bluuebunny/crossref_metadata_2025 huggingface dataset:
Directional and non‐directional vegetation changes in a temperate salt marsh in relation to biotic and abiotic factors
Authors: Schröder Henning K. , Kiehl Kathrin , Stock Martin
Published: February 2009

Abstract. The effects of reduction and cessation of sheep grazing on salt‐marsh vegetation were studied on a formerly intensively grazed salt marsh in northern Germany. Plant species cover was recorded in 45 permanent plots from 1992 to 2000. In 1995, physical and chemical soil parameters were analysed. Results of Redundancy Analysis (RDA) indicated that salinity and the depth of anoxic conditions below the surface were the most important soil factors related to the spatial vegetation pattern. Furthermore, plant species distribution was influenced by present and past grazing intensity, by soil grain size and nitrogen content.

Vegetation changes over 9 yr were analysed by non‐linear regression. The cover of Aster tripolium, Atriplex portulacoides, and, to a lesser extent, Artemisia maritima and Elymus athericus increased due to reduced grazing pressure, whereas the cover of Salicornia europaea decreased. After a strong increase in the first years Aster decreased 2 to 6 yr after abandonment. In the mid salt‐marsh zone Puccinellia maritima was replaced by Festuca rubra. The cover of Puccinellia, Festuca, Suaeda maritima, Glaux maritima and Salicornia fluctuated strongly, probably due to differences in weather conditions and inundation frequency. Species richness per 4 m2 generally increased while vegetation evenness decreased during the study period. Only in the high salt marsh abandoned for 9 yr did the number of species decrease slightly. Thus far, cessation of grazing did not lead to large‐scale dominance of single plant species.
Restoration of wooded meadows ‐ a comparative analysis along a chronosequence on Öland (Sweden)
Authors: Mitlacher K. , Poschlod P. , Rosén E. , Bakker J.P.
Published: February 2009

Abstract. Wooded meadows on the Baltic Island of Öland result from traditional agricultural management over centuries which has led to a species‐rich vegetation with high species diversity. Today, nearly all of these meadows have been abandoned and became rapidly overgrown by deciduous shrub and tree species forming a closed canopy which resulted in a rapid and strong decrease in species numbers of the herb layer. Recent efforts aim to restore overgrown wooded meadows by cutting single shrubs and trees to open the canopy. However, the effects of abandonment as well as of any restoration management in wooded meadows have rarely been documented until now. Mechanisms driving succession after restoration such as the dispersal potential of the respective species over time and space have not been analysed yet. Therefore, a chronosequence was studied which included a traditionally managed wooded meadow, an overgrown meadow which has been abandoned for more than 100 yr and a meadow which was restored 36 yr ago by cutting and is now grazed. We analysed the soil seed bank of the 3 meadows in comparison with the established vegetation and endozoochorous seed dispersal by cattle and sheep. After abandonment 87% of the typical grassland species vanished from the established vegetation and were replaced by species characteristic of woodland and disturbed grassland communities. The mean number of species decreased from 52 species per plot (4 m2) to 18 species. Mean species number and number of seeds in the seed bank declined significantly from the traditionally managed to the overgrown meadow. Most of the grassland species were assigned to a transient seed bank type while only 1/3 could be classified as having a short‐term persistent seed bank. Thus, restoration of wooded meadows cannot rely on the soil seed bank. Endozoochorous seed dispersal by cattle and sheep was shown for 15% of the species with seed densities per 100 g air dried dung of 737 and 767, respectively. Movement of animals between ancient and restored wooded meadows is recommended since many of the species only occurred in low densities and therefore, will probably not be found in the dung samples.
Species spread and persistence: implications for experimental design and habitat re‐creation
Authors: Pakeman Robin J. , Pywell Richard F. , Wells Terry C.E.
Published: February 2009

Abstract. The patterns of species establishment, persistence and spread in a long‐term experiment investigating the recreation of chalk grassland using different seed mixtures on ex‐arable land were analysed with the intention of providing enhanced re‐creation/restoration prescriptions and a critique of experimental designs. Species had a wide range of behaviours; (1) species that did not establish from seed e.g. Blackstonia perfoliata, (2) establishment but poor persistence in closed sward e.g. Hieracium pilosella, (3) establishment and persistence but little spread e.g. Onobrychis viciifolia and (4) good establishment and spread over all treatments e.g. Centaurea nigra and Trisetum flavescens. Persistence appeared greater in species with lower germination rates in both light and dark. Spread was greater in species with higher seed mass and lower dark germination rates.

However, results from small‐plot experiments should be critically analysed. Though initial results show the potential for re‐establishment of vegetation, subsequent vegetation dynamics may be more closely related to the invasion of species from other treatments than the original species sown. Experimental designs should employ either large plots and/or wide guard rows to extend their useful life span. Long‐term data show which species are useful for cost‐effective restoration. Some species need to be sown over the whole area to provide cover (a ‘grass matrix’) and competition with arable weeds. Others need to be sown over wide areas as they spread poorly. Some species can be sown at low densities or in small patches as they have the ability to spread in closed vegetation.
Comparison of species composition between different grassland management treatments after 25 years
Authors: Moog D. , Poschlod P. , Kahmen S. , Schreiber K.‐F.
Published: February 2009

Abstract. To identify management treatments suitable for the conservation of extensively managed grasslands, the ‘Fallow experiments in Baden‐Württemberg’ were set up in 1975. In this investigation, species composition of the grazing, mowing, mulching, controlled burning and unmanaged (succession) treatments were analysed after 25 yr of continuous management in Arrhenatherum elatius and Bromus erectus grasslands. Through ordination analyses it was found that species composition is strongly dependent on the management treatment. The first axis, identified by ordination analysis, essentially corresponded to a gradient of decreasing disturbance frequency. Controlled burning resulted in a unique species composition. Grazing, mowing and mulching twice a year were found to be most suitable for the conservation of unimproved, species‐rich grasslands.
Enhancing a regional vegetation map with predictive models of dominant plant species in chaparral
Authors: Franklin Janet
Published: February 2009

Abstract. Data from more than 900 vegetation plots surveyed in the evergreen shrublands of southern California were used to develop predictions of the distributions of eight dominant shrub species for a 3880 km2 region. The predictions, based on classification tree (CT) models, were validated using independent field data collected during a vegetation survey conducted in the 1930s. Presence and absence were correctly predicted an average of 75% of the time for the eight species. At the same time, these models minimized false positives, so that presence was predicted in the correct proportion of the cases for most species. The areal proportion of the landscape on which the species were predicted to occur was in the same rank order, and of the same magnitude, as their frequency (proportion of plots in which they occurred) within the field data sets. Predictive maps of species presence were overlaid and combined with an existing regional vegetation map. The shrub species ‘assemblages’ that resulted from this procedure had analogs with vegetation series defined using field data in previous studies. The resulting multiple species map will be used in a landscape simulation model of fire disturbance and succession.
Vegetation distribution in relation to topographically driven processes in southwestern Australia
Authors: Dirnböck T. , Hobbs R.J. , Lambeck R.J. , Caccetta P.A.
Published: February 2009

Abstract. This study assesses the utility of modelling approaches to predict vegetation distribution in agricultural landscapes of southwestern Australia. Climate surfaces, hy‐drologic and erosion process models are used to link vegetation to environmental variables. Generalized additive models (GAM) are derived for presence/absence data of mapped vegetation types. Vegetation distribution shows significant responses to rainfall and subsequent water redistribution due to the relief; however, these variables are insufficient to effectively explain vegetation patterns at the local scale. Accordingly, prediction accuracy remains low (κ‐values below 0.5). The striking unpredictability of the local distribution of the vegetation in the Wheatbelt is discussed with regard to the performance of topographically driven processes in subdued landscapes and with regard to geological, historical and biological factors determining the southwestern Australian plant species distribution.
Are invaders disturbance‐limited? Conservation of mountain grasslands in Central Argentina
Authors: Petryna L. , Moora M. , Nuñes C.O. , Cantero J.J. , Zobel M.
Published: February 2009

Abstract. Extensive areas in the mountain grasslands of central Argentina are heavily invaded by alien species from Europe. A decrease in biodiversity and a loss of palatable species is also observed. The invasibility of the tall‐grass mountain grassland community was investigated in an experiment of factorial design. Six alien species which are widely distributed in the region were sown in plots where soil disturbance, above‐ground biomass removal by cutting and burning were used as treatments. Alien species did not establish in undisturbed plots. All three types of disturbances increased the number and cover of alien species; the effects of soil disturbance and biomass removal was cumulative. Cirsium vulgare and Oenothera erythrosepala were the most efficient alien colonizers. In conditions where disturbances did not continue the cover of aliens started to decrease in the second year, by the end of the third season, only a few adults were established. Consequently, disturbances are needed to maintain alien populations in tall‐grass mountain grasslands. Burning also increased the species richness of native species. We conclude that an efficient way to control the distribution of alien species is to decrease grazing pressure while burning as a traditional management tool may be continued.
Differential and reversible responses of common fen meadow species to abandonment
Authors: Billeter Regula , Hooftman Danny A.P. , Diemer Matthias
Published: February 2009

Abstract. We studied the effects of abandonment on two common fen plant species. In mown and a chronosequence of abandoned fen meadows spanning 35 yr, we measured fitness traits of the sedge Carex davalliana and the forb Succisa pratensis. Cessation of mowing had little effect on fitness traits and seed production of C. davalliana, but seedling density decreased more than threefold. Population density of S. pratensis decreased with increasing community biomass, but was not affected by the cessation of mowing. However, flowering frequency increased threefold and seed production was 20% higher in fallow meadows. Consequently, seedling density of S. pratensis increased nearly threefold after abandonment. However, these changes were not dependent on the age of the fallow. In a common garden and germination experiment, we found no differences in either species between plants from fallows and mown fen meadows, except for the height of the flowering stalk of S. pratensis. The combined results from the common garden experiment and the field studies indicate that changes in fitness traits observed in fallows were mostly phenotypic and likely to be reversible. If other species react in similar ways, there is a high potential for re‐establishing traditional fen meadow communities from fallows by mowing.
Use of sheep grazing in the restoration of semi‐natural meadows in northern Finland
Authors: Hellström Kalle , Huhta Ari‐Pekka , Rautio Pasi , Tuomi Juha , Oksanen Jari , Laine Kari
Published: February 2009

Abstract.The biodiversity of species‐rich semi‐natural meadows is declining across Europe due to ceased management. In this study we aimed to find out how successfully the local species richness of an overgrown semi‐natural mesic meadow could be restored by sheep grazing after a long period of abandonment. The cover of vascular plant species in grazed plots and ungrazed exclosures was studied for five years and the responses of different functional plant groups were followed (herbs vs grasses, tall vs short species, species differing in flowering time, species representing different Grime's CSR strategies and species indicative of rich vs poor soil). Grazing increased species number by nearly 30%. On grazed plots the litter cover practically disappeared, favouring small herbs such asRhinanthus minor, Ranunculus acris, Trifolium pratenseand the grassAgrostis capillaris.Grazing decreased the cover of the late flowering tall herbEpilobium angustifoliumbut had no effect on the abundance of the early flowering tall herbsAnthriscus sylvestrisorGeranium sylvaticum.We suggest that to succeed in restoration it is useful to determine the responses of different functional plant groups to grazing. Grassland managers need this information to optimize the methods and timing of management used in restoration. Additional management practices, such as mowing, may be needed in mesic meadows to decrease the dominance of tall species. The availability of propagules seemed to restrict further increase of species richness in our study area.
Floristic variation and willow carr development within a southwest England wetland
Authors: Southall EJ. , Dale M.P. , Kent M.
Published: February 2009

Abstract. Woodland colonization on wetlands is considered to have a detrimental effect on their ecological value, even though detailed analysis of this process is lacking. This paper provides an evaluation of the ecological changes resulting from succession of poor fen (base‐poor mire) to willow wet woodland on Goss Moor NNR in Cornwall, UK. Different ages of willow carr were associated with eight understorey communities. During willow colonization, in the ground flora, there was a progressive decrease in poor fen species and an associated increase in woodland species, which appeared to be related to an increase in canopy cover and therefore shade. The most diverse community was found to be the most recent willow and was dominated by poor fen species. The oldest willow was the second most diverse and was associated with a reduction in poor fen species and an increase in woodland species. Architectural features were used successfully to assess the general condition and structure of willow. Tree height and DBH were identified as useful parameters to accurately assess willow age in the field. The implications of active intervention to remove willow in order to conserve the full range of communities within the hydrosere are discussed.
Restoration of cut‐over bogs by floating raft formation: An experimental feasibility study
Authors: Tomassen Hilde B.M. , Smolders Alfons J.P. , van Herk J.M. (Marjo) , Lamers Leon P.M. , Roelofs Jan G.M.
Published: February 2009

Abstract.Stimulation of floating peat by the introduction of poorly humified peat from four cut‐over bogs in The Netherlands was studied in a one‐year outdoor experiment. The pH of the various peat substrates was increased by adding different amounts of lime: 0–2 to 4–8 g‐CaCO3.kg‐1fresh peat. Both peat type and lime addition were found to affect the buoyancy of the peat substrates. Low nutrient concentrations in the peat, together with a high bulk density, proved to be unfavourable for creating floating peat. Three of the peat types proved to be too acidic (pH < 4.5) to produce sufficient methane (ca. 400–600 μmol.L‐1), and buoyancy was only achieved if lime was mixed in with the peat. The smallest amount of lime added (2 g.kg‐1fresh peat) was sufficient to maintain buoyancy for at least one year. Lime addition did not stimulate nutrient mobilization by mineralization, although P, N and K concentrations in the peat water were relatively high. It is concluded that floating peat can be initiated by the introduction of poorly humified peat. If the peat substrates are too acidic, lime can be added to stimulate buoyancy of the peat. Results are discussed in relation to restoration prospects.
Ecohydrology of saline grasslands: Consequences for their restoration
Authors: Beyen Wouter , Meire Patrick
Published: February 2009

Abstract. By the approval of the European Bird Directive (79/409/EEC) in 1979 and the Habitat Directive (92/43/EEC) in 1992, nature protection has become an important part of European law with direct consequences for land use, industrial development and agriculture. If a member state reclaims an area that is protected by these directives, it has to take compensational measures. When such an area includes saline grasslands that require very specific abiotic conditions, a place with similar conditions must be available to re‐establish those grasslands at another location in a sustainable way. This will limit the number and extent of possible sites for compensation.

In the conflict between economy and ecology in the Schelde polders, Flanders has chosen to expand the port of Antwerp in the polders at the left Schelde bank and destroy a protected saline grassland site. As a consequence, it has to compensate for this loss. Therefore, we made a detailed study of the hydrology, geology and soil conditions of the endangered saline grassland site. The same was done in four possible compensation sites, all situated in nearby polders. We found that the presence of upwelling groundwater flowing through a saline peat layer is necessary for the occurrence of saline grasslands. Only in one of the four possible compensation sites, called Muggenhoek, we found such conditions. So, we indicate this place as a possible site for the re‐creation of saline grasslands and give some recommendations for their development.
Restoration prospects of abandoned species‐rich sandy grassland in Hungary
Authors: Matus G. , Tóthmérész B. , Papp M.
Published: February 2009

Abstract. Secondary succession and seed bank formation was studied in a formerly grazed, abandoned, eastern Hungarian sandy steppe‐meadow (Pulsatillo‐Festucetum). The vegetation was sampled at different elevations of a sand dune which became partly invaded by the tree Robinia pseudo‐acacia ca. 10 yr ago. Pre‐abandonment vegetation records were used as historic references. Though composition of the non‐invaded grassland only changed moderately, dominance of tall grasses (Elymus hispidus, Poa angustifolia) increased significantly at the cost of annuals and low stature perennials. In the stand invaded by Robinia most grassland species were lost and replaced by nitrophytes. Vertical position influenced species abundance, but affected the composition only moderately. Fine‐scale zonation of the vegetation also changed with time. Species richness of the above‐ground vegetation and the seed density of soil samples at the lower elevation were slightly greater than at the higher sites.

Seed banks of sensitive grassland specialists (e.g. Pulsatilla pratensis subsp. hungarica) disappeared during grass encroachment. Following extinction from above‐ground vegetation, restoration must rely on dispersal from adjacent areas. In contrast, several annuals and perennials, which survived this degradation stage in the above‐ground vegetation, possessed seed banks. Many of these species became extinct from the vegetation during the Robinia invasion but left viable persistent seeds. This fact is promising for restoration of the Potentillo‐Festucetum sandy pasture. Competitive weedy species and sprouting Robinia can, however, limit seedling establishment.
Spontaneous vegetation dynamics and restoration prospects for limestone quarries in Lebanon
Authors: Khater Carla , Martin Arnaud , Maillet Jacques
Published: February 2009

Abstract. In terms of restoration planning, the analysis of natural regeneration processes represents a valuable starting point for the selection of suitable species to be used. This paper aims to identify colonizing key species among the pioneer vegetation of limestone quarries in Lebanon, to identify potential restoration strategies in terms of reconstitution of the pre‐mining vegetation cover. Characteristics of the major ground colonizers after disturbance were identified in a representative quarry in the thermo‐Mediterranean biozone. The floristic inventories resulted in a matrix of cover values of 107 species × 14 plots. Correspondence analyses were used to pinpoint similarities in the distribution of key species among the different environmental characteristics of sites. The main results reveal a heterogeneous floristic composition along the regeneration gradient, where annual R‐strategy taxa such as Inula viscosa and Ainsworthia cordata dominate on very perturbed and degraded sites. Less degraded areas within the quarry were rich in herbaceous perennial or shrub species such as Geranium dissectum, Stachys distans, Salvia triloba and Ptilostemon chamaepeuce. On relatively non‐degraded areas woody and shrub perennials such as Pinus brutia, Pistacia palaestina and Quercus calliprinos dominate, along with less stress tolerant taxa such as Arbutus andrachne and Cistus creticus. Species to be used in restoration projects should be chosen from among the local vegetation, according to frequency of occurrence during the whole succession process which will reflect their adaptability to local conditions and their relevance to restoration objectives.
Effects of winter mowing on vegetation succession in a lakeshore fen
Authors: Güsewell Sabine , Le Nédic Christophe
Published: February 2009

Abstract. To assess whether winter mowing in wetlands fulfils the aim of preventing succession towards drier communities, 34 permanent quadrats (15 m2) were surveyed annually from 1984–1985 to 2000 within large mown and unmown (control) areas (several ha) in a calcareous lake shore fen (W Switzerland). Three trends were noticed: decrease of aquatic species, spread of Cladium mariscus and establishment of woody species (especially Alnus glutinosa and Frangula alnus). None of these trends was prevented by mowing, but mowing did prevent the accumulation of C. mariscus litter and kept woody saplings small. Succession was generally slow and often occurred in the form of sudden, discrete changes. Plant species richness increased with mowing and remained constant without mowing. Soil disturbance by the mowing machine contributed more to the effects of management on species composition than the periodic removal of biomass. It is concluded that mowing every three years in winter is insufficient to preserve semi‐aquatic communities against succession but sufficient to maintain the plant species richness of a low productive, regularly flooded fen.
Developing a classifier for the Habitats Directive grassland types in Denmark using species lists for prediction
Authors: Ejrnaes Rasmus , Bruun Hans Henrik , Aude Erik , Buchwald Erik
Published: February 2009

Abstract. This paper describes the use of supervised methods for the classification of vegetation. The difference between supervised classification and clustering is outlined, with reference to their current use in vegetation science. In the paper we describe the classification of Danish grasslands according to the Habitats Directive of the European Union, and demonstrate how a supervised classification can be used to achieve a standardized and statistical interpretation within a local flora. We thereby offer a statistical solution to the legal problem of protection of certain selected habitat types. The Habitats Directive protects three types of Danish grassland habitats, whereas two remaining types fall outside protection. A classification model is developed, using available Danish grassland data, for the discrimination of these five types based on their species composition. This new Habitats Directive classification is compared to a previously published unsupervised classification of Danish grassland vegetation. An indicator species analysis is used to find significant indicator species for the three protected habitat types in Denmark, and these are compared to the characteristic species mentioned in the interpretation manual of the Habitats Directive. Eventually, we discuss the pros and cons of supervised and unsupervised classification and conclude that supervised methods deserve more attention in vegetation science.
Seed dispersal by cattle may cause shrub encroachment of Grewia flava on southern Kalahari rangelands
Authors: Tews Jörg , Schurr Frank , Jeltsch Florian
Published: February 2009

Abstract. Shrub encroachment, i.e. the increase in woody plant cover, is a major concern for livestock farming in southern Kalahari savannas. We developed a grid‐based computer model simulating the population dynamics of Grewia flava, a common, fleshy‐fruited encroaching shrub. In the absence of large herbivores, seeds of Grewia are largely deposited in the sub‐canopy of Acacia erioloba. Cattle negate this dispersal limitation by browsing on the foliage of Grewia and dispersing seeds into the grassland matrix. In this study we first show that model predictions of Grewia cover dynamics are realistic by comparing model output with shrub cover estimates obtained from a time series of aerial photographs. Subsequently, we apply a realistic range of intensity of cattle‐induced seed dispersal combined with potential precipitation and fire scenarios. Based on the simulation results we suggest that cattle may facilitate shrub encroachment of Grewia. The results show that the severity of shrub encroachment is governed by the intensity of seed dispersal. For a high seed dispersal intensity without fire (equivalent to a high stocking rate) the model predicts 56% shrub cover and 85% cell cover after 100 yr. With fire both recruitment and shrub cover are reduced, which may, under moderate intensities, prevent shrub encroachment. Climate change scenarios with two‐fold higher frequencies of drought and wet years intensified shrub encroachment rates, although long‐term mean of precipitation remained constant. As a management recommendation we suggest that shrub encroachment on rangelands may be counteracted by frequent fires and controlling cattle movements to areas with a high proportion of fruiting Grewia shrubs.
Relative growth rate and hemerobiotic state in the assessment of disturbance gradients
Authors: Fanelli G. , De Lillis M.
Published: February 2009

Abstract. A method is discussed for describing the intensity of disturbance, based on the floristic composition of vegetation types. It includes the development of a hemerobiotic scale (from hemeros= cultivated). We attempted to relate this scale based on floristic patterns with functional parameters.

Following a large phytosociological survey of the Roman area, we selected 19 species of herbs and grasses, widely differing in ‘hemeroby’, and measured their Relative Growth Rate (RGR). RGR varies between 0.13 and 0.21 d‐1. A significant correlation between mean hemerobiotic value, resulting from the phytosociological study, and measured RGR of juvenile plants emerges. Although Specific Leaf Area (SLA) is highly correlated with RGR, and thus explains most of its variations, as previously found in other studies, it is only weakly related to hemerobiotic state. An additional data set with 78 species from the literature supports the conclusions. This approach allows a functional quantification of hemeroby which enables useful applications, for instance in cartography. A biotope map showing a steep gradient of disturbance impact in the city of Rome is presented as a preliminary test.
Impact of management and habitat on demographic traits of Primula vulgaris in an agricultural landscape
Authors: Endels Patrick , Jacquemyn Hans , Brys Rein , Hermy Martin
Published: February 2009

Question: Is demographic performance of Primula vulgaris correlated with habitat characteristics of the small landscape elements in which it occurs? Can we use this species as an indicator for species‐rich semi‐natural habitats?

Location: Flanders, Belgium.

Methods: To capture differences in demographic traits and habitat characteristics, both within and between populations, a two‐level survey was carried out. Population size and structure of 89 P. vulgaris populations in different types of small landscape elements was recorded in 1999. At plot level, densities of different life stages were determined and these were related to edaphic conditions and vegetation structure and composition.

Results: Three different population types were distinguished: (1) dynamic populations, characterized by seedling and juvenile proportions, (2) normal populations with relatively more adults, but with considerable numbers of seedlings and juveniles and (3) senescent populations, mainly consisting of adults. Senescent populations were significantly smaller than populations with a dynamic demographic structure. At plot level, comparison of demographic characteristics between different management regimes revealed that recruitment rates and total plant density of P. vulgaris were highest in plots that received a regime that included mowing and clearing of ditch banks whereas densities were lower along forest edges. For these plots, it was shown that nutrient levels were higher. Densities of adults as well as juvenile and seedling densities were negatively correlated with vegetation height.

Conclusions: Local disturbance and heterogeneity may mask the relationship between unfavourable conditions and demographic characteristics at population level, but it is clear that in small populations recruitment needs to be lifted to guarantee its persistence. Performance of P. vulgaris in small landscape elements can be a first indication of plant species diversity in small landscape elements.
Vegetation ofSphagnumbogs in highly disturbed landscapes: relative influence of abiotic and anthropogenic factors
Authors: Lachance Daniel , Lavoie Claude
Published: February 2009

Question:Has the vegetation ofSphagnumbogs been affected by more than 200 years of human activities?

Location:Bas‐Saint‐Laurent region, southeastern Québec, Canada.

Methods:Data (species assemblages, abiotic and spatio‐historical variables) were collected in 16 bogs ranging from 2 to 189 ha, and incorporated in a geographical information system. Major gradients in vegetation composition were identified using DCA. CCA was used to relate vegetation gradients to abiotic and spatio‐historical variables.

Results:A clear segregation of species assemblages was observed, from open and undisturbed bogs to forested and highly disturbed sites. Among abiotic factors, tree basal area, water table level and peat thickness had a significant influence on plant species composition. Among spatio‐historical factors, disturbance level, area loss and fire were the most influential factors. Variance partitioning between these groups of factors suggests that spatio‐historical factors had a major influence on peatlands, representing 22% of the variation observed in the plant species assemblages while abiotic factors represent only 17% of the variation.

Conclusions:The results highlight the influence of agricultural and other anthropogenic activities on plant assemblages and suggest that even wetlands apparently resistant to disturbances, such as peatlands, can be severely affected by anthropogenic factors. Plant species assemblages of ombrotrophic peatlands of the Bas‐Saint‐Laurent region were, and still are, largely influenced by human activities.
A test of the use of NDVI data to predict secondary productivity
Authors: Posse Gabriela , Cingolani Ana María
Published: February 2009

Question: How well does the use of NDVI predict secondary productivity at landscape scales? What is the influence of vegetation quality and phenology over secondary productivity?

Location: Magellanic steppe in Tierra del Fuego, Argentina. (52°45’to 54° S, 68°15’to 67°30’W).

Methods: Monthly and yearly integrated NDVI (NDVI‐I) were calculated from AVHRR/NOAA 14, as estimators of phenology and aerial net primary productivity respectively. From a vegetation map we obtained the proportional cover of different physiognomic types and calculated the palatable fraction (forage) productivity that were used as estimators of vegetation quality. Data were analysed through correlations and regressions.

Results: NDVI‐I was not related with secondary productivity indices, while December and annual maximum NDVI, proportion of lawns and tussock grasslands and forage productivity were positively related with secondary productivity. A negative relationship was found between the proportion of heathlands and secondary productivity, but a positive relationship between heathland's proportion and NDVI‐I was found.

Conclusions: NDVI‐I is not a good predictor of secondary productivity at the scale of our study. These results could be due to: (1) NDVI‐I is not related to primary productivity and (2) primary productivity is not related to secondary productivity.
Experimental restoration of a fen plant community after peat mining
Authors: Cobbaert D. , Rochefort L. , Price J.S.
Published: February 2009

Question: Which restoration measures (introduction of donor diaspore material, application of straw mulch, alteration of residual peat depths) contribute to the establishment of a fen plant community on minerotrophic surfaces after peat mining?

Location: Rivière‐du‐Loup peatland, southern Québec, Canada at 100 m a.s.1.

Methods: The effectiveness of introducing fen plants with the application of donor diaspore material was tested. The donor diaspore material, containing seeds, rhizomes, moss fragments, and other plant propagules, was collected from two different types of natural fens. We tested whether the application of straw mulch would increase fen species cover and biodiversity compared to control plots without straw mulch. Terrace levels of different peat depths (15 cm, 40 cm, and 56 cm) were created to test the effects of different environmental site conditions on the success of re‐vegetation.

Results: Applying donor seed bank from natural fens was found to significantly increase fen plant cover and richness after the two growing seasons. Straw mulch proved to significantly increase fen plant richness. The intermediate terrace level (40 cm) had the highest fen plant establishment. Compared to reference sites, the low terrace level (15 cm) was richer in base cations, whereas the high terrace level (56 cm) was much drier.

Conclusions: The application of donor diaspore material was demonstrated as an effective technique for establishing vascular fen plants. Further re wetting measures are considered necessary at the restoration site to create a fen ecosystem rather than simply restoring some fen species.
Development ofBrachystegia‐Julbernardiawoodland after clear‐felling in central Zambia: Evidence for high resilience
Authors: Chidumayo E.N.
Published: February 2009

Question:Does the development ofBrachystegia‐Julbernardia(miombo) woodland after felling, and under a variable fire regime, occur via a serai stage of fire‐tolerant species?

Location:Four sites in central Zambia, Africa.

Methods:Trees in replicate plots were clear‐cut and stumps and resprouts enumerated. Species recruited into the tree layer (> 2.0 m tall) were monitored for 11 years (1991–2001) and fire occurrence and herbaceous biomass assessed annually to determine fuel loads.

Results:Fire frequency was variable at the study sites and fuel loads were generally too low to suppress woodland regeneration after felling. However, at one site a change from low to high fire frequency arrested woodland development and triggered a regression towards a ‘fire‐trap’ vegetation type in which a few fire‐tolerant species survived. There was no evidence to support the hypothesis that miombo woodland regeneration is facilitated by a sere of fire‐tolerant species. All regrowth after felling was from resprouting plants present before felling. Trees with a previous history of felling sprouted more vigorously than trees that had not been felled before. Species richness in the tree layer increased with time since felling because resprout species had different height growth rates.

Conclusion:The resilience of miombo trees after clear‐felling is largely due to their capacity to regenerate vegetatively from resprouts and stumps after release from frequent fires. Coppicing is therefore recommended as a suitable management technique for miombo woodland in central southern Africa.
Effects of leaf litter and precipitation on germination and seedling survival of the endangered tree Beilschmiedia miersii
Authors: Becerra Pablo I. , Celis‐Diez Juan L. , Bustamante Ramiro O.
Published: February 2009

Question: What effects do leaf litter and rainfall regime have on seed germination (time and probability) and seedling survival of the endangered tree species Beilschmiedia miersii (Lauraceae)?

Location: The species is a native tree from the mediterranean climate region of Chile. Seeds were collected from La Campana National Park (Chile). The study was carried out under controlled conditions at the Laboratory of Ecology, University of Chile, Santiago, Chile.

Methods: During April 2001,200 seeds were assigned to four experimental treatments: high precipitation, with and without litter and low precipitation, with and without litter. Each treatment had 50 individual seeds, each seed in an individual pot. For statistical purposes, we considered each seed as one replicate. High and low values of artificial rainfall corresponded to mean dry and wet years, respectively, for the period 1958–1993 in the central zone of Chile.

Results: Seeds germinated earlier, and in higher proportion, in the presence of leaf litter, but only under low rainfall. Seedling survival was insensitive to both litter and precipitation.

Conclusions: We conclude that the presence of litter in native populations facilitates seed germination and recruitment of B. miersii, particularly during dry years. We suggest that the reduction of leaf litter due to extraction for gardens and horticultural activities might preclude regeneration of this endangered species.
Does the seed bank contribute to the restoration of species‐rich vegetation in wet dune slacks?
Authors: Bakker Chris , de Graaf Heiko F. , Ernst Wilfried H.O. , van Bodegom Peter M.
Published: February 2009

Questions: What is the contribution of the seed bank to restoration of species‐rich vegetation in oligotrophic wet dune slacks? Does the restoration management affect the seed bank?

Location: Calcareous coastal dune slacks at the west coast of The Netherlands.

Methods: Species composition of the seed bank and the above‐ground vegetation was sampled in dune slacks that had a variable extent of groundwater level rise in combination with either topsoil removal or mowing.

Results: The seed bank had a high potential for restoration of species‐rich vegetation: 60 species were found in the seed bank of which 14 were characteristic of oligotrophic, wet dune vegetation. While topsoil removal almost completely removed the seed bank, groundwater level rise did not permanently submerge the seed bank of species of oligotrophic, wet conditions. Changes in abundance in the established vegetation were unrelated to species abundance in the seed bank. Of all new species establishments in the vegetation relevés, 76% occurred where the species was not found in the seed bank. The chance that presence of a species in the seed bank led to establishment the following year was only 11%.

Conclusion: The seed bank was not the dominant source for newly establishing species following the large disturbance that was induced by restoration management. Changes in species abundance after the restoration impact were not related to species abundance in the seed bank, but to ongoing succession and current year dispersal. To attain a high number of new establishments, restoration projects should preferably be planned in the proximity of refuge populations, rather than relying on the seed bank alone.
Invasion of Pinus halepensis from plantations into adjacent natural habitats
Authors: Lavi Ayala , Perevolotsky Avi , Kigel Jaime , Noy‐Meir Imanuel
Published: February 2009

Questions: Do invasions of P. halepensis (Aleppo pine) from plantations into adjacent natural communities occur in the Mediterranean region, where the species is native? What are the spatio‐temporal processes involved in pine invasions in contrasting Mediterranean and semi‐arid climatic regions?

Location: Mediterranean and semi‐arid regions of Israel.

Methods: The density of invading Pinus was measured in relation to the distance from the plantation edge. Plants were categorized by age, height, basal stem girth and developmental stage, their spatial distribution was also recorded.

Results: Analysis of plant age distribution indicates that the invasion process started when the plantations were 20–25 years old. Most invading plants were found within 20 m from the plantation edge, but a few individuals reached distances up to 100 m and became new invasion foci. Plant density declined sharply with distance from adult trees, data showing a better fit to a power model than to a negative exponential model. Invading Pinus began to produce cones earlier in the semi‐arid than in the Mediterranean region (9 vs 12 years to 50% reproductive plants). In both regions, higher densities of invading plants were found on the west side of the plantation, the opposite direction to the hot winds that prevail during seed release.

Conclusion: The frontal advance of P. halepensis from plantations is relatively slow, but the populations also expand by a saltation process, creating spreading ‘islands’ of pine trees in the natural vegetation. Spatial pattern of recruits with distance from the source population was remarkably similar to the pattern of seed dispersal in the same region (Nathan et al. 1999). This implies that the probability of a dispersed seed developing into a plant is independent of the distance from the forest edge.
Soil seed banks in Pinus ponderosa forests in Arizona: Clues to site history and restoration potential
Authors: Korb Julie E. , Springer Judith D. , Powers Stephanie R. , Moore Margaret M.
Published: February 2009

Question: How does the relationship between the viable soil seed bank species composition and the above‐ground vegetation in northern Arizona Pinus ponderosa forests differ under varying historical land use disturbances (low, intermediate, high)? Is above‐ground vegetation correlated to the viable soil seed bank immediately following soil disturbance from restoration thinning treatments?

Location: Northern Arizona, USA.

Methods: Soil seed bank samples were taken along replicated transects and collected with a 5‐cm diameter bulk density hammer. Samples included a 5 ‐cm diameter O‐horizon sample (at varying depths) plus the underlying mineral soil to a depth of 5 cm. The seedling emergent method was used to quantify seed bank species composition and density. The herbaceous and shrub plant community was quantified along the same transects using the point intercept method.

Results: Early‐successional or ruderal species were common in the soil seed bank at all three disturbance sites. Non‐native species, notably Verbascum thapsus, were more numerous (up to 940 seeds/m2) under high disturbance with overgrazing and logging, and less common or absent under low disturbance. Most viable seeds were found in the O‐horizon and the upper 5 cm of mineral soil; there was little correlation between species in the soil seed bank and the above‐ground vegetation.

Conclusions: We recommend that restoration plans be geared toward minimizing activities, such as severe soil disturbance, that may promote the spread of non‐native invasive species, and that manual seeding be explored as an option to restore plant species diversity and abundance.
Combining land cover mapping of coastal dunes with vegetation analysis
Authors: Acosta A. , Carranza M.L. , Izzi C.F.
Published: February 2009

Question: Coastal dune systems are characterized by a natural mosaic that promotes species diversity. This heterogeneity often represents a severe problem for traditional mapping or ground survey techniques. The work presented here proposes to apply a very detailed CORINE land cover map as baseline information for plant community sampling and analysis in a coastal dune landscape.

Location: Molise coast, Central Italy.

Method: We analysed through an error matrix the coherence between land cover classes and vegetation types identified through a field survey. The CORINE land cover map (scale 1: 5000) of the Molise coast was used with the CORINE legend expanded to a fourth level of detail for natural and semi‐natural areas. Vegetation data were collected following a random stratified sampling design using the CORINE land cover classes as strata. An error matrix was used to compare, on a category‐by‐category basis, the relationship between vegetation types (obtained by cluster analyses of sampling plots) and land cover classes of the same area.

Results: The coincidence between both classification approaches is quite good. Only one land cover class shows a very weak agreement with its corresponding vegetation type; this result was interpreted as being related to human disturbance.

Conclusions: Since it is based on a standard land cover classification, the proposal has a potential for application to most European coastal systems. This method could represent a first step in the environmental planning of coastal systems.
Effects of tree species composition on within‐forest distribution of understorey species
Authors: van Oijen Danielle , Feijen Markus , Hommel Patrick , den Ouden Jan , de Waal Rein
Published: February 2009

Question: Do tree species, with different litter qualities, affect the within‐forest distribution of forest understorey species on intermediate to base‐rich soils? Since habitat loss and fragmentation have caused ancient forest species to decline, those species are the main focus of this study.

Location: Three ancient forests, along a soil gradient from acidification‐sensitive to base‐rich, were studied: Limbrichterbosch and Savelsbos in The Netherlands and Holtkrat in Denmark.

Methods: Canopy and soil surveys along transects generated data for Redundancy Analysis on tree – humus relationships. We analysed the distribution of forest plant species with Canonical Correspondence Analysis. The explanatory factors were soil characteristics (pH, organic matter, loam content and thickness of the humus layers), external crown projection, ground water and canopy data. We further analysed the relationship between forest species and humus characteristics with Spearman correlations.

Results: Tree species have a significant impact on humus characteristics through the nature of their litter. Humus characteristics significantly explain the distribution of forest understorey species. The pH of the first 25 cm mineral soil and the thickness of the F‐ (fermentation) layer are the primary factors affecting the distribution of ancient forest species.

Conclusion: This study indicates that the species composition of the forest canopy affects the distribution of forest understorey species. Ancient forest species are more abundant and frequent underneath trees with base‐rich litter. On acidification‐sensitive soils these relationships were stronger than on more base‐rich, loamy soils.