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1.
Human‐induced changes to fire regimes result in smaller, more patchy fires in many peri‐urban areas, with a concomitant increase in potential edge effects. In sclerophyll vegetation, many structurally dominant serotinous plants rely on the immediate post‐fire environment for recruitment. However, there is little information about how fire attributes affect seed predation or recruitment for these species. We examined the influence of distance to unburnt vegetation on post‐dispersal seed predation for five serotinous species from sclerophyll vegetation in the Sydney region, south‐eastern Australia; Banksia serrata L.f., Banksia spinulosa Sm. var. spinulosa, Hakea gibbosa (Sm.) Cav., Hakea teretifolia (Salisb.) Britten (all Proteaceae) and Allocasuarina distyla (Vent.) L. Johnson (Casuarinaceae). We used cafeteria trials and differential exclusion of vertebrates and invertebrates to test whether rates of seed removal for these five species differed among (i) unburnt, (ii) burnt‐edge (approx. 10 m from unburnt vegetation) and (iii) burnt‐interior (approx. 100 m from unburnt vegetation) locations. When all animals had access to seeds, seeds were removed at lower rates from burnt‐interior areas than from other locations. Vertebrates (small mammals) showed this pattern markedly the first time the experiment was run, but in a repeat trial this effect disappeared. Rate of seed removal by invertebrates differed among plant species but we did not detect any such differences for removal by vertebrates. Overall rates of seed removal also differed significantly between the two fires studied. Our results indicate that small mammal seed predation can be substantial for large‐seeded serotinous shrubs, and that differences in the perimeter: area ratio, severity or size of a fire are likely to affect seed predation.  相似文献   

2.
    
Seed dynamics of the annual tropical grasses Schizachyrium fragile (R. Br.) A. Camus, S. pachyarthron C. Gardner and S. pseudeulalia (Hosok.) S.T. Blake were studied with the aim of documenting fluxes in granivore food resources. In S. fragile, seed production began in the early dry season, and seed output was primarily influenced by seedling survival. Following seed-fall, there were 651 S. fragile seeds/m2 (393 kernels/m2) and 1014 S. pachyarthron seeds/m2 (593 kernels/m2) across the study area, with a combined kernel biomass of 14.1 × 103 g/ha. Seed densities remained stable through the dry season, then declined rapidly after wet season rain. Initial wet season rains of up to 25 mm, 40 mm and 50 mm resulted in seed-bank germination of < 5%, 57%, and 93%, respectively. Some seeds were buried by rain and resurfaced or germinated later, but about 30% was lost. Widespread and abrupt depletion of the seed-bank is likely to occur at the start of about 8% of wet seasons on central Cape York Peninsula, leaving little seed, either for subsequent germination or as food for granivores. Burning early in the dry season, when most seeds were still on the plants, reduced seed densities by 85%. The proportion of seeds with sound kernels was reduced in areas burnt by dry season fires, both directly after the fires and, subsequently, as a result of preferential granivore activity. Areas burnt in the dry season were thus depleted of seed earlier than were unburnt areas. Food availability for granivores should therefore be optimized by fire regimes that include a range of burning histories, including fires in both early dry and early wet seasons as well as keeping other areas unburnt.  相似文献   

3.
    
Abstract The germinable soil seed bank of a tropical eucalypt savanna of north‐eastern Australia was found to be dominated by grasses and forbs, with seed bank density ranging from 58 to 792 seeds per square metre, from a total of 53 species. Late dry season fires and the fire‐related cues, heat shock and smoke, broke the seed dormancy of a range of tropical savanna species. Heat shock promoted the germination of the species groups natives, exotics, subshrubs, ephemeral and twining perennial forbs, and the common species Indigofera hirsuta, Pycnospora lutescens and Triumfetta rhomboidea. Exposure to smoke at ambient temperature promoted germination from the soil seed bank of the species groups combined natives, upright perennial forbs and grasses, as well as the common grasses Digitaria breviglumis and Heteropogon triticeus. The germinable soil seed bank varied seasonally, increasing from the mid wet season (February) and early dry season (May) to a maximum in the late dry season (October). The effect of recent fire history on soil seed bank dynamics was limited to the immediate release of some seed from dormancy; a reduction in seed densities of subshrubs and monocots, other than grasses, in recently burnt savanna; and enhanced seed density of the ephemeral I. hirsuta in the year following fire. The seed banks of most savanna species were replenished in the year following burning.  相似文献   

4.
    
In arid Australia, changes to historic fire regimes may now produce more large‐scale wildfire events. The impacts of these fires on fauna communities are poorly known. We sought to test the impacts of fire on the occurrence of two arid‐zone snake species, the desert death adder (Acanthophis pyrrhus) and monk snake (Parasuta monachus), specialist inhabitants of hummock grassland and mulga shrubland, respectively. We also examined the influence of fire on the occurrence of a habitat generalist, the sympatric Stimson's python (Antaresia stimsoni). Under an Information‐Theoretic framework we modelled the occurrence of each species with a range of habitat variables, including fire history, using logistic regression. As predicted, the two habitat specialists were more likely to be encountered at locations that had a lower percentage of surrounding area burnt in the most recent wildfires (2002), while fire variables failed to predict the occurrence of the habitat generalist. Acanthophis pyrrhus, already predisposed to endangerment through a suite of life‐history characteristics, may be at increased risk through accidental and deliberate burning and fragmentation of old‐growth hummock grasslands. We stress the importance of prescribed burning and natural fire breaks in maintaining areas of old‐growth hummock grassland across the landscape.  相似文献   

5.
    
Hummock grasses in the genus Triodia R. Br. were examined at 116 recently burned locations across mainland Australia, and were recorded as regenerating by resprouting, or by seed only. Prior to this survey it was known that the capacity to resprout varies considerably in Triodia, but it was unclear whether some species might be entirely resprouting and other species entirely fire-killed; whether this might be associated with particular traits of species or particular landscape types; or whether resprouting might be more common in particular regions such as the northern monsoonal grasslands. Seven species had both fire-killed and resprouting populations represented among the sites examined. Three species [T. basedowii E. Pritzel, T. marginata N.T. Burbidge and T. melvillei (C.E. Hubbard) Lazarides] were recorded as fire-killed at all sites examined, and five species [T. bynoei (C.E. Hubbard) Lazarides, T. bunicola (S.W.L. Jacobs) Lazarides, T. intermedia Cheel, T. molesta N.T. Burbidge and T. spicata N.T. Burbidge] were recorded as resprouting at all sites. Another seven species were recorded at one site only. There was no clear overall trend for fire-killed populations to be more prevalent in south rather than north, or east vs west, or coastal vs inland parts of the continent. No clear relationships were found between regeneration strategy and site attributes. Considered as a group, resprouting species were more likely to have an open growth form than a dense growth form, whereas the opposite was true for fire-killed species. Given that no trait either of species or of landscape was found to be a consistent correlate of resprouting, a likely inference is that resprouting might vary between different fires, even for a given population at a given site. Against this inference, fire-killed populations had substantial densities of seedlings much more often. Longitudinal studies would be needed to demonstrate directly whether resprouting varied between different fires at a site, and to investigate the implications of this for maintenance or extinction of local populations.  相似文献   

6.
7.
    
The abundance and composition of seed rain was measured over 14 months (February 2004 to March 2005) in Currawinya National Park, western Queensland. The experimental design included four measurement periods, three vegetation communities and two grazing regimes. A total of 12 586 seeds from 104 species were captured. There were significantly more seeds and species captured during the measurement period with the least rainfall, although no significant correlation was found between the amount of rainfall and the number of seeds or species captured. More seeds and species were captured where native and feral grazing pressure was removed, but this was only significant for the number of species. The above‐ground vegetation showed no significant difference between grazing treatments over the study period and exhibited far fewer species than the seed rain. However, the majority of species found in the above‐ground vegetation were represented in the seed rain. Hypotheses are explored as an attempt to understand the apparent lack of a relationship between seed rain and rainfall. The effects of grazing and seed movement and storage are also discussed.  相似文献   

8.
    
Recent evidence shows that warm semi‐arid ecosystems are playing a disproportionate role in the interannual variability and greening trend of the global carbon cycle given their mean lower productivity when compared with other biomes (Ahlström et al. 2015 Science, 348, 895). Using multiple observations (land‐atmosphere fluxes, biomass, streamflow and remotely sensed vegetation cover) and two state‐of‐the‐art biospheric models, we show that climate variability and extremes lead to positive or negative responses in the biosphere, depending on vegetation type. We find Australia to be a global hot spot for variability, with semi‐arid ecosystems in that country exhibiting increased carbon uptake due to both asymmetry in the interannual distribution of rainfall (extrinsic forcing), and asymmetry in the response of gross primary production (GPP) to rainfall change (intrinsic response). The latter is attributable to the pulse‐response behaviour of the drought‐adapted biota of these systems, a response that is estimated to be as much as half of that from the CO2 fertilization effect during 1990–2013. Mesic ecosystems, lacking drought‐adapted species, did not show an intrinsic asymmetric response. Our findings suggest that a future more variable climate will induce large but contrasting ecosystem responses, differing among biomes globally, independent of changes in mean precipitation alone. The most significant changes are occurring in the extensive arid and semi‐arid regions, and we suggest that the reported increased carbon uptake in response to asymmetric responses might be contributing to the observed greening trends there.  相似文献   

9.
    
Abstract Seedling emergence in a eucalypt savanna of north‐eastern Australia was documented over a 12‐month period, between May 1999 and May 2000. Seedling emergence for grasses, forbs and subshrubs was found to mainly occur in a brief pulse at the start of the wet season following fire or the removal of grass biomass. Only a minor number of tree and shrub seedlings were detected overall. Burning, or cutting away the grass layer in unburnt savanna, in both the early (i.e. May) and the late (i.e. October) dry seasons significantly increased seedling emergence over undisturbed savanna that had been unburnt for 3 years. Removing the grass layer in unburnt savanna, during either the early or the late dry season, triggered similar seedling densities to savanna burnt in the early dry season. Late dry season fires promoted the greatest seedling density. We attribute this to the higher intensity, late dry season fires releasing a greater proportion of seed from dormancy, coupled with the higher density of soil seed reserves present in the late dry season.  相似文献   

10.
    

Questions

Fire is a crucial component of many ecosystems. Plants whose seeds germinate in response to smoke may benefit from resource availability in the post‐fire environment. Smoke can influence germination timing and success, as well as seedling vigour, resulting in burgeoning research interest in smoke‐responsive germination. Research in this field has largely focused on four key ‘Mediterranean‐type’ fire‐prone ecosystems: the Mediterranean Basin, South African fynbos, Californian chaparral and Western Australia. There are far fewer studies from south‐eastern Australia, a fire‐prone but not “Mediterranean‐type” region. How does smoke‐responsive germination in this region vary according to ecological, phylogenetic, and methodological variables?

Location

South‐eastern Australia.

Methods

We investigated patterns of smoke‐promoted germination in south‐eastern Australian plants across habitat types, growth forms, fire response strategies, phylogeny, taxonomic levels and smoke application methods. We compiled and interrogated data comprising 303 entries on germination responses to smoke in 233 south‐eastern Australian plant species, from 33 different sources.

Results

Smoke‐responsive germination occurs at a lower rate (~41% of tested species) in south‐eastern Australian flora than it does in fynbos and Western Australian floras, and there is clear patterning within these data. Obligate‐seeding species were more likely to respond, Leguminosae and Rubiaceae were less likely to respond (although we question the generality of these results), while Poaceae were more likely to respond to smoke. Finally, studies using aerosol smoke and studies conducted in situ were most likely to find smoke‐promoted germination.

Conclusions

Obligate seeders and Poaceae may be selected for in habitats with higher fire frequencies, consistent with literature suggesting that short inter‐fire intervals favour grasslands over forests. These findings may be particular to south‐eastern Australia, or more widely applicable; more broad‐scale comparative research will reveal the answer. By synthesizing the south‐eastern Australian smoke germination literature we broaden our understanding beyond the better‐studied Mediterranean‐type floras.
  相似文献   

11.
    
Abstract Temperatures that significantly increase seed germination of some tropical legumes (i.e. 80–100°C) were documented in the topsoil during the passage of early (May) and late (October) dry season fires in a tropical eucalypt savanna of north‐eastern Australia. Elevated temperatures penetrated at least 30 mm into the soil during the higher‐intensity, late dry season fires, but were only detected at 10 mm during the early dry season fires. The depth from which germination of two native legume forbs Galactia tenuiflora and Indigofera hirsuta occurred was positively related to the temperature elevation in the topsoil and was greater after late compared with early dry season fires. A broader range in germination depth, resulting in higher seedling densities, was recorded for I hirsuta after late dry season fires. These results suggest that seedling emergence of native leguminous forbs is likely to occur at a greater density after late rather than early dry season fires in tropical eucalypt savannas of north‐eastern Australia. Therefore, the season of burning, as a result of its relationship to fire intensity, can influence species composition through its effect on seed germination.  相似文献   

12.
The relation of fire with the reproductive process of species from tropical grasslands and savannas has long been investigated. Post-fire flowering is well documented in the Cerrado, but fire-mediated fruit opening and seed dispersal has rarely been described, with very few historical records being known. Even less is known about the effects of different fire seasons on species reproduction. Here, we describe the fire-stimulated fruit opening of Jacaranda ulei, an endemic Cerrado shrub with medical importance to traditional communities. We show that fruits opened within 2 weeks after an early dry season fire, but there were almost no viable seeds as fruits were still immature when burned. When put together with the known records for other species, dry dehiscent fruits and anemochory arise as common traits that favour fire-mediated fruit opening. As these are common attributes in the Cerrado, it is possible that several other species also have fire-stimulated seed dispersal but remain vastly unnoticed and underreported in the literature. Additionally, the peak reproductive effort of these species coincides with the period of prescribed burns of the Integrated Fire Management Program and, consequently, several species could also have their reproductive cycle interrupted to disperse immature seeds. We hope our note encourages further studies on the fire-mediated fruit opening and seed dispersal of Cerrado species, particularly in relation to fire season and seed quality.  相似文献   

13.
Serious infestations of Helicoverpa punctigera are experienced yearly in the eastern cropping regions of Australia. Regression analysis was used to determine whether the size of the first generation in spring (G1), which is comprised mostly of immigrants from inland Australia, was related to monthly rainfall in inland winter breeding areas. Data from two long series of light-trap catches at Narrabri in New South Wales (NSW) and Turretfield in South Australia (SA) were used in the analyses. The size of G1 at Narrabri in each year was significantly regressed on the amount of rainfall in western Queensland and NSW in May and June. The size of G1 at Turretfield each year was significantly regressed on the amount of rain in May, June and July in western Queensland and NSW and also in the desert of central Western Australia. Low r 2 values of the regressions suggest that rainfall data for more sites, as well as biological and other physical factors, such as temperature, evaporation, and prevailing wind systems, may need to be included to improve forecasts of the potential magnitude of the infestations in coastal cropping regions.  相似文献   

14.
    
Abstract Most ecologists are comfortable with the notion of habitats as recognizable entities and also with situations where the junction between two adjacent habitats forms a discrete edge. Such edges form naturally because of sharp changes in important edaphic, geomorphological, climatic or chemical properties to which plants, in particular, respond. Less clear is the effect of such edges on assemblages of mobile organisms, especially invertebrates that operate at relatively small spatial scales. The objective of the present study was to sample invertebrate composition across a natural edge between a well‐developed riparian habitat on fluvial sands and a saltbush habitat developed on a stony gibber plain in a semi‐arid region of New South Wales, Australia. A total of 150 pitfall traps on five 1‐km‐long transects that straddled the edge produced more than 13 000 adult specimens from 21 ordinal invertebrate taxa. A total of 10 446 beetle, ant, wasp, fly and springtail specimens were further sorted into 426 morphospecies. Comparisons and estimates of trends in abundance and richness were made, along with computation of multivariate dissimilarity and permutation statistics, to determine if the land system edge was coincident with changes in invertebrate abundance and composition. These analyses were unable to detect disjunctions in diversity coincident with the edge. The data suggest that many taxa are either present consistently in both habitats or are mostly found in one habitat but ‘leak’ several hundred metres across into the other. Few taxa were unique to either habitat. The result is that assemblage composition for invertebrates changes gradually over distances of up to 400 m either side of the edge and that the distance to a recognizable change in composition is taxon dependent. Even sharp habitat edges, as defined by discrete changes in soils and plants, are not edges but broad transition zones for many invertebrate taxa. There are several implications of these results, especially for landscape ecology.  相似文献   

15.
    
Fire is widely used for conservation management in the savannah landscapes of northern Australia, yet there is considerable uncertainty over the ecological effects of different fire regimes. The responses of insects and other arthropods to fire are especially poorly known, despite their dominant roles in the functioning of savannah ecosystems. Fire often appears to have little long‐term effect on ordinal‐level abundance of arthropods in temperate woodlands and open forests of southern Australia, and this paper addresses the extent to which such ordinal‐level resilience also occurs in Australia’s tropical savannahs. The data are from a multidisciplinary, landscape‐scale fire experiment at Kapalga in Kakadu National Park. Arthropods were sampled in the two major savannah habitats (woodland and open forest) using pitfall traps and sweep nets, in 15–20 km2 compartments subjected to one of three fire regimes, each with three replicates: ‘early’ (annual fires lit early in the dry season), ‘late’ (annual fires lit late in the dry season), and ‘unburnt’ (fires absent during the five‐year experimental period 1990–94). Floristic cover, richness and composition were also measured in each sampling plot, using point quadrats. There were substantial habitat differences in floristic composition, but fire had no measured effect on plant richness, overall composition, or cover of three of the four dominant species. Of the 11 ordinal arthropod taxa considered from pitfall traps, only four were significantly affected by fire according to repeated‐measures ANOVA . There was a marked reduction in ant abundance in the absence of fire, and declines in spiders, homopterans and silverfish under late fires. Similarly, the abundances of only four of the 10 ordinal taxa from sweep catches were affected by fire, with crickets and beetles declining in the absence of fire, and caterpillars declining under late fires. Therefore, most of the ordinal taxa from the ground and grass‐layer were unaffected by the fire treatments, despite the treatments representing the most extreme fire regimes possible in the region. This indicates that the considerable ordinal‐level resilience to fire of arthropod assemblages that has previously been demonstrated in temperate woodlands and open forests of southern Australia, also occurs in tropical savannah woodlands and open forests of northern Australia.  相似文献   

16.
Aim A common strategy for conserving biodiversity in fire‐prone environments is to maintain a diversity of post‐fire age classes at the landscape scale, under the assumption that ‘pyrodiversity begets biodiversity’. Another strategy is to maintain extensive areas of a particular seral state regarded as vital for the persistence of threatened species, under the assumption that this will also cater for the habitat needs of other species. We investigated the likely effects of these strategies on bird assemblages in tree mallee vegetation, characterized by multi‐stemmed Eucalyptus species, where both strategies are currently employed. Location The semi‐arid Murray Mallee region of south‐eastern Australia. Methods We systematically surveyed birds in 26 landscapes (each 4‐km diameter), selected to represent gradients in the diversity of fire age classes and the proportion of older vegetation (> 35 years since fire). Additional variables were measured to represent underlying vegetation‐ or fire‐mediated properties of the landscape, as well as its biogeographic context. We used an information‐theoretic approach to investigate the relationships between these predictor variables and the species richness of birds (total species, threatened species and rare species). Results Species richness of birds was not strongly associated with fire‐mediated heterogeneity. Species richness was associated with increasing amounts of older vegetation in landscapes, but not with the proportion of recently burned vegetation in landscapes. Main conclusions The preference of many mallee birds for older vegetation highlights the risk of a blanket application of the ‘pyrodiversity begets biodiversity’ paradigm. If application of this paradigm involved converting large areas from long unburned to recently burned vegetation to increase fire‐mediated heterogeneity in tree mallee landscapes, our findings suggest that this could threaten birds. This research highlights the value of adopting a landscape‐scale perspective when evaluating the utility of fire‐management strategies intended to benefit biodiversity.  相似文献   

17.
18.
    
  1. In Australia, the dingo Canis lupus dingo is the largest terrestrial predator. Dingoes contribute to ecological processes and functions throughout their continental geographic range. Their generalist diet enables daily energetic requirements to be met even in the resource‐limited deserts of central Australia, where irregular rainfall drives extreme fluctuations in mammal assemblages. Given that predation is a primary driver of declining mammal populations and failed reintroductions, it is necessary to understand the dietary intake of the continent's apex predator if conservation outcomes are to be achieved.
  2. We performed a meta‐analysis of the mammalian composition of the dingo's diet throughout Australia's arid zone, an area covering c. 5.4 million km2. We used 25 data sets from 11 studies to measure the effects of resource booms and anthropogenic disturbance (pastoralism) on diet. We explored whether the probability of prey species occurring in the diet was related to the size of the prey or to prevailing conditions. We also investigated the similarities in diet between dingo populations from across the arid zone, and how dietary overlap was affected by opposing land uses.
  3. Dingoes primarily consumed medium‐sized (35–5500 g) and large (>5500 g) mammals, whereas most small mammals (<35 g) were consumed infrequently, or not at all.
  4. The composition of the diet changed dramatically during resource booms to exploit irruptive prey species such as long‐haired rats Rattus villosissimus (native; 144 g) and house mice Mus musculus (introduced; 20 g). During resource booms, the consumption of large mammals decreased significantly, whereas the occurrence in the diet of medium‐sized mammals remained high. The diversity of species consumed by dingoes was significantly lower during boom periods than during non‐boom periods.
  5. The dingo's heightened consumption of hyper‐abundant species has the potential to release many non‐target species from direct predation pressure during boom times. This could be advantageous for remnant and reintroduced populations of mammals, which are especially susceptible to predation.
  相似文献   

19.
    
Landscape genetics offers a powerful approach to understanding species' dispersal patterns. However, a central obstacle is to account for ecological processes operating at multiple spatial scales, while keeping research outcomes applicable to conservation management. We address this challenge by applying a novel multilevel regression approach to model landscape drivers of genetic structure at both the resolution of individuals and at a spatial resolution relevant to management (i.e. local government management areas: LGAs) for the koala (Phascolartos cinereus) in Australia. Our approach allows for the simultaneous incorporation of drivers of landscape‐genetic relationships operating at multiple spatial resolutions. Using microsatellite data for 1106 koalas, we show that, at the individual resolution, foliage projective cover (FPC) facilitates high gene flow (i.e. low resistance) until it falls below approximately 30%. Out of six additional land‐cover variables, only highways and freeways further explained genetic distance after accounting for the effect of FPC. At the LGA resolution, there was significant variation in isolation‐by‐resistance (IBR) relationships in terms of their slopes and intercepts. This was predominantly explained by the average resistance distance among LGAs, with a weaker effect of historical forest cover. Rates of recent landscape change did not further explain variation in IBR relationships among LGAs. By using a novel multilevel model, we disentangle the effect of landscape resistance on gene flow at the fine resolution (i.e. among individuals) from effects occurring at coarser resolutions (i.e. among LGAs). This has important implications for our ability to identify appropriate scale‐dependent management actions.  相似文献   

20.
    
The effect of different levels of cattle grazing on an arid Australian small terrestrial mammal and lizard assemblage was assessed in a long‐tem series of cross‐fence comparisons. Cross‐fenced sites were closely matched for edaphic and vegetation characteristics and experienced near identical weather patterns, to ensure that cattle grazing pressure was the principal determinant of any differences in fauna assemblages. In addition, the effects of removal of cattle, cats, foxes and rabbits from three of these long‐term monitoring sites were assessed to determine the relative impacts of cattle grazing and feral animals. Small mammal captures, with the exception of Mus musculus, revealed a significant negative response to cattle grazing pressure but this response was of a considerably lower magnitude than the dramatic increase in rodent captures and species richness within the feral animal‐proof Arid Recovery Reserve. Higher kangaroo numbers in ungrazed controls, compared with treatments grazed by cattle, possibly negated the benefits to small mammals of removing cattle grazing. No reptile species responded significantly to the grazing treatments although reptile richness and captures of geckos and skinks were the lowest and agamid captures were the highest at heavily grazed sites. Nephrurus levis was the only reptile species to increase significantly, while captures of some smaller geckoes declined, within the feral‐proof treatment. Feral predation exerted a more significant effect on most small mammal species than the levels of cattle grazing assessed in this study, yet reptile responses to grazing or feral animals were less apparent and were likely primarily driven by changes in vegetation cover or secondary trophic impacts.  相似文献   

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