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1.
Changes in structure and composition of miombo woodlands mediated by elephants and fire were studied in 26-year-old permanent transects established in 1972 in north-western Zimbabwe. Elephants caused 48% decline in proportions of large trees (>11 cm diameter), significant reductions (30.9–90.9%) in tree heights, reductions in stem areas (43.5%) and densities (2.5%) of all trees. There were increases in proportions of small trees (64.8%), shrub canopy volumes (271%) and shrub densities (172%). These increases are attributed to natural recruitment because of longer fire-free periods and reduction of tree suppression effects on lower strata as a result of elephant-induced tree declines. Frequencies of occurrence of most species dropped by 28–89.6%. Brachystegia boehmii was replaced by Pseudolachnostylis maprouneifolia as the most dominant tree, largely because of high elephant preference for Brachystegia boehmii . A new suite of species, dominated by Combretaceae, increased in dominance resulting in local floristic changes. Reductions in old elephant (33.4%), old unknown (89.9%) and new elephant (13.7%) damage suggest that elephant occupancy of miombo woodlands has declined, possibly because of limited availability of preferred browse species. This study clearly shows that elephants and fire have contributed significantly to the changes in miombo woodlands in the area. 相似文献
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Kelly M. Dixon Geoffrey J. Cary Michael Renton Graeme L. Worboys Philip Gibbons 《Austral ecology》2019,44(7):1150-1162
The composition of mammalian communities in Australia's Eucalyptus forests and woodlands is known to be affected by fire. However, there are few published studies that compare mammal assemblages in recently burnt and long‐unburnt forests because there are few areas with long‐term fire history data. Understanding the value of long‐unburnt forest is important because it is becoming rare in fire‐prone regions of the world, such as south‐eastern Australia, partly because of the widespread use of prescribed burning. We deployed wildlife cameras for 28 trap‐nights at each of 81 sites that ranged from 0.5 to at least 96 years since the last fire. We recorded a total of 15 native mammal species. At least one mammal species was recorded at 80 of the 81 sites. Significantly more species were detected at long‐unburnt sites (>96 years since fire) than sites 0.5–12 years since the last fire. Species composition varied significantly between sites 0.5–12 years and >96 years since the last fire but did not vary between sites 0.5–2 years and 6–12 years since the last fire. Although there was not one category of time since fire (i.e. 0.5–2 years, 6–12 years and >96 years) in which all 15 native mammal species were recorded, long‐unburnt sites were significantly more important for the occurrence of seven mammal species; intermediate and recently burnt sites were significantly more important for one species. Our results suggested that, while a diversity of fire ages is important for conserving mammalian diversity, long‐unburnt forests and woodlands (which comprised only 8% of our study area) are disproportionately important for mammal conservation. Our results add to a growing body of the literature from south‐eastern Australia, suggesting that remaining long‐unburnt forest should be afforded protection from fire and more forest should be transitioned to long unburnt. 相似文献
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Ecosystems managed with contrasting fire regimes provide insight into the responses of vegetation and soil. Heathland, woodland and forest ecosystems along a gradient of resource availability were burnt over four decades in approximately 3- or 5-year intervals or were unburnt for 45–47 years (heathland, woodland), or experienced infrequent wildfires (forest: 14 years since the last fire). We hypothesized that, relative to unburnt or infrequent fires, frequent burning would favour herbaceous species over woody species and resprouting over obligate seeder species, and reduce understorey vegetation height, and topsoil carbon and nitrogen content. Our hypothesis was partially supported in that herbaceous plant density was higher in frequently burnt vegetation; however, woody plant density was also higher in frequently burnt areas relative to unburnt/infrequently burnt areas, across all ecosystems. In heathland, omission of frequent fire resulted in the dominance of fern Gleichenia dicarpa and subsequent competitive exclusion of understorey species and lower species diversity. As hypothesized, frequent burning in woodland and forest increased the density of facultative resprouters and significantly reduced soil organic carbon levels relative to unburnt sites. Our findings confirm that regular burning conserves understorey diversity and maintains an understorey of lower statured herbaceous plants, although demonstrates the potential trade-off of frequent burning with lower topsoil carbon levels in the woodland and forest. Some ecosystem specific responses to varied fire frequencies were observed, reflecting differences in species composition and fire response traits between ecosystems. Overall, unburnt vegetation resulted in the dominance of some species over others and the different vegetation types were able to withstand relatively high-frequency fire without the loss of biodiversity, mainly due to high environmental productivity and short juvenile periods. 相似文献
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TRENT D. PENMAN DOUG L. BINNS ROY J. SHIELS RUTH M. ALLEN RODNEY P. KAVANAGH 《Austral ecology》2008,33(2):197-210
Abstract The impacts of prescribed burning and timber harvesting on species diversity have been the subject of considerable debate. The temporal and spatial scale of these disturbances often presents major limitations to many studies. Here we present the medium‐term results of a planned long‐term study examining the impacts of logging and prescribed burning on the understorey floristic richness in shrubby dry sclerophyll forest in the south‐east of New South Wales, Australia. Generalized estimating equations were used to model the effect of environmental factors and disturbance variables on species richness at the coupe (～30 ha) and plot (～0.01 ha) scale. At the plot scale, fire effects on separate components of the vegetation were broadly consistent with other studies, with frequent fire resulting in a relative increase of species richness for species less than 1 m in height and a decline of larger species taller than this height. At the coupe scale, there was no decline in richness of larger shrub species, possibly owing to the spatial heterogeneity of fire frequency at this scale. Logging resulted in significantly greater species richness in the shrub layer, but had no significant effect on species richness in the ground layer. During the study period, there was a general decline in plant species richness at both coupe and plot scales which occurred independently of imposed management regimes. This is thought to be related to a natural succession following wildfire, and may be due to the absence of high‐intensity fire in the study area since 1973, or to an effect related to season of burning. 相似文献
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BURAK K. PEKIN ROY S. WITTKUHN MATTHIAS M. BOER CRAIG MACFARLANE PAULINE F. GRIERSON 《Austral ecology》2012,37(3):330-338
Frequent fires reduce the abundance of woody plant species and favour herbaceous species. Plant species richness also tends to increase with decreasing vegetation biomass and cover due to reduced competition for light. We assessed the influence of variable fire histories and site biomass on the following diversity measures: woody and herbaceous species richness, overall species richness and evenness, and life form evenness (i.e. the relative abundance or dominance among six herbaceous and six woody plant life forms), across 16 mixed jarrah (Eucalyptus marginata) and marri (Corymbia calophylla) forest stands in south‐west Australia. Fire frequency was defined as the total number of fires over a 30‐year period. Overall species richness and species evenness did not vary with fire frequency or biomass. However, there were more herbaceous species (particularly rushes, geophytes and herbs) where there were fewer shrubs and low biomass, suggesting that more herbaceous species coexist where dominance by shrubs is low. Frequently burnt plots also had lower number and abundance of shrub species. Life form evenness was also higher at both high fire frequency and low biomass sites. These results suggest that the impact of fire frequency and biomass on vegetation composition is mediated by local interactions among different life forms rather than among individual species. Our results demonstrate that measuring the variation in the relative diversity of different woody and herbaceous life forms is crucial to understanding the compositional response of forests and other structurally complex vegetation communities to changes in disturbance regime such as increased fire frequency. 相似文献
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Plant communities dominated by narrow‐leaved mallee (Eucalyptus cneorifolia) are almost entirely confined to north‐eastern Kangaroo Island, South Australia, an area which has been extensively cleared for agriculture. Consequently, surviving examples consist mostly of small remnants which are thought to be senescent due to the exclusion of fire. This senescence is associated with the loss of many native understory species. Prescribed burns have been suggested as a management tool to stimulate the restoration of native plants from the soil seed bank; however, no seed bank studies have previously been conducted on Kangaroo Island and the seed bank literature usually focuses on particular species rather than on plant communities. We conducted an experiment to investigate the effects of the fire‐related cues heat and smoke on the germination of plants from the seed bank in soil sampled from 10 long‐ungrazed narrow‐leaved mallee sites on Kangaroo Island. Eighty trays of soil were monitored in a controlled glasshouse for five months after being subjected to heat and/or smoke treatments. The overall number of native, but not exotic, plant species germinating from the soil seed bank was significantly increased by all three fire‐related treatments (heat, smoke and heat plus smoke) compared with the control (no fire‐related treatment). Different plant life forms exhibited varying responses to heat and smoke treatments. The results of this study illustrate that the application of fire‐related treatments to soil seed banks in controlled glasshouse conditions can stimulate the recruitment of native species, including several species of conservation concern. These findings also indicate the potential of using these treatments for the ex situ germination of fire dependent species for revegetation purposes and indicate aspects of prescribed burns that may be important for restoring different components of native vegetation. 相似文献
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Mitchell C. Lettow Lars A. Brudvig Christie A. Bahlai Jason Gibbs Robert P. Jean Douglas A. Landis 《Restoration Ecology》2018,26(5):882-890
North American Midwestern oak (Quercus spp.) savannas are rare fire‐dependent ecosystems that can support high levels of biodiversity and are the focus of considerable restoration effort due to widespread fire suppression. Due to the predominance of understory forbs in oak savannas, many of which require insect pollination, restoration practices should be evaluated for their potential impacts on pollinator communities. We evaluated bee community responses during the first 2 years of experimental restoration of fire‐suppressed oak savanna in southern Michigan. We used unmanaged references and two different restoration methods (burning only and burning with thinning) to examine the effects of restoration intensity on the abundance, diversity, and functional groups of bees. We found that thinning and burning rapidly increased bee abundance, richness, and Shannon's diversity, relative to unmanaged references, whereas burn‐only restoration largely failed to do so. Thinning and burning also resulted in a distinct bee community after two seasons, while bee communities in burn‐only restoration plots were similar to those from unmanaged references. Differences in bee diversity and community structure between treatments may be due to the influence of restoration on nesting resources, which is reflected in the differential captures of various nesting guilds. Overall, oak savanna restoration by thinning and burning had positive effects on bee diversity, while burning alone only increased bee abundance. We thus illustrate how restoration strategies that typically target plants have broader‐reaching biodiversity benefits. Although restoring savannas through burning alone may eventually shift bee communities, coupling thinning with burning will influence pollinator communities over the shorter term. 相似文献
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Dominik Thom Rupert Seidl 《Biological reviews of the Cambridge Philosophical Society》2016,91(3):760-781
In many parts of the world forest disturbance regimes have intensified recently, and future climatic changes are expected to amplify this development further in the coming decades. These changes are increasingly challenging the main objectives of forest ecosystem management, which are to provide ecosystem services sustainably to society and maintain the biological diversity of forests. Yet a comprehensive understanding of how disturbances affect these primary goals of ecosystem management is still lacking. We conducted a global literature review on the impact of three of the most important disturbance agents (fire, wind, and bark beetles) on 13 different ecosystem services and three indicators of biodiversity in forests of the boreal, cool‐ and warm‐temperate biomes. Our objectives were to (i) synthesize the effect of natural disturbances on a wide range of possible objectives of forest management, and (ii) investigate standardized effect sizes of disturbance for selected indicators via a quantitative meta‐analysis. We screened a total of 1958 disturbance studies published between 1981 and 2013, and reviewed 478 in detail. We first investigated the overall effect of disturbances on individual ecosystem services and indicators of biodiversity by means of independence tests, and subsequently examined the effect size of disturbances on indicators of carbon storage and biodiversity by means of regression analysis. Additionally, we investigated the effect of commonly used approaches of disturbance management, i.e. salvage logging and prescribed burning. We found that disturbance impacts on ecosystem services are generally negative, an effect that was supported for all categories of ecosystem services, i.e. supporting, provisioning, regulating, and cultural services (P < 0.001). Indicators of biodiversity, i.e. species richness, habitat quality and diversity indices, on the other hand were found to be influenced positively by disturbance (P < 0.001). Our analyses thus reveal a ‘disturbance paradox’, documenting that disturbances can put ecosystem services at risk while simultaneously facilitating biodiversity. A detailed investigation of disturbance effect sizes on carbon storage and biodiversity further underlined these divergent effects of disturbance. While a disturbance event on average causes a decrease in total ecosystem carbon by 38.5% (standardized coefficient for stand‐replacing disturbance), it on average increases overall species richness by 35.6%. Disturbance‐management approaches such as salvage logging and prescribed burning were neither found significantly to mitigate negative effects on ecosystem services nor to enhance positive effects on biodiversity, and thus were not found to alleviate the disturbance paradox. Considering that climate change is expected to intensify natural disturbance regimes, our results indicate that biodiversity will generally benefit from such changes while a sustainable provisioning of ecosystem services might come increasingly under pressure. This underlines that disturbance risk and resilience require increased attention in ecosystem management in the future, and that new approaches to addressing the disturbance paradox in management are needed. 相似文献
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We compared soil nutrient availability and soil physical properties among four treatments (high-intensity fire, low-intensity fire, plant removal, and harvesting gap) and a control (intact forest understory) over a period of 18 months in a tropical dry forest in Bolivia. The effect of treatments on plant growth was tested using a shade intolerant tree species (Anadenanthera colubrina Vell. Conc.) as a bioassay. Surface soils in high-intensity fire treatments had significantly greater pH values, concentrations of extractable calcium (Ca), potassium (K), magnesium (Mg), and phosphorus (P), and amounts of resin-available P and nitrogen (N) than other treatments; however, a loss of soil organic matter during high-intensity fires likely resulted in increased bulk density and strength, and decreased water infiltration rates. Low intensity fires also significantly increased soil pH, concentrations of extractable Ca, K, Mg, and P, and amounts of resin-available P and N, although to a lesser degree than high-intensity fires. Low-intensity fires did not lower soil organic matter contents or alter soil physical properties. Plant removal and harvesting gap treatments had little effect on soil chemical and physical properties. Despite the potentially negative effects of degraded soil structure on plant growth, growth of A. colubrina seedlings were greater following high-intensity fires. Evidently, the increase in nutrient availability caused by high-intensity fires was not offset by degraded soil structure in its effects on seedling growth. Long-term effects of high intensity fires require further research. 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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随着全球人口增长,世界范围内野地-城市交界域(WUI)正在加速扩张。美国的WUI面积大、分布广、聚集人口多,由于交界域直接与森林植被相贯通,极易受到林火影响,区域范围内人类生命财产安全面临巨大威胁。经过长期的火灾管理实践,美国形成了一套较为完善的WUI林火预防、扑救管理体系。本文从美国WUI的形成方式、火灾发生情况、预防扑救措施等几方面系统总结了美国WUI火灾的管理体系。此外,本文分析了我国WUI火灾管理的现状及存在问题,并基于美国经验提出了完善我国WUI火灾管理的六点建议:(1)制定交界域消防管理计划;(2)合理利用计划火烧;(3)研发火灾预警系统;(4)增强社区防火能力;(5)提高消防员灭火水平;(6)完善火灾扑救策略。 相似文献
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Owen F. Price Trent D. Penman Ross A. Bradstock Matthias M. Boer Hamish Clarke 《Journal of Biogeography》2015,42(11):2234-2245
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Anna Butler Craig A. Davis Samuel D. Fuhlendorf Shawn M. Wilder 《Ecology and evolution》2021,11(1):427-442
Arthropods are abundant and diverse animals in many terrestrial food webs. In western Oklahoma, some shrublands are interspersed with discrete, dense thickets of tall, woody vegetation, known as mottes. Some of these shrublands are managed with prescribed burning. The goal of this study was to examine whether prescribed burning interacted with habitat type (i.e., shrubland versus mottes) to affect ground‐dwelling arthropod communities. Arthropods were collected in pitfall traps at four sampling locations in relation to mottes; in the center of mottes, and three plot location in shrublands; 1 m, 15 m, and 50 m away from the edge of the motte. There were three treatment levels for burning: one year postburn (burned in dormant months of 2017), two years postburn (burned in dormant months of 2016), and unburned (burned in dormant season of 2014 and prior). There were no significant interactions between prescribed burning and habitat type. Mottes had a different community of arthropods compared with the surrounding shrubland. Mottes also had lower overall abundance, but a higher diversity of arthropods. In terms of fires, arthropod communities one year after burning were different from those two or more years after burning. There was no effect of burning on overall arthropod abundance, but plots that were one year since burning had significantly lower diversity compared with plots that were two or more years postburn. The results of this study suggest that both fire and mottes can independently facilitate heterogeneity in arthropod communities, but they do not appear to interact with one another. 相似文献
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Abstract Background: Accumulating evidence, mainly from small-scale experiments, suggests that species diversity helps stabilise ecological communities; however, this relationship needs testing at larger scales in a wider range of natural communities. Aims: In experimentally burnt ericaceous shrub stands, we aimed to determine whether more diverse stands had more stable vegetation cover. Methods: Using two prescribed fire management experiments – one on heathland and one in forest – at scales of 100–700 m2, we compared pre-disturbance vegetation characteristics (measures of diversity, traits and composition) with resistance (degree of perturbation on disturbance), resilience (here defined as post-disturbance recovery rate) and stability (the inverse of temporal variability). Results: Responses to disturbance were usually best explained by a measure of dominance: Simpson's index. High dominance was associated with high resilience, but low resistance and low stability. Within the forest, the shrub community had lower dominance and higher stability than it did on heathland. Dominance and diversity were strongly linked as opposite poles of a principal axis of vegetation variation; therefore, more diverse vegetation was more stable. Conclusions: Ericaceous shrub cover is known to support important ecosystem services, such as soil protection, carbon sequestration, flood prevention and livestock grazing. Our results suggest that high shrub diversity would support stable provision of these services. Land managers who prioritise this aim in British heathlands and pinewoods should consider a wider range of management approaches than those of typical current practice. 相似文献
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Phillip J. van Mantgem Jonathan C. B. Nesmith MaryBeth Keifer Eric E. Knapp Alan Flint Lorriane Flint 《Ecology letters》2013,16(9):1151-1156
Pervasive warming can lead to chronic stress on forest trees, which may contribute to mortality resulting from fire‐caused injuries. Longitudinal analyses of forest plots from across the western US show that high pre‐fire climatic water deficit was related to increased post‐fire tree mortality probabilities. This relationship between climate and fire was present after accounting for fire defences and injuries, and appeared to influence the effects of crown and stem injuries. Climate and fire interactions did not vary substantially across geographical regions, major genera and tree sizes. Our findings support recent physiological evidence showing that both drought and heating from fire can impair xylem conductivity. Warming trends have been linked to increasing probabilities of severe fire weather and fire spread; our results suggest that warming may also increase forest fire severity (the number of trees killed) independent of fire intensity (the amount of heat released during a fire). 相似文献
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Woody plant encroachment has degraded grassland and savanna ecosystems worldwide by decreasing herbaceous production and diversity, and altering these physiognomies toward woodlands. This study evaluated the long-term efficacy of fire and herbicide restoration strategies used in the southern Great Plains to reduce Honey mesquite ( Prosopis glandulosa ) dominance, restore a grassland/savanna physiognomy, and increase herbaceous production and diversity. Three treatments were evaluated: high-intensity winter fire, aerial spray of clopyralid + triclopyr (C + T), and aerial spray of clopyralid and were compared to untreated mesquite woodland (control). Post-treatment mesquite stand physiognomy was different between fire (low mortality, high basal sprouting), C + T (high mortality, high basal sprouting of surviving plants), and clopyralid (moderate mortality, low basal sprouting of surviving plants) treatments. From 6 to 8 years post-treatment, herbaceous production was increased in C + T and clopyralid treatments but not in the fire treatment. Mesquite regrowth in the fire treatment exerted a competitive influence that limited herbaceous production. Herbaceous functional group diversity was increased in fire and C + T treatments due to a decrease in C3 perennial grass dominance and an increase in C4 perennial grasses and/or C3 forbs. Treatments that maintained mesquite overstory (control and clopyralid) had lower herbaceous diversity due to C3 perennial grass dominance and lower C4 perennial grass cover. The clopyralid treatment demonstrated greatest potential for long-term restoration of southern Great Plains savanna by reducing mesquite canopy cover to historic levels, limiting mesquite basal regrowth and increasing grass production. 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.