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1.
The target rate of afforestation in Ireland over the next 30 years is 20,000 ha per year, which would result in an increase of the forest cover from the current 10% to 17%. In order to promote sustainable forest management practices, it is essential to know the composition and conservation value of habitats where afforestation is planned and the effects of subsequent planting upon biodiversity. The objectives of this study were to investigate changes in vegetation composition and diversity of grasslands 5 years after afforestation with Sitka spruce (Picea sitchensis) and determine the primary ecological and management factors responsible for these changes. Species cover, environmental and management data were collected from 16 afforested and unplanted improved and wet grassland site pairs in Ireland. Our results indicate that 5 years after tree planting, there were significant changes in richness, composition, and abundance of species. Competitive and vigorous grasses were more abundant in planted than in unplanted sites, as were generalist species found in both open and wooded habitats, while small-stature shade-sensitive species were less abundant. Vascular plant species richness and Shannon’s diversity index were higher in unplanted wet grassland, than in the planted sites. Bryophyte species richness was higher in planted improved grassland than in unplanted sites. The differences were primarily the result of the exclusion of grazing, ground preparation, changes in nutrient management and drainage for afforestation. Drainage ditches provided a temporary habitat for less competitive species, but the overall effect of drainage was to reduce the diversity of species dependent on wet conditions. Variance partitioning showed differences in the relative influences of environmental and management variables on biodiversity in the two habitats, probably due to the greater pre-afforestation grazing pressure and fertilisation levels in improved grasslands. The differences in biodiversity between planted and unplanted grasslands indicate that afforestation represents a threat to semi-natural habitats where distinctive and highly localised plant communities could potentially occur.  相似文献   

2.
Declines of West European farmland birds have been associated with intensive agricultural practices, while in Central and Eastern European countries grasslands still harbour a diverse and unique bird community. However, in these countries comparative studies on the effects of agricultural intensity on biodiversity are virtually missing. We compared bird communities of paired extensively and intensively grazed cattle pastures in three different regions of the Hungarian Great Plain. The influence of grazing intensity, landscape and regional effects were tested on the abundance and species richness of two ecological groups of bird species (grassland and non-grassland birds), as well as on the abundance of the three commonest grassland bird species (Skylark, Yellow wagtail, Corn bunting) in linear mixed models. We found significant effects of grazing intensity on the abundance of grassland birds, which were more abundant on the extensive sites, whereas no effects were found on non-grassland birds. This could be explained by a closer dependence of grassland birds on grasslands for nesting and foraging, whereas non-grassland birds only used grasslands opportunistically for foraging. Landscape effect was shown on grassland bird abundance, but not on non-grassland birds. The regions did affect only the species richness of grassland birds. At species level, the effect of management was significant for the three commonest grassland species, which were more abundant on the extensive fields in all regions. Additionally, on Skylark abundance landscape and regional effects were also shown. These findings suggest that conservation of biodiversity in agricultural systems requires the consideration of landscape perspective to apply the most adequate management.  相似文献   

3.
Plantations are established for a variety of reasons including wood production, soil and water conservation, and more recently, carbon sequestration. The effect of this growing land-use change on biodiversity, however, is poorly understood and considerable debate exists as to whether plantations are ‘green deserts’ or valuable habitat for indigenous flora and fauna. This paper synthesizes peer-reviewed articles that provide quantitative data on plant species richness in plantations and paired land uses, most often representative of pre-plantation land cover. The results of this synthesis suggest that the value of plantations for biodiversity varies considerably depending on whether the original land cover is grassland, shrubland, primary forest, secondary forest, or degraded or exotic pasture, and whether native or exotic tree species are planted. The results of this study suggest that plantations are most likely to contribute to biodiversity when established on degraded lands rather than replacing natural ecosystems, such as forests, grasslands, and shrublands, and when indigenous tree species are used rather than exotic species. These findings can help guide afforestation and reforestation programs, including those aimed at increasing terrestrial carbon sequestration.  相似文献   

4.
Demand for bioenergy is increasing, but the ecological consequences of bioenergy crop production on working lands remain unresolved. Corn is currently a dominant bioenergy crop, but perennial grasslands could produce renewable bioenergy resources and enhance biodiversity. Grassland bird populations have declined in recent decades and may particularly benefit from perennial grasslands grown for bioenergy. We asked how breeding bird community assemblages, vegetation characteristics, and biomass yields varied among three types of potential bioenergy grassland fields (grass monocultures, grass-dominated fields, and forb-dominated fields), and assessed tradeoffs between grassland biomass production and bird habitat. We also compared the bird communities in grassland fields to nearby cornfields. Cornfields had few birds compared to perennial grassland fields. Ten bird Species of Greatest Conservation Need (SGCN) were observed in perennial grassland fields. Bird species richness and total bird density increased with forb cover and were greater in forb-dominated fields than grass monocultures. SGCN density declined with increasing vertical vegetation density, indicating that tall, dense grassland fields managed for maximum biomass yield would be of lesser value to imperiled grassland bird species. The proportion of grassland habitat within 1 km of study sites was positively associated with bird species richness and the density of total birds and SGCNs, suggesting that grassland bioenergy fields may be more beneficial for grassland birds if they are established near other grassland parcels. Predicted total bird density peaked below maximum biomass yields and predicted SGCN density was negatively related to biomass yields. Our results indicate that perennial grassland fields could produce bioenergy feedstocks while providing bird habitat. Bioenergy grasslands promote agricultural multifunctionality and conservation of biodiversity in working landscapes.  相似文献   

5.
Question: What is the impact of grazing and/or afforestation on grassland diversity, species composition and cover parameters? Location: Semi‐arid Mediterranean grasslands of Jordan. Methods: Vegetation, litter, bare soil and rock cover were compared among four management types – free grazing and protected from grazing with three levels of tree cover. Species composition, plant cover, species richness and evenness were used to evaluate differences in vegetation among management types. Species composition differences among management types were also investigated. Results: Semi‐arid Mediterranean grasslands harbour appreciable levels of plant biodiversity. Grazing did not affect plant diversity, indicating the high resilience against and adaptation to grazing; however,grazing affected species composition and cover parameters. Afforestation seems to protect soil through higher litter cover but its impact on plant biodiversity was negative and markedly affected species composition. Conclusions: Neither protection from grazing or massive afforestation alone are sufficient for conserving biodiversity in this system. A management model is suggested where the landscape should be maintained as a mosaic of four management types: complete protection from grazing, grazing rotation, planting sparse trees in eroded areas and revegetating degraded areas using native, herbaceous and grazing tolerant species.  相似文献   

6.
Forest plantations of exotic conifers represent an important economic activity in NW Patagonia, Argentina. However, there is a remarkable lack of information on the impact of forestry on native biodiversity. We analyzed the effect of Pinus ponderosa plantations on bird communities, considering different stand management practices (dense and sparse tree covers), and different landscape contexts where they are planted (Austrocedrus chilensis forest and steppe). Ultimately we wished to assess in which way plantations may be designed and managed to improve biodiversity conservation. Bird richness and abundance did not change significantly in the steppe, although community composition did, and was partially replaced by a new community, similar to that of ecotonal forests. In contrast, in the A. chilensis forest areas, species richness decreased in dense plantations, but bird community composition remained relatively constant when replacing the native forest with pine plantations. Also, in A. chilensis forest, stand management practices aiming at maintaining low tree densities permit the presence of many bird species from the original habitat. In the steppe area in turn, both dense and sparse plantations are unsuitable for most steppe species, thus it is necessary to manage them at higher scales, maintaining the connectivity of the native matrix to prevent the fragmentation of bird populations. We conclude that pine plantations can provide habitat for a substantial number of native bird species, and this feature varies both with management practices and with the landscape context of areas where afforestation occurs.  相似文献   

7.
We investigated the densities of the Redwing Francolinus levaillantii and Greywing Francolins F. africanus and the diversity of grassland birds in general along a land-use gradient in the highlands of Mpumalanga province, South Africa. Redwing Francolins cannot tolerate intensive grazing and frequent burning and are confined largely to unburnt, ungrazed grasslands. Their density and the species richness of grassland birds in general are negatively correlated with grazing intensity. Redwing populations drop to densities that cannot be utilised by hunters on a sustainable basis in grasslands that are grazed at even moderate levels or burned annually. Nineteen bird species (including five threatened species) were confined to essentially pristine grassland and were never observed in grazed/annually burned grasslands. The Greywing Francolin is more evenly distributed (although always at sub-utilisation densities) along the grassland land-use gradient, and its density is positively correlated with grazing intensity. There are two assemblages of grassland bird species that appear to be indicative of the intensity of habitat utilisation. Populations of grassland birds in the study area are becoming increasingly dependent on isolated patches of pristine grassland and are threatened by management involving annual burning and high stocking rates on a landscape scale.  相似文献   

8.
The global decline of biodiversity makes it important to find affordable ways to conserve and restore habitats. Restoration is useful for conserving native grasslands, with passive restoration defined as either natural colonization or unassisted recovery. Grasslands in southeastern South America have been transformed into croplands and impacted by other human activities. We describe the first assessment of passive restoration as a management tool to conserve birds in the Pampa grasslands of Brazil. We compared bird species richness using coverage‐based rarefaction and extrapolation, applying PERMANOVA for composition, and the abundance of bird communities between sites undergoing passive restoration (PR) and sites with native grasslands (NG). We employed fitted generalized linear mixed models (GLMM) to quantify relationships between bird occurrence and vegetation structure and cover. We recorded 61 species of birds during our study (45 in PR and 46 in NG) and 762 individuals (333 in PR and 429 in NG). Of these species, 15 were restricted to PR and 16 to NG. Grassland specialists and threatened species were found in both PR and NG, and only vegetation height differed between PR and NG. We detected eight species of conservation concern, including three recorded only in PR, three only in NG, and two in both PR and NG. The absence of marked differences in species richness and composition of bird communities between passive‐restoration and native grasslands in our study suggests that grasslands in the process of passive restoration can provide habitat for many species of grassland birds and that passive restoration is an appropriate management tool for biodiversity conservation in Brazilian grasslands.  相似文献   

9.
Aims South American Pampa grasslands are habitats of great conservation interest, with a distinct and rich flora, but have been intensely converted to other land uses, including tree plantations. While necessity for restoration grows, no information on restoration potential of grasslands after afforestation exists. Here, we aim at analyzing composition and structure of grassland vegetation with a history of eucalyptus plantations in order to assess recovery potential of these areas. We hypothesized that areas with history of eucalyptus would differ from reference grasslands with no history of land-use change in terms of floristic and functional composition and would present lower species richness.  相似文献   

10.
The soil seed bank can be an important source for vegetation regeneration, and data on the similarity between aboveground vegetation and the seed bank can provide information about successional pathways after disturbances or land-use change. We conducted this study in natural grasslands in the subtropical highland region in southern Brazil. We evaluated the effect of silviculture on richness, density, and composition of the seed bank at former grassland sites converted to pine plantations 25 years ago. We worked at six grassland sites and three pine plantation sites and used the seedling emergence method. Seed bank density and richness in grasslands were lower than those reported in similar environments in other regions. Species richness and density varied considerably within each vegetation type; therefore, richness and density were not statistically significant, while composition varied among vegetation types. In terms of species, the pine plantation seed bank was a small subset of the grassland seed bank. Seeds of typical grassland species were missing in the pine plantation, but also had only low abundances in the grassland, and similarity of seed bank and vegetation were low (less than 20%). The low seed density found in this study, including in grasslands areas, indicates that regeneration of species from the soil seed bank likely is of a limited role for the maintenance of plant populations after disturbances in this system. Our data further suggest that natural regeneration after tree planting in grasslands is reduced due to seed limitation.  相似文献   

11.
This study examined the effects of forest structure (tree species richness, canopy height, percent canopy cover, understory density, tree density and DBH) and avian species traits (nest type and indicator list status) on the diversity, abundance and dissimilarity of bird communities in forest remnants and reforestation areas adjacent to Costa Rican banana plantations. Bird species richness and abundance were significantly related to tree species richness, canopy height and canopy cover in multiple linear regressions, the latter two forest structure variables being the best statistical predictors. Stratification of analyses by bird species indicator categories improved fits of regressions, because correlations with environmental variables differed in sign for different guilds of birds, a result likely to hold for other avifaunas. Analysis of avifauna dissimilarities among sites demonstrated that the species composition of bird communities was highly correlated with forest structure and tree species composition. Logistic regressions indicated that birds making protected (cavity, burrow, pendant, sphere and covered) nests were 2–6 times more likely to be present in the study avifauna than birds making open (cup, saucer, platform and scrape) nests and indicators of disturbed habitats were 11 times more likely to be present than indicators of primary forest. The forest structure data used were simple and inexpensive to collect, and data on avian traits were drawn from the literature. Thus, these methods could easily be replicated at other locations and would be valuable management aids and biodiversity assessment tools for conservation planning.  相似文献   

12.
We evaluated the effects of afforestation on the composition and structure of southern Brazilian subtropical grasslands directly beneath tree plantations, in pastures, and in permanent protection areas near watercourses. Cover of plants was registered in 120 plots of 1 m2 in grasslands located at two distances from small watercourses in pasture and eucalypt plantation areas within a livestock ranching landscape. Livestock density is reduced in plantation areas. Species composition beneath tree plantations was significantly different from both pasture and nearby permanent protection areas. Permanent protection areas near plantations were also compositionally different from pastures. Eucalypt plantation was the environment type where ruderals were most abundant. Growth form cover distribution in pasture areas showed a consistent pattern, with graminous herbs being the most common growth form followed by prostrate herbs, prostrate subshrubs, and standing subshrubs. In plantation areas, the dominance of the graminoid herb growth form increased markedly, as well as standing herbs. These increases occurred mainly at the expense of prostrate herbs and subshrubs, which were significantly reduced. Plot-level species density was significantly affected by distance from watercourse and, more importantly, was significantly influenced by the interaction between management regime and distance to watercourse. It was reduced in eucalypt plantations relative to permanent protected areas. Current management of eucalypt plantations in southern Brazil produce unsuitable conditions for grassland species to thrive within plantations. Livestock densities <1.0 animal unit ha?1 in eucalypt plantations undermines the ability of surrounding permanent protection areas to act as ecological networks for biodiversity conservation.  相似文献   

13.
The Serengeti–Mara ecosystem holds one of the largest natural grasslands of the world, which is well known for its large herds of mammals. However, the bird community structure of these grasslands has hardly ever been studied. For the first time, a large‐scale study on grassland bird communities has been conducted in all typical open grasslands of the Serengeti National Park. We used ten grassland plots representing a gradient of increasing vegetation height and also including shrubs and trees to analyse the influence of vegetation structure on the composition of grassland bird communities. Three communities of breeding birds were identified in relation to (a) short grass, (b) intermediate and long grass and (c) wooded grasslands. The bird communities of intermediate, long and wooded grassland were very similar, because of identical dominant bird species. Our results suggest that breeding birds of East African grasslands exhibit two contrasting habitat relationships: (1) birds that are restricted to short grass, and (2) species that are tolerant to vegetational shifts from intermediate grass via long grass to early stages of woody vegetation. Because the vegetation is often driven beyond this range in managed tropical grasslands through high grazing pressure or through shrub encroachment, we expect that the long‐grass bird communities will not generally resist anthropogenic disturbance.  相似文献   

14.
Tropical ecosystems are globally important for bird diversity. In many tropical regions, land‐use intensification has caused conversion of natural forests into human‐modified habitats, such as secondary forests and heterogeneous agricultural landscapes. Despite previous research, the distribution of bird communities in these forest‐farmland mosaics is not well understood. To achieve a comprehensive understanding of bird diversity and community turnover in a human‐modified Kenyan landscape, we recorded bird communities at 20 sites covering the complete habitat gradient from forest (near natural forest, secondary forest) to farmland (subsistence farmland, sugarcane plantation) using point counts and distance sampling. Bird density and species richness were on average higher in farmland than in forest habitats. Within forest and farmland, bird density and species richness increased with vegetation structural diversity, i.e., were higher in near natural than in secondary forest and in subsistence farmland than in sugarcane plantations. Bird communities in forest and farmland habitats were very distinct and very few forest specialists occurred in farmland habitats. Moreover, insectivorous bird species declined in farmland habitats whereas carnivores and herbivores increased. Our study confirms that tropical farmlands can hardly accommodate forest specialist species. Contrary to most previous studies, our findings show that structurally rich tropical farmlands hold a surprisingly rich and distinct bird community that is threatened by conversion of subsistence farmland into sugarcane plantations. We conclude that conservation strategies in the tropics must go beyond rain forest protection and should integrate structurally heterogeneous agroecosystems into conservation plans that aim at maintaining the diverse bird communities of tropical forest‐farmland mosaics.  相似文献   

15.
As conservation reserves expand, the likelihood that they will capture areas degraded by previous land use increases. Ecological restoration of such areas will therefore play an increasing role in biodiversity conservation. On the New South Wales North Coast, recent expansion in the conservation estate has captured over 300 softwood and hardwood plantations, many with understoreys dominated by exotic weeds. Here we present an overview of the practices we have adopted in managing flooded gum (Eucalyptus grandis) plantations infested with lantana (Lantana camara) to enhance their biodiversity value. Experiments designed to overcome barriers limiting regeneration of native forest in conjunction with measurement of soil and plant responses yielded insights into the management of former timber plantations for biodiversity. Canonical Correspondence Analysis indicated that the level of canopy retention (or logging intensity) within sites consistently explained the greatest amount of variation in plant community composition (32–38% post-treatment). Thinning and burning stimulated regeneration of native species. Retained canopy cover was proportional to the richness or abundance of native woody shrubs, understorey trees and native perennial herbs, indicating that management intensity can be varied to promote a range of conservation values. A state-and-transition model summarising purported management actions and likely outcomes for these plantations is presented. This is the first time plantations have been managed solely for biodiversity. Logging income means that plantation restoration can be cost-neutral, and the positive influence of a cover crop of trees means that plantation management may generally be manipulated to promote biodiversity conservation.  相似文献   

16.
Background: The rapid decline of semi-natural grasslands in Japan threatens many relic and endemic plant species. There is insufficient knowledge on how the impacts of land-use changes and management of grasslands have been affecting grassland ecosystems and what conservation measures may be taken to conserve as much of the existing plant diversity as possible.

Aim: We assessed the existing management regimes for their suitability for conserving Red Data Book (RDB) species.

Methods: We conducted our study in four districts of Kushima, Kyushu, south-west Japan, with different land-use histories. We compared species richness, plant density and abundance in six grassland types: regularly burnt, regularly mown, paddy levee, roadside, landslip and wetland communities in a total of 289 1 m x 1 m quadrats, recorded in172 grassland patches. Species richness plant density and abundance were analysed with special reference to RDB species under different land use history.

Results: Species richness of grasslands did not differ across different land use histories, yet our analysis showed that the reduced area of grasslands markedly affected the density of RDB species. Grassland types differed in their ability to support RDB species: regularly burnt grasslands were the richest in RDB species and poorest in alien species, followed by regularly mown grasslands, paddy levees, landslip, wetland and roadside communities.

Conclusions: Traditional management regimes, such as regular burning or mowing of grasslands have the best potential for conserving RDB species, and thus should be part of conservation management practices of semi-natural grasslands.  相似文献   

17.

Semi-natural grasslands in Japan have decreased due to management abandonment and urbanization over the last 100 years, but they remain in suburban areas in addition to rural areas. Because suburban grasslands have various land-use histories and disturbance regimes, plant and herbivorous insect communities are likely to differ among grassland types. To identify grasslands with high conservation value, we conducted a comprehensive survey of grasshoppers and plants in 150 grasslands with 5 grassland types differing in land-use history and current management in northern Chiba prefecture, Japan. We then analyzed the association of the distributions of grasshopper and plant species compositions. Our results showed that grasshoppers were classified into habitat specialists and generalists. Three out of four habitat specialists were almost exclusively found in semi-natural grasslands and vacant lots, while habitat generalists were commonly observed at the cropland margins. This habitat specialist–generalist distribution gradient corresponded well to that found in plant communities, which was probably due to current disturbance regimes. We suggest that vacant lots as well as semi-natural grasslands have high conservation value for grassland organisms of various taxa in suburban areas, and grasshoppers are candidate indicator species for monitoring grassland environments.

  相似文献   

18.
Land-use intensification leads to species loss and shifts in community composition, but only few studies examine how these dynamics affect ecological and life-history traits. We thus investigated whether ecological and life-history traits differ between butterfly communities of grasslands with different land-use intensity. We conducted butterfly transect surveys in 137 grassland sites in three regions of Germany and compiled 10 species-specific ecological and life-history traits from the literature. These traits are associated with food plant specialisation, dispersal, distribution, reproduction and development. We calculated a land-use intensity gradient based on the amount of fertilise mowing frequency and grazing intensity. We analysed differences of traits characteristics between butterfly communities along the land-use intensity gradient in a fourth-corner analysis, thus considering correlations between traits. Six ecological and life-history traits changed from characteristics associated with specialists to such associated with generalists with increasing land-use intensity. These traits characteristics in intensified grasslands were: high dispersal propensity, large distribution range, low population density, more than one generation per year, hibernation in a more advanced developmental stage and a long flight period. The functional homogenisation of the butterfly communities with changes from specialist to generalist trait characteristics with increasing land-use intensity may have severe consequences for ecosystem functioning and services.  相似文献   

19.
Islands are vulnerable ecosystems worldwide, increasingly exposed to human pressure, global climate change and invasive species. Thus, understanding island species diversity is key for nature conservation. Recent studies on insular plant communities indicated that habitat-specific species composition and richness might largely affect diversity patterns observed at the island scale. In consequence, habitat-based approaches are needed to (i) estimate how environmental changes at the habitat scale may affect island diversity, and to (ii) estimate the contribution of different patches of the same habitat to island diversity with respect to habitat-specific environmental constraints.In the present study, we tested these habitat-to-island diversity relationships for shoreline habitats (brackish reeds, salt marsh, rocky shore, tall herbs) and island interior habitats (rocks, semi-natural grassland, pioneer forest, coniferous forest, mixed forest) using 108 islands of three Baltic archipelagos in Sweden. These islands differed in terms of island-scale variables describing effects of island configuration and distance, and habitat-scale variables representing the effects of habitat area, abiotic environment and land-use.The studied habitats differed in their contribution to island species diversity, called habitat specificity. Shoreline habitats shared many common specialist species adapted to extreme conditions like sea salt or bird grazing, while habitats of the island interior harbored mainly species adapted to the specific conditions of a single habitat. We found high variability in habitat specificity as a consequence of habitat-specific environmental factors. Variability was highest for grasslands, where it was related to abandonment and soil fertility, stressing the importance of grassland management for maintaining island biodiversity. Habitats with high habitat specificity through either high species richness or many habitat-specific specialists should be the primary targets for biodiversity management.  相似文献   

20.
Anthropogenic habitat modifications, including conversion of forest to agricultural production cause losses of native species. In this study we examined the losses suffered by ant communities in relation to the intensity of management in cocoa plantations established in former tropical forest. An extensive sampling protocol consisting of pitfall trapping, leaf litter sampling, soil sampling and hand sampling was used to characterize ant species richness and composition in the native forest and compare it with three cocoa farms differing in their management intensity. Species richness was negatively correlated with management intensity and differed greatly between management practices and the forest. Two subfamilies (Myrmicinae and Amblyoponinae) showed a significant negative correlation with agricultural intensification probably because their species are constrained to living in forest like habitat. The species composition differed greatly between management practices and the forest. Intensively and moderately managed cocoa plantations were most dissimilar to the forest. In contrast, forest ants were well represented in the least intensively managed plantation. Overall, the findings of this study show that only slightly managed cocoa plantations sustain an ant diversity that comes close to that of the forest. This also holds true for cocoa plantations on former agricultural, and thus previously heavily used, land. The findings may help in the conservation of biodiversity as management practices most likely to sustain forest like ant communities have been identified.  相似文献   

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