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1.
We studied the vegetational and avifaunistic changes following rural depopulation in an area covering 2,600 ha north of Montpellier (Southern France). The study area is covered by a mosaic of Mediterranean habitats that includes cultivation, grasslands, shrublands, and woodlands and is representative of the natural features present and of the human usage practiced so far in this part of the Mediterranean. We sampled the vegetation and the bird fauna in the same 193 census plots in 1978 and in 1992. At both the habitat and landscape scales the cover of woody plants increased significantly. Open habitats tend to disappear. As a consequence the abundance of open-habitat bird species decreased significantly whereas the abundance of forest birds increased significantly. These changes favor a pool of forest species widespread in western Europe and reduce habitat availability for open habitat and shrubland species. Many of the latter are Mediterranean species whose distribution in Western Europe could become reduced under current landscape dynamics. Our observation of more woodlands and their typical birds and of less open habitats and their associated avifauna is not consistent with the traditional worry shown by the public and the managers about the regression of forests and woodlands in the Northern Mediterranean as a consequence of fire.  相似文献   

2.
Mediterranean landscapes are suffering two opposing forces leading to large-scale changes in species distribution: land abandonment of less productive areas and an increase in wildfire impact. Here, we test the hypothesis that fires occurred in recent decades drive the pattern of expansion of early-successional, open-habitat bird species by aiding in the process of colonisation of newly burnt areas. The study was carried out in Catalonia (NE Spain). We selected 44 burnt sites occurring between 2000 and 2005 to model colonisation patterns under different assumptions of potential colonisers’ sources and evaluated the colonisation estimates with empirical data on six bird species especially collected for this purpose. We first defined three landscape scenarios serving as surrogates of potential colonisers’ sources: open-habitats created by fire, shrublands and farmlands. Then, we used a parameter derived from a functional connectivity metric to estimate species colonization dynamics on the selected sites by each particular scenario. Finally, we evaluated our colonisation estimates with the species occurrence in the studied locations by using generalized linear mixed models. The occurrence of the focal species on the newly burnt sites was significantly related to the connectivity patterns described by both the recent fire history and the other open-habitat types generated by a different type of disturbance. We suggest that land use changes in recent decades have produced a shift in the relative importance of habitats acting as reservoirs for open-habitat bird species dynamics in Mediterranean areas. Before the middle of the twentieth century species’ reservoirs were probably constituted by relatively static open habitats (grassland and farmland), whereas afterwards they likely consist of a shifting mosaic of habitat patches where fire plays a key role as connectivity provider and largely contributes to the maintenance of species persistence.  相似文献   

3.
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   

4.
Worldwide forests fragmentation has lead to a massive increase of habitat edges, creating both negative and positive impacts on birds. While busy highways dissecting forested areas create edges which are known to reduce bird densities due to the disturbing effect of noise, the impacts of logging forest roads with low traffic volumes have rarely been studied. In this study, we compared species richness and similarity of canopy, cavity and shrub guilds of birds along low-traffic forest roads, in forest interior, and at forest edges in secondary forests in central Europe, where the forests have passed through extensive changes toward uniformly compact growths dominated by production conifers. Although we found tree diversity as positively affecting bird richness across all habitats, the bird richness along forest roads was higher than in forest interior but lower than along forest edges. The shrub guild of birds along forest roads resembled this guild along forest edges while canopy and cavity guilds at the roads were more similar to these guilds in forest interior. Forest interior had the highest probability for some guild to be absent. We conclude that low-traffic roads lead to increase of habitat heterogeneity in structurally poor forests and attract birds due to additional habitat attributes—including better light conditions—that are scarce in forest interior. Therefore, broader support for higher structural diversification of uniform plantations in central European production forests would benefit bird communities inhabiting these areas.  相似文献   

5.
Ekroos  Johan  Tiainen  Juha  Seimola  Tuomas  Herzon  Irina 《Landscape Ecology》2019,34(2):389-402
Context

The current Common Agricultural Policy (CAP) of the European Union includes three greening measures, which are partly intended to benefit farmland biodiversity. However, the relative biodiversity effects of the greening measures, including joint effects of landscape context, are not well understood.

Objectives

We studied the effects of increasing crop diversity, proportions of production grasslands and fallows, corresponding to CAP greening measures, on open farmland bird diversity, whilst controlling for the effects of distance to forests, field edge density and proportion of built-up areas.

Methods

We surveyed open farmland birds using territory mapping in Southern Finland. We modelled effects of greening measures and landscape structure on farmland birds (7642 territories) using generalised linear mixed models.

Results

Increasing proportions of grasslands increased farmland bird species richness and diversity in open farmland, whereas increasing proportions of fallows increased bird diversity. Increasing crop diversity benefited individual species, but not species richness or diversity. Increasing field edge densities consistently increased the species richness of all farmland species, in-field nesters and non-crop nesters, as well as total farmland bird diversity. The relative effect of edge density was much stronger compared to the three greening measures.

Conclusions

Our results show that promoting fallows and grasslands, in particular grazed grasslands and various types of semi-natural grasslands, has the highest potential to benefit farmland bird diversity. Maintaining or increasing field edge densities, currently not supported, seems to be of even more benefit. In open farmland, with little or no field edges, fallows and grasslands are particularly beneficial.

  相似文献   

6.
The parameters referring to landscape structure are essential in any evaluation for conservation because of the relationship that exists between the landscape structure and the ecological processes. This paper presents a study of the relationships between landscape structure and species diversity distribution (estimated in terms of richness of birds, amphibians, reptiles and butterflies) in the region of Madrid, Spain. The results show that the response of species richness to landscape heterogeneity varies depending on the group of species considered. For birds and lepidopterans, the most important factor affecting the distribution of richness of species is landscape heterogeneity, while other factors, such as the specific composition of land use, play a secondary role at this scale. On the other hand, richness of amphibians and reptiles is more closely related to the abundance of certain land-use types. The study highlights the importance of heterogeneity in Mediterranean landscapes as a criterion for landscape planning and for definition of management directives in order to maintain biodiversity.  相似文献   

7.
Farina  Almo 《Landscape Ecology》1997,12(6):365-378
Richness, abundance and distribution of birds were investigated in the Aulella watershed,a mountainous area of 300 km2, located in the extreme northwestern corner of Tuscany, Italy in spring and summer, 1995. The study area encompasses five vegetation types (from Mediterranean maqui to upland beech forest) and three main land use categories (woodlands, mixed cultivated + urban areas, montane prairies). The recent history of land abandonment in the study area has produced a rapid expansion of shrubland and woodland, reducing cultivated areas to small patches interspersed in a woodland matrix. Richness, abundance and distribution of birds recorded at 414 points, randomly selected along secondary roads, and located using a Global Positioning System (GPS), were compared with topography, vegetation type and land use in a Geographic Information Systems (GIS) with a grid cell resolution of 200 × 200 m. Bird richness (55 species in all) and abundance are correlated: (a) negatively with the increasing altitude and increasing distance from cultivated areas; (b) positively with the increasing distance from woodlands and mountain prairies. Slope orientation appears to have a negligible effect on bird assemblages. Bird richness and abundance are significantly correlated with vegetation type. Cultivated areas support the highest bird richness and abundance that increase with patch size of the cultivated areas. Local extinction and/or reduction in within-species abundance of birds are expected to continue if the process of land abandonment continues. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

8.
Based on recent needs to accurately understand fire regimes and post-fire vegetation resilience at a supra-level for carbon cycle studies, this article focusses on the coupled history of fire and vegetation pattern for 40 years on a fire-prone area in central Corsica (France). This area has been submitted since the beginning of the 20th century to land abandonment and the remaining land management has been largely controlled by frequent fires. Our objectives were to rebuild vegetation and fire maps in order to determine the factors which have driven the spatial and temporal distribution of fires on the area, what were the feed backs on the vegetation dynamics, and the long-term consequences of this inter-relationship. The results show a stable but high frequency of small fires, coupled with forest expansion over the study period. The results particularly illustrate the spatial distribution of fires according to topography and vegetation, leading to a strong contrast between areas never burnt and areas which have been burnt up to 7 times. Fires, when occuring, affect on average 9 to 12% of the S, SE and SW facing slopes (compared to only 2 to 5% for the N facing slopes), spread recurrently over ridge tops, affect all the vegetation types but reburn preferentially shrublands and grasslands. As these fire-proning parameters have also been shown to decrease the regeneration capacity of forests, this study highlights the needs in spatial studies (both in terms of fire spread and vegetation dynamic) to accurately apprehend vegetation dynamic and functionning in fire-prone areas.This revised version was published online in May 2005 with corrections to the Cover Date.  相似文献   

9.
In response to the processes threatening biodiversity such as habitat loss, effective selection of priority conservation areas is required. However, reserve selection methods usually ignore the drivers of future habitat changes, thus compromising the effectiveness of conservation. In this work, we formulated an approach to explicitly quantify the impact of fire on conservation areas, considering such disturbance as a driver of land-cover changes. The estimated fire impact was integrated as a constraint in the reserve selection process to tackle the likely threats or opportunities that fire disturbance might cause to the targeted species depending on their habitat requirements. In this way, we selected conservation areas in a fire-prone Mediterranean region for two bird assemblages: forest and open-habitat species. Differences in conservation areas selected before and after integrating the impact of fire in the reserve selection process were assessed. Integration of fire impact for forest species moved preferences towards areas that were less prone to burn. However, a larger area was required to achieve the same conservation goals. Conversely, integration of fire impacts for open-habitat species shifted preferences towards conservation areas in locations where the persistence of their required habitat is more likely (i.e. shrublands). In other words, we prioritized the conservation of not only the current distribution of open-habitat birds, but also the disturbance process (i.e. fire) that favours their preferred habitat and distributions in the long term. Finally, this work emphasizes the need to consider the opposing potential impacts of wildfires on species for an effective conservation planning.  相似文献   

10.
The factors responsible for widespread declines of grassland birds in the United States are not well understood. This study, conducted in the short-grass prairie of eastern Wyoming, was designed to investigate the relationship between variation in habitat amount, landscape heterogeneity, prey resources, and spatial variation in grassland bird species richness. We estimated bird richness over a 5-year period (1994–1998) from 29 Breeding Bird Survey locations. Estimated bird richness was modeled as a function of landscape structure surrounding survey routes using satellite-based imagery (1996) and grasshopper density and richness, a potentially important prey of grassland birds. Model specification progressed from simple to complex explanations for spatial variation in bird richness. An information-theoretic approach was used to rank and select candidate models. Our best model included measurements of habitat amount, habitat arrangement, landscape matrix, and prey diversity. Grassland bird richness was positively associated with grassland habitat; was negatively associated with habitat dispersion; positively associated with edge habitats; negatively associated with landscape matrix attributes that may restrict movement of grassland bird; and positively related to grasshopper richness. Collectively, 62% of the spatial variation in grassland bird richness was accounted for by the model (adj-R2 = 0.514). These results suggest that the distribution of grassland bird species is influenced by a complex mixture of factors that include habitat area affects, landscape pattern and composition, and the availability of prey.  相似文献   

11.
Long-term societal trends which include decreasing population in structurally poorer regions and changes in agricultural policies have been leading to land abandonment in various regions of Europe. One of the consequences of this development includes spontaneous forest regeneration of formerly open-land habitats with likely significant effects on plant and animal diversity. We assess potential effects of agricultural decline in Switzerland (41,000 km2) and potential impacts on the spatial distribution of seven open-land species (insects, reptile, birds) under land-use change scenarios: (1) a business-as-usual scenario that extrapolates trends observed during the last 15 years into the future, (2) a liberalisation scenario with limited regulation, and (3) a lowered agricultural production scenario fostering conservation. All scenarios were developed in collaboration with socio-economists. Results show that spontaneous reforestation is potentially minor in the lowlands since combinations of socio-economic (better accessibility), topographic (less steep slopes), and climatic factors (longer growing seasons) favour agricultural use and make land abandonment less likely. Land abandonment, spontaneous reforestation, and subsequent loss of open-land, however, are potentially pronounced in mountainous areas except where tourism is a major source of income. Here, socio-economic and natural conditions for cultivation are more difficult, leading to higher abandonment and thus reforestation likelihood. Evaluations for open-land species core habitats indicate pronounced spatial segregation of expected landscape change. Habitat losses (up to 59%) are observed throughout the country, particularly at high elevation sites in the Northern Alps. Habitat gains under the lowered agricultural production scenario range between 12 and 41% and are primarily observed for the Plateau and the Northern Alps.  相似文献   

12.
In this paper we test the hypothesis that landscape changes in a region of Northern Portugal (Minho) in the last 40 years could be predicted from socioeconomic and political history. The major predicted changes were related to agricultural abandonment and afforestation. We further predicted that these changes contributed to increased fire risk. Analysis of aerial photography for the years 1958, 1968, 1983 and 1995 in a study area of 3700 ha revealed a significant decline in agricultural areas and low shrublands and an increase in tall shrublands and forests. This represented a 20–40% increase in fuel accumulation at a landscape level, suggesting that the abandonment of farming activities is a major driving force of increasing fire occurrence in the region. With one exception, all the predictions were partly or totally confirmed. This study confirms that socioeconomic factors might explain a significant part of the variation in landscape composition across time, in the Mediterranean region.  相似文献   

13.
The present study assesses the spatial distribution of selected land cover classes at two years (1975 and 2000) in a Mediterranean urban area (Athens, Greece) to test the hypothesis that land cover changes determine an increase in the sensitivity of landscape to forest fires on a regional scale. While urban and agricultural areas increased, although with different rates of growth, forests and semi-natural areas decreased in the study area. These changes are reflected in a significant increase of vegetation sensitivity to forest fires measured by the forest fire risk (FR) index developed in the framework of MEDALUS project. The cover classes which contributed the most to the increase of the FR index were crop mosaic, mixed agricultural-natural areas and discontinuous, low-density settlements. Results of the present study indicate that the transformation of the fringe landscape towards low-quality agricultural and pasture areas and fragmented forest patches is potentially detrimental for environmental quality and the ecological fragility of land.  相似文献   

14.
Forests within and adjacent to cities are important habitats for native species and provide vital ecosystem services to cities and their residents. Herbaceous plants represent over 80% of all plant species in these forests, yet little is known about the long-term effects of management and landscape context on the understory of suburban forests. In this study, we used a 30-year dataset to fill this knowledge gap and evaluate the effect of prescribed burns on native forest herbs in suburban forest preserves of DuPage County, Illinois, USA. We also evaluated how the amount and configuration of forest habitat at multiple spatial scales affects native herb richness, gains, and losses in these forests over 30 years. We found that forests managed with prescribed burns increased in native herb richness over time, while unburned forests did not. Managed forests now have more native herb species than unburned forests. We also found that habitat amount in the surrounding landscape, but not the configuration of that habitat, had a positive effect on native herb richness and species gains over 30 years. Overall, we conclude that prescribed burns are effective in maintaining native forest herb richness in suburban forests. However, additional management actions such as seed augmentation may be required in areas with little surrounding forest herb habitat, as both overall richness and species gains over time are reduced in isolated forests.  相似文献   

15.
For some time, ecologists have known that spatial patterns of forest structure reflected disturbance and recovery history, disturbance severity and underlying influences of environmental gradients. In spite of this awareness, historical forest structure has been little used to expand knowledge of historical fire severity. Here, we used forest structure to predict pre-management era fire severity across three biogeoclimatic zones in eastern Washington State, USA, that contained extensive mixed conifer forests. We randomly selected 10% of the subwatersheds in each zone, delineated patch boundaries, and photo-interpreted the vegetation attributes of every patch in each subwatershed using the oldest available stereo-aerial photography. We statistically reconstructed the vegetation of any patch showing evidence of early selective harvesting, and then classified them as to their most recent fire severity. Classification used published percent canopy mortality definitions and a dichotomized procedure that considered the overstory and understory canopy cover and size class attributes of a patch, and the fire tolerance of its cover type. Mixed severity fires were most prevalent, regardless of forest type. The structure of mixed conifer patches, in particular, was formed by a mix of disturbance severities. In moist mixed conifer, stand replacement effects were more widespread in patches than surface fire effects, while in dry mixed conifer, surface fire effects were more widespread by nearly 2:1. However, evidence for low severity fires as the primary influence, or of abundant old park-like patches, was lacking in both the dry and moist mixed conifer forests. The relatively low abundance of old, park-like or similar forest patches, high abundance of young and intermediate-aged patches, and widespread evidence of partial stand and stand-replacing fire suggested that variable fire severity and non-equilibrium patch dynamics were primarily at work.  相似文献   

16.
In Mediterranean France, land abandonment is a widespread change. To understand and predict the land abandonment process and its consequences, land cover change models are used. An essential step in the development of a land cover change model is the identification and quantification of the factors controlling land cover change. In this paper we present a change detection study using aerial photographs in combination with an extensive dataset of field data and geographical data, to identify and quantify these factors for a study area in Mediterranean France, 60 km west of the city of Montpellier. We distinguished 11 land cover change classes and 7 associated “time since abandonment” classes at a detailed scale. Several environmental and non-environmental factors were found to be important variables for the land abandonment process. Differences in soil class explain a large part of the land abandonment pattern and the associated transition paths and transition rates. Most abandoned lands are located on regosols and lithosols, which are marginal soils with respect to water holding capacity. Within soil classes, we could recognise different transition paths and transition rates. However, within the 55 years covered by this dataset detailed transitions from pioneer vegetation to vegetation higher in the succession, as described by other authors, were only found for a limited number of vegetation/soil combinations. We relate these slow transitions for some areas to ongoing grazing and for some other areas to irreversible degradation.  相似文献   

17.
Two hundred years of landscape changes were studied on a 3,760 ha area of central Corsica (France) representing a typical Mediterranean environment. Different historical sources, including an accurate land-cover map from 1774 and statistics on land cover from 1848 and 1913, were used. Three additional maps (1960, 1975 and 1990) were drawn, and a complete fire history from 1957 to 1997 was created. Forests expanded slowly by a border effect. Forest expansion was more rapid in unburnt sites (0.59% per year) than in burnt sites (0.23% per year), mostly because the initial amount of forests was greater. Because of the border effect, the combination of past landscape pattern and short distance colonization abilities of forest species may have allowed the shrublands to persist in some places after land abandonment. This persistence may explain the pattern of fire in the landscape, since shrubland burn more readily than forests.  相似文献   

18.
We examined factors that affect egg distributions of amphibians, which are currently declining globally, in urban areas. We counted the number of egg masses of two amphibian species (Hynobius retardatus and Rana pirica) in ponds in urban green spaces during two years (2011 and 2012) and investigated the effects of local and landscape factors on them. Forest area in green spaces and pond area had positive effects, and distance from continuous forests in the suburbs and the rate of pond shore protection had negative effects on the number of eggs. Among these factors, distance from continuous forests and pond area had strong effects on egg distributions. These results suggest the importance of water habitat size and the need for colonization by amphibians from surrounding continuous forests. To conserve urban amphibian assemblages, the preservation of ponds with sufficient area and continuous forests close to urban habitats would be important.  相似文献   

19.
Fire-induced changes in northern Patagonian landscapes   总被引：4，自引：0，他引：4  
In northern Patagonia, Argentina we quantify changes in fire frequency along a gradient from mesic Nothofagus dombeyi forest to xeric woodlands of Austrocedrus chilensis at the steppe ecotone, and we examine patterns of vegetation change coincident with the changes in fire regimes across a range of spatial scales. At a regional scale changes in land cover types are documented by comparing 1:250000 scale cover type maps from 1913 and 1985. Changes in landscape structure are analyzed by comparing vegetation patterns on 1:24000 scale aerial photographs taken in 1940 and 1970. Fire frequency peaked in the late nineteenth-century due to widespread burning and clearing of forests by European settlers late in the century. Subsequently, fire frequency declined dramatically about 1910 due to the cessation of intentional fires and has remained low due to increasingly effective fire exclusion. At a regional scale there has been a dramatic increase during the twentieth century in the proportion of forest cover relative to areas mapped as recent burns or shrublands in 1913. Remnant forest patches that survived the widespread late-nineteenth century burning have coalesced to form more continuous forest covers, and formerly continuous areas of shrublands have become dissected by forest. Under reduced fire frequency there has been a shift in dominance from short-lived resprouting species (mostly shrubs) towards longer-lived species and obligate seed-dispersers such as Austrocedrus chilensis and Nothofagus dombeyi. Due to limited seed dispersal of these tree species, the spatial configuration of remnant forest patches plays a key role in subsequent changes in landscape pattern.  相似文献   

20.
Abandoned fields are perceived as potential habitats for species of threatened semi-natural dry grasslands. However, information is lacking regarding how the spontaneous colonization of abandoned fields depends on the broader spatial context. We recorded the occurrence of 87 target species in 46 abandoned fields and 339 dry grasslands. We tested the effect of the isolation of abandoned fields from source grasslands on the number of dry grassland species occurring in abandoned fields either with or without habitat characteristics being used as covariates. The isolation of the fields was calculated using the distance and area (I A ) or distance and species richness (I S ) of source habitats. I S always explained the number of grassland species in the abandoned fields better than I A . The effect of isolation became smaller or even non-significant with the inclusion of covariates; it also changed with the method used for measuring distance (edge-to-edge or center-to-center), and it was lower when other abandoned fields were considered as additional source habitats. The different performance of the two isolation measures can be explained by the weak species–area relationship in the grasslands, indicating differences in their habitat quality. Species richness is a better proxy of habitat importance in terms of propagule source than habitat area, and the new isolation measure is therefore suitable for studying the effects of landscape structure on species richness in landscapes presenting a weak species–area relationship, such as areas exhibiting pronounced effects of land-use history. Inclusion of habitat characteristics as covariates may considerably alter conclusions regarding the effect of isolation, which might actually be overestimated when assessed separately.  相似文献   

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