首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
Wildland fire activity has increased in many parts of the world in recent decades. Ecological disturbance by fire can accelerate ecosystem degradation processes such as erosion due to combustion of vegetation that otherwise provides protective cover to the soil surface. This study employed a novel ecological indicator based on remote sensing of vegetation greenness dynamics (phenology) to estimate variability in the window of time between fire and the reemergence of green vegetation. The indicator was applied as a proxy for short-term, post-fire disturbance windows in rangelands; where a disturbance window is defined as the time required for an ecological or geomorphic process that is altered to return to pre-disturbance levels. We examined variability in the indicator determined for time series of MODIS and AVHRR NDVI remote sensing data for a database of ∼100 historical wildland fires, with associated post-fire reseeding treatments, that burned 1990–2003 in cold desert shrub steppe of the Great Basin and Columbia Plateau of the western USA. The indicator-based estimates of disturbance window length were examined relative to the day of the year that fires burned and seeding treatments to consider effects of contemporary variability in fire regime and management activities in this environment. A key finding was that contemporary changes of increased length of the annual fire season could have indirect effects on ecosystem degradation, as early season fires appeared to result in longer time that soils remained relatively bare of the protective cover of vegetation after fires. Also important was that reemergence of vegetation did not occur more quickly after fire in sites treated with post-fire seeding, which is a strategy commonly employed to accelerate post-fire vegetation recovery and stabilize soil. Future work with the indicator could examine other ecological factors that are dynamic in space and time following disturbance – such as nutrient cycling, carbon storage, microbial community composition, or soil hydrology – as a function of disturbance windows, possibly using simulation modeling and historical wildfire information.  相似文献   

2.
Fire is an integral disturbance shaping forest community dynamics over large scales. However, understanding the relationship between fire induced habitat disturbance and biodiversity remain equivocal. Ecological theories including the intermediate disturbance hypothesis (IDH) and the habitat accommodation model (HAM) offer predictive frameworks that could explain faunal responses to fire disturbances. We used an 80 year post-fire chronosequence to investigate small reptile community responses to fires in temperate forests across 74 sites. First, we evaluated if changes in species richness, abundance and evenness post-fire followed trends of prior predictions, including the IDH. Second, using competing models of fine scale habitat elements we evaluated the specific ways which fire influenced small reptiles. Third, we evaluated support for the HAM by examining compositional changes of reptile community post-fire. Relative abundance was positively correlated to age post-fire while richness and evenness showed no associations. The abundance trend was as expected based on the prior prediction of sustained population increase post-disturbance, but the trend for richness contradicted the prediction of highest diversity at intermediate levels of disturbance (according to IDH). Abundance changes were driven mainly by changes in overstorey, ground layer, and shelter, while richness and evenness did not associate with any vegetation parameter. Community composition was not strongly correlated to age since fire, thus support for the HAM was weak. Overall, in this ecosystem, frequent fire disturbances can be detrimental to small reptiles. Future studies utilizing approaches based on species traits could enhance our understanding of biodiversity patterns post-disturbance.  相似文献   

3.
Patch mosaic burning, in which fire is used to produce a mosaic of habitat patches representative of a range of fire histories (‘pyrodiversity’), has been widely advocated to promote greater biodiversity. However, the details of desired fire mosaics for prescribed burning programs are often unspecified. Threatened small to medium-sized mammals (35 g to 5.5 kg) in the fire-prone tropical savannas of Australia appear to be particularly fire-sensitive. Consequently, a clear understanding of which properties of fire mosaics are most instrumental in influencing savanna mammal populations is critical. Here we use mammal capture data, remotely sensed fire information (i.e. time since last fire, fire frequency, frequency of late dry season fires, diversity of post-fire ages in 3 km radius, and spatial extent of recently burnt, intermediate and long unburnt habitat) and structural habitat attributes (including an index of cattle disturbance) to examine which characteristics of fire mosaics most influence mammals in the north-west Kimberley. We used general linear models to examine the relationship between fire mosaic and habitat attributes on total mammal abundance and richness, and the abundance of the most commonly detected species. Strong negative associations of mammal abundance and richness with frequency of late dry season fires, the spatial extent of recently burnt habitat (post-fire age <1 year within 3 km radius) and level of cattle disturbance were observed. Shrub cover was positively related to both mammal abundance and richness, and availability of rock crevices, ground vegetation cover and spatial extent of ≥4 years unburnt habitat were all positively associated with at least some of the mammal species modelled. We found little support for diversity of post-fire age classes in the models. Our results indicate that both a high frequency of intense late dry season fires and extensive, recently burnt vegetation are likely to be detrimental to mammals in the north Kimberley. A managed fire mosaic that reduces large scale and intense fires, including the retention of ≥4 years unburnt patches, will clearly benefit savanna mammals. We also highlighted the importance of fire mosaics that retain sufficient shelter for mammals. Along with fire, it is clear that grazing by introduced herbivores also needs to be reduced so that habitat quality is maintained.  相似文献   

4.
Climate change has increased the occurrence, severity, and impact of disturbances on forested ecosystems worldwide, resulting in a need to identify factors that contribute to an ecosystem’s resilience or capacity to recover from disturbance. Forest resilience to disturbance may decline with climate change if mature trees are able to persist under stressful environmental conditions that do not permit successful recruitment and survival after a disturbance. In this study, we used the change in proportional representation of black spruce pre- to post-fire as a surrogate for resilience. We explored links between patterns of resilience and tree ring signals of drought stress across topographic moisture gradients within the boreal forest. We sampled 72 recently (2004) burned stands of black spruce in interior Alaska (USA); the relative dominance of black spruce after fire ranged from almost no change (high resilience) to a 90% decrease (low resilience). Variance partitioning analysis indicated that resilience was related to site environmental characteristics and climate–growth responses, with no unique contribution of pre-fire stand composition. The largest shifts in post-fire species composition occurred in sites that experienced the compounding effects of pre-fire drought stress and shallow post-fire organic layer thickness. These sites were generally located at warmer and drier landscape positions, suggesting they are less resilient to disturbance than sites in cool and moist locations. Climate–growth responses can provide an estimate of stand environmental stress to climate change and as such are a valuable tool for predicting landscape variations in forest ecosystem resilience.  相似文献   

5.
A. M. Persiani 《Plant biosystems》2013,147(4):1104-1106
Mediterranean ecosystems are among those most significantly modified by fires. Such fires lead to evident disturbance of the above- and below-ground ecosystem components, at various spatial and temporal scales, including soil microfungi. The ecological parameters used to measure the effects of disturbance on soil fungal communities include species-abundance distribution patterns, which reflect changes in the relationships between species numbers and their relative abundance, and serve as a critical measure of community organization. Species-abundance distribution patterns were used to assess the disturbance impact of experimental fires on soil fungal communities in Mediterranean maquis (southern Italy) in the short- to mid-term. The trend in the distribution patterns of heat-stimulated and xerotolerant soil fungi over time, their varying responses to low- and high-intensity fire, the efficiency of the soil germplasm bank, and the pivotal role of Neosartorya spp. in post-fire community structure in Mediterranean burned soils may all be used as tools to accurately assess the effects of fire on soil mycobiota.  相似文献   

6.

Fire is a key factor triggering ecological processes in old-growth grasslands and savannas and could have strong implications for reproduction via seeds for the herbaceous layer. In the Neotropical savannas, grasses show strong synchronous post-fire flowering, and their reproduction is often considered fire-dependent, with their massive post-fire seed production being suggested as a source of population maintenance. However, literature lacks studies to provide evidence of fire-dependent flowering and no study has assessed the quality of the post-fire seed production. Therefore, we aimed to describe a phenological pattern across early-flowering Neotropical savanna grasses in both recently burnt and unburnt cerrado communities addressing three questions: (1) Do the early-flowering species rely on fire for reproduction via seeds? (2) If no, what are the effects of fire on their reproductive phenology? (3) Does the massive seed production in post-fire cerrado communities lead to high-quality seeds? We recorded the reproductive phenology of nine early-flowering grasses for 17 weeks in unburnt and recently burnt cerrado communities. We collected the seeds, estimated the production of fertile seeds, and tested germination. No species showed a pattern of fire-dependent reproduction. Fire stimulated earlier flowering while reproduction in the unburnt community was related to continuous rainfall. Seed production following fire was of low quality, and no species produced?>?7% fertile seeds. Seed germination remained below 50% for most species. Post-fire seed production of early-flowering species led to poor seed quality, suggesting a constraint to the recruitment of new individuals of early-flowering Neotropical savanna grasses in recently burnt cerrados.

  相似文献   

7.
8.
Boreal forests are highly susceptible to wildfire, and post-fire changes in soil temperature and moisture have the potential to transform large areas of the landscape from a net sink to a net source of carbon (C). Understanding the ecological controls that regulate these disturbance effects is critical to developing models of ecosystem response to changes in fire frequency and severity. This paper combines laboratory and field measurements along a chronosequence of burned black spruce stands into regression analyses and models that assess relationships between moss succession, soil microclimate, decomposition, and C source-sink dynamics. Results indicate that post-fire changes in temperature and substrate quality increased decomposition in humic materials by a factor of 3.0 to 4.0 in the first 7 years after fire. Bryophyte species exhibited a distinct successional pattern in the first five decades after fire that corresponded to decreased soil temperature and increased C accumulation in organic soils. Potential rates of C exchange in mosses were greatest in early successional species and declined as the stand matured. Residual sources of CO2 (those not attributed to moss respiration or humic decomposition) increased as a function of stand age, reflecting increased contributions from roots as the stand recovered from disturbance. Together, the field measurements, laboratory experiments, and models provide strong evidence that interactions between moss and plant succession, soil temperature, and soil moisture largely regulate C source-sink dynamics from black spruce systems in the first century following fire disturbance.  相似文献   

9.
Fire disturbance patterns influence forest communities at a range of spatial scales. Forest community structure may also influence fire disturbance patterns, because tree species vary in their fuel value and in their tolerance to fire damage. However, the influence of community structure on fire disturbance likely depends on latent ecological differences between fires and on the spatial scale at which patterns are observed. Using data on fire intensity, community structure, and post-fire tree survival in four systematically sampled boreal forest fires, we tested the hypotheses that: (1) patterns in post-fire tree survival reflect interactions between fire intensity and community structure; (2) these relationships change with the spatial scale of observation. To test the first hypothesis, we used information theoretic methods to compare eight generalized linear mixed effects models describing the influence of community structure and fire intensity on tree survival in a 500 m2 sample plot, accounting for latent fire-to-fire differences in response. To test the scaling hypothesis, we reaveraged the data at nine successively larger spatial resolutions up to approximately 2 km2, at each resolution tracking the parameter values of the best model. When fit to the plot-level data, the dominant feature of the best model was a strong intensity–survival correlation which varied from fire to fire, and depended on plot-level community structure. In some fires, community structure and survival became more tightly coupled at larger scales, whereas fire intensity became less important. These results support the view that fire disturbance patterns are influenced by cross-scale interactions between community structure and fire intensity.  相似文献   

10.
Fire is a major disturbance event that affects biomes worldwide, altering vegetation structure and flora and fauna assemblages. Here, we investigated the effects of an extensive wildfire (~?6240 ha) on small mammal assemblages in savanna woodland (cerradão) at two spatial scales (meso- and macrohabitat) in a neotropical savanna (Brazilian Cerrado). At each spatial scale, we assessed relationships between habitat structure and small mammal species composition and abundance before and after the fire in four natural patches (one burned, three unburned) using partial redundancy analysis. From July 2009 to October 2013, we captured 1319 individuals belonging to 14 species. Our results showed that the fire had consequences for small mammal assemblage at both scales. After the fire, the burned patch differed from the other patches in vegetation attributes and species composition. At a fine scale, fire increased the herbaceous layer and decreased the litter layer and understory obstruction. On a larger scale, the main consequences of fire on vegetation structure were increased variation in litter depth, tree diameter, and distance to the nearest tree. We observed a relationship between mesohabitat structure and the abundance of species with different habitat requirements during the post-fire succession. Fire favored the invasion of generalist species from open Cerrado habitats (rodents Calomys tener, Calomys expulsus, Cerradomys scotti, and Necromys lasiurus) at the expense of more specialized forest species. Our results reinforce the relevance of incorporating multi-scale habitat heterogeneity in future studies assessing the effects of fire on wildlife.  相似文献   

11.
Azeria ET  Ibarzabal J  Hébert C 《Oecologia》2012,168(4):1123-1135
It is often suggested that habitat attributes and interspecific interactions can cause non-random species co-occurrence patterns, but quantifying their contributions can be difficult. Null models that systematically exclude and include habitat effects can give information on the contribution of these factors to community assembly. In the boreal forest, saproxylic beetles are known to be attracted to recently burned forests where they breed in dead and dying trees. We examined whether species co-occurrences of saproxylic beetles that develop in, and emerge from, boles of recently burned trees show non-random patterns. We also estimated the extent to which both the post-fire habitat attributes and interspecific interactions among beetles contribute to such patterns. We sampled tree boles encompassing key attributes (tree species, tree size/dbh and burn severity) that are thought to characterize species–habitat associations of saproxylic beetles, a proposition that we tested using indicator species analysis. Two null models with no habitat constraints (“unconstrained”) indicated that a total of 29.4% of the species pairs tested had significant co-occurrence patterns. Habitat-constrained null models indicated that most of the detected species aggregations (72%) and segregations (59%) can be explained by shared and distinct species–habitat relationships, respectively. The assembly pattern was also driven by interspecific interactions, of which some were modulated by habitat; for example, predator and prey species tended to co-occur in large-sized trees (a proxy of available bark/wood food resource primarily for the prey). In addition, some species segregation suggesting antagonistic, competitive, or prey–predator interactions were evident after accounting for the species’ affinities for the same tree species. Overall, our results suggest that an intimate link between habitat and interspecific interactions can have important roles for community assembly of saproxylic assemblages even following disturbance by fire. We also show that a systematic application of null models can offer insight into the mechanisms behind the assembly of ecological communities.  相似文献   

12.
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.  相似文献   

13.
Fire is an important natural disturbance in the Okefenokee Swamp. From April–June 2007, wildfire burned 75% of the wetland area. With the existence of extensive pre-fire data sets on community structure and total mercury of invertebrates, the fire presented an opportunity to assess impacts of wildfire on invertebrates. Post-fire collection of samples occurred in September, December, and May, 2007–2009. Sample sites included 13 burned and 8 non-burned (reference) sites. Comparisons of data among pre-fire, post-fire reference, and post-fire burned sites revealed that the major difference between pre-fire communities and post-fire communities was a decrease in the number of water mites. We also found a decrease in mercury concentrations in amphipods, odonates, and crayfish post-fire. The differences between pre-fire and post-fire samples may be confounded by drought conditions during the baseline study. NMDS ordinations and ANOSIM tests suggested that habitat was an important factor; communities in burned cypress differed from reference cypress. Unexpectedly, burned sites had lower mercury concentrations in odonates and crayfish, with variation again being greatest in cypress stands. These findings and others suggest mercury levels do not follow a predictable pattern but can vary with pre-fire concentrations, variation in water levels, and burn intensity. We found that wildfire in the Okefenokee had little impact on invertebrates in prairies and scrub-shrub thickets, but can affect indicator organisms (Oecetis, Ischnura, and Sigara) in cypress stands. Our study suggests that vegetation type and burn intensity may have impacts on the invertebrate communities and mercury concentrations of organisms.  相似文献   

14.
Resprouting is an efficient life history strategy by which woody savanna species can recover their aboveground biomass after fire. However, resprouting dynamics after fire and the time it takes to start producing flowers and fruits are still poorly understood, especially for the Brazilian savanna (Cerrado biome), where fire is an important driver of vegetation structure and ecosystem functioning. We investigated the resprouting dynamics and production of flowers and fruits of 26 woody species (20 tree and 6 shrub species for a total of 485 individuals) that were burned and the production of flowers and fruits for a subset of 12 species (139 individuals) in an unburned area in a Brazilian savanna. We classified the species’ resprouting strategies as hypogeal (at the soil level, with main stem death), epigeal (on the main stem or crown), and hypogeal + epigeal. We used generalized linear mixed-effect models to identify the post-fire recovery patterns for five years. Individuals with basal resprouts (hypogeal and hypogeal + epigeal resprouting) produced an average of 6 basal resprouts, but only 33% of resprouts survived after five years. Individuals in burned areas produced fewer flowers and fruits than individuals in unburned areas. At least a subset of individuals in all the resprouting strategies started to produce flowers and fruits in the first-year post-fire. About 68% of the species with hypogeal resprouts produced flowers and fruits in the first-year post-fire, but the intensity of flowering and fruiting was lower compared to individuals with other resprouting strategies over time. Although woody species have invested in post-fire growth and sexual reproduction in all resprouting strategies, the long time needed to recover these processes can make these species more vulnerable to frequent fires.  相似文献   

15.
黑龙江省大兴安岭林区火烧迹地森林更新及其影响因子   总被引:8,自引:0,他引:8  
林火干扰是大兴安岭森林更新的影响因子之一,研究火烧迹地森林更新的影响因子(立地条件、火前植被、火干扰特征)对理解生态系统的结构、功能和火后演替轨迹具有重要意义。选取呼中及新林林业局55个代表性火烧样地,利用增强回归树分析法分析了火烧迹地森林更新的影响因素。结果表明:(1)立地条件是影响针、阔叶树更新苗密度的主要因素;海拔对针叶树更新苗密度的影响最大;坡度对阔叶树更新苗密度影响最大;(2)距上次火烧时间对针叶树更新苗比重影响最大,其次是林型;(3)中度林火干扰后森林更新状况好于轻度和重度火烧迹地。根据火烧迹地森林更新调查分析可知:林型影响火后演替模式,火前为针叶树或阔叶树纯林,火后易发生自我更新(火后树种更新组成与火前林型相同),而针阔混交林在火干扰影响下易于发生序列演替(火后初期以早期演替树种更新为主)。  相似文献   

16.
Fire is an important determinant of many aspects of savanna ecosystem structure and function. However, relatively little is known about the effects of fire on faunal biodiversity in savannas. We conducted a short‐term study to examine the effects of a replicated experimental burn on bird diversity and abundance in savanna habitat of central Kenya. Twenty‐two months after the burn, Shannon diversity of birds was 32% higher on plots that had been burned compared with paired control plots. We observed no significant effects of burning on total bird abundance or species richness. Several families of birds were found only on plots that had been burned; one species, the rattling cisticola (Cisticola chiniana), was found only on unburned plots. Shrub canopy area was negatively correlated with bird diversity on each plot, and highly correlated with grass height and the abundance of orthopterans. Our results suggest that the highest landscape‐level bird diversity might be obtained through a mosaic of burned and unburned patches. This is also most likely to approximate the historical state of bird diversity in this habitat, because patchy fires have been an important natural disturbance in tropical ecosystems for millennia.  相似文献   

17.
1. Disturbance is a strong driver of community assembly and fire has long been recognised as one of the main disturbances of terrestrial ecosystems. This study tested the resilience of dung beetles to fire events in campos rupestres, which is a tropical savanna ecosystem that evolved under a frequent fire regime, by assessing the resistance and recovery of their communities. 2. Dung beetles were sampled before and after a fire event and the effect of fire on dung beetle richness, abundance, mean community biomass and composition was tested. The effects of time since last fire and fire frequency on the community were also tested. 3. No effect of fire occurrence, time since last fire and fire frequency on any community variable was found. 4. Some non‐mutually exclusive mechanisms promoting the resistance and recovery of dung beetles in campos rupestres could be acting in synergy. One potential mechanism is the mismatched seasonality between fire events and dung beetle occurrence, as fires occur during the dry season and dung beetles are present above ground during the rainy season. Furthermore, dung beetles are insects that remain buried during most of their lifetime, which could protect individuals from being burned. Another potential mechanism is the replacement of species in burned areas by the movement of individuals from unburned areas, attracted by resources and/or by metacommunity dynamics. 5. It is concluded that in this ‘fire‐dependent’ ecosystem, dung beetle communities are resilient to fire and seem not to be structured by this disturbance.  相似文献   

18.
Fire is a common disturbance in the Mediterranean ecosystem. A fire that broke out in the eastern Mediterranean pine forest on Mount Carmel in September 1989 destroyed thousands of hectares of natural forest. We carried out a comparative study of rodent recovery after fire under three different management regimes in order to establish the best treatment for recovery. Rodents were used as bio-indicators, because of their limited home range, to assess the best management practice to be used in the recovery of the post-fire habitat. Our results show that the three arboreal Palaeoarctic species which lived in this habitat before the fire either died during the fire or left the habitat as a result of its destruction. A succession of rodent species was observed. The untreated burned forest had the highest species diversity in the initial stage, while during a later stage the highest diversity was observed in plots where the burned trees were cut down, the trunks removed and the twigs collected into small piles. The results also suggest that removing the trunks and twigs at the initial stage of recolonization results in a more xeric and warm habitat which will postpone the reinvasion of the forest species.  相似文献   

19.
The study of plant functional types (PFTs) has been widely emphasized when analysing plant community changes in relation to variations in climate and disturbance regime. In this study, we search for PFTs of woody species near forest–grassland boundaries in South Brazil where, due to climate, forests tend to expand over grassland but are being restricted by frequent fires. We aimed at answering the questions: (i) which plant functional types of forest woody species can establish in adjacent grassland subject to fire disturbance and (ii) which plant functional types of forest and grassland woody species are related to short-term community dynamics in frequently burned grassland. Traits were assessed in woody plants in 156 plots (6.75 m2) arranged in 12 transects across forest–grassland boundaries with different fire history in their grassland part. The analysis used a recursive algorithm to search for traits and PFTs maximally associated to spatial distance from forest limit in one analysis, and elapsed time since last fire in another. As a result, nine PFTs of forest woody species were identified that best described community patterns associated to distance from forest. Resprouting ability characterized forest plants able to colonize grasslands. PFT diversity was higher in border plots than inside forest or grassland. Four PFTs of forest and grassland woody species best described woody species community patterns in the grassland associated to elapsed time since fire. Taller individuals of single-stemmed shrubs predominated in late post-fire recovery (3–4 years), while shorter multi-stemmed shrubs in recently burned areas (3 months to 1 year). PFTs of forest trees occurred in border plots or, as established adults, in grassland, remaining unaffected by fire. We conclude that easily measurable structural plant traits, such as those used in our study, are sufficient to evaluate post-fire community dynamics. Forest PFTs in burned grassland are restricted to those with resprouting ability to survive recurrent fire events. Establishment success is highest on protected sites with lesser or low-intensity fire.  相似文献   

20.
Canada's federal recovery strategy for boreal woodland caribou (Rangifer tarandus caribou) classifies areas burned by forest fire as disturbed habitat. This assignment of fire as a disturbance has potential economic and social implications across Canada, and influences plans and actions to achieve caribou conservation and recovery. Previous researchers have reported caribou avoid burned habitat, but these studies did not typically consider unburned residual patches within fire perimeters. Additionally, the implications of burned habitat on individual caribou survival is unclear. We examined resource selection by boreal woodland caribou of burns, and unburned residual patches, using global positioning system (GPS) locations for 201 caribou across 6 caribou populations in Alberta, Canada. We also examined if burned habitat affected the survival of adult female caribou. Caribou avoided burns and unburned residual patches. Increased use of burned habitats, however, did not lower the survival of adult caribou. Collectively, these results provide evidence to support current assertions that burns, and the embedded unburned residual patches are not preferred caribou habitat and increase our understanding of the implications of forest fire for caribou vital rates. Our investigation offers important information about the role of forest fire in caribou ecology and enhances the identification of disturbed habitat under recovery strategy guidelines to effectively address caribou population declines. © 2021 The Wildlife Society.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号