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Don A. Driscoll Dolors Armenteras Andrew F. Bennett Lluís Brotons Michael F. Clarke Tim S. Doherty Angie Haslem Luke T. Kelly Chloe F. Sato Holly Sitters Núria Aquilué Kristian Bell Maria Chadid Andrea Duane María C. Meza-Elizalde Katherine M. Giljohann Tania Marisol González Ravi Jambhekar Juliana Lazzari Alejandra Morán-Ordóñez Tricia Wevill 《Biological reviews of the Cambridge Philosophical Society》2021,96(3):976-998
Biodiversity faces many threats and these can interact to produce outcomes that may not be predicted by considering their effects in isolation. Habitat loss and fragmentation (hereafter ‘fragmentation’) and altered fire regimes are important threats to biodiversity, but their interactions have not been systematically evaluated across the globe. In this comprehensive synthesis, including 162 papers which provided 274 cases, we offer a framework for understanding how fire interacts with fragmentation. Fire and fragmentation interact in three main ways: (i) fire influences fragmentation (59% of 274 cases), where fire either destroys and fragments habitat or creates and connects habitat; (ii) fragmentation influences fire (25% of cases) where, after habitat is reduced in area and fragmented, fire in the landscape is subsequently altered because people suppress or ignite fires, or there is increased edge flammability or increased obstruction to fire spread; and (iii) where the two do not influence each other, but fire interacts with fragmentation to affect responses like species richness, abundance and extinction risk (16% of cases). Where fire and fragmentation do influence each other, feedback loops are possible that can lead to ecosystem conversion (e.g. forest to grassland). This is a well-documented threat in the tropics but with potential also to be important elsewhere. Fire interacts with fragmentation through scale-specific mechanisms: fire creates edges and drives edge effects; fire alters patch quality; and fire alters landscape-scale connectivity. We found only 12 cases in which studies reported the four essential strata for testing a full interaction, which were fragmented and unfragmented landscapes that both span contrasting fire histories, such as recently burnt and long unburnt vegetation. Simulation and empirical studies show that fire and fragmentation can interact synergistically, multiplicatively, antagonistically or additively. These cases highlight a key reason why understanding interactions is so important: when fire and fragmentation act together they can cause local extinctions, even when their separate effects are neutral. Whether fire–fragmentation interactions benefit or disadvantage species is often determined by the species' preferred successional stage. Adding fire to landscapes generally benefits early-successional plant and animal species, whereas it is detrimental to late-successional species. However, when fire interacts with fragmentation, the direction of effect of fire on a species could be reversed from the effect expected by successional preferences. Adding fire to fragmented landscapes can be detrimental for species that would normally co-exist with fire, because species may no longer be able to disperse to their preferred successional stage. Further, animals may be attracted to particular successional stages leading to unexpected responses to fragmentation, such as higher abundance in more isolated unburnt patches. Growing human populations and increasing resource consumption suggest that fragmentation trends will worsen over coming years. Combined with increasing alteration of fire regimes due to climate change and human-caused ignitions, interactions of fire with fragmentation are likely to become more common. Our new framework paves the way for developing a better understanding of how fire interacts with fragmentation, and for conserving biodiversity in the face of these emerging challenges. 相似文献
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Identifying factors that influence the survival of individuals during disturbance is critical to understanding patterns of species reassembly within ecological communities. Although most studies of recovery of populations post‐burning acknowledge the potentially important contribution of animals surviving in situ, few have measured the effectiveness of refugia. This paper tests the hypothesis that some plants with tightly packed leaf‐bases provide a refuge for invertebrates during fire (even when the plants themselves burn) by using the highly flammable grass tree (Xanthorrhoeaceae: Xanthorrhoea). Invertebrates were sampled from four unburnt and five experimentally burnt grass trees (Xanthorrhoea preissii Endl.). Also collected were invertebrates fleeing during burning. The dataset comprises 949 specimens, representing 81 species from 18 orders, of which 749 individuals were from unburned plants. Slaters (Isopoda), silverfish (Thysanura), spiders (Araneae) and bugs (Hemiptera) dominated assemblages of the unburnt grass trees. Despite grass trees burning at temperatures of up to 515°C, some invertebrates survived in situ. Species‐specific microhabitat preferences within the plant appeared to influence survivorship. Species collected in the crown of unburned plants were found more often alive on burnt plants than species typically inhabiting the dead skirt of decaying leaves (thatch). We contend that the mechanism causing differential mortality is fire temperature. In the dead skirt, temperatures reached 225.33 ± 66.57°C. In contrast, a region of mild temperature (25.00 ± 3.54°C) persisted throughout burning near the apical meristem (within the crown). We conclude that grass trees are a potential reservoir from which invertebrates might re‐colonize recently burnt areas. However, owing to species‐specific microhabitat preferences and differential mortality across microhabitats, the invertebrate assemblage remaining in situ will be restricted taxonomically compared with the original grass tree fauna. Moreover, different fire regimes might mediate the effectiveness of grass trees as refugia. Finally, we argue that in situ survival of invertebrates within plants with tightly packed leaf‐bases is an unrecognized global phenomenon applicable to a wide array of plant taxa. 相似文献
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Time since last fire and fire frequency are strong determinants of plant community composition in fire‐prone landscapes. Our study aimed to establish the influence of time since last fire and fire frequency on plant community composition and diversity of a south‐west Australian semi‐arid shrubland. We employed a space‐for‐time approach using four fire age classes: ‘young’, 8–15 years since last fire; ‘medium’, 16–34; ‘old’, 35–50; and ‘very old’, 51–100; and three fire frequency classes: burnt once, twice and three times within the last 50 years. Species diversity was compared using one‐way ANOVA and species composition using PERMANOVA. Soil and climatic variables were included as covariables to partition underlying environmental drivers. We found that time since last fire influenced species richness, diversity and composition. Specifically, we recorded a late successional transition from woody seeders to long‐lived, arid‐zone, resprouting shrub species. Fire frequency did not influence species richness and diversity but did influence species composition via a reduction in cover of longer‐lived resprouter species – presumably because of a reduced ability to replenish epicormic buds and/or sufficient starch stores. The distinct floristic composition of old and very old habitat, and the vulnerability of these areas to wildfires, indicate that these areas are ecologically important and management should seek to preserve them. 相似文献
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Louise A. Pastro Christopher R. Dickman Mike Letnic 《Global Ecology and Biogeography》2014,23(10):1146-1156
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Vegetation management practices have been applied worldwide to enhance habitats for a variety of wildlife species. Big sagebrush (Artemisia tridentata spp.) communities, iconic to western North America, have been treated to restore herbaceous understories through chemical, mechanical, and prescribed burning practices thought to improve habitat conditions for greater sage‐grouse (Centrocercus urophasianus) and other species. Although the response of structural attributes of sagebrush communities to treatments is well understood, there is a need to identify how treatments influence wildlife population dynamics. We investigated the influence of vegetation treatments occurring in Wyoming, United States, from 1994 to 2012 on annual sage‐grouse population change using yearly male sage‐grouse lek counts. We investigated this response across 1, 3, 5, and 10‐year post‐treatment lags to evaluate how the amount of treated sagebrush communities and time since treatment influenced population change, while accounting for climate, wildfire, and anthropogenic factors. With the exception of chemical treatments exhibiting a positive association with sage‐grouse population change 11 years after implementation, population response to treatments was either neutral or negative for at least 11 years following treatments. Our work supports a growing body of research advocating against treating big sagebrush habitats for sage‐grouse, particularly in Wyoming big sagebrush (A. t. wyomingensis). Loss and fragmentation of sagebrush habitats has been identified as a significant threat for remaining sage‐grouse populations. Because sagebrush may take decades to recover following treatments, we recommend practitioners use caution when designing projects to alter remaining habitats, especially when focused on habitat requirements for one life stage and a single species. 相似文献
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1. The complex effects of disturbances on ecological communities can be further complicated by subsequent perturbations within an ecosystem. We investigated how wildfire interacts with annual variations in peak streamflow to affect the stability of stream macroinvertebrate communities in a central Idaho wilderness, USA. We conducted a 4‐year retrospective analysis of unburned (n = 7) and burned (n = 6) catchments, using changes in reflectance values (Δ NBR) from satellite imagery to quantify the percentage of each catchment’s riparian and upland vegetation that burned at high and low severity. 2. For this wildland fire complex, increasing riparian burn severity and extent were associated with greater year‐to‐year variation, rather than a perennial increase, in sediment loads, organic debris, large woody debris (LWD) and undercut bank structure. Temporal changes in these variables were correlated with yearly peak flow in burned catchments but not in unburned reference catchments, indicating that an interaction between fire and flow can result in decreased habitat stability in burned catchments. 3. Streams in more severely burned catchments exhibited increasingly dynamic macroinvertebrate communities and did not show increased similarity to reference streams over time. Annual variability in macroinvertebrates was attributed, predominantly, to the changing influence of sediment, LWD, riparian cover and organic debris, as quantities of these habitat components fluctuated annually depending on burn severity and annual peak streamflows. 4. These analyses suggest that interactions among fire, flow and stream habitat may increase inter‐annual habitat variability and macroinvertebrate community dynamics for a duration approaching the length of the historic fire return interval of the study area. 相似文献
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David M. J. S. Bowman Grant J. Williamson Lynda D. Prior Brett P. Murphy 《Global Ecology and Biogeography》2016,25(10):1166-1172
Forests that regenerate exclusively from seed following high‐severity fire are particularly vulnerable to local extinction if fire frequency leaves insufficient time for regenerating plants to reach sexual maturity. We evaluate the relative importance of extrinsic (such as fire weather and climate cycles) and intrinsic (such as proneness to fire due to stand age and structural development) factors in driving the decline of obligate seeder forests. We illustrate this using obligate seeding alpine ash (Eucalyptus delegatensis) forests in the montane regions of Victoria, Australia, that were burnt by megafires in 2003 (142,256 ha) or 2007 (79,902 ha), including some twice‐burnt areas (11,599 ha). Geospatial analyses showed only a small effect of stand age on the remote sensing estimates of crown defoliation, but a substantial effect of forest fire weather, as measured by forest fire danger index (FFDI). Analysis of meteorological data over the last century showed that 5‐year increases in FFDI precede cycle major fires in the E. delegatensis forests. Such strong extrinsic climate/weather driving of high‐severity fires is consistent with the ‘interval squeeze model’ that postulates the vulnerability of obligate seeder forests to landscape‐scale demographic collapse in response to worsening fire weather under climate change. 相似文献
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Edges are ecologically important environmental features and have been well researched in agricultural and urban landscapes. However, little work has been conducted in flammable ecosystems where spatially and temporally dynamic fire edges are expected to influence important processes such as recolonization of burnt areas and landscape connectivity. We review the literature on fire, fauna, and edge effects to summarize current knowledge of faunal responses to fire edges and identify knowledge gaps. We then develop a conceptual model to predict faunal responses to fire edges and present an agenda for future research. Faunal abundance at fire edges changes over time, but patterns depend on species traits and resource availability. Responses are also influenced by edge architecture (e.g., size and shape), site and landscape context, and spatial scale. However, data are limited and the influence of fire edges on both local abundance and regional distributions of fauna is largely unknown. In our conceptual model, biophysical properties interact with the fire regime (e.g., patchiness, frequency) to influence edge architecture. Edge architecture and species traits influence edge permeability, which is linked to important processes such as movement, resource selection, and species interactions. Predicting the effect of fire edges on fauna is challenging, but important for biodiversity conservation in flammable landscapes. Our conceptual model combines several drivers of faunal fire responses (biophysical properties, regime attributes, species traits) and will therefore lead to improved predictions. Future research is needed to understand fire as an agent of edge creation; the spatio‐temporal flux of fire edges across landscapes; and the effect of fire edges on faunal movement, resource selection, and biotic interactions. To aid the incorporation of new data into our predictive framework, our model has been designed as a Bayesian Network, a statistical tool capable of analyzing complex environmental relationships, dealing with data gaps, and generating testable hypotheses. 相似文献
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Maitane Erdozain;Adrián Cardil;Sergio de-Miguel; 《Global Change Biology》2024,30(7):e17389
Freshwater ecosystems host disproportionately high biodiversity and provide unique ecosystem services, yet they are being degraded at an alarming rate. Fires, which are becoming increasingly frequent and intense due to global change, can affect these ecosystems in many ways, but this relationship is not fully understood. We conducted a systematic review to characterize the literature on the effects of fires on stream ecosystems and found that (1) abiotic indicators were more commonly investigated than biotic ones, (2) most previous research was conducted in North America and in the temperate evergreen forest biome, (3) following a control-impact (CI) or before-after (BA) design, (4) predominantly assessing wildfires as opposed to prescribed fires, (5) in small headwater streams, and (6) with a focus on structural and not functional biological indicators. After quantitatively analyzing previous research, we detected great variability in responses, with increases, decreases, and no changes being reported for most indicators (e.g., macroinvertebrate richness, fish density, algal biomass, and leaf decomposition). We shed light on these seemingly contradicting results by showing that the presence of extreme hydrological post-fire events, the time lag between fire and sampling, and whether the riparian forest burned or not influenced the outcome of previous research. Results suggest that although wildfires and the following hydrological events can have dramatic impacts in the short term, most biological endpoints recover within 5–10 years, and that detrimental effects are minimal in the case of prescribed fires. We also detected that no effects were more often reported by BACI studies than by CI or BA studies, raising the question of whether this research field may be biased by the inherent limitations of CI and BA designs. Finally, we make recommendations to help advance this field of research and guide future integrated fire management that includes the protection of freshwater ecosystems. 相似文献
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Once widespread, Australia's bluegrass tussock grasslands (dominated by Dichanthium sp.) of the Queensland Central Highlands are now severely endangered. Despite being biodiversity rich and highly valued as low input, nutrient‐dense grazing systems, bluegrass tussock grasslands have suffered extensive clearing and degradation over the last 150 years. Natural recovery of these grasslands is possible but rates of recovery are slow. As such, there is an urgent need to assess practical management strategies to accelerate recovery of these grasslands, with a particular focus on early‐successional stages, when aggressive exotic species are most prevalent. To date, no studies have tested whether commonly used grassland restoration strategies can enhance early‐successional stages and accelerate regeneration in this system. Here, we examine the early short‐term impacts (first two seasons) of two common grassland restoration approaches, with two variations each: direct seeding (single species and low seed diversity) and vegetation clearing (prescribed burning and glyphosate application) across two common starting points: a formerly cropped old field and a historically overgrazed natural grassland. No treatment increased native diversity (Shannon's or richness) in plots but the composition of burned plots in the old field did become more similar to healthy reference sites after two seasons. Burning combined with direct seeding also increased the abundance of the dominant grass, Dichanthium sericeum, toward healthy reference levels within the first two seasons post seeding. This study provides a practical assessment of the short‐term impacts and capacity of common grassland restoration treatments to enhance the recovery of Australia's tussock grassland systems. 相似文献
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- Grassland butterflies are undergoing worldwide population decline due to habitat loss and degradation. Rangelands in the Southern Great Plains can provide a habitat for grassland butterflies depending on management practices. Patch-burn grazing is a management regime that involves burning portions of grazed pastures at different times. The combination of rotational fire and grazing creates a shifting mosaic of recently burned to older burned areas and lightly grazed to heavily grazed areas. However, the impact of fire and grazing on butterfly communities is complex and the effects of different management regimes on butterfly communities are not clear.
- We investigated the impact of time since prescribed fire and season of fire on butterfly communities in eight cattle-grazed pastures, each with three burn units, in northern Oklahoma. Treatments included units burned in spring 2018, summer 2018, summer 2019, and spring 2020, with three replicates of each for a total of 12 burn units. Surveys were conducted three times per year in each burn unit in 2019 and 2020 using two standardised Pollard transects.
- A total of 909 butterflies and 35 species were observed. Species diversity varied by time since fire and season of fire, with spring-burned sites having the lowest species diversity and summer-burned sites having the highest. Dominant vegetation cover and blooming forb presence differed with time since fire and season of fire.
- Patch-burn grazing creates a mosaic of successional vegetation stages which can benefit different butterfly species and support the overall community. Some species such as Cercyonis pegala, Danaus plexippus, and Atrytone arogos may benefit from fire every 1–2 years, while other species such as Echinargus isola may need longer times between fire treatments. Patch-burn grazing regimes can support butterfly communities with species that need different fire return intervals by providing a mosaic of areas with different times since fire and associated grazing intensities.
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Cogongrass is a nonindigenous species perceived to threaten native communities of the southeastern United States through modification of species composition and alteration of community processes. To examine how gap size and disturbance type influence the invasion of wet pine savannas by cogongrass, we performed three field experiments to evaluate the response of cogongrass seeds and transplanted seedlings to four different gap sizes, four types of site disturbance, and recent burning of savanna vegetation. Cogongrass germinated, survived, and grew in all gap sizes, from 0 to 100 cm in diameter. Similarly, disturbance type had no effect on germination or seedling and transplant survival. Tilling, however, significantly enhanced transplanted seedling growth, resulting in a tenfold increase in biomass over the other disturbance types. Seedling survival to 1 and 2 mo was greater in burned savanna than unburned savanna, although transplant survival and growth were not affected by burning. Results of this study suggest that cogongrass can germinate, survive, and grow in wet pine savanna communities regardless of gap size or type of disturbance, including burning. Burning of savanna vegetation may enhance establishment by improving early seedling survival, and soil disturbance can facilitate invasion of cogongrass by enhancing plant growth. 相似文献
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We present logistic regression models predicting the distribution and abundance of a threatened cryptic lizard, Delma impar (Pygopodidae), in the Australian Capital Territory (ACT). The models incorporate current habitat and historical land use and habitat change (woodland clearance, ploughing, grazing, fertilizer application). Information on historical land use was acquired from land survey maps, aerial photographs and from floristic indices of land management. Floristic indices were developed from a survey of local agronomists who scored individual plant species, responses to grazing, ploughing and fertilizer application. Floristic indicies proved to be more informative than floristic ordination analyses. It emerged that historical factors were of key importance for predicting the distribution and abundance of D. impar. Since European settlement, D. impar has apparently spread from primary (naturally treeless grasslands) into secondary grasslands (grassland formerly with an overstorey of trees) and has been locally excluded by some farming activities such as ploughing. We conclude that a combination of current habitat and past changes in habitat may be necessary to understand the current distributions of plant and animal species that have limited dispersal ability and that are susceptible to local temporary habitat destruction. Active conservation strategies involving, for example, assisted dispersal, may be important for these species. 相似文献
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Abstract Germinable seed stores were estimated for 12–13 year old rehabilitation sites in the jarrah forest over two seasons (autumn and spring). Collected soils were subjected to combinations of smoking and heating treatments before the germination procedure was commenced. The mean topsoil seed reserve to a depth of 10 cm was 1938 seeds m?2. Of this total reserve, more than 80% was found in the upper 5 cm of soil. The topsoil seed reserve of these rehabilitation areas was almost seven times that of the adjacent native jarrah forest (292 seeds m?2; Ward et al. 1997). There was a seasonal effect with autumn-collected soils having significantly more germinable seeds (2723 seeds m?2) than soils collected in spring (1153 seeds m?2). More than half (53%) of the topsoil seed reserve in rehabilitated areas was composed of annual weed species, dominated by Aira caryophyllea, Centaurium erythraea and the native Levenhookia pusilla. Of the total of 70 species identified, 13 species showed significantly higher germination in smoked trays while 11 species exhibited significantly higher germination in heated trays. Species responding to the smoking treatment tended to be annuals while those responding to the heating treatment were typically legume shrub species. Examination of the topsoil seed reserve and the vegetation present in these areas showed that while the species composition was similar between the seed store and the vegetation, there was a large difference in densities, with species occurring at much higher densities in the topsoil than in the vegetation. However, the rankings of species were significantly correlated between the topsoil seed reserve and the vegetation present at the site. The implications of these results to prescribed burning of these rehabilitated areas is discussed. 相似文献
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The effects of herbivory and the season of disturbance on species composition and algal succession were experimentally tested at a tropical intertidal shore, Phuket Island, Thailand. Dead coral patches were cleared of all organisms during both the dry and rainy seasons in order to study the effects of season on algal succession and cages were set up to exclude fish herbivory. Algal succession in this intertidal habitat showed a simple pattern and took a year from the early Ulva paradoxa C. Agardh stage to the late Polysiphonia sphaerocarpa Børgesen stage. The abundance of algae during succession was under the influence of seasonal change. U. paradoxa reproduced and recruited throughout the year. Caging effects did not apparently influence algal abundance, perhaps because resident herbivorous damselfishes excluded other herbivores from their territories and maintained their algal “farms”. Unexpectedly, the percent cover of Ulva in the caged plots was lower than in uncaged plots. This pattern may indicate that caging excluded damselfishes only, but allowed small herbivores that consumed substantial amounts of soft filamentous algae in the cages. 相似文献
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In many fire-prone habitats around the world, natural fire regimes have shaped the evolution of the associated flora. Critical life history stages are often linked to fire in species that occur in these fire-prone habitats but many species are unstudied. We investigated seedling emergence patterns over time, after several fires in south-eastern Australia, for three obligate seeders in the Genus Leucopogon (Family Epacridaceae): L. setiger, L. esquamatus and L. exolasius. Fixed quadrats were monitored for 12 to 30 months for newly emerged seedlings, both after fire and in unburnt L. exolasius and L. esquamatus habitats. There was a flush of seedling emergence in the first year after fire for all three Leucopogon species, with smaller pulses recorded in subsequent years. Time elapsed between fire and the onset of emergence differed between fires, but not between Leucopogon species. Whatever the timing of the fire, seedling emergence was restricted to the late autumn and winter periods, coinciding with emergence in unburnt habitat. This contrasts with patterns of emergence previously reported for other taxa, and also in this study, where emergence of the Leucopogon species after fire was delayed compared with co-occurring species in other genera. Our results suggest that seasonal factors are important to the germination ecology of these species and that combinations of fire-related and seasonal factors are necessary to maximise germination. Rainfall has a non-seasonal pattern in the study region and seasonal emergence post-fire has not previously been recorded. The magnitude of delay to emergence of species with seasonal emergence patterns will be determined by the season of fire but not by a seasonal pattern of rainfall in the post-fire year. A shift of the peak fire season could increase this delay, possibly affecting plant population recovery. This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献