Dynamics of understory vegetation in an old-growth boreal coniferous forest, 1988–1993

Abstract. Understorey vegetation changes in a South Norwegian old-growth coniferous forest were studied between 1988 and 1993 in 200 1-m² vegetation plots. Our aims were to quantify the amount of between-year compositional change, and to elaborate the environmental basis for long-term vegetation change, including the previously identified gradient structure with a major gradient related to topography (and soil nutrient status and soil depth) and a minor gradient reflecting paludification and canopy coverage. Species richness (yearly mean and cumulative species number) and change in species richness differed between vascular plants and cryptogams, and between forest types. The number of vascular plant species decreased in pine forest in dry years; bryophyte species number increased in spruce forest. Statistically significant vegetation change, as tested by constrained ordination (CCA) with time as the constraining variable, is demonstrated for most one-year periods and for the five-year period in most forest types. Vegetation change along identified gradients, measured as plot displacement along DCA ordination axes, also occurred. The magnitude of year-to-year vegetation change was related neither to forest type nor to one-year period; different responses to climatic and environmental change were observed in each forest type. The largest average displacement observed, from medium-rich spruce forest towards poor spruce forest, was interpreted as a long-term trend. Humus-layer pH decreased by ca. 0.25 units from 1988 to 1993, most strongly in medium-rich spruce forest where exchangeable Ca decreased and Al and Mn increased strongly. Our study supports the hypothesis that vascular plants show a long-term and broad-scale response to soil acidification. Change in bryophyte composition is linked to some very long growing-seasons. Detailed analysis of short-term vegetation dynamics enhances the interpretation of long-term changes and stresses the complementarity of univariate and multivariate methods in the analysis of vegetation change.     

Tracing and interpreting fine-scale human impact in northern Fennoscandia with the aid of modern pollen analogues

A set of moss samples (n=58) was collected and analysed to obtain modern pollen analogues for both natural and human induced vegetation types in northern Fennoscandia. Vegetation types with settlement, trampling and grazing were selected from the different latitudinal forest zones (birch, pine, and mixed forest). The moss species varied between samples but the size of the sample was kept constant. Numerical analyses such as Redundancy Analysis (RDA) indicate that in northern areas human presence is mainly visible as increased values of Gramineae, Rumex acetosa/acetosella, R. obtusifolius, Solidago-type and Achillea-type pollen. Partial RDA further reveals that settlement is strongly correlated with high values of Rumex acetosa/acetosella, whereas trampled sites are significantly characterised by Gramineae and, to a smaller extent, Cyperaceae pollen. It is therefore possible to distinguish the impact of different types of human activities on vegetation on the basis of the pollen spectra. Later, these data will be used to interpret the presence, nature, and duration of human impact from fossil records from the same area. Received June 6, 2001 / Accepted December 12, 2001     

Do moss samples,pollen traps and modern lake sediments all collect pollen in the same way? A comparison from the forest limit area of northernmost Europe

Moss polsters, pollen traps and lake surface sediment samples are commonly used as climate calibration data or as modern analogues for reconstructing vegetation from fossil profiles, but the differences in pollen content between these media have received little attention. This study aims to analyse how the three media differ in reflecting individual vegetation types and spatial differences in vegetation. 119 modern samples (64 moss polsters, 37 lake surface sediment samples and 18 pollen traps from which a collection was made annually) were taken from northern Fennoscandia and the Kola Peninsula as a broad transect crossing the northernmost forest limits of Betula pubescens ssp. czerepanovii (mountain birch), Pinus sylvestris (Scots pine) and Picea abies (Norway spruce). The pollen assemblages from these samples were compared with the surrounding vegetation visually and via PCA (principle components analysis) and cluster analysis. Both comparisons allow a correct distinction between pollen assemblages of arctic/alpine heath, mountain birch dominated areas, and boreal coniferous forests. The differences between the vegetation zones are stronger than the differences between the sampling media. Nevertheless, lake sediment samples from the mountain birch woodland zone tend to overestimate pine and underestimate birch. Pollen traps are biased towards lower tree pollen percentages and higher values of shrubs, herbs and Cyperaceae. This bias is especially strong in traps that have missing years in the data. Irrespective of the vegetation zone, pollen traps tend to have lower Pinus pollen percentages than in the adjacent moss polsters.     

Digitized photographs in vegetation analysis ‐ a comparison of cover estimates

Abstract. The use of digital images in measuring plant species cover and species number in boreal forest vegetation was studied. Plant cover was estimated by manual delineation on photographs and subsequent digitized measurement of the areas. This value was regarded as the reference and compared with cover obtained by visual estimate, point frequency and automatic image analysis methods. The automatic image analysis was based on scanned photographs. Supervised image classification with ERDAS software was then used to distinguish between the covers of different plant species. When comparing the ability of the methods to detect species, the visual estimate method gave values similar to the reference. The study material was collected from three sites along a heavy‐metal pollution transect in western Finland. All four methods detected, in a similar manner, differences between the plant species abundances along the transect. Compared with the reference, the digital images underestimated the cover of the lichens Cladina spp. and Cetraria islandica, but gave similar estimates for the dwarf shrubs Empetrum nigrum and Vaccinium vitis‐idaea. The point frequency method overestimated the cover of all the species studied. The visual estimates of lichens were close to the reference, while the dwarf shrub covers were overestimated. The number of species detected using supervised image analysis and the point frequency method was lower than that with visual estimation. Visual estimation was faster, and the estimate closer to the reference cover values than the others. Digital images may be useful in detecting changes in some selected species in vegetation with a simple vertical structure but with taller, multilayered vegetation and a higher species number, the reliability of the cover estimates is lower.     

Modern pollen representation of source vegetation in the Qaidam Basin and surrounding mountains, north-eastern Tibetan Plateau

We use a data set of 35 surface pollen samples from lake sediments, moss polsters and top soils on the north-eastern Tibetan Plateau to explore the relationship between modern pollen assemblages and contemporary vegetation patterns. The surface pollen transect spanned four vegetation zones––alpine meadow, steppe, steppe desert and desert––under different climatic/elevational conditions. Relative representation (R _rel) values and Principal Components Analysis (PCA) were used to determine the relationships between modern pollen and vegetation and regional climate gradients. The results show that the main vegetation zones along the regional and elevational transects can be distinguished by their modern pollen spectra. Relative to Poaceae, a high representation of Artemisia, Nitraria and Chenopodiaceae was found, while Cyperaceae and Gentiana showed values in the middle range, and Ranunculaceae, Asteraceae, Ephedra and Fabaceae had low relative representation values. PCA results indicate a high correlation between the biogeoclimatic zones and annual precipitation and annual temperature and July temperature. The Artemisia/Chenopodiaceae ratio and the Artemisia/Cyperaceae ratio are useful tools for qualitative and semi-quantitative palaeoenvironmental reconstruction on the north-eastern Tibetan Plateau. Surface lake sediments are found to have different palynomorph spectra from moss cushion and soil samples, reflecting the larger pollen source area in the contemporary vegetation for lakes.     

A comparison between modern pollen spectra of moss cushions and Cundill pollen traps

Pollen spectra of 23 Cundill pollen traps from 23 different sampling sites in Southwest Turkey are compared with the corresponding pollen spectra of moss cushions from the same sites. The Cundill pollen traps represent the modern pollen rain data from one year whereas the moss cushions represent the pollen rain of several years. The comparative study reveals some main differences between the two pollen entrapment media. The one-year entrapment medium (pollen trap) appears to be more sensitive for local (releve area 10x10 m) and regional (100-500 m, or a few kilometres for Olea europaea) vegetation. Pollen spectra of moss cushions are dominated by high pine pollen percentage values and hardly sense fine vegetation structures. The conclusion of this comparative modern pollen study allows to interpret fossil sediment spectra from the Near East in a more critical way. It is concluded that one should preferably sample rapidly deposited sediments for palynological analyses, as the resulting highresolution pollen diagrams will be most informative about the former vegetation patterns.     

Aerobiology and palaeoecology

Summary Aerobiology involves the study of particles present in the air. Of these, palaeoecologists are most interested in pollen and spores, specially those which come to rest on the surface of the ground. Pollen sampling in palaeoecological studies, therefore, uses a pollen trap which is placed at ground level and the sampling period is a whole season or year.Using examples from northern Finland, for each vegetation type sampled, a pollen analogue is obtained which comprises percentage presence and deposition values cm^–2 year^–1 for the pollen types recorded. This analogue is used to interpret pollen assemblages from the past. In general, the tree pollen provides information of the regional situation and the herbaceous pollen of specific local conditions. Both natural and man-made environments are considered. The absolute deposition values are often crucial in distinguishing between two plant communities with otherwise similar percentage pollen values. They can also be used to follow the location of the boundaries between different vegetation types through time. Seasonal records of pollen deposition are sometimes useful in distinguishing the different source of the pollen reaching a specific site. In certain instances, annual pollen deposition values can be employed to estimate the rate of accumulation of a peat deposit. In addition, long series of annual pollen deposition values can be compared with meteorological data for the same period to test for trends and correlations. This, potentially, allows both a more detailed interpretation of past climatic changes and provides a basis for models predicting futures ones.     

A two-year report of pollen influx into Tauber traps in Mar Chiquita coastal lagoon,Buenos Aires,Argentina

Modern pollen deposition and its relationship to the surrounding vegetation were studied at a coastal lagoon from the southeast of Buenos Aires Province (Argentina). Tauber traps were monitored monthly over a 2-year period in a coastal dune barrier, salt marsh and continental freshwater lake. Pollen deposition exhibited seasonal patterns with maximum values during summer and a spatial variability of increasing deposition from the coast to inland sites. The pollen spectra suggest that airborne pollen originates mainly from local vegetation with scarce representation of extraregional sources. Herbaceous pollen predominates, comprising up to 90% of the total amount with Poaceae, Chenopodiineae and Asteroideae as the main types. Hydrophytic, psammophytic and extraregional types had little influence on the pollen spectra, generally comprising <5% of the total pollen. Pollen influx–vegetation abundance discrepancies were explained considering pollination syndrome, spatial distribution and structure of vegetation.     

Tree line identification from pollen data: beyond the limit?

Aim The boreal tree line is a prominent biogeographic feature, the position of which reflects climatic conditions. Pollen is the key sensor used to reconstruct past tree line patterns. Our aims in this study were to investigate pollen–vegetation relationships at the boreal tree line and to assess the success of a modified version of the biomization method that incorporates pollen productivity and dispersal in distinguishing the tree line. Location Northern Canada (307 sites) and Alaska (316 sites). Methods The REVEALS method for estimating regional vegetation composition from pollen data was simplified to provide correction factors to account for differential production and dispersal of pollen among taxa. The REVEALS‐based correction factors were used to adapt the biomization method and applied as a set of experiments to pollen data from lake sediments and moss polsters from the boreal tree line. Proportions of forest and tundra predicted from modern pollen samples along two longitudinal transects were compared with those derived from a vegetation map by: (1) a tally of ‘correct’ versus ‘incorrect’ assignments using vegetation in the relevant map pixels, and (2) a comparison of the shape and position of north–south forest‐cover curves generated from all transect pixels and from pollen data. Possible causes of bias in the misclassifications were assessed. Results Correcting for pollen productivity alone gave fewest misclassifications and the closest estimate of the modern mapped tree line position (Canada, + 300 km; Alaska, + 10 km). In Canada success rates were c. 40–70% and all experiments over‐predicted forest cover. Most corrections improved results over uncorrected biomization; using only lakes improved success rates to c. 80%. In Alaska success rates were 70–80% and classification errors were more evenly distributed; there was little improvement over uncorrected biomization. Main conclusions Corrected biomization should improve broad‐scale reconstructions of spatial patterns in forest/non‐forest vegetation mosaics and across climate‐sensitive ecotones. The Canadian example shows this is particularly the case in regions affected by taxa with extremely high pollen productivity (such as Pinus). Improved representation of actual vegetation distribution is most likely if pollen data from lake sediments are used because the REVEALS algorithm is based on the pollen dynamics of lake‐based systems.     

Post-fire bryophyte dynamics in Mediterranean vegetation

Abstract. Bryophyte dynamics after fire in the Mediterranean macchia of Southern Italy was studied both by diachronic and synchronic approaches. Changes of bryophyte cover and species composition were found in relation to both age and fire intensity. During the first 2 yr after fire, bryophytes dominated the plots which had experienced the highest fire intensity while herbs were dominant in plots affected by lighter fires. Pioneer species, such as Funaria hygrometrica, Barbula convoluta and Bryum dunense, characterized recent intense fires, whereas Bryum torquescens, B. radiculosum and B. ruderale were dominant after less intense burning. Pleurochaete squarrosa, Tortula ruraliformis and Tortella flavovirens dominated intermediate successional stages. Pleurocarpous mosses were dominant only in the older closed stands. Different patterns of regeneration strategies were described: spores dominated early stages of intense fire, while vegetative propagules characterized later successional stages and less severely burned areas. Although bryophytes usually have a low abundance in Mediterranean vegetation, their role in post-fire vegetation dynamics may be locally enhanced according to burning conditions.     

Vegetation patterns,pollen deposition and distribution of non-pollen palynomorphs in an ice-wedge polygon near Kytalyk (NE Siberia), with some remarks on Arctic pollen morphology

In ice-wedge polygon mires, small-scaled microrelief of ridges enclosing small depressions results in a short-distance vegetation mosaic. The correct recognition of these landscape elements in palaeoecological studies of peat sections in order to reconstruct their patterns and dynamics requires insight in the short-distance relationship between vegetation and pollen deposition. This paper presents an analysis of pollen surface samples in a high-resolution (1 m) transect across an ice-wedge polygon near Kytalyk (NE Siberia), including a discussion on the morphology of some critical pollen types and non-pollen palynomorphs (NPPs). We found a strong correlation between vegetation and surface elevation and a fair correspondence between pollen deposition and vegetation. Distribution of NPPs reflects surface elevation well, with algal spores dominating deep spots and testate amoebae prevailing on higher spots. Peak pollen/spore values unrelated to high species coverages (e.g. of Salix, Betula, Sphagnum, Poaceae) indicate that single plants within a population may cause the bulk of the pollen production. The absence of pollen of taxa with an important presence in the vegetation (e.g. Utricularia) must be attributable to low pollen productivity. Distributional patterns point at pollen transport by water in the polygon troughs/depressions. Our study shows that Arctic pollen records mainly reflect short-distance vegetation patterns. Palaeosequences consequently allow accurate reconstruction of local microtopography and its dynamics, but should not be over-interpreted in terms of changing (over)regional vegetation patterns and associated drivers.     

Altitudinal zonation of evergreen broad-leaved forest on Mount Lopei,Taiwan

Abstract. Evergreen broad-leaved forest was studied in a transect on the northwestern slope of Mount Lopei in order to reveal altitudinal zonation in structure and floristic composition and the decisive environmental factors. 20 plots of 20 m × 20 m at altitudes from 540 m to 1320 m were analysed. 144 woody species were found. The results of a DCA ordination clearly pointed to a single dominant altitudinal gradient. Nevertheless, wind-exposure associated topography was found to account for additional variation for a given altitudinal range. Along the altitudinal gradient, four dominance-based forest types were recognized. Tree density, species diversity and evenness of the four types differed significantly but total basal area and tree volume were not significantly different. The 95 % turnover range for woody species as measured by the Community Coefficient was calculated as 1030 m, and the 50 % turnover range as 238 m. For the understorey, the change in species composition with altitude was less obvious. Species population structures of 57 sufficiently abundant species revealed four characteristic patterns, but most species showed a good fit to the negatively exponential or power function distribution and thus appeared to have good reproduction and regular recruitment. Both ANOVA and Redundancy Analysis (RDA) showed that significant differences among forest types were found for most soil variables. Organic C, exchangeable Na and K tended to increase with altitude, while pH and available N showed a reverse trend. There was little evidence that the differences in soil pH and available N were responsible for the variation in forest growth.     

Modern pollen–vegetation relationships in subarctic southern Greenland and the interpretation of fossil pollen data from the Norse landnám

Aim The objective of this paper is to explore the relationships that exist between vegetation and modern pollen rain in the open, largely treeless landscape of subarctic Greenland. The implications of these results for the interpretation of fossil pollen assemblages from the time of the Norse landnám are then examined. Location The study area is the sheep farming district of Qassiarsuk in the subarctic, subcontinental vegetational and climatic zone of southern Greenland (61° N, 45° W). Between c.ad 1000–1500 this region was contained within the Norse Eastern Settlement. Methods Detrended Correspondence Analysis (DCA) of harmonized plant–pollen data sets is used to compare plant cover in 64 vegetation quadrats with pollen assemblages obtained from moss polsters at matching locations. Presence/absence data are also used to calculate indices of association, over‐ and under‐representation for pollen types. Results Good correspondence between paired vegetation–pollen samples occurs in many cases, particularly in locations where Salix glauca–Betula glandulosa dwarf shrub heath is dominant, and across herbaceous field boundaries and meadows. Pollen samples are found to be poor at reflecting actual ground cover where ericales or Juniperus communis are the locally dominant shrubs. Dominant or ubiquitous taxa within this landscape (Betula, Salix and Poaceae) are found to be over‐represented in pollen assemblages, as are several of the ‘weeds’ generally accepted as introduced by the Norse settlers. Main conclusions Due to their over‐representation in the pollen rain, many of the Norse apophytes and introductions (e.g. Rumex acetosa and R. acetosella) traditionally used to infer human activity in Greenland should be particularly sensitive indicators for landnám, allowing early detection of Norse activity in fossil assemblages. Pteridophyte spores are found to be disassociated with the ground cover of ferns and clubmosses, but are over‐represented in pollen assemblages, indicating extra‐local or regional sources and long residence times in soil/sediment profiles for these microfossils. A pollen record for Hordeum‐type registered in close proximity to a field containing barley suggests that summer temperatures under the current climatic regime are, at least on occasion, sufficient to allow flowering.     

Vegetation and climatic history of southwest Africa: A marine palynological record of the last 300,000 years

A continuous palynological record from the marine core GeoB1016-3 from the Angola Basin reveals the regional vegetation and climate history of the last 300 ka. Pollen and spores found at the studied site have their source areas in the different vegetation zones of the adjacent part of the West African continent. Those vegetation zones comprise tropical rain forest, coastal mangrove swamp, Miombo woodland, dry forest, Afromontane forest, desert and semi-desert. The main pollen transport agent is the southeast trade wind system. Ocean currents also partly play a role in transporting pollen and spores. During the interglacial periods, ocean currents also transported palynomorphs southward. During the glacial periods, increased trade winds are indicated by high influx of pollen and spores and high pollen percentages of Poaceae and taxa from desert and semidesert vegetations. Reconstruction of the geographical position of palaeo-vegetation zones shows that the northern boundary of the Namib Desert did not move north of 12°S during the last 300 ka. This implies that northward shifts of the Angola-Benguela Front did not pass the latitude of 12°S.     

Spatial variation of modern pollen in Oregon and southern Washington, USA

Surface sediments from 95 lakes provide information on the spatial variation of modern pollen spectra in Oregon and southern Washington. Percentages for 13 pollen types were compared within and between vegetation zones to characterize regional patterns of pollen spectra. The percentage data were also compared with climate variables to determine relationships between pollen percentages and regional climate gradients. The composition of modern pollen spectra corresponds well with the distribution of the pollen producers. Most pollen assemblages were generally dominated by Pinus, but those west of the Cascade Range were dominated by Alnus. Low percentages of Pseudotsuga/Larix, Tsuga mertensiana, Abies, and Picea pollen coincided with local occurrence of the trees. The distributions of the pollen data were arranged along gradients of temperature and effective moisture. West of the Cascade Range, Alnus, Tsuga heterophylla, Pseudotsuga/Larix, and Cupressaceae pollen were abundant and correlate well with moderate temperature and high effective moisture. In the shrub-steppe and woodlands east of the Cascade Range, where effective moisture is low, Artemisia, Cupressaceae, and Pinus pollen were dominant. At high elevations, Pinus, T. mertensiana, Abies, and Picea were common pollen types in areas with short growing seasons and high effective moisture. Pollen percentages collected from lake surface sediments, moss polsters, and soils were compared within a number of vegetation types to assess their similarity. The three types of sample yielded similar results for forested areas, but lake sediment samples from upper- and lower-treeline sites captured a more regional picture of the vegetation.     

Spatial variation in a grassland on soil rich in heavy metals

Abstract. The vegetation in a grassland area in the prefecture of Kilkis (N. Greece), known for its surface Cu-mineralization, was studied. 43 quadrats were established along a transect through an area where the vegetation formed patches of different size. Cover-abundance and frequency estimates for all species were made. Normal Association Analysis revealed five quadrat groups characterized by Trifolium scabrum, Linaria pelisseriana, Anthoxanthum ovatum, Gypsophila muralis and Minuartia hirsuta ssp. falcata. 43 soil samples were analysed for pH, organic C, CaCO₃, total content of Fe, Zn, Pb, Cu, Mn, Ca, Mg, K, Na and soil texture. From a discriminant analysis performed on soil data five soil groups resulted, which are highly related to the five vegetation groups. Thymus sibthorpii, Minuartia hirsuta ssp. falcata and Rumex acetosella are the most important taxa with respect to physiognomy and patchi-ness of the vegetation. The number of species in each group of quadrats is affected by the relative favourableness or severity of the soil conditions. Metal contents, mainly Zn, Cu, Mg and Na, and soil texture are considered to be among the main factors controlling the structure and physiognomy of the vegetation.     

Geothermal bryophyte habitats in the South Sandwich Islands,maritime Antarctic

Question: How does geothermal activity influence terrestrial plant colonization, species composition and community development in the Antarctic? Location: South Sandwich Islands, maritime Antarctic. Methods: Bryophytes were documented during a biological survey of the archipelago in January and February 1997. Particular attention was given to sites under current or recent influence of geothermal activity. Temperature profiles obtained across defined areas of activity on several islands were linked with the presence of specific bryophytes. Results: Greatest bryophyte richness was associated with geothermally influenced ground. Of 35 moss and nine liverwort species recorded, only four mosses were never associated with heated ground, while eight of the liverworts and 50% of the mosses were found only on actively or recently heated ground. Some species occur in unheated sites elsewhere in the maritime Antarctic, but were absent from such habitats on the South Sandwich Islands. Several species occurred in distinct zones around fumaroles. Maximum temperatures recorded within the upper 0.5 cm of the vegetation surface were 40 ‐ 47 °C, with only Campylopus introflexus tolerating such temperatures. Maximum temperatures 2.5 or 5 cm below the vegetation surface of this moss reached 75 °C. Other bryophytes regularly present in zoned vegetation included the mosses Dicranella hookeri, Sanionia georgico‐uncinata, Pohlia nutans and Notoligotrichum trichodon, and the liverworts Cryptochila grandiflora and Marchantia berteroana. Surface temperatures of 25 ‐ 35 °C and subsurface temperatures of 50 ‐ 60 °C were recorded in these species. Conclusions: These exceptional plant communities illustrate the transport of viable propagules into the Antarctic. Individually ephemeral in nature, the longer term existence of geothermal habitats on islands along the Scotia Arc may have provided refugia during periods of glacial expansion, facilitating subsequent recolonization of Antarctic terrestrial habitats.     

Modern pollen–vegetation relationships along transects on the Whangapoua Estuary, Great Barrier Island, northern New Zealand

Aims To quantify pollen–vegetation relationships from saline to freshwater in an estuarine gradient from surface samples of the modern pollen rain, to allow more accurate interpretations of the stratigraphic palynological record. Location Whangapoua Estuary, Great Barrier Island, northern New Zealand. Methods Six transects were laid out along a vegetation sequence running from estuarine mud to freshwater swamp. Along these transect lines, 108 plots were sampled for vegetation and surface sediments from wet sand, mud, plant litter or moss (sand and mud sites are inundated by most tides, other sites less frequently). All sediment samples were analysed for pollen. The relationships between plant species frequency and pollen representation were examined at a community scale using twinspan and ordination analyses, and for individual species using fidelity and dispersibility indices, regression and box‐plot analyses. Results The quantitative relationships between source taxon vegetation frequency and its pollen representation varied between species due to differential pollen production and dispersal. twinspan of the surface pollen samples suggests five vegetation types: (A) mangrove (Avicennia marina); (C) Leptocarpus similis salt meadow; (D) Baumea sedges; (E) Leptospermum shrubland; and (F) Typha/Cordyline swamp forest. The (B) Juncus kraussii community is not represented palynologically owing to the destruction of its delicate pollen grains during acetolysis of samples. Detrended correspondence analysis places these communities on an estuarine‐to‐freshwater gradient. However, pollen assemblages at the seaward end of the salinity gradient are less clearly representative of the associated vegetation than those at the landward end, probably because the open vegetation at the former allows the influx of wind‐ and water‐dispersed pollen from surrounding vegetation. Main conclusions The vegetation pattern (zonation) at Whangapoua is reflected in the pollen rain. When the long‐distance and over‐represented pollen types are excluded, five out of six of the broad vegetation communities can be identified by their pollen spectra. Species with high fidelity and low‐to‐moderate dispersibility indices can be used to identify the vegetation types in the sedimentary sequences. The more open vegetation types at the ‘marine end’ of the sequence tend to be ‘overwhelmed’ by regional pollen, but the nature of the sediments and the presence of discriminatory species (e.g. A. marina, Plagianthus divaricatus, Cordyline australis), even in small amounts, will allow correct identification of the local vegetation represented in sedimentary palynological sequences. A box‐plot analysis indicates that the pollen and spore types A. marina (mangroves), Sarcocornia quinqueflora (salt meadow), P. divaricatus (sedges), Gleichenia (shrubland) and C. australis (swamp forest) are highly discriminatory in relation to vegetation type. These discriminatory palynomorphs help with the interpretation of stratigraphic pollen studies. However, salt marsh vegetation communities in the sediments must be interpreted with caution as the marine sediments are easily affected by erosion, bioturbation and tidal inundation effects.     

Regeneration by seeds in alpine meadow and heath vegetation in sub‐arctic Finland

Abstract. This paper compares the regeneration by seeds of heath and meadow and studies relationships between the floristic composition of phases in the regeneration pathway. Seed densities in the seed rain and seed bank as well as the densities of emerged seedlings in gaps and in closed vegetation were greater in the meadow than in the heath. In the heath, environmental constraints hindered seedling emergence almost completely so seeds accumulated in the seed bank. In the meadow, the decrease in the seed bank was due to high seedling emergence. Within both plant communities, seedling emergence in gaps and in closed vegetation was comparable. In the meadow, the seed rain and seedling emergence in gaps, as well as the seed bank and seedling emergence in gaps were positively correlated. Differences in seed and adult plant sizes were reasons for the low correlation between the standing vegetation and the other phases. In DCA ordination the first axis separated the phase of seedling emergence in closed vegetation and seed bank. The second axis separated the standing vegetation from the other phases. The structure of the seed rain was more heterogeneous than that of other phases. In the heath, the standing vegetation and the seed rain were positively correlated. The ordination of these phases reflected the patchiness of standing vegetation and the ability of the diaspores of Betula nana to disperse over long distances.     

Nutrient supply in undrained and drained Calthion meadows

Abstract. Plant species-rich Calthion meadows on mesotrophic fen peat soil extensively cut for hay are among the endangered semi-natural vegetation types in northwestern Europe. They are often badly affected by lowering the groundwater table (drainage) and fertilization. In a comparative study of an undrained site with a Calthion meadow and an adjacent drained site, availability of N, P and K was biologically assessed under field conditions (for two years) as well as in a greenhouse (for 18 weeks) by measuring shoot responsiveness. Also, experimental wetting of intact turf samples taken from both sites was applied in order to study the interaction between nutrient supply and anaerobic soil conditions. It was concluded that the above-ground phytomass yield in the undrained site was restricted by a major shortage of N-supply and a moderate shortage of K-supply by the fen peat soil. The above-ground phytomass yield of the drained site was only reduced by a strongly limited supply of K by the soil. The extent of K-deficiency was larger for the drained site. No P-deficiency was observed in any of the drained or undrained sites. Rewetting turf samples, taken from the drained site, did not change above-ground phytomass yields, suggesting that nutrient supplies were not affected by rewetting. Leaching has likely resulted in a strong reduction of K-supply in the drained site. It is assumed that a shortage in K-supply from the peat soil may have become an important environmental constraint for characteristic plant species of Calthion meadows. This may hamper the development of this meadow type on drained peat soils after rewetting by groundwater discharge.