bluuebunny/crossref_metadata_2025 huggingface dataset:
Plant communities in kettle‐holes in central Poland: chance occurrence of species?
Authors: Ka'mierczak Ewa , van der Maarel Eddy , Noest Vera
Published: May 2006

Abstract. Plant communities occurring in kettle‐holes in the Ziemia ChemiÄska area, northern central Poland are described. These depressions of Late‐Glacial origin have gradually become part of the agricultural landscape, but many of them still have semi‐natural vegetation. 829 phytosociological relevés were made in 116 kettle‐holes; an environmental description included (a) for each relevé: soil type, depth of phreatic water table in summer, pH; and (b) for the depression as a whole: size, form, distance to nearest kettle‐hole, distance to nearest potential source of disturbance, actual occurrence of a severe disturbance, notably inflow of liquid manure.

On the basis of various cluster analyses 120 basic clusters with 113 characterizing species (out of a total of 217 species) were obtained. No less than 29 clusters consist of only one relevé and 57% have no more than four relevés. Most clusters have only one constant ‐ and often dominant ‐ species. 49 species occur only once and 62 % occur in less than 1 % of the relevés. The clusters show little ecological coherence.

Correspondence Analysis of the data set showed the occurrence of many outlier samples and species; a moisture and a eutrophication gradient were revealed by Canonical Correspondence Analysis.

The lack of coherence between the variation in community types and variation in environmental factors is explained by assuming a chance occurrence of species, which appear and disappear as in the case of species‐rich grasslands where a large small‐scale species turnover takes place (described as the carousel model). The kettle‐holes may provide a small number of broad habitat types, within each of which several species may form short‐lived plant communities. Indeed, many locally dominant kettle‐hole species are short‐lived perennials or therophytes, which may come and go, while sharing the same habitat. This hypothesis has to be tested through repeated vegetation analysis.
Seed demography of three co‐occurring Acer species in a Japanese temperate deciduous forest
Authors: Tanaka Hiroshi
Published: May 2006

Abstract. Seed demography of three co‐occurring Acer species in an old‐growth mixed deciduous forest in Japan was studied. Almost all of the seeds of A. mono germinated in the first spring, while those of A. palmatum var. amoenum showed a delay in germination of almost one year. A. rufinerve showed a rather opportunistic germination habit. Both A. palmatum var. amoenum and A. rufinerve form short‐term persistent seed banks, but without input of newly dispersed seeds they may become extinct in about one year. The seed bank for these two species is not as significant as for a typical pioneer species, and the seedling bank is important for all three species. Only a small proportion of the dispersed propagules contained viable embryos, mainly due to pollination failure or abortion (A. mono and A. palmatum var. amoenum), and invertebrate predation (A. rufinerve). For all three species, larger seed crops had a higher percentage of viable seeds. Even for these relatively small, wind‐dispersed seeds, the predation pressure was very high. A large part of the dispersed seeds was eaten by wood mice during the first winter (30–80 %). Estimation from the 5‐yr average of seed dispersal and seedling emergence showed that only 7–16 % of the dispersed viable seeds succeeded in germinating.
Disturbance effects on herbaceous layer vegetation and soil nutrients in Populus forests of northern lower Michigan
Authors: Roberts M.R. , Gilliam F.S.
Published: May 2006

Abstract. Recent disturbance models have identified changes in resource availability as factors that control plant community response. Soil nutrient resources typically are assumed to change following forest disturbance, usually with nutrient availablity increasing initially and subsequently decreasing through later stages of succession. We examined the effects of disturbance (clearcut harvesting with a brief recovery period) on soil organic matter, pH and extractable soil nutrients in successional aspen forests of northern lower Michigan to determine relationships of these variables to changes in herbaceous layer vegetation. Two site types were identified: drymesic (glacial outwash sands, low in organic matter) and mesic (calcareous clay till, high in organic matter). Extractable nutrient concentrations were 1.5 to 3 times higher in the A1 horizon of mesic sites than those of dry‐mesic sites. Soil pH and cations increased after disturbance on mesic sites, but not on dry‐mesic sites. Patterns of change with disturbance were less pronounced in lower horizons on both site types. Herblayer species diversity increased after disturbance on mesic sites, but with decreases in the importance of shade‐tolerant tree species and Maianthemum canadense. Species characteristic of open habitats (e.g. Pteridium aquilinum, Rubus spp., Fragaria virginiana, and Diervilla lonicera), increased in importance. Soil factors, species composition and diversity on dry‐mesic sites changed little after disturbance, with Pteridium aquilinum and ericaceous species remaining dominant in both mature (55–82 yr) and disturbed (≤ 15 yr) stands.

These results suggest that soil nutrient resources do not always change through secondary succession and that patterns of change can be distinctly site‐dependent. Disturbance response patterns in the herbaceous layer of these aspen forests are also site‐dependent.
Pattern and process in the plant community: Fifty years after A.S. Watt
Authors: Van Der Maarel Eddy
Published: May 2006

Abstract. This paper is a tribute to A.S. Watt who published his ‘Pattern and process in the plant community’ almost 50 years ago. Watt's interpretation of the plant community “as a working mechanism, which maintains and regenerates itself” is still highly relevant, although the keywords have changed. ‘Process’ in Watt's view involves both upgrade and downgrade aspects, whereas ‘Pattern’ was not specified, neither quantified. Nowadays, process is mainly approached as ‘disturbance’, that is natural disturbance and ‘pattern’ as patch structure. Together they make up the ‘patch dynamics’ of the community. Some implications of patch dynamics for phytosociology are discussed. A ‘Wattian’ concept of the plant community combines the Gleasonian idea of individualistic behaviour of species with the Clementsian (or rather Braun‐Blanquetian) notion of community dynamics. Later work by Harper (demography), Grubb (regeneration niche) and earlier work of Sernander (forest gap dynamics) is significant for the understanding of the patch‐dynamic nature of the community.

Recent interest in plant species mobility can easily be linked to the concept of patch dynamics. Examples of mobility in a limestone grassland are given and a system of mobility types is proposed.

Some perspectives for the study of patch dynamics are mentioned. Numerical pattern analysis should have a more prominent place in this type of study; the significance of the study of small permanent plots in a stand is emphasized, and unprejudiced demographic studies, as well as experimental studies of small‐scale species replacement are recommended.
The Dynamic keyhole‐key model of coexistence to explain diversity of plants in limestone and other grasslands
Authors: Gigon A. , Leutert A.
Published: May 2006

Abstract. This paper is a tribute to A.S. Watt who published his ‘Pattern and process in the plant community’ almost 50 years ago. Watt's interpretation of the plant community “as a working mechanism, which maintains and regenerates itself” is still highly relevant, although the keywords have changed. ‘Process’ in Watt's view involves both upgrade and downgrade aspects, whereas ‘Pattern’ was not specified, neither quantified. Nowadays. process is mainly approached as ‘disturbance’, that is natural disturbance and ‘pattern’ as patch structure. Together they make up the ‘patch dynamics’ of the community. Some implications of patch dynamics for phytosociology are discussed. A ‘Wattian’ concept of the plant community combines the Gleasonian idea of individualistic behaviour of species with the Clementsian (or rather Braun‐Blanquetian) notion of community dynamics. Later work by Harper (demography), Grubb (regeneration niche) and earlier work of Sernander (forest gap dynamics) is significant for the understanding of the patch‐dynamic nature of the community.

Recent interest in plant species mobility can easily be linked to the concept of patch dynamics. Examples of mobility in a limestone grassland are given and a system of mobility types is proposed.

Some perspectives for the study of patch dynamics are mentioned. Numerical pattern analysis should have a more prominent place in this type of study; the significance of the study of small permanent plots in a stand is emphasized, and unprejudiced demographic studies, as well as experimental studies of small‐scale species replacement are recommended.
Contributions of Quaternary palaeoecology to nature conservation
Authors: Birks H.J.B.
Published: May 2006

Abstract. Quaternary palaeoecology has traditionally been associated with the reconstruction of past biota and past environments over long time periods such as the Holocene period. Recent methodological developments and conceptual advances have resulted in an ‘applied palaeoecology’ that can address specific ecological and environmental questions over the last 100‐200 yr, the time span of primary interest to nature conservationists. The contributions of palaeoecology to the assessment of naturalness of ecosystems, to the assessment of the fragility of ecosystems, to the assessment of the conservation status of rare species, and to the development of a factual basis for attempts at ecosystem enhancement and restoration are discussed, with reference to palaeoecological studies in Scotland, England, southwest Ireland, and Sweden. Palaeoecological results indicate that few, if any, vegetation types in western Europe are natural. Palaeoecology can provide unique insights into the fragility of ecosystems in response to human activity and other biotic factors such as grazing and to acidification. Palaeoecology can contribute basic information required for understanding the causes of recent decline of taxa such as the natterjack toad, aquatic macrophytes, and arcticalpine plants. Palaeoecology is often the only source of baseline data about past ecosystem composition and function that are essential for any realistic attempts at ecosystem restoration or enhancement.
European Vegetation Survey: update on progress
Authors: Rodwell J.S. , Pignatti S. , Mucina L. , Schaminée J.H.J.
Published: May 2006

Abstract. Progress in the European Vegetation Survey is described. 25 countries are now represented in a network committed to common data standards in phytosociological survey, the development of compatible software for data analysis and mapping, the encouragement of national programmes and the development of an overview of European plant communities. Advances in each of these areas of activity is summarised and plans for the future are outlined, most notably the production of a book ‘The Vegetation of Europe’.
Vegetation succession in a floating mire in relation to management and hydrology
Authors: van Diggelen R. , Molenaar W.J. , Kooijman A.M.
Published: May 2006

Abstract. The vegetation succession in a floating mire was studied in relation to management and hydrological conditions in a former peat cutting area in the northern part of the Netherlands. An existing map showed that in 1956 the vegetation consisted mainly of meadows, reedbeds and rich fen vegetation while a recent survey revealed that this picture had completely changed in 1989. The area had mainly become woodland but part had remained open, due to the continuation of a mowing regime. The timing of the mowing appears to be critical, especially during the earlier phases of the succession. Winter‐mowing favours the development of eutrophic reedbeds, while summer‐mowing promotes mesotrophic sedge communities. In the course of time these succession lines converge increasingly towards acidic vegetation types.

The development from open water to embryonic bog differed greatly between sites with a similar management regime. Mostly this took only a few decades but in a few sites the vegetation had hardly changed since 1956. Whereas the former sites were acid throughout the profile, the latter showed a high pH from top to bottom. It is obvious that acidification does not occur as long as alkaline surface water can move freely underneath the floating mat. As soon as a given site becomes disconnected from the surface water the depletion of bases by infiltrating rainwater is no longer compensated. A rough estimate of the acidification rate shows that in an infiltration area three decades are sufficient for a floating mat of 40 cm to become completely decalcified. This corresponds well to the observed succession from rich fens to embryonic bogs in the same period. It is suggested that the best way to preserve rich fen vegetation is to start the succession anew by digging turf ponds.
Microclimatic convergence of high‐elevation tropical páramo and temperate‐zone alpine environments
Authors: Diemer Matthias
Published: May 2006

Abstract. Plant microclimates of three tropical superpáramo sites at 4100–4600 m a.s.l. in Ecuador were monitored over a five‐month period and results were evaluated in local and biogeographical contexts. Soil temperatures tended to decrease with altitude, whereas quantum flux density (QFD) exhibited no consistent altitudinal pattern. Leaf temperatures of prostrate rosette and cushion plants exhibited diurnal amplitudes of 30 °C independent of altitude, while herbaceous perennials and woody shrubs, which were situated higher above the soil surface, had lower maxima and lower daily amplitudes as a result of aerodynamic coupling to the atmosphere. Long‐term growth measurements and an analysis of a stem cross‐section of the shrub Loricaria indicated that growth conditions at 4060 m a.s.l. were constant over a 4‐yr to > 25‐yr period.

Means and frequency distributions of QFD as well as soil and leaf temperatures in the Ecuadorean Andes closely resemble growing season averages at high alpine sites in the European Central Alps at 2600 m a.s.l. Equivalent growth conditions in equatorial tropical páramo sites and seasonal temperate zone mountains extending to the arctic, suggest that, aside from the duration of the growing season, similar abiotic selection pressures operate on high elevation plants in humid mountain ecosystems, which are largely independent of latitude.
Differences in forest composition in two boreal forest ecoregions of Quebec
Authors: Gauthier Sylvie , De Grandpré Louis , Bergeron Yves
Published: May 2006

Abstract. In order to describe and compare the post‐fire succession patterns of the two ecological regions (mixed‐wood and coniferous ecoregions) of northwestern Quebec, 260 forest stands were sampled with the point‐centred plot method. The mixed‐wood ecological region belongs to the Abies balsamea‐Betula papyrifera bioclimatic domain whereas the coniferous ecological region belongs to the Picea mariana‐moss bioclimatic domain. In each plot, tree composition was described, surficial deposits and drainage were recorded, and fire history was reconstructed using standard dendro‐ecological methods. Ordination techniques (Correspondence Analysis and Canonical Correspondence Analysis) were used to describe the successional patterns of forest vegetation and to correlate them with the explanatory variables. The results showed the importance of surficial deposits, the time since fire and the ecoregion in explaining the variation of stand composition. Abies balsamea tends to increase in importance with an increase in time since fire, and this trend is more pronounced in the mixed‐wood region. Even when controlling both for surficial deposits and time since fire, differences in successional trends were observed between the two ecoregions. As all the species are present in both ecoregions and as they are all observed further north, our results suggest that both the landscape configuration and fire regime parameters such as fire size and fire intensity are important factors involved in these differences.
Changes in two Minnesota forests during 14 years following catastrophic windthrow
Authors: Arévalo José Ramón , DeCoster James K. , McAlister Suzanne D. , Palmer Michael W.
Published: May 2006

Abstract. We measured tree damage and mortality following a catastrophic windthrow in permanent plots in an oak forest and a pine forest in central Minnesota. We monitored changes in forest structure and composition over the next 14 years. Prior to the storm, the oak forest was dominated by Quercus ellipsoidalis, and the pine forest by Pinus strobus. The immediate impacts of the storm were to differentially damage and kill large, early‐successional hardwoods and pines. Subsequent recovery was characterized by the growth of late‐successional hardwoods. In both forests the disturbance acted to accelerate succession. Ordination of tree species composition confirmed the trend of accelerated succession, and suggested a convergence of composition between the two forests.
BOOK REVIEWS
Authors: Braakhekke Wim
Published: May 2006

Abstract. Benstead, P.J., José, P.V., Joyce, C.B. & Wade, P.M. 1999. European wet grassland: guidelines for management and restoration. xii + 169 pp. RSPB, Sandy UK. ISBN 1 901930 01 7 (softback). Price: GBP 15.95.
Quantifying the deciduousness of tropical forest canopies under varying climates
Authors: Condit Richard , Watts Kristina , Bohlman Stephanie A. , Pérez Rolando , Foster Robin B. , Hubbell Stephen P.
Published: May 2006

Abstract.Deciduousness is an important functional attribute of tropical trees, reflecting climatic conditions. Precisely quantifying and mapping deciduousness in tropical forests will be necessary for calibrating remote sensing images which attempt to assess canopy properties such as carbon cycling, productivity, or chlorophyll content. We thus set out to assess the degree of canopy deciduousness in three moist, semi‐deciduous tropical forests in central Panama. One site is a 6‐ha research plot near the Atlantic coast of Panama, where rainfall is 2830 mm/yr. The second site is a 50‐ha plot on Barro Colorado Island, near the center of the isthmus of Panama, where rainfall is 2570 mm/yr, and the final site is a 4‐ha plot near the Pacific coast of Panama, where rainfall is 2060 mm/yr. At each site, a random sample of trees from all canopy species (those with individuals ≥ 30 cm DBH) were visited and scored for deciduousness three times during the 1997 dry season. The estimated peak fraction of deciduous individuals in the canopy at the wetter site was 4.8%, at the intermediate site, 6.3%, and at the drier site, 24.3%. The estimated fraction of crown area deciduous peaked at 3.6%, 9.7%, and 19.1% at the wet, medium, and dry sites respectively. The percentage of canopy species that was deciduous –14%, 28%, and 41%–was much higher than the percentage of deciduous individuals, because not all individuals of deciduous species were deciduous. During the 1999 dry season, every individual of all the deciduous species was visited at the two drier sites, and the total number of deciduous trees observed closely matched the estimated numbers based on the smaller 1997 samples.
Effects of soil erosion on the floristic composition of plant communities on marl in northeast Spain
Authors: Guerrero‐Campo Joaquín , Montserrat‐Martí Gabriel
Published: May 2006

Abstract. This study explored the validity of three responses of vegetation to increased soil erosion: reduction of vegetation cover, number of species and reduced substitution of species.

201 relevés, including edaphic and geomorphological data, were surveyed in the intensely eroded Eocene marls of the Prepyrenees (NE Spain). Changes in plant species’ presence in relevés from different degradation stages were compared. The level of vegetation degradation was defined as the total phanerogam cover which, in the studied area, was correlated to the degree of soil erosion. The considered trends were validated. Reduction of phanerogam cover and species number were gradual from low to high‐eroded areas. Vegetation degradation explained 48% of the species number variance. In the later stages of degradation a significant substitution of species was not observed, only a lower frequency of occurrence of several species that appeared in the whole set of relevés. Through the process of degradation, 47% of species displayed significantly reduced frequencies as degradation increased, none showed a significant increase in frequency.

It is concluded that there are no characteristic species in these plant communities that survive in the severely eroded marls. Among the few species that had increased in frequency, most only colonised favourable micro‐environments.
Availability of coarse woody debris in a boreal old‐growth Picea abies forest
Authors: Jonsson Bengt Gunnar
Published: May 2006

Abstract. This study reports temporal (based on cross‐dated dead trees) and spatial patterns of availability of coarse woody debris (CWD) from Picea abies in a Swedish boreal landscape with discrete old‐growth forest patches in a wetland matrix. Data were collected from 29 patches ranging in size from 0.3 to 28 ha. A total of 897 dead trees with a minimum diameter of > 15 cm occurred on the 7.2 ha area analysed. The year of death was established for 50% of these trees.

CWD volume ranged from 17 to 65 m3/ha for downed logs and from 0.5 to 13 m3/ha for standing snags. CWD of all decay stages and diameter classes occurred abundantly and the probability of finding logs of all decay stages and sizes was very high at the scale of single hectares. Tree mortality differed among 5 yr periods. However, during the last 50 yr no 5 yr period produced less than 3 logs/ha. Decay rates were highly variable among different logs. Logs with soft wood and some wood pieces lost (decay stage 5) died ca. 34 years ago. This suggests a fairly rapid decay in this northern forest. The data indicate a high and continuous availability of CWD of all types. It is likely, therefore, that selection pressures for efficient dispersal among CWD dependent species may not be very high. Consequently, species with narrow habitat demands and/or low dispersal ability may have evolved and this may contribute to the decrease of certain species in the managed landscape.
Factors determining the centrifugal organization of remnant Festuca grassland communities in Alberta
Authors: Vujnovic K. , Wein Ross W. , Dale M.R.T.
Published: May 2006

Abstract. This paper describes the species composition of remnant grasslands in the aspen parkland region of Alberta and its relation to soil characteristics and small‐scale disturbance. Our findings are consistent with the centrifugal model of communities with Festuca hallii dominating undisturbed ‘core’ habitat and the composition of more ‘peripheral’ habitats varying in soil properties and in the magnitude of disturbance. Invasive non‐native species are not present in the core habitat and are present only in the disturbed sites, most abundantly in those with the highest soil nitrogen. The centrifugal model, as it applies to these remnant grasslands, differs from its previous application to wetlands and forests in that the core communities are not on the most fertile sites, but on the least disturbed. These findings have implications for the management of prairie remnants to exclude invasive exotic species.
Seed banks of Erica australis and Calluna vulgaris in a heathland subjected to experimental fire
Authors: Valbuena Luz , Tárrega Reyes , Luis‐Calabuig Estanislao
Published: May 2006

Abstract. Soil samples were collected before and after an experimental fire on a heathland in the province of León (Spain). The seed banks were assessed by counting the numbers of seedlings appearing of Erica australis and Calluna vulgaris. A total of 2285 germinable seeds/m2 before burning and 1177 germinable seeds/m2 after the fire were estimated for Erica australis, and 90 and 690 germinable seeds/m2, respectively, for Calluna vulgaris. After the fire the number of germinable seeds/m2 of Erica australis had decreased, whilst there was a considerable increase in the number of germinable seeds/m2 of Calluna vulgaris. Neither seedlings nor sprouts of Calluna vulgaris had appeared in the field plots 10 months after the fire. Erica australis did recover mainly by sprouting after fire.
Spatial patterns of plant association in grazed and ungrazed shrublands in the semi‐arid Karoo, South Africa
Authors: Bossdorf Oliver , Schurr Frank , Schumacher Jens
Published: May 2006

Abstract. The investigation of vegetation pattern and plant association by spatial statistics has become increasingly popular among plant ecologists. Recently, Individual‐centered analysis (ICA) has been introduced as a new tool for analysis of multi‐species co‐occurrence patterns. We tested this new technique by applying it to spatial data from grazed and ungrazed shrub communities in the semi‐arid Great Karoo, South Africa. There were substantial but complex and scale‐dependent differences in pattern between grazed and ungrazed vegetation. Unpalatable species that increase in abundance in grazed vegetation possibly play a key role in the change of vegetation pattern. At small scales we found indications of aggregation (< 30 cm) at the ungrazed, but of repulsion (30 – 40 cm) at the grazed site. An additional non‐random pattern at 60 – 170 cm at the grazed site was probably due to the clumped distributions of some species on broader scales. We show that the interpretability of ICA results is improved when the actual observed and expected frequencies of species combinations are added to the program output. The main strength of ICA is that it has the potential to detect association patterns that involve more than two species.
Fine‐scale persistence of boreal bog plants
Authors: Nordbakken Jørn‐Frode
Published: May 2006

Abstract. Persistence, or the tendency of a species to remain in its original position without colonizing new sites, is studied for 24 species on the ombrotrophic Northern Kisselbergmossen in SE Norway. Data sets comprise presence/absence in 436 sample plots (16 cm x 16 cm) and 6976 subplots (4 cm x 4 cm) analysed with a 5‐yr interval. Persistence was calculated for both spatial scales, and the observed values were compared with null models of completely random presence/absence of species. Species characteristics (plot occurrences and persistence) were related to depth to the water table and species optima along ecologically interpreted DCA ordination axes. The observed persistence was significantly higher than predicted from the random model for all vascular plants and cryptogams at both spatial scales. All taxonomic groups showed higher persistence at the sample plot scale than at the subplot scale. No general relationship between persistence and depth to the water table was found, but for the cryptogams there was somewhat higher persistence for the less peat‐producing species. The persistence of the vascular plants depended on ramet longevity, growth form and vegetative mobility. In general, the observed persistence of most cryptogams was high, probably because of their perenniality, low growth rates and high reproductive output. Differences in growth‐form and life history, as well as the higher number of occurrences, are the most likely reasons for somewhat higher mean persistence of hepatics and Sphagna than of vascular plants at the subplot scale.
BOOK REVIEWS
Authors: Walck Jeffrey L.
Published: May 2006

Bailey, Robert G. 1998. Ecoregions: the ecosystem geography of the oceans and continents. ix + 176 pp. Springer‐Verlag, New York. ISBN 0–387–98311–2 (softcover), 0–387–98305–8 (hardcover). Price: USD 39.95 (soft cover); USD 79.95 (hard cover).
Phenological shifts of the alien colonizer Bunias orientalis: Image‐based analysis of temporal niche separation
Authors: Dietz Hansjörg , Ullmann Isolde
Published: May 2006

Abstract. Phenological development of the colonizer Bunias orientalis L. was investigated in permanent plots in herbaceous vegetation, using photography and image analysis. In all habitats but one, B. orientalis showed a two‐phased rosette growth behaviour, with a first peak cover reached in spring, roughly coinciding with an early peak cover of the matrix vegetation, and a second autumn growth flush occurring in a phase of reduced matrix vegetation cover. This seasonally bimodal growth pattern of B. orientalis appears to partly compensate for its competitive inferiority in crowded herbaceous vegetation. Small or overshadowed individuals of this species particularly profit from higher above‐ground performance or release from overlap in autumn. The significance of temporal niche separation for survival and growth of B. orientalis individuals varies with habitat conditions, being most apparent in occasionally disturbed habitats with a relatively low frequency of gap formation. Despite some limitations, image analysis proved to be useful for phenological investigations within herbaceous plant stands.
Composition, structure and diversity of cove forest stands in the Great Smoky Mountains: a patch dynamics perspective
Authors: Busing Richard T.
Published: May 2006

Abstract.Cove forests of the Great Smoky Mountains are North American examples of old‐growth temperate forest. Ecological attributes of seven stands were studied using one 0.6 ‐ 1.0 ha plot per stand. Stand basal area (39 ‐ 55 m2/ha) and biomass (326 ‐ 471 Mg/ha) were high for temperate deciduous forest. Density ranged from 577 to 1075 stems/ha. All stands had a mixture of deciduous canopy species. Only rarely did a single species comprise more than half of the stand by density, basal area or biomass. Shade‐intolerant species were present at low levels (1 ‐ 5 % of total stand density). A wide range of stem diameters was characteristic of most species. However, some species lacked small stems, indicating discontinuous regeneration. Stands tended to have 10 ‐ 20 tree species per ha and at least five species had biomass levels > 10 Mg/ha, indicating high evenness. Canopy gaps covered 10 % of the total area (2 ‐ 21 % by stand). Gaps and conspecific patches of canopy trees > 0.05 ha in size were infrequent. Spatial analyses revealed a variety of patterns among species at inter‐tree distances of 1 to 25 m. When all species were combined, juveniles showed aggregation, and adults were often hyperdispersed. Analyses for individual species confirmed that the mosaic of canopy species is influenced by non‐random spatial processes. Adults of several species were aggregated at distances > 10 m. Juveniles of all major species exhibited aggregation. Several species exhibited regeneration near conspecific adults. This pattern suggested limited mobility for such species within the shifting mosaic. A diverse patchwork resulted despite the fact that many species did not exhibit segregation of adults and juveniles. Further understanding of patch dynamics and the potential for compositional steady state in cove forests requires long‐term study with spatial data.
Distribution of plant species in Israel in relation to spatial variation in rainfall
Authors: Kadmon Ronen , Danin Avinoam
Published: May 2006

Abstract. Relations between the distribution of herbaceous and woody species from the flora of Israel and the variation (25–900 mm) in mean annual rainfall are described using a grid‐based approach integrating multivariate techniques (cluster analysis and DCA‐ordination) and GIS. The analysis was based on an extensive data base of vascular plant records in 10 km × 10 km grid cells representing the climatic zones of Israel. Cluster analysis revealed three geographically distinct clusters of grid cells which could be arranged along the main rainfall gradient in the study area. The main subdivision is between cells from the Mediterranean region and cells from the more arid region. The second subdivision separated cells from the arid region into two distinct groups which differed significantly in rainfall. Clustering of herbaceous and woody species was similar, but boundaries separating adjacent clusters based on woody species were consistently linked to more rainy areas. Cell scores on the first DCA‐axis were significantly correlated with mean annual rainfall, but this relationship was not linear. Log‐transformation of the rainfall data resulted in a higher correlation between the DCA‐scores and rainfall, indicating that variation in rainfall had a stronger effect on species composition in relatively dry than in more mesic regions. Slopes of linear regression models relating cell scores on the first DCA‐axis to mean annual rainfall, as well as the corresponding R2‐values, were highest in the desert, intermediate in the dry Mediterranean, and lowest in the mesic Mediterranean territory. These results indicate that both the per‐unit effect of rainfall on plant species composition and its relative importance as a determinant of compositional variation decreased from relatively dry to more mesic regions.

The length of the first axis, as well as the slopes of regression models relating cell scores on the first DCA‐axis to mean annual rainfall were consistently higher in the case of woody species which are characterized by a higher rate of compositional variation. Due to lack of comparable data, it is difficult to evaluate whether our results can be generalized to other regions. However, an analysis of data obtained from different parts of the world points to a considerable variability in the degree to which rainfall affects patterns of floristic variation. Our findings that compositional responses to rainfall may vary between different groups of species and may depend on the part of the rainfall range which is being considered may partially explain this inconsistency.
The effect of shrub clearing and grazing on the composition of a Mediterranean plant community: functional groups versus species
Authors: Hadar Liat , Noy‐Meir Imanuel , Perevolotsky Avi
Published: May 2006

Abstract. Fuel‐breaks to impede the spread of fires in Mediterranean woody vegetation are created by clearing of shrubs, followed by very intensive cattle grazing before the fire season. The present research analysed the effects of these two disturbance types on herbaceous community composition at the functional group and the species level, by using canonical discriminant ordination analysis and by categorical modeling methods. Grazing caused an increase in the abundance of small species, geophytes, and species with an early flowering period that ends before the grazing period. The abundance of many different species increased as a result of clearing. However, no association was found between positive or negative response to clearing and any species attribute tested. Several a priori functional groups defined by life form and family showed responses to either grazing or clearing. Links between these responses and individual species attributes are discussed. The results emphasize the different nature of the two disturbances: grazing as a selective agent, and shrub clearing as a generalized one. It also stresses the importance of the plant architecture and the morphological and phenological niche in determining community composition under extremely intensive grazing conditions.
Distribution of plant functional types along gradients of disturbance intensity and resource supply in an agricultural landscape
Authors: Kleyer Michael
Published: May 2006

Abstract. In this study, plant functional types are understood as groups of plants with similar biological traits displaying significant optima or maxima on a gradient plane of resource supply and disturbance intensity. The biological traits refer to expansion, vegetative regeneration, generative reproduction, dispersal and seed bank longevity.

129 vegetation samples were taken in an agricultural landscape in southwestern Germany, covering a wide range of terrestrial vegetation types – but with the exception of forests and wetlands. For each site, also soil data were recorded. Mean daily soil moisture was estimated with a simple model. Soil moisture, balanced nitrogen supply and available phosphorus were combined into a factor ‘resource supply’. In addition, disturbance intensity was estimated for each site. This factor was based on (1) frequency of disturbance, (2) disturbance depth below or above the soil surface, and (3) proportion of the area affected by a discrete disturbance event. 30 plant groups with similar biological characteristics resulted from a cluster analysis, based on a compilation of 19 biological traits for a regional species pool. Logistic regression on a gradient plane of disturbance intensity and resource supply yielded response curves for 28 groups. The dependent variable was defined as the probability of encountering all members of a group in a sample. 17 groups display a significant response curve on the gradient plane. Plants with a potential for long‐ range dispersal are concentrated on sites with low or high disturbance intensities (e.g. fallow land, fields, lawns). On sites with medium disturbance intensity (e.g. meadows) and low to medium resource supply, small‐range dispersal predominates. There are no distinct trends concerning seed bank longevity. The potential for vertical and lateral expansion increases with decreasing disturbance intensity. Only at medium disturbance intensities does vertical expansion correlate positively with resource supply. Rapid detachment of daughter individuals occurs more often on productive sites than on less productive sites. Diversity of groups with similar biological traits is highest on sites with medium disturbance intensities.
Edaphic relationships amongCirsio‐Molinietumand related wet grassland communities in lowland Wales
Authors: Blackstock T.H. , Stevens D.P. , Stevens P.A. , Mockridge C.P. , Yeo M.J.M.
Published: May 2006

Abstract.Soil properties are characterized for a range of theMolinietaliavegetation types in lowland Wales. In this oceanic region there is overlap in the distribution of various forms of wet pasture dominated byMolinia caeruleaandJuncus acutiflorus.There is subtle and continuous variation in species composition among four communities investigated; this has been analysed by Detrended Correspondence Analysis and partitioned between subcommunities recognized in Rodwell (1991). Canonical Variates Analysis indicated that the main differences in soil conditions between the vegetation classes are related to gradients in base‐status; apparent variation in soil fertility may also be significant and requires further investigation. In general,Molinia‐Cirsium dissectumfen‐meadow soils have higher pH, higher Ca‐levels, greater base saturation and lower acidity thanMolinia‐Potentilla erectawet grasslands; those ofJuncus‐Galium palustrerush‐pasture andMolinia‐Crepis paludosamire had relatively high levels of inorganic N. The findings are discussed with reference to ecological and phytosociological relationships, and also in the context of nature conservation.
Compositional dynamics of natural forests in the Bialowieza National Park, northeastern Poland
Authors: Bernadzki Eugeniusz , Bolibok Leszek , Brzeziecki Bogdan , Ząjaczkowski Jacek , Żybura Henryk
Published: May 2006

Abstract. This paper presents results of a long‐term study on natural forest dynamics in the Białowieza National Park (BNP), northeastern Poland. Five permanent sample areas were used, each consisting of a transect of varying width (40 ‐ 60 m) and length (200 ‐ 1380 m). The total sample area is 14.9 ha. The study covers the period 1936–1992. During this period measurements were made on five occasions at approximately 10‐yr intervals. On each measurement date all trees with DBH > 5 cm were identified and their spatial location, diameter, crown condition and position in the canopy determined.

During the study period the stands underwent noticeable changes, mainly in terms of tree species composition. The major change was a quantitative increase of the late‐successional species: Tilia cordata and Carpinus betulus, also to a lesser degree Fraxinus excelsior and, in the last period, of the early successional Alnus glutinosa. Declining species included both early‐ and late‐succession species. Among the latter group, Picea abies ranked first. This species lost much of its importance during the last few decades. P. abies was followed by Pinus sylvestris which is an important component of the climax vegetation under the conditions prevailing in Bialowieza, at least on more oligotrophic sites. Still, this species has not been able to regenerate during the whole study period. Some other late‐succession species, Acer platanoides and Quercus robur, were also amongst the declining species. Although the basal area of Q. robur increased, its population was getting older and the process of natural regeneration was markedly impeded.

All typical pioneer, short‐lived species: Betula pendula and B. pubescens, Salix caprea and Populus tremula also decreased, which was probably caused by a lack of major disturbances during the study period.

In general, the results obtained for the semi‐natural conditions of Bialowieza during the 56‐yr observation period suggest a rather high compositional instability of the forest stands there. A more precise identification of the role of particular factors in the observed stand dynamics is difficult because of the paucity of appropriate historical and environmental data which refer directly to the study plots; moreover, the data are generally incompatible and of different resolution.
Plant species decline due to abandonment of meadows cannot easily be reversed by mowing. A case study from the southern Alps
Authors: Stampfli Andreas , Zeiter Michaela
Published: May 2006

Abstract. We resumed mowing in two plots of ca. 100 m2 in an abandoned meadow dominated by Brachypodium pinnatum on the slope of Monte Generoso (Switzerland). We monitored species composition and hay yield using point quadrats and biomass samples. Species frequencies changed little during 10 yr (1988–1997) while hay yields showed large fluctuations according to mean relative humidity in April‐June. We performed a seed‐addition experiment to test whether the establishment of meadow species is limited by lack of diaspores or favourable microsites for germination and recruitment from the seed bank. We sowed ca. 12 000 seeds of 12 species originating from a nearby meadow individually in plots of a 4 × 6 unbalanced Latin square with four treatments, burning, mowing, mowing and removal of a layer of decayed organic matter, and a control. We monitored the fate of seedling individuals for 24 months. Seedlings of all species were established and survived for 12 months, 10 species survived during at least 24 months, some reached a reproductive stage. Species responded to different qualities of microsites provided by the different treatments thus required different regeneration niches. Spontaneous long‐distance immigration was insignificant. We conclude that the former species composition of abandoned meadows cannot easily be restored by mowing alone because many plant species of meadows do not have persistent seed banks and immigration over distances of more than 25 m and successful establishment is very unlikely.
Nutrient status, disturbance and competition: an experimental test of relationships in a wet meadow
Authors: Lepš Jan
Published: May 2006

Abstract. In many species‐rich hay meadows in Central Europe, the traditional extensive (low input, low output) management is no longer economical and meadows are either fertilized or abandoned. Both these practices lead to changes in species composition and usually to a loss in species diversity. The response of a species‐rich meadow plant community to fertilization, mowing and removal of dominant species was studied in a manipulative factorial experiment over four years. Both species richness and seedling recruitment were positively influenced by mowing and to a lesser extent by removal of the dominant species, Molinia caerulea, and were negatively influenced by fertilization. Fertilization caused an immediate increase in community biomass. Response to removal of the dominant species was delayed by one season, continued over the whole period, and by the fourth year the biomass reached a similar value as in the plots with Molinia present. Changes in species composition were evaluated by RDA for repeated measurements. The best and only significant predictor of species response to fertilization was plant height. This shows that with increased nutrient availability, nutrient limitation weakens and competition for light becomes the decisive factor. Competition for light appears to be more asymmetric than competition for nutrients, and consequently, it is more likely to drive inferior species to extinction. This is, together with seedling recruitment limitations, the most important cause of a decrease in species richness under high nutrient levels.
Effects of area, environmental status and environmental variation on species richness per unit area in Mediterranean wetlands
Authors: Rey Benayas Jose M. , Colomer Manuel G.S. , Levassor Catherine
Published: May 2006

Abstract. We propose a mechanistic model to relate α‐ and γ‐diversity to area per se, moisture status and environmental variation (local and total), and explored the effects these abiotic variables have on species richness per unit area (α‐diversity) for plant communities in a network of wetland habitats located in a Mediterranean mountainous region of central Spain. In this study, environmental status is measured as actual evapotranspiration (as an expression of energy), slope and soil wetness, and environmental variation refers to slope variation and soil wetness variation. Species richness per unit area was related to soil wetness, soil wetness variation, ground slope and ground slope variation. There were also positive correlations among moisture status and environmental variation variables. There is a joint effect of slope and soil wetness variation in explaining species richness per unit area of these wetland habitats, but area effects and energy are relatively unimportant. We conclude that species richness per unit area of wetland vegetation can be explained by moisture status and local environmental variation, and that habitat area may not have an important effect. Area could affect γ‐diversity directly through random sampling and/or indirectly through increasing β‐diversity, and energy may be important in areas with larger energy ranges. Complete surveys of environmental status, local and total environmental variation, and their associated species assemblages are needed to explain the processes that give rise to the rule that larger areas have larger species richness.
Plant functional types in coastal foredunes in relation to environmental stress and disturbance
Authors: García‐Mora M. Rosario , Gallego‐Fernández Juan B. , García‐Novo Francisco
Published: May 2006

Abstract. The foredune vegetation in the Gulf of Cadiz (SW Spain, S Portugal) was studied by means of morphological characters and functional traits of plants. The 55 vascular species recorded in the area were classified into three functional types: Type I consists mainly of winter annuals of moderate size with soft leaves, showing no presumed adaptations to the dune environment. Plants of Type II are mostly perennials with a below‐ground spreading root network and leaves with presumed adaptations to coastal environmental stress. Type III includes plants mostly capable of being dispersed by sea‐water and of withstanding sand burial.

In relatively unstable soil, Type II and Type III plants were found to be more abundant, their relative proportion depending on the dominance of accretion/erosion processes. Increasing cover of Type I plants was associated with relatively more stable soils. The ratios in occurrences of the three types can be used as an indicator of foredune dynamics.