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1.
We assessed the possible influences of dominant tree density (Butia yatay palm trees) and fire on the expansion of a riparian tree population (Myrcianthes cisplatensis) over El Palmar National Park, a protected savanna in Argentina. Our approach is based on Skellam’s model of population expansion, which predicts that populations with density-independent reproduction and random dispersal will exhibit Gaussian-shaped expansion fronts. Using Poisson regression, we fitted Gaussian curves to Myrcianthes density data collected at varying distances from a riparian forest, within four environmental conditions resulting from combinations of palm density (dense and sparse) and fire history (burned and unburned). Based on the estimated parameters, we derived statistics appropriate to compare attained expansion velocity, mean squared effective dispersal distance, and density-independent population growth among environmental conditions. We also analyzed the effects of palm density, fire history, and distance from the riparian forest on local maximum size of Myrcianthes individuals. Gaussian curves fitted the data reasonably well and slightly better than two alternative front models. Palm density and fire history interacted to control Myrcianthes spread, making unburned dense palm savannas the preferential avenue for Myrcianthes population expansion across the landscape. Limitation of Myrcianthes expansion by fire appeared to result from low survival of small individuals to fire, whereas facilitation of Myrcianthes expansion by palm trees may have resulted from increased population growth. Our results stress the interactive role of fire regime and local biotic influences in determining propagule pressure and tree establishment at the forefront, and the overall vulnerability of savannas to colonization by forest species. 相似文献
2.
Expansion of Pinus and Juniperus species into shrub steppe in semi-arid regions of the western United States has been widely documented and attributed in
part to fire exclusion. If decreased fire frequency has been an important cause of woodland expansion, one would expect to
find age structures dominated by younger trees on more fire-prone sites, with old-growth pinyon-juniper woodland limited to
sites with lower fire risk. We compared current old-growth distribution with spatial models for fire risk in a 19-km2 watershed in central Nevada, USA. Multiple GIS models were developed to represent fire susceptibility, according to abiotic
factors representing fuels and topographic barriers to fire spread. We also developed cellular automata models to generate
fire susceptibility surfaces that additionally account for neighborhood effects. Rule-based GIS models failed to predict old-growth
distribution better than random models. Cellular automata models incorporating spatial heterogeneity of site productivity
predicted old-growth distribution better than random models but with low accuracy, ranging from 58% agreement at the single-pixel
(0.09-ha) scale to 80% agreement for 20-pixel neighborhoods. The best statistical model for predicting old-growth occurrence
included the negative effect of topographic convergence index (local wetness), and the positive effects of solar insolation
and proximity to rock outcrops. Results support the hypothesis that old-growth woodlands in the Great Basin are more likely
to occur on sites with low fire risk. However, weak relationships suggest that old-growth woodlands have not been confined
to fire-safe sites. Conservation efforts should consider the landscape context of old-growth woodlands across a broad landscape,
with an emphasis on conserving landscape variability in tree age structure. 相似文献
3.
Yan Boucher Maude Perrault-Hébert Richard Fournier Pierre Drapeau Isabelle Auger 《Landscape Ecology》2017,32(2):361-375
Context
Although logging has affected circumboreal forest dynamics for nearly a century, very few studies have reconstructed its influence on landscape structure at the subcontinental scale.Objectives
This study aims to document spatiotemporal patterns of logging and fire since the introduction of logging in the early twentieth-century, and to evaluate the effects of these disturbances on landscape structure.Methods
We used historical (1940–2009) logging and fire maps to document disturbance patterns across a 195,000-km2 boreal forest landscape of eastern Canada. We produced multitemporal (1970s–2010s) mosaics providing land cover status using Landsat imagery.Results
Logging significantly increased the rate of disturbance (+74 %) in the study area. The area affected by logging increased linearly with time resulting in a significant rejuvenation of the landscape along the harvesting pattern (south–north progression). From 1940 to 2009, fire was the dominant disturbance and showed a more random spatial distribution than logging. The recent increase of fire influence and the expansion of the proportion of area classified as unproductive terrestrial land suggest that regeneration failures occurred.Conclusions
This study reveals how logging has modified the disturbances dynamics, following the progression of the logging frontier. Future management practices should aim for a dispersed spatial distribution of harvests to generate landscape structures that are closer to natural conditions, in line with ecosystem-based management. The challenges of defining sustainable practices will remain complex with the predicted increase in fire frequency, since this factor, in combination with logging, can alter both the structure and potentially the resilience of boreal forest.4.
General Land Office Survey (GLOS) records from the A.D. 1840s provide data for quantitative characterization of presettlement
vegetation across western Mackinac County, Michigan, located within the mixed conifer-northern hardwoods forest region. We
analyzed data from land survey plat maps and 1958 bearing, witness, and line trees from 162 surveyed section and quarter-section
corners in order to map vegatation cover types at a level of spatial resolution appropriate for characterizing landscape heterogeneity
using standard landscape ecological metrics. As also demonstrated by a number of both classic and contemporary plant-ecological
studies, the distribution of landforms, soils properties, hydrology, and location of fire breaks all contribute to the heterogeneity
in vegetation observed at a landscape scale in the region. Through a series of spatial landscape analyses with differing grain
of resolution, in this study we determine that a grid cell size of 65 ha (0.5 mi×0.5 mi or 0.25 mi2) to 259 ha (1 mi2) gives a conservative characterization of landscape heterogeneity using standard metrics and is therefore appropriate for
use of GLOS data to study historical landscape changes. 相似文献
5.
Forest fragmentation, climate change and understory fire regimes on the Amazonian landscapes of the Xingu headwaters 总被引：1，自引：1，他引：0
Britaldo Soares-Filho Rafaella Silvestrini Daniel Nepstad Paulo Brando Hermann Rodrigues Ane Alencar Michael Coe Charton Locks Letícia Lima Letícia Hissa Claudia Stickler 《Landscape Ecology》2012,27(4):585-598
Understory fire modeling is a key tool to investigate the cornerstone concept of landscape ecology, i.e. how ecological processes relate to landscape structure and dynamics. Within this context, we developed FISC??a model that simulates fire ignition and spread and its effects on the forest carbon balance. FISC is dynamically coupled to a land-use change model to simulate fire regimes on the Amazonian landscapes of the Xingu Headwaters under deforestation, climate change, and land-use management scenarios. FISC incorporates a stochastic cellular automata approach to simulate fire spread across agricultural and forested lands. CARLUC, nested in FISC, simulates fuel dynamics, forest regrowth, and carbon emissions. Simulations of fire regimes under modeled scenarios revealed that the major current and future driver of understory fires is forest fragmentation rather than climate change. Fire intensity proved closely related to the landscape structure of the remaining forest. While climate change may increase the percentage of forest burned outside protected areas by 30% over the next four decades, deforestation alone may double it. Nevertheless, a scenario of forest recovery and better land-use management would abate fire intensity by 18% even in the face of climate change. Over this time period, the total carbon balance of the Xingu??s forests varies from an average net sink of 1.6?ton?ha?1?year?1 in the absence of climate change, fire and deforestation to a source of ?0.1?ton?ha?1?year?1 in a scenario that incorporates these three processes. 相似文献
6.
7.
Brandon M. Collins Maggi Kelly Jan W. van Wagtendonk Scott L. Stephens 《Landscape Ecology》2007,22(4):545-557
The effects of fire on vegetation vary based on the properties and amount of existing biomass (or fuel) in a forest stand,
weather conditions, and topography. Identifying controls over the spatial patterning of fire-induced vegetation change, or
fire severity, is critical in understanding fire as a landscape scale process. We use gridded estimates of fire severity,
derived from Landsat ETM+ imagery, to identify the biotic and abiotic factors contributing to the observed spatial patterns
of fire severity in two large natural fires. Regression tree analysis indicates the importance of weather, topography, and
vegetation variables in explaining fire severity patterns between the two fires. Relative humidity explained the highest proportion
of total sum of squares throughout the Hoover fire (Yosemite National Park, 2001). The lowest fire severity corresponded with
increased relative humidity. For the Williams fire (Sequoia/Kings Canyon National Parks, 2003) dominant vegetation type explains
the highest proportion of sum of squares. Dominant vegetation was also important in determining fire severity throughout the
Hoover fire. In both fires, forest stands that were dominated by lodgepole pine (Pinus contorta) burned at highest severity, while red fir (Abies magnifica) stands corresponded with the lowest fire severities. There was evidence in both fires that lower wind speed corresponded
with higher fire severity, although the highest fire severity in the Williams fire occurred during increased wind speed. Additionally,
in the vegetation types that were associated with lower severity, burn severity was lowest when the time since last fire was
fewer than 11 and 17 years for the Williams and Hoover fires, respectively. Based on the factors and patterns identified,
managers can anticipate the effects of management ignited and naturally ignited fires at the forest stand and the landscape
levels. 相似文献
8.
Land use history has altered natural disturbance dynamics, causing widespread modifications of the earth’s forests. The aim of this study is to reconstruct a regional, spatially-explicit, fire and logging history for a large southern boreal forest landscape (6,050 km2) of eastern Canada. We then examined the long-term influence of land use history, fires, and physiographical gradients on the area’s disturbances regimes, present-day age structure and tree species composition. Spatially-explicit fire (1820–2005) and logging (1900–2005) histories were reconstructed from forestry maps, terrestrial forest inventories and historical records (local newspapers, travel notes, regional historical reviews). Logistic regression was used to model the occurrence of major boreal tree species at the regional scale, in relation to their disturbance history and physiographical variables. The interplay of elevation and fire history was found to explain a large part of the present-day distribution of the four species studied. We conclude that human-induced fires following the colonization activities of the nineteenth and twentieth centuries have increased fire frequency and the dominance of fire-adapted species at lower elevations. At higher elevations, the low historical fire frequency has fostered the dominance of fire-sensitive species. Twentieth-century forestry practices and escaped settlement fires have generated a forest landscape dominated by younger forest habitats than in presettlement times. The expected increase of wildfire activity in North America’s eastern boreal forest, in conjunction with continued forest management, could have significant consequences on the resilience of boreal forests. 相似文献
9.
Studies on the distribution of mammalian carnivores in fragmented landscapes have focused mainly on structural aspects such
as patch and landscape features; similarly, habitat connectivity is usually associated with landscape structure. The influence
of food resources on carnivore patch use and the important effect on habitat connectivity have been overlooked. The aim of
this study is to evaluate the relative importance of food resources on patch use patterns and to test if food availability
can overcome structural constraints on patch use. We carried out a patch-use survey of two carnivores: the beech marten (Martes foina) and the badger (Meles meles) in a sample of 39 woodland patches in a fragmented landscape in central Italy. We used the logistic model to investigate
the relative effects on carnivore distribution of patch, patch neighbourhood and landscape scale variables as well as the
relative abundance of food resources. Our results show how carnivore movements in fragmented landscapes are determined not
only by patch/landscape structure but also by the relative abundance of food resources. The important take-home message of
our research is that, within certain structural limits (e.g. within certain limits of patch isolation), by modifying the relative
amount of resources and their distribution, it is possible to increase suitability in smaller/relatively isolated patches.
Conversely, however, there are certain thresholds above which an increase in resources will not achieve high probability of
presence. Our findings have important and generalizable consequences for highly fragmented landscapes in areas where it may
not be possible to increase patch sizes and/or reduce isolation so, for instance, forest regimes that will increase resource
availability could be implemented.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
10.
Andrew G. Merschel Emily K. Heyerdahl Thomas A. Spies Rachel A. Loehman 《Landscape Ecology》2018,33(7):1195-1209
Context
In the interior Northwest, debate over restoring mixed-conifer forests after a century of fire exclusion is hampered by poor understanding of the pattern and causes of spatial variation in historical fire regimes.Objectives
To identify the roles of topography, landscape structure, and forest type in driving spatial variation in historical fire regimes in mixed-conifer forests of central Oregon.Methods
We used tree rings to reconstruct multicentury fire and forest histories at 105 plots over 10,393 ha. We classified fire regimes into four types and assessed whether they varied with topography, the location of fuel-limited pumice basins that inhibit fire spread, and an updated classification of forest type.Results
We identified four fire-regime types and six forest types. Although surface fires were frequent and often extensive, severe fires were rare in all four types. Fire regimes varied with some aspects of topography (elevation), but not others (slope or aspect) and with the distribution of pumice basins. Fire regimes did not strictly co-vary with mixed-conifer forest types.Conclusions
Our work reveals the persistent influence of landscape structure on spatial variation in historical fire regimes and can help inform discussions about appropriate restoration of fire-excluded forests in the interior Northwest. Where the goal is to restore historical fire regimes at landscape scales, managers may want to consider the influence of topoedaphic and vegetation patch types that could affect fire spread and ignition frequency.11.
Effects of site,landscape features,and fire regime on vegetation patterns in presettlement southern Wisconsin 总被引：2，自引：0，他引：2
Lawrence A. Leitner Christopher P. Dunn Glenn R. Guntenspergen Forest Stearns David M. Sharpe 《Landscape Ecology》1991,5(4):203-217
The presettlement tree cover (1831–33) of 3 townships in a southern Wisconsin landscape was analyzed using original survey records. Four forest types were identified: closed forest, open forest, savanna, and prairie. Comparisons of vegetation types and landscape pattern were made between the east and west sides of the Pecatonica River, which bisects the landscape and could have acted as a natural fire barrier. West of the river, presettlement tree species richness and diversity were lower and trees were smaller in diameter and less dense than to the east. The major vegetation types to the west were prairie (42% of landscape) and savanna (40%), both fire-susceptible types. Prairie was more common on gentle slopes than on other landforms. To the east, the landscape was 70% forested (closed plus open forest). Here, prairie was more frequent on steep dry sites. These vegetation differences, including the contrasting landscape placement of prairie, are attributed to distinct site characteristics and to disturbance (fire) regimes, with the west likely having more frequent fires. In terms of the four vegetation types, the east landscape was more homogeneous, being dominated by closed forest (50%). West of the Pecatonica River, the landscape was more heterogeneous because of the high proportion of both prairie and savanna; however, in terms of flammability of vegetation, the west was essentially homogeneous (82% prairie plus savanna). 相似文献
12.
It is reasonable to assume that there is a relationship between the spatial distribution of forest fuels and fire hazards.
Therefore, if fire risk is to be included into numerical forest planning, the spatial distribution of risky and non-risky
forest stands should be taken into account. The present study combines a stand-level fire risk model and landscape level optimization
to solve forest planning problems in which the fire risk plays an important role. The key point of the method was to calculate
forest level fire resistance metrics from stand level indices and use these metrics as objective variables in numerical optimization.
This study shows that maximizing different landscape metrics produces very different landscape configurations with respect
to the spatial arrangement of resistant and risky stands. The landscapes obtained by maximizing different metrics were tested
with a fire spread simulator. These tests suggested that the mean fire resistance of the landscape, which is a non-spatial
metric, is the most important factor affecting the burned area. However, spatial landscape metrics that decrease the continuity
of fire resistance in the landscape can significantly improve the fire resistance of the landscape when used as additional
objective variables. 相似文献
13.
Jones Gavin M. Kramer H. Anu Whitmore Sheila A. Berigan William J. Tempel Douglas J. Wood Connor M. Hobart Brendan K. Erker Tedward Atuo Fidelis A. Pietrunti Nicole F. Kelsey Rodd Gutiérrez R. J. Peery M. Zachariah 《Landscape Ecology》2020,35(5):1199-1213
Context
Climate and land-use change have led to disturbance regimes in many ecosystems without a historical analog, leading to uncertainty about how species adapted to past conditions will respond to novel post-disturbance landscapes.
ObjectivesWe examined habitat selection by spotted owls in a post-fire landscape. We tested whether selection or avoidance of severely burned areas could be explained by patch size or configuration, and whether variation in selection among individuals could be explained by differences in habitat availability.
MethodsWe applied mixed-effects models to GPS data from 20 spotted owls in the Sierra Nevada, California, USA, with individual owls occupying home ranges spanning a broad range of post-fire conditions after the 2014 King Fire.
ResultsIndividual spotted owls whose home ranges experienced less severe fire (<?5% of home range severely burned) tended to select severely burned forest, but owls avoided severely burned forest when more of their home range was affected (~ 5–40%). Owls also tended to select severe fire patches that were smaller in size and more complex in shape, and rarely traveled?>?100-m into severe fire patches. Spotted owls avoided areas that had experienced post-fire salvage logging but the interpretation of this effect was nuanced. Owls also avoided areas that were classified as open and/or young forest prior to the fire.
ConclusionsOur results support the hypothesis that spotted owls are adapted to historical fire regimes characterized by small severe fire patches in this region. Shifts in disturbance regimes that produce novel landscape patterns characterized by large, homogeneous patches of high-severity fire may negatively affect this species.
相似文献14.
Fire is an important natural disturbance in the Mediterranean-climate coastal shrublands of southern California. However,
anthropogenic ignitions have increased fire frequency to the point that it threatens the persistence of some shrub species
and favors the expansion of exotic annual grasses. Because human settlement is a primary driver of increased ignitions, we
integrated a landscape model of disturbance and succession (LANDIS) with an urban growth model (UGM) to simulate the combined
effects of urban development and high fire frequency on the distribution of coastal shrublands. We tested whether urban development
would contribute to an expansion of the wildland-urban interface (WUI) and/or change in average fire return intervals and
compared the relative impacts of direct habitat loss and altered fire regimes on functional vegetation types. We also evaluated
two methods of integrating the simulation models. The development pattern predicted by the UGM was predominantly aggregated,
which minimized the expansion of the WUI and increase in fire frequency, suggesting that fire risk may be higher at intermediate
levels of urbanization due to the spatial arrangement of ignition sources and fuel. The comparison of model coupling methods
illustrated how cumulative effects of repeated fires may occur gradually as urban development expands across the landscape.
Coastal sage scrub species and resprouting chaparral were more susceptible to direct habitat loss, but increased fire frequency
was more of a concern to obligate seeder species that germinate from a persistent seed bank. Simulating different scenarios
of fire frequency and urban growth within one modeling framework can help managers locate areas of highest risk and determine
which vegetation types are most vulnerable to direct habitat loss, altered fire regimes, or both. 相似文献
15.
The protean relationship between boreal forest landscape structure and red squirrel distribution at multiple spatial scales 总被引：3，自引：0，他引：3
This paper investigates two fundamental questions in landscape ecology: what influence does landscape context, or the composition of the matrix, have on an animals’ response to landscape structure, and how does this relationship extrapolate between landscapes? We investigate how the distribution of North American red squirrels (Tamiasciurus hudsonicus) in the boreal mixedwood forest is influenced by anthropogenically (forest harvest) and naturally (forest fire) derived landscape structure. We studied the presence and absence of red squirrels over two years in three landscape types: one managed for timber harvest, one recently burned by wildfire, and a third unburned unmanaged landscape. Landscape composition and configuration, measured at several spatial scales, predicted red squirrel’s distribution in all three landscapes, but the significant landscape variables changed across spatial scales, across time, and across landscapes. These findings emphasize the variability in landscape structure/animal distribution relationships, and enforce the need to link pattern-finding studies, such as this one, with searches for the mechanisms behind the observed pattern. 相似文献
16.
Effects of changing spatial scale on the analysis of landscape pattern 总被引：68，自引：6，他引：62
Monica G. Turner Robert V. O'Neill Robert H. Gardner Bruce T. Milne 《Landscape Ecology》1989,3(3-4):153-162
The purpose of this study was to observe the effects of changing the grain (the first level of spatial resolution possible with a given data set) and extent (the total area of the study) of landscape data on observed spatial patterns and to identify some general rules for comparing measures obtained at different scales. Simple random maps, maps with contagion (i.e., clusters of the same land cover type), and actual landscape data from USGS land use (LUDA) data maps were used in the analyses. Landscape patterns were compared using indices measuring diversity (H), dominance (D) and contagion (C). Rare land cover types were lost as grain became coarser. This loss could be predicted analytically for random maps with two land cover types, and it was observed in actual landscapes as grain was increased experimentally. However, the rate of loss was influenced by the spatial pattern. Land cover types that were clumped disappeared slowly or were retained with increasing grain, whereas cover types that were dispersed were lost rapidly. The diversity index decreased linearly with increasing grain size, but dominance and contagion did not show a linear relationship. The indices D and C increased with increasing extent, but H exhibited a variable response. The indices were sensitive to the number (m) of cover types observed in the data set and the fraction of the landscape occupied by each cover type (P
k); both m and P
kvaried with grain and extent. Qualitative and quantitative changes in measurements across spatial scales will differ depending on how scale is defined. Characterizing the relationships between ecological measurements and the grain or extent of the data may make it possible to predict or correct for the loss of information with changes in spatial scale. 相似文献
17.
Context
Fires and insect outbreaks are important agents of forest landscape change, but the classification and distribution of these combined processes remain unstudied aspects of forest disturbance regimes.Objectives
We sought to map areas of land characterized by homogenous fire regime (HFR) attributes and by distinctive combinations of fire, bark beetles and defoliating insect outbreaks, and how their distribution might change should current climatic trends continue.Methods
We used a 41-year history of mapped fires and forest insect outbreaks to classify HFRs and combined fire and insect disturbance regimes (HDRs). Spatially constrained cluster analysis of 2524 20-km grid cells used mean annual area burned, ignition Julian date, fire size and fire frequency to delineate HFR zones. Mean annual areas burned, affected by bark beetles, and affected by defoliators were used to delineate HDR zones. Random forests classification used climate associations of HDRs to project likely changes in their distribution.Results
Eighteen HFR zones accounted for 30% of variance, compared to 27 HDR zones accounting for 59% of variance. Fire regime designation had low predictive power in explaining 23 homogenous insect outbreak regimes or the 27 HDRs. Climate change projections indicate a northward migration of current HDR zones. Conditions suitable for defoliator outbreaks are projected to increase, resulting in a projected increase in the total rate of forest disturbance.Conclusions
When describing forest disturbance regimes, it is important to consider the combined and possibly interacting agents of tree mortality, which can result in emergent properties not predictable from any single agent.18.
Besides providing habitat to the grizzly bear (Ursus arctos) and other wildlife, the Rocky Mountain foothills of Alberta, Canada hosts considerable mining, seismic oil and gas exploration
and production, and forest harvesting activities. Worldwide, such human activities influence the configuration and composition
of the landscape. We assessed seismic cutline effects on landscape structure and grizzly bear use during early summer of 1999
and 2000. We studied five female and two male bears, which were GPS-collared in the spring following den emergence. The area
available to this population was stratified into 49 km2 hexagon-shaped sub-landscapes. The scale of this stratification was determined by patterns of bear movement. Fourteen compositional
and configurational landscape metrics were calculated within each landscape unit, and bear use points were pooled or ‘binned’
within each unit. Landscape use was related to landscape metrics using a Generalized Linear Model (GLM). We found that seismic
cutline proportion did not explain landscape use by grizzly bears; however secondary effects of cutlines on landscape structure
did. Declining use was mainly associated with increasing proportions of closed forest, and increasing variation of inter-patch
distances, while use was mainly increasing with increasing mean patch size. An earlier investigation had demonstrated that
adding seismic cutlines to grizzly bear habitat caused increases in the variation of inter-patch distances. Since the landscape
structure of this grizzly bear population will continue to change as a function of increased levels of resource extraction
activities in the near future, it is crucial to further study the detailed meaning of landscape structure at the large and
small scale for effective conservation efforts. 相似文献
19.
Landscape dynamics in crown fire ecosystems 总被引：21，自引：3，他引：18
Crown fires create broad-scale patterns in vegetation by producing a patch mosaic of stand age classes, but the spread and behavior of crown fires also may be constrained by spatial patterns in terrain and fuels across the landscape. In this review, we address the implications of landscape heterogeneity for crown fire behavior and the ecological effects of crown fires over large areas. We suggest that fine-scale mechanisms of fire spread can be extrapolated to make broad-scale predictions of landscape pattern by coupling the knowledge obtained from mechanistic and empirical fire behavior models with spatially-explicit probabilistic models of fire spread. Climatic conditions exert a dominant control over crown fire behavior and spread, but topographic and physiographic features in the landscape and the spatial arrangement and types of fuels have a strong influence on fire spread, especially when burning conditions (e.g., fuel moisture and wind) are not extreme. General trends in crown fire regimes and stand age class distributions can be observed across continental, latitudinal, and elevational gradients. Crown fires are more frequent in regions having more frequent and/or severe droughts, and younger stands tend to dominate these landscapes. Landscapes dominated by crown fires appear to be nonequilibrium systems. This nonequilibrium condition presents a significant challenge to land managers, particularly when the implications of potential changes in the global climate are considered. Potential changes in the global climate may alter not only the frequency of crown fires but also their severity. Crown fires rarely consume the entire forest, and the spatial heterogeneity of burn severity patterns creates a wide range of local effects and is likely to influence plant reestablishment as well as many other ecological processes. Increased knowledge of ecological processes at regional scales and the effects of landscape pattern on fire dynamics should provide insight into our understanding of the behavior and consequences of crown fires. 相似文献
20.
The distribution of woody vegetation was studied in forest edges and hedgerows in a 28 km2 southern Swedish agricultural area, characterised by species-rich edge zones. The occurrence of 21 selected woody species (taxa) was related to differences in both edge structure and landscape structure. All the species studied were represented in both edge types, but a higher frequency of animal-dispersed species was found in hedgerows.Animal dispersed species were more affected by edge width and density than wind dispersed species. A higher number of wind-dispersed species were more frequent in forest edges, in hedgerows near to forest, or with a high proportion of forest within 500 m. A clear relationship was found between the number of physically connected elements in hedgerow networks and increasing frequency of occurrence for Corylus avellana, Crataegus spp., Euonymus europaeus, and Quercus robur; which indicate the ecological significance of connectedness for certain animal dispersed species. The study supports the general principle that woody species distribution and landscape structure are linked in a positive feedback loop. The results match findings from studies in other countries and are interpreted in the context of landscape processes and the ecological characteristics of woody plant species. We emphasise the importance of understanding dispersal mechanisms of woody species for the design and improvement of edge habitats in agricultural landscapes. 相似文献