, but not disturbance by fire, and the composition of each assemblage between years was more dissimilar in burned than unburned sites.     

Comparison of regeneration following burning,clearing or mineral sand mining at Tomago,NSW: I. Structure and growth of the vegetation

Abstract We have begun a long-term ecological research project to address questions about the impact of multiple disturbances on the species richness of communities and whether multiple disturbances are additive or interactive. A protected water catchment area was chosen, which is subjected to fires, sand mining and clearing, and for which detailed records are available. The study area, at Tomago (32°52′S, 151°45′E), has forest, woodland, shrubland and swamp on a sand substrate, with the vegetated dunes forming part of a coastal embayment. Forty-four sites were located in forested areas that had undergone disturbance by either fire, sand mining or clearing. Sites of each disturbance type were grouped into four age classes: less than 1 year since disturbance, nominally 1991; 5 years, nominally 1986; 11 years, nominally 1980; and 17 years, nominally 1974. A set of burned sites, with the time of the last fire matched to the times of the other disturbances, was used as the control response. In this paper we describe the study area and sites, then examine the effects of each single disturbance on vegetation structure. Canopy cover increased with time and type of disturbance, with 17 year old cleared or mined sites similar to the cover of 11 year old burned sites. In the first two years after disturbance, burned sites had significantly more understorey vegetation than cleared or mined sites, but by 5 years all three were similar. The data presented here show that regeneration of mined sites at Tomago is substantially slower than regeneration following disturbance by fire, with the regeneration of cleared sites intermediate but closer to mining than fire. After 17 years regeneration, cleared and sand mined sites had not returned to the vegetation structure of the pre-disturbance state. Understorey height and the amount of vegetation on cleared or mined sites have not achieved the levels in the original forest, although canopy cover did seem to have reached pre-disturbance levels. Current rehabilitation techniques are more sophisticated than those used 17 years ago and continued monitoring of sites currently being rehabilitated may show a faster return to pre-disturbance states. Having established the hierarchy and nature of the response to each single disturbance here, we are now in a position to investigate the impact of multiple disturbances.     

Fire effect on ground-foraging ant assemblages in northeastern Argentina

Fire is an important component of many natural ecosystems affecting plant communities and arthropods by mortality during combustion and/or indirectly through the modification of the habitat. The Iberá Natural Reserve (INR) is one of the most diverse ecosystems in northern Argentina; it is dominated by grasslands commonly affected by disturbances, such as grazing and fire. The objective of this work was to study the response of ground-foraging ant assemblages, particular species, and functional groups to an extended fire of high intensity in four natural INR habitats with >5 years of cattle exclusion (strict conservation area). A total of 12,798 ant workers of 67 species were captured in 39 sampling stations. The ant fauna was less abundant in burned sites only a few days after the fire; 6 months later, no effect was detected. Richness and abundance of ants differed among unburned habitats. However, fire effect on species richness and composition remained unclear. The rapid recovery of the ant fauna made these insects poor indicators of long-term fire-promoted changes on biodiversity in open habitats dominated by grassland, though some ant species showed a high level of habitat fidelity mainly in unburned habitats. These results agree with those from other areas of the world, indicating that ants are particularly unreliable biodiversity indicators, with the exception of severe disturbance with long-term habitat restoration. Management decisions at the INR should be oriented to preserve the closed savanna, one of the most diverse and threatened habitat of Argentina.     

Long‐term Changes in Bird Communities after Wildfires in the Central Brazilian Amazon

We examined long‐term responses of an Amazonian bird assemblage to wildfire disturbance, investigating how understory birds reacted to forest regeneration 1, 3, and 10 years after a widespread fire event. The bird community was sampled along the Arapiuns and Maró river catchments in central Brazilian Amazonia. Sampling took place in 1998, 2000, and 2008 using mist‐nets in eight plots (four burned, four unburned sites). Species richness did not change significantly in unburned sites. In burned sites, however, we found significantly lower richness in 1998, higher richness in 2000, and similar richness in 2008. Multi‐dimensional scaling ordination showed consistent differences in bird communities both within burned sites sampled in different sampling years, and between burned and unburned sites in all years. Of the 30 most abundant species, 12 had not recovered 10 years after the fires, including habitat specialists such as mixed flocks specialists and ant‐followers. Fire‐disturbance favored three species (two hummingbirds and a manakin) in the short term only. All other species were either favored throughout the study (seven species of omnivores and small insectivores) or did not show a clear response (eight species). In burned sites, we also found significantly lower abundance of species sensitive to disturbances and habitat specialists over the entire study period. Although the bird community seems to be recovering in terms of richness, the overall community composition and abundance of some species in post‐burned and unburned sites remain very different, and have not recovered after 10 years of forest regeneration.     

Interaction of multiple disturbances: importance of disturbance interval in the effects of fire on rehabilitating mined areas

Abstract Multiple disturbance regimes are increasingly common as novel anthropogenic disturbances are added to existing natural disturbances. However, it is generally unknown whether simultaneous or sequential effects of different forms of disturbance are predictable from the independent effects of each disturbance. This study examines the short‐term effects of sequential disturbance by mineral sand‐mining followed by fire in a forest community in south‐eastern Australia. Four combinations of disturbance were sampled: unburned mined, burned mined, unburned forest (unmined) and burned forest (unmined, with between‐fire interval matching the disturbance interval between mining and fire of the burned mined treatment). All combinations were sampled approximately 12 months following fire on the burned sites. The impact of fire after mining depended on disturbance interval. Sites burned 0.5–2.4 years since mining had fewer native vascular plant species than unburned mined sites of the same mined age, whereas sites with 10–16 years or 20–26 years between mining and fire had greater native species richness than unburned mined sites of the same age. Burning 20–26 years after mining brought native species richness within the range of burned forest. For both unmined and mined sites native seedling densities increased with burning, and with longer disturbance intervals. Weed species richness and weed seedling densities were greater on mined sites than in forest, and burning mined sites elevated weed seedling densities further, particularly for short intervals. Both disturbance interval and fire intensity are likely to have contributed to these results, as intensity on mined areas increased with interval, and at 20–26 years post‐mining was equivalent to unmined forest. These results suggest that fire could be used to promote rehabilitation of these mined areas after at least 10 years, but should be excluded from earlier stages of post‐mining regeneration. However, other sources of spatial and temporal variability should be considered in addition to interval and intensity, as variation among mined areas was correlated with post‐fire weather conditions and available weed sources. Finally, the combined effects of mining and fire could not be predicted from knowledge of the disturbances operating separately, indicating that effects of multiple disturbance may be synergistic rather than additive.     

Ant diversity in relation to time since fire in a mallee landscape of South-Eastern Australia

Fire is a dominant process shaping the Australian landscape and in many regions the frequency and severity of wildfires are predicted to increase under climate change. The primary impact of fire on fauna is typically indirect through habitat change. In particular, in mesic forests different animal species are favoured at different times since fire as habitat complexity increases with vegetation recovery. However, this will not necessarily be the case in habitats with low complexity such as many of those occurring in arid and semi-arid regions. Here, we investigate the relationship between fire history and ant diversity and composition in semi-arid mallee of south-eastern Australia. We surveyed ants at 11 sites in the Little Desert National Park and nearby private land that last burnt 0.5, 6 or 40 years ago. We found no relationship between time since fire and either ant diversity or composition, and this can be explained by a lack of relationship between time since fire and vegetation cover. Our findings contrast with those for mallee bird species, which show clear successional patterns following fire, but are likely to be typical of ground-foraging fauna that lack specialized habitat requirements.     

Effects of forest disturbance on the structure of ground-foraging ant communities in central Amazonia

This study evaluates biotic responses, using ants as bio-indicators, to relatively recent anthropogenic disturbances to mature forest in central Amazonia. The structure of the ground-foraging ant community was compared in four habitats that represented a gradient of disturbance associated with differences in land use. Ants were collected in undisturbed, mature forest, in an abandoned pasture, in a young regrowth forest (situated in a former pasture area), and in an old regrowth forest (established where mature forest was just cleared and abandoned). More ant species were found in mature and old regrowth forest than in the abandoned pasture. By contrast, ant abundance tended to decrease with forest maturity. Both pasture and young regrowth forest exhibited a distinct ant species composition compared to mature forest, whereas species composition in the old regrowth forest showed greater similarity to that of mature forest. In spite of differences in fallow time between former pasture areas and non-pasture areas, there is evidence that different land-management practices do result in different rates of recovery of the ant forest fauna after land abandonment. In any case, recuperation of the ground-foraging ant fauna appears to be faster than regeneration of the woody-plant community. In this sense, regrowth forests may be valuable for the conservation of ground-foraging ants and perhaps for other components of mature-forest leaf-litter fauna within the context of a fragmented landscape.     

Assembly rules of ground-foraging ant assemblages are contingent on disturbance, habitat and spatial scale

Aim A major endeavour of community ecology is documenting non‐random patterns in the composition and body size of coexisting species, and inferring the processes, or assembly rules, that may have given rise to the observed patterns. Such assembly rules include species sorting resulting from interspecific competition, aggregation at patchily distributed resources, and co‐evolutionary dynamics. However, for any given taxon, relatively little is known about how these patterns and processes change through time and vary with habitat type, disturbance history, and spatial scale. Here, we tested for non‐random patterns of species co‐occurrence and body size in assemblages of ground‐foraging ants and asked whether those patterns varied with habitat type, disturbance history, and spatial scale. Location Burned and unburned forests and fens in the Siskiyou Mountains of southern Oregon and northern California, USA. Methods We describe ground‐foraging ant assemblages sampled over two years in two discrete habitat types, namely Darlingtonia fens and upland forests. Half of these sites had been subject to a large‐scale, discrete disturbance – a major fire – in the year prior to our first sample. We used null model analyses to compare observed species co‐occurrence patterns and body‐size distributions in these assemblages with randomly generated assemblages unstructured by competition both within (i.e. at a local spatial scale) and among (i.e. at a regional scale) sites. Results At local spatial scales, species co‐occurrence patterns and body‐size ratios did not differ from randomness. At regional scales, co‐occurrence patterns were random or aggregated, and there was evidence for constant body‐size ratios of forest ants. Although these patterns varied between habitats and years, they did not differ between burned and unburned sites. Main conclusions Our results suggest that the operation of assembly rules depends on spatial scale and habitat type, but that it was not affected by disturbance history from fire.     

Effects of prescribed burning and harvesting on ground-dwelling spiders in the Canadian boreal mixedwood forest

The ‘Natural Disturbance Paradigm’ for forest management seeks to meet conservation goals by modeling industrial harvest in fire-driven forest systems on patterns associated with wildfire. Fire suppression and increased forest harvesting may have detrimental effects on biodiversity, and therefore prescribed burning is suggested to retain legacies of wildfire not emulated under natural disturbance based approaches. The merits of this approach are being tested in the EMEND experiment in the Canadian boreal mixedwood forest. We compared responses of ground-dwelling spiders between sites subjected to prescribed post-harvest burning and retention harvest during three seasons during the first 7 years after disturbance. Overall, 38,661 adult spiders representing 190 species were collected. Estimated species richness was highest in undisturbed sites in all 3 years. Burning had the strongest negative effect on species richness 1–2 years after treatment; however, richness was higher in burns than in harvested sites 5–6 years post-disturbance. Species turnover was highest within controls but tended to increase over time between burned and harvested plots. Lower turnover in burned and harvested sites may reflect habitat homogenization by disturbance, suggesting a management and conservation challenge in relation to naturally disturbed and undisturbed areas. Species were grouped into disturbance-specialists, disturbance-tolerant, disturbance-generalists and generalists; 22 species were significant indicators for untreated sites, 18 for the burn and three for the harvest treatments. No major differences were observed in the spider fauna between harvested and burned areas within the first 6–7 years post-disturbance, and little evidence of recovery toward the pre-harvest fauna was evidenced. However, long term experiments may improve understanding of natural disturbance processes and improve management of boreal forests.     

Dependence on Fire in Wood-living Insects: An Experiment with Burned and Unburned Spruce and Birch Logs

Several boreal wood-living insect species breed exclusively in recently burned forest. However, the reason for this dependence on fire is largely unknown. Here wood-living insects and other arthropods were sampled from burned and unburned logs of birch and spruce in a burned forest, together with unburned logs at a clearing and in an uncut forest, during two years of succession after tree death. Burned spruce logs hosted fewer beetles than unburned logs. Notably, bark-beetles and their associated fauna, responded negatively to fire-scorching of the logs while arthropods that feed on ascomycete fungi responded positively. Fire-scorched logs more often had visible ascomycete fungi, and lost their bark faster than unburned logs. However, despite this obvious effect of fire-scorching of the logs, the species composition in burned and unburned logs at the burned site was more similar than in unburned logs at the three different sites. A larger diversity of beetles, when measured with rarefaction, was found for fire-scorched logs. When sites were compared, birch logs had the most diverse fauna at the burned site and spruce logs in the uncut forest. Pyrophilous insect species were almost exclusively confined to the burned forest, but occurred in both burned and unburned logs. These species may be divided into two groups: (1) mycophagous species that need burned substrate per se because ascomycete fungi are favoured by burning, and (2) phloem-feeders and predators that are favoured by some habitat characteristic of recently burned forest rather than of burned wood.     

Frequent fuel‐reduction burning: the role of logs and associated leaf litter in the conservation of ant biodiversity

Frequent low‐intensity fires are used in management of Australian forests to reduce fuel loads and protect natural resources and human property. Low‐intensity fires are typically patchy and unburned litter microhabitats are often associated with large objects such as logs, which may act as refuges both for vertebrate and for invertebrate fauna. The aim of this study was to determine whether ants were using unburned leaf litter microhabitats associated with logs as a refuge after fire. The study was carried out in Bulls Ground State Forest, New South Wales, Australia, where experimentally burned and unburned sites had previously been established. Species richness and abundance of ants in leaf litter did not differ between habitats adjacent to logs and away from logs, in burned and unburned sites. Fifteen of the 42 ant species were found in all four habitats, and contributed 94% of total ant abundance. Every habitat had a group of unique species, which together made up 30% of the total species richness. There was also a distinct group of species that was not found in the leaf litter associated with the burned/open habitat. However, as 45% of all species were found in low abundance (less than 10 individuals), care must be taken in inferring patterns for these groups. When functional groups were used to assess community structure, ‘cryptic’ species were found to be common in all habitats, whereas ‘subordinate Camponotini’ were found in burned habitats only. This study indicates that in an area where frequent burning is applied on a broad scale, preserving a range of microhabitats, including those associated with retained logs, may make a substantial contribution to conserving ant biodiversity.     

Genotypic diversity of a dominant C4 grass across a long-term fire frequency gradient

Aims and Methods Diversity-disturbance research has focused on community diversity, but disturbance frequency could impact diversity within species as well, with important consequences for community diversity and ecosystem function. We examined patterns of genetic diversity of a dominant grass species, Andropogon gerardii, in native North American tallgrass prairie sites located in eastern Kansas that have been subjected to a gradient of fire frequency treatments (burned every 1, 2, 4 or 20 years) since the 1970s. In addition, we were able to assess the relationships between genetic diversity of A. gerardii, species diversity and productivity across this range of fire frequencies.Important findings We found no significant relationships between genetic diversity of A. gerardii at the local scale (1 m 2 plot level) and disturbance frequency (burned 2 to 32 times over a 38-year period). However, at the site level (i.e. across all plots sampled within a site, ~100 m 2) there were differences in genotype richness and composition, as well as genomic dissimilarity among individuals of A. gerardii. Genotype richness was greatest for the site burned at an intermediate (4-year) frequency and lowest for the infrequently (20-year) burned site. In addition, genotypes found in the frequently burned sites were more similar from each other than expected by random chance than those found in the infrequently burned sites. Genotype composition of A. gerardii was not significantly different between the frequently burned sites (annual vs. 2 year) but did differ between frequently burned and infrequently burned sites (1 and 2 year vs. 4 and 20 year, etc.). Together, these results suggest site-level ecological sorting of genotypes in intact prairie across a broad gradient of disturbance frequencies, likely driven by alterations in environmental conditions. Frequent fire promotes the abundance of dominant grass species, reduces plant community diversity and impacts ecosystem processes such as productivity. Our study suggests that genetic diversity within dominant grass species also may be affected by disturbance frequency, which could have important implications for how species are able to respond to disturbance.     

Impacts of clearing,fragmentation and disturbance on the bird fauna of Eucalypt savanna woodlands in central Queensland,Australia

Abstract This study reports on the responses of bird assemblages to woodland clearance, fragmentation and habitat disturbance in central Queensland Australia, a region exposed to very high rates of vegetation clearance over the last two to three decades. Many previous studies of clearing impacts have considered situations where there is a very sharp management contrast between uncleared lands and cleared areas: in this situation, the contrast is more muted, because both cleared lands and uncleared savanna woodlands are exposed to cattle grazing, invasion by the exotic grass Cenchrus ciliaris and similar fire management. Bird species richness (at the scale of a 1‐ha quadrat) was least in cleared areas (8.1 species), then regrowth areas (14.6 species), then uncleared woodlands (19.9 species). Richness at this scale was unrelated to woodland fragment size, connectivity or habitat condition; but declined significantly with increasing abundance of miners (interspecifically aggressive colonial honeyeaters). At whole of patch scale, richness increased with fragment size and decreased with abundance of miners. This study demonstrates complex responses of individual bird species to a regional management cocktail of disturbance elements. Of 71 individual bird species modelled for woodland fragment sites, the quadrat‐level abundance of 40 species was significantly related to at least one variable representing environmental position (across a rainfall gradient), fragment condition, fragment size and/or connectivity. This study suggests that priorities for conservation management include: cessation of broad‐scale clearing; increased protection for regrowth (particularly where this may bolster connectivity and/or size of woodland fragments); control of miners; maintenance of fallen woody debris in woodlands; increase in fire frequency; and reduction in the incidence of grazing and exotic pasture grass.     

Post-fire recovery of Mediterranean ground ant communities follows vegetation and dryness gradients

Aim In the Mediterranean Basin, the main forest communities vary in their ability to recover after fire. In this study we analyse the effects of fire on ant communities occurring in various vegetation types distributed along a geographical gradient in the western Mediterranean region. Location The study was carried out in burned and unburned habitats of 22 sites corresponding to eight vegetation types distributed along a gradient of dryness throughout Catalonia (north‐east Spain). Methods We placed five pairs of plots (one plot located in the burned area and the second one placed in the unburned margin) per site. We compared ant communities in these unburned and burned plot types 8 years after fire using pitfall traps. Traps were set out in mid‐May and mid‐July. We analysed the structure and composition of ant communities in the burned and unburned areas of these vegetation types using anova tests, correspondence analysis (CA) and linear regression. Results The resilience of ant communities varies with vegetation type. Ant communities in forests with high resilience also recover rapidly after fire, while those in forests that do not recover after fire show the lowest resilience. Species richness does not depend on burning or vegetation type. The resilience of these Mediterranean ant communities to fire is related to the environmental characteristics of the region where they live. Accordingly, differences between burned and unburned habitats are smaller for ant communities in areas with higher water deficit in summer than for those in moister ones. Main conclusions The structure and composition of ant communities after fire depends on the level of direct mortality caused by the fire. It affects ant species differently, as determined by the habitats used for nesting and foraging. The reestablishment of vegetation cover depends on forest composition before the fire. As vegetation cover determines resource and microhabitat availability and competitive relationships among species, forest composition before the fire also affects post‐fire recovery of ant communities to the medium‐term. Finally, ant communities living in drier areas recover more quickly after fire than those living in moister ones. This pattern might be because in areas with higher water deficit there are more species characteristic of open environments, which are habitats similar to those generated after fire.     

Recovery of ground ant (Hymenoptera: Formicidae) communities six years after a major environmental disaster

The recovery of ant communities at the Guadiamar River bank (southwest Spain) was studied across 5 yr, after an environmental disaster caused by the spill of toxic sludge over the river caused by a mine accident. Three affected and three control sites were sampled from 2000 to 2004 using pitfall traps. The last year of study, a more exhaustive sampling was conducted at the affected area (eight sampling sites). Additionally, four adjacent study sites not affected by the toxic spill were also studied. Ants showed clear responses to the restoration of the area. Mean ant species richness in spillage affected sites showed a significant increase over the 5 yr. Moreover, multivariate analysis showed distinct changes of ant community composition of the affected area over the years that were not observed in control sites. Six years after the disaster, one half of the species recorded in control sites were also present in the affected area, with only one species exclusive to this area, Cardiocondyla mauritanica Forel (tramp species). However, not only habitat specialist species but also some generalist and conspicuous species within the river basin are not present along the affected area, including species of the genera Camponotus, Messor, Cataglyphis, and Aphaenogaster. This study shows an incipient recovery of ant communities 6 yr after a major environmental disturbance, highlighting the absence of any invasive ant species in the restored area.     

Ants as bioindicators of habitat disturbance: validation of the functional group model for Australia's humid tropics

A functional group model of ant community composition has been widely used in Australia to analyse biogeographical patterns of ant community structure and the responses of ant communities to disturbance. The model has provided valuable support to the widespread use of ant communities as bioindicators of ecological change. However, the model was developed from studies of arid-zone faunas, and its applicability to the World Heritage rainforests of Queensland's humid tropics has not yet been validated. Here we test predictions based on the functional group model for ant communities in Queensland's humid rainforests, by documenting ant community composition and its responses to disturbance on the Atherton Tablelands. Five sites were studied, comprising two relatively undisturbed reference sites representing contrasting rainforest types, and three previously cleared sites, two of which were undergoing revegetation. A variety of sampling techniques were employed, including pitfall trapping, litter extractions, baiting, and general searching. A total of 50 ant species from 29 genera were collected. Site species richness was highest at the reference sites, and lowest at the unvegetated disturbed site, and overall was negatively related to mean ground temperature. As predicted by the functional group model, behaviorally dominant dolichoderines were uncommon or absent at the reference sites, and the most common ants were Generalized myrmicines and Opportunists. Also as predicted, habitat disturbance favored Opportunists, and, as the disturbance involved canopy clearance, this led to colonization by Iridomyrmex and other Dominant dolichoderines. Opportunists represented about 40% of total ants in traps at the reference sites, compared with 80–95% at the disturbed sites. Except one species, Tropical Climate Specialists and Specialist Predators were absent from disturbed sites.In conclusion, patterns of ant composition in relation to disturbance on the Atherton Tablelands conform to the functional group model that has been widely applied to ant faunas elsewhere in Australia. The model may therefore play an important role in the use of ants as bioindicators of ecological change in the World Heritage rainforests of this region.     

The effects of fire on ant communities in north-western Patagonia: the importance of habitat structure and regional context

Abstract. We investigated the effects of recent fires on the native ant communities in two habitats of north-west Patagonia that differ in vegetation structural complexity. Using bait traps, we sampled ants in replicated scrub and steppe areas including paired burned and unburned sites. Fires significantly reduced plant cover and ant diversity only in scrub sites. The drop in diversity was due to (a) a reduction in the abundance of rare species associated with woody vegetation, and (b) an increase in the abundance of the dominant species, which thrive in more xeric microclimatic conditions. Consequently, ant assemblage structure of burned scrub approaches that of steppe sites. Our findings suggest that the effects of disturbances on ant assemblages depends both on habitat characteristics, which in turn determine the extent of the changes induced by the disturbance, and on the regional context of the ant fauna, which in turn determines the ability of the ants to deal with the post-disturbance conditions.     

Fire severity mediates climate‐driven shifts in understorey community composition of black spruce stands of interior Alaska

Question: How do pre‐fire conditions (community composition and environmental characteristics) and climate‐driven disturbance characteristics (fire severity) affect post‐fire community composition in black spruce stands? Location: Northern boreal forest, interior Alaska. Methods: We compared plant community composition and environmental stand characteristics in 14 black spruce stands before and after multiple, naturally occurring wildfires. We used a combination of vegetation table sorting, univariate (ANOVA, paired t‐tests), and multivariate (detrended correspondence analysis) statistics to determine the impact of fire severity and site moisture on community composition, dominant species and growth forms. Results: Severe wildfires caused a 50% reduction in number of plant species in our study sites. The largest species loss, and therefore the greatest change in species composition, occurred in severely burned sites. This was due mostly to loss of non‐vascular species (mosses and lichens) and evergreen shrubs. New species recruited most abundantly to severely burned sites, contributing to high species turnover on these sites. As well as the strong effect of fire severity, pre‐fire and post‐fire mineral soil pH had an effect on post‐fire vegetation patterns, suggesting a legacy effect of site acidity. In contrast, pre‐fire site moisture, which was a strong determinant of pre‐fire community composition, showed no relationship with post‐fire community composition. Site moisture was altered by fire, due to changes in permafrost, and therefore post‐fire site moisture overrode pre‐fire site moisture as a strong correlate. Conclusions: In the rapidly warming climate of interior Alaska, changes in fire severity had more effect on post‐fire community composition than did environmental factors (moisture and pH) that govern landscape patterns of unburned vegetation. This suggests that climate change effects on future community composition of black spruce forests may be mediated more strongly by fire severity than by current landscape patterns. Hence, models that represent the effects of climate change on boreal forests could improve their accuracy by including dynamic responses to fire disturbance.     

Dynamics of the Leaf-Litter Arthropod Fauna Following Fire in a Neotropical Woodland Savanna

Fire is an important agent of disturbance in tropical savannas, but relatively few studies have analyzed how soil-and-litter dwelling arthropods respond to fire disturbance despite the critical role these organisms play in nutrient cycling and other biogeochemical processes. Following the incursion of a fire into a woodland savanna ecological reserve in Central Brazil, we monitored the dynamics of litter-arthropod populations for nearly two years in one burned and one unburned area of the reserve. We also performed a reciprocal transplant experiment to determine the effects of fire and litter type on the dynamics of litter colonization by arthropods. Overall arthropod abundance, the abundance of individual taxa, the richness of taxonomic groups, and the species richness of individual taxa (Formiciade) were lower in the burned site. However, both the ordinal-level composition of the litter arthropod fauna and the species-level composition of the litter ant fauna were not dramatically different in the burned and unburned sites. There is evidence that seasonality of rainfall interacts with fire, as differences in arthropod abundance and diversity were more pronounced in the dry than in the wet season. For many taxa the differences in abundance between burned and unburned sites were maintained even when controlling for litter availability and quality. In contrast, differences in abundance for Collembola, Formicidae, and Thysanoptera were only detected in the unmanipulated samples, which had a lower amount of litter in the burned than in the unburned site throughout most of our study period. Together these results suggest that arthropod density declines in fire-disturbed areas as a result of direct mortality, diminished resources (i.e., reduced litter cover) and less favorable microclimate (i.e., increased litter desiccation due to reduction in tree cover). Although these effects were transitory, there is evidence that the increasingly prevalent fire return interval of only 1–2 years may jeopardize the long-term conservation of litter arthropod communities.     

Colonization of dynamic Mediterranean landscapes: where do birds come from after fire?

Aim Two main mechanisms may explain post‐disturbance species colonization patterns of early successional habitats such as those originated by wildfires. First, post‐disturbance colonization is not limited by the dispersal ability of the species to reach the newly created open areas and, secondly, colonization is limited by dispersal. Under the first hypothesis, we expect, at a regional scale, to find similar post‐disturbance communities to develop on recently burned sites. However, colonization limited by dispersal will lead to strong between‐site variations in species composition. Location To test these hypotheses, we studied the post‐fire colonization patterns of nine open‐habitat bird species in eight distantly located wildfires in the north‐eastern Iberian Peninsula. Methods We censused post‐fire bird composition by means of field transects and identified potential colonization sources from species–habitat suitability maps derived from atlas data. Results Our results showed strong significant differences in post‐fire species composition between burnt areas. Burnt areas located in areas with low probability of species presence before the fire event showed lower species occurrence and richness after the fire. Main conclusions These results do not support the idea that early successional stages and open habitats have a homogeneous community structure at regional scales and suggest that dispersal is a key constraint determining bird colonization of post‐fire habitats. Further attention should be paid to landscape heterogeneity as a key factor in determining population dynamics of open‐habitat species in the light of current and future land‐use changes in Mediterranean regions.