Long-term vegetation dynamics and the infilling process of a former lake (Švarcenberk, Czech Republic)

Natural lakes are a rare phenomena within extraglacial areas of Central Europe. Almost all have been completely terrestrialized during the Holocene. This paper deals with one such former lake, located in southern Bohemia. Its extensive lacustrine and peat deposits were subjected to a multidisciplinary study that resulted in high-resolution pollen, macrofossil, algal and sediment-chemistry data interpreted in terms of past climate, geomorphology, soil, and regional vegetation development over the last 16,000 years. Against the background of these large-scale processes, local development took place, comprising the lake’s ontogeny from an arctic-type ecosystem hosting pioneer aquatic communities, through a highly diversified mosaic of eutrophic hydrosere habitats (shallow pools,Phragmites andCarex fen, alder carr), towards an oligotrophic mire that started to dome over the terrestrialized lake. At every individual development stage, specific processes characterized ecosystem function and composition: during the Late-Glacial with its rapid climatic changes, external forces induced the major stresses; while during the Holocene, autogenic changes of the wetland ecosystem played the most important role.     

Short-Term Vegetation Dynamics of Alnus Dominated Peatlands: a High Resolution Palaeoecological Case Study from Western Pomerania (NE Germany)

Actual ecological research postulates for alder carrs a cyclic alternation of Alnus tree vegetation with open fen or Salix dominated vegetation. Such cycles are also indicated in palaeo-ecological studies, but normally the temporal resolution of these studies is insufficient to resolve the duration of short-term cycles in vegetation development. This paper presents a high resolution palaeoecological study (including pollen, macrofossils and non-pollen palynomorphs) of a Late Holocene wood peat section from the small, long-term Alnus dominated peatland ‘Heger Soll’ in the ‘Rodder Forst’ in Western Pomerania (NE Germany) to reconstruct short-term vegetation changes. During a time-span of ca. 800 years, sedge-dominated fen vegetation types alternated with two phases of Alnus carr and one phase of Salix shrubland. The alder carr decline coincided with the beginning of intensified human activity in the surroundings of the mire and was probably connected to increased water discharge resulting from large-scale deforestation, after which willow scrub and sedge fen became established. Growth of Alnus trees was associated with prolonged phases of reduced human impact and probably less water supply. This study shows that human impact on the uplands surrounding the mire and on the alder carr itself may explain the observed “cyclic” vegetation development of alder carrs, willow scrubs and sedge fens in Central Europe.     

How soil characteristics and water quality influence the biogeochemical response to flooding in riverine wetlands

Although phosphate concentrations have been reduced, the rivers Meuse and Rhine are still polluted with sulphate, which most probably affects vegetation development in newly created riverine wetlands. The influence of flooding with river water rich in sulphate was tested on three soil types from floodplains of the river Meuse using flow-through and batch experiments. Soils were selected for contrasting concentrations of iron and organic matter and originated from a floating fen (iron-poor, organic), an alder carr (iron-rich, organic) and a clay pit (iron-rich, low in organic matter). Flooding induced mobilisation of phosphate. Sulphate only enhanced this effect in the alder carr soil, where sulphide and phosphate competed for binding to iron. Only in the floating fen soil did the addition of sulphate result in the formation of free sulphide, which reduced the growth of Glyceria maxima, serving as a phytometer. In addition, the floating soil started to sink, due to falling methane concentrations. In the different soil types methane production was hampered by the presence of more favourable electron acceptors such as sulphate in the water and Fe(III) in the soil. It was concluded that the effects of inundation with sulphate-polluted water strongly depend on the soil type: under iron-poor circumstances, free sulphide may accumulate, leading to phytotoxicity, while in soils rich in iron, sulphide toxicity is prevented, but phosphate availability may be increased. In addition, shortage of easily degradable organic matter can limit the formation of potential toxicants such as ammonium, iron and sulphide. Results are discussed in terms of their implications for nature management.     

Multiproxy study of anthropogenic and climatic changes in the last two millennia from a small mire in central Poland

The Żabieniec kettle hole is the first peatland in central Poland analyzed quantitatively with four biotic proxies (plant macrofossils, pollen, testate amoebae and chironomids) to reconstruct the past environmental change. Palaeoecological data were supported by historical and archaeological records. We focused on autogenic vegetation change and human impact in relation to climatic effects. The aims of our study were (a) to describe the development history of the mire during the last 2,000 years, (b) to date and reconstruct the anthropogenic land-use changes and (c) to discuss a possible climatic signal in the peat archive. The combination of proxies revealed dramatic shifts that took place in the peatland since the Roman Period. Żabieniec was a very wet telmatic habitat until ca. AD 600. Then, the water table declined, and the site transformed into a Sphagnum-dominated mire. This dry shift took place mainly during the Early Medieval Period. Human impact was gradually increasing, and it was particularly emphasized by deforestation since AD 1250 (beginning of the Late Medieval Period). Consequently, surface run-off and aeolian transport from the exposed soils caused the eutrophication of the mire. Furthermore, chironomids and testate amoebae reveal the beginning of a wet shift ca. AD 1350. Openness considerably increased in the Late Medieval and the Modern Periods. The highest water table during the last 1,000 years was recorded between AD 1500 and 1800. This wet event is connected with deforestation, but it could be also associated with the Little Ice Age. Our study shows plant succession in the Żabieniec peatland, which can be explained with the recent landscape transformation. However, such changes are also possibly linked with the major climatic episodes during the last two millennia, such as the Medieval Warm Period and the Little Ice Age. Guest editors: K. Buczkó, J. Korponai, J. Padisák & S. W. Starratt Palaeolimnological Proxies as Tools of Environmental Reconstruction in Fresh Water     

Accumulation rates of organic matter associated with different successional stages from open water to carr forest in former turbaries

This paper investigates the rates of peat accumulation associated with different phases in the succession from open water to carr forest in shallow ponds created by peat dredging in The Netherlands. Four phases had been recognized in a previous study of aerial photographs for the period 1937–1990, i.e. open water (Aq), reed swamp (SA), brownmoss quaking fen (BM) and carr forest (CF). Peat accumulation rates were estimated by relating the amounts of organic matter stored to the data on the successional history for 21 different sites.The organic matter accumulation rates were highest in the SA phase (1.12 kg m^-2 y^-1 on a dry weight basis), intermediate in the BM and CF phases (0.49 and 0.58 kg m^-2 y^-1), and lowest in the Aq phase (0.26 kg m^-2 y^-1). These values are high in comparison with values determined for fen ecosystems with stratigraphic methods in combination with radiocarbon dating. The accumulation rates were inversely related to the average duration of the successional phases, suggesting that peat accumulation is a major driving force behind the succession.     

Seasonal succession and strategies of phytoplankton development in two lakes of different trophic states

This study describes the metabolism and structure of phytoplanktoncommunities during seasonal periodicity and discusses strategiesof development adopted by species during succession. The studywas conducted in two trophically different lakes. Each lakedemonstrates a different degree of the ecological succession,which prescribes an increasingly complex taxocenose. In oligomesotrophicLake Pavin the autogenic succession lasts from spring overturnuntil mid-summer. In eutrophic Lake Aydat the autogenic successionis strictly limited to spring. The seasonal changes of the communityproductivity, turnover rate (P/B) and adenylate energy chargeconfirm the hypothesis of a change of the ‘metabolic orientation’of phytoplankton cells during seasonal succession. The autogenicsuccession represents the progression from a growth-orientedstrategy to an equilibrium-oriented one.     

Germination and seedling survival in fens undergoing succession

We studied mechanisms of vegetation change in fens subject to succession from open water to floating mats and finally herbaceous rich-fens. Earlier research showed that these systems are characterized by transient seed banks. Our main question was whether seedlings of later successional fen stages are already present in earlier stages, remaining subordinate in the vegetation until conditions become suitable for them. If, however, conditions during succession change in a way that only a limited set of species can survive as seedlings during each of the successional stages, no seedling bank will exist. The transient character of the seeds would then imply that seeds will not germinate and will subsequently die and that seeds that have germinated in the “wrong” stage will not become established. We hypothesized that: (1) germination and seedling survival of fen species are significantly better in the successional fen stage for which these species are characteristic, (2) as a consequence no seedling banks occur in these fens. In a field experiment, seeds of five characteristic fen species in the standing vegetation of three successional fen stages i.e. raft fen, quaking fen and rich fen were sown in each of these stages in a turf pond in the Tienhoven area, The Netherlands. Germination and seedling survival were measured over two growing seasons together with environmental variables. Germination was higher in the “own” stage for all species groups as was survival for quaking fen species and rich fen species. For both these stages, percentage of germination and survival of four out of five characteristic species were significantly higher in the “own” stage. Germination and survival can be considered stage-dependent and it was concluded that seedling banks do not exist in these fens. Site-specific environmental variables act as a sieve and differentiate on species presence already during early life history stages. We found clues that the environmental sieve acts at the level of nutrient availability, tolerance for high sulphide concentration and light climate. Because of the transient seed bank and absence of a seedling bank in these fen wetlands, successful establishment of species necessitates a continuous dispersal of characteristic species until the environmental conditions permit establishment. This also implies that species of the whole successional sere should be present within dispersal distance.     

Late-glacial and Holocene climate dynamics at the steppe/forest ecotone in southernmost Patagonia, Argentina: the pollen record from a fen near Brazo Sur, Lago Argentino

We present a pollen record from a fen at the eastern shore of Brazo Sur south of Lago Argentino, Argentina (core BRS 1/06, 50°34′54″S, 72°54′52″W, 198 m a.s.l.). The coring site is located in the transition zone from humid grass steppe to Andean Nothofagus forest. With the exception of a mid-Holocene sand layer, the record covers the interval between 13,350 and 1,700 cal b.p., indicating that there could have been no recurrence of Late-glacial conditions in Brazo Sur, as has been suggested in the literature as having been contemporary with the Younger Dryas interval in the northern hemisphere. The Late-glacial and early Holocene periods at Brazo Sur are characterized by fluctuations between humid grass-dominated steppe associations and drier ones dominated by Asteraceae and Ericaceae. At the start of the Holocene, the pollen influx increased. Nothofagus dominance began by 7,700 cal b.p. probably due to increasing moisture. Present-day closed Nothofagus forest developed around 2,500 cal b.p., related to a further increase in moisture.     

The interpretation of fen carr pollen diagrams: pollen–vegetation relationships within the fen carr

Sediments deposited in fen carr environments are frequently used in pollen-based reconstructions of vegetation history, although few studies of modern pollen–vegetation relationships in fen carr have been undertaken to aid the interpretation of fossil assemblages. It is often assumed that the wetland pollen signal will reflect the overall composition of the fen carr system although, given the closed canopy context, it may actually be dominated by local vegetation elements. This paper seeks to determine whether the vegetation heterogeneity within a modern fen carr is reflected in the pollen signal of the wetland taxa. Vegetation composition was recorded around a series of moss polster sample points at Calthorpe and Wheatfen, two areas of fen carr in the Norfolk Broadland, UK. The spatial interrelationship between the wetland components of the vegetation and their palynological equivalents in the moss polster pollen assemblages is explored through trend surfaces and a correlation based statistical test (the Mantel Test). The representation of the major vegetation components in the pollen record is highly variable. Values for Alnus glutinosa, a dominant canopy species, range from 5.3% to 73% of total land pollen (TLP) at Calthorpe and 2.5–61% TLP at Wheatfen. In part, this variation reflects the enhanced input of pollen from dry land sources close to the wetland edge although the variation recorded at points equidistant from the dry land margin suggests that other processes are also influential. The strongest positive associations in the Mantel Test are for under-storey and ground flora elements that are poorly represented in the pollen record. Taxa for which there is no association include those with few vegetation occurrences and those for which a large proportion of the pollen appears to have been derived from outside the study areas. We conclude that modern pollen samples collected from fen carr broadly reflect the vegetation composition of the study areas. However, the input of pollen from fen carr species is spatially inconsistent. Differences between the sample points can be attributed to the distribution and pollination biology of the under-storey and ground flora elements and the structure of the vegetation around sites. The results caution against assuming that changes in the pollen representation of wetland taxa, in fossil sequences constructed from fen carr deposits, necessarily reflect changes in the overall composition of the community.     

Fine-Scale Horizontal and Vertical Micro-distribution Patterns of Testate Amoebae Along a Narrow Fen/Bog Gradient

The ecology of peatland testate amoebae is well studied along broad gradient from very wet (pool) to dry (hummock) micro-sites where testate amoebae are often found to respond primarily to the depth to water table (DWT). Much less is known on their responses to finer-scale gradients, and nothing is known of their possible response to phenolic compounds, which play a key role in carbon storage in peatlands. We studied the vertical (0–3, 3–6, and 6–9 cm sampling depths) micro-distribution patterns of testate amoebae in the same microhabitat (Sphagnum fallax lawn) along a narrow ecological gradient between a poor fen with an almost flat and homogeneous Sphagnum carpet (fen) and a “young bog” (bog) with more marked micro-topography and mosaic of poor fen and bog vegetation. We analyzed the relationships between the testate amoeba data and three sets of variables (1) “chemical” (pH, Eh potential, and conductivity), (2) “physical” (water temperature, altitude, i.e., Sphagnum mat micro-topography, and DWT), and (3) phenolic compounds in/from Sphagnum (water-soluble and primarily bound phenolics) as well as the habitat (fen/bog) and the sampling depth. Testate amoeba Shannon H′ diversity, equitability J of communities, and total density peaked in lower parts of Sphagnum, but the patterns differed between the fen and bog micro-sites. Redundancy analyses revealed that testate amoeba communities differed significantly in relation to Eh, conductivity, water temperature, altitude, water-soluble phenolics, habitat, and sampling depth, but not to DWT, pH, or primarily bound phenolics. The sensitivity of testate amoebae to weak environmental gradients makes them particularly good integrators of micro-environmental variations and has implications for their use in paleoecology and environmental monitoring. The correlation between testate amoeba communities and the concentration of water-soluble phenolic suggests direct (e.g., physiological) and/or indirect (e.g., through impact on prey organisms) effects on testate amoebae, which requires further research.     

Reed die-back related to increased sulfide concentration in a coastal mire in eastern Hokkaido,Japan

A drastic decline of Phragmites australis was observed along the middle reaches of Ichibangawa River in Kiritappu Mire, eastern Hokkaido, Japan, during the last 50 years. In an area of ~30 ha, reed-sedge vegetation and alder forest have been replaced by bare soil and patches of salt marsh vegetation. A gradual increase in frequency of flooding by brackish water probably was the ultimate cause of the vegetation change. We measured redox potentials and oxygen and sulfide concentrations in soil profiles using needle electrodes. Measurements were carried out in areas where reed has disappeared and in sites where reed stands were still healthy. The concentration of selected ions in the surface water was also measured at various sites. Surface water in low-lying areas was clearly influenced by seawater. Very high sulfide concentrations were measured in bare peat sites (more than 600 mol l^–1), which exceeded P. australis tolerance 2 – 3 times. In a healthy reed zone adjacent to an area with poor fen vegetation, sulfide concentration in the rooting zone of Phragmites was also high (300–400 mol l^–1), particularly during the night. The fact that Phragmites in this zone was still healthy indicates that sulfide did not reach toxic levels in the direct vicinity of the roots. Sulfide that is produced in this area is probably fixed by iron, which is supplied through a continuous discharge of iron-rich groundwater. An increase in frequency of flooding by brackish water could be related to ongoing subsidence of this part of the Pacific coast which is located at the Kuril subduction zone. Sea level rise could also contribute to a stronger inflow of seawater into the mire system.     

A three thousand year succession of plant communities on a valley bottom in the Vosges Mountains, NE France, reconstructed from fossil pollen, plant macrofossils, and modern phytosociological communities

Pollen and macrofossils were studied in a core from a fen at the foot of a slope in the Vosges Mountains, NE France. The present-day vegetation of little disturbed Abies, Fagus, and Picea forest and wetlands has been described in detail in terms of phytosociological communities using the Braun-Blanquet approach. Past ecological conditions are reconstructed in five steps: (1) The modern vegetation types are described as combinations of phytosociological species groups. (2) Micro- and macrofossils are assigned to these groups. (3) These in combination determine the past vegetation types at the site; there were simultaneously several such types in some biozones. (4) The sequence of past vegetation types is interpreted as successional pathways. (5) Past ecological conditions are inferred from these pathways. Results are: (1) The types of local forest and fen were the same around 1000 b.c. as today. (2) Rising groundwater around 650 b.c. caused a natural wet meadow to develop at the site. (3) Trees were felled near the site in the first century b.c. (Late Iron Age), facilitating the immigration of Picea. (4) Groundwater level rose during early Medieval times because of a wetter climate and alder carr replaced the dry-soil forest close to the site. (5) During High Medieval Times (10th–13th century) the nearby raised bog expanded over the site. (6) Forestry starting around a.d. 1750 caused nutrient-rich water to reach the site, resulting in abrupt vegetation change. (7) The creation of a forest road around a.d. 1855 (historical information) caused further nutrient enrichment of the site. The validity of the method used depends on the assumption that past and present vegetation types are virtually identical, which is true in our study area and study period, according to all the indications that we have.     

Key variables controlling the vegetation of a cool-temperate mire in northern Japan

Abstract. In the cool-temperate Bibi Mire, Hokkaido, Japan, valley fens and flood-plain fens have quite different vegetation. The main variables controlling the vegetation were all hydrological: mean water level, water level fluctuation and surface water flow. Chemical factors such as electrical conductivity, dissolved oxygen and related peat decomposition were less important. The pH was about neutral and has little effect. The flood-plain fen developed under fluctuating water table conditions. The dominant species are Calamagrostis langsdotffii and Carex pseudocuraica. When temporal inundation occurs in the rainy or typhoon seasons, the submergence stimulates bud germination of the stoloniferous C. pseudocuraica, which can rapidly elongate its stolons upward. Some large floating peat mats occurred in the flood-plain fen zone. On these mats some Alnus japonica saplings establish and patches of alder forest can arise. Here the water level was higher than in the peripheral alder forest zone. The valley fen is dominated by Carex lasiocarpa var. occultans and/or C. limosa. It is formed under stable water table conditions in the inundated parts of the mire -where the non-inundated wet areas are dominated by alder trees. In the area where the surface water is flowing, these two fen sedges grow in deeper water since the high oxygen content is considered to compensate the flooding stress.     

Functional Diversity of Culturable Bacterial Communities in the Rhizosphere in Relation to Fine-root and Soil Parameters in Alder Stands on Forest, Abandoned Agricultural, and Oil-shale Mining Areas

Grey alder (Alnus incana) and black alder (Alnus glutinosa) stands on forest land, abandoned agricultural, and reclaimed oil-shale mining areas were investigated with the aim of analysing the functional diversity and activity of microbial communities in the soil–root interface and in the bulk soil in relation to fine-root parameters, alder species, and soil type. Biolog Ecoplates were used to determine community-level physiological profiles (CLPP) of culturable bacteria in soil–root interface and bulk soil samples. CLPP were summarized as AWCD (average well color development, OD 48 h⁻¹) and by Shannon diversity index, which varied between 4.3 and 4.6 for soil–root interface. The soil–root interface/bulk soil ratio of AWCD was estimated. Substrate-induced respiration (SIR) and basal respiration (BAS) of bulk soil samples were measured and metabolic quotient (Q = BAS/SIR) was calculated. SIR and Q varied from 0.24 to 2.89 mg C g⁻¹ and from 0.12 to 0.51, respectively. Short-root morphological studies were carried out by WinRHIZO^TM Pro 2003b; mean specific root area (SRA) varied for grey alder and black alder from 69 to 103 and from 54 to 155 m² kg⁻¹, respectively. The greatest differences between AWCD values of culturable bacterial communities in soil–root interface and bulk soil were found for the young alder stands on oil-shale mining spoil and on abandoned agricultural land. Soil–root interface/bulk soil AWCD ratio, ratio for Shannon diversity indices, and SRA were positively correlated. Foliar assimilation efficiency (FOE) was negatively correlated with soil–root interface/bulk soil AWCD ratio. The impact of soil and alder species on short-root morphology was significant; short-root tip volume and mass were greater for black alder than grey alder. For the investigated microbiological characteristics, no alder-species-related differences were revealed.     

The role of human disturbance in the local Late Holocene establishment of Fagus and Picea forests at Flahult, Western Småland, Southern Sweden

A pollen record from a small alder carr located in the centre of aFagus stand near the hamlet of Flahult in southern Småland has shown thatFagus became established in a semi open cultural landscape about 900 B.P. Human disturbance seems to have controlled the local establishment ofFagus at this site through an expansion of pastoral farming. TheFagus dominance in the present stand seems to be of recent origin, asFagus pollen percentages and influx values have increased considerably only during the last 50 years. The modern composition and structure of theFagus stand are probably an effect of changes in land-use and decreased human activity at the end of the last century. Today, only occasionalPicea individuals occur in the studied stand, andPicea does not appear to have been more abundant in the recent past. The regional expansion ofPicea has probably occurred during this century and has been favoured by modern forestry during the last 50 years.     

Microenvironmental conditions for Japanese alder seedling establishment in a hummocky fen

In this article, we focused on hummocky microtopography as a prominent feature of mires and explored the microenvironmental conditions suitable for alder seedling establishment. Japanese alder (Alnus japonica) forest is widely distributed in wetlands in northern Japan. However, because alder seedlings are rare in mires, alder population dynamics and conditions that favor the establishment of alder seedlings are still unknown. The study was conducted in northern Japan at a site in mesotrophic mire. We surveyed the seedling density, the microenvironmental conditions (light, litter cover, and soil quality), and the density of dispersed seeds in alder forest and in the adjacent herbaceous fen. In addition, we performed a laboratory experiment to examine the germination characteristics of alder. Seedlings grew only on hummocks in alder forest. The percentage of litter cover on hummocks was lower than in hollows, and the density of dispersed seeds in alder forest was much higher than in herbaceous fen. Seeds of Japanese alder germinated under both light and dark conditions, and the germination rate were high under light and high-temperature conditions. Our results suggest that litter cover may inhibit seedling establishment and hummocks that characterized by less litter cover are suitable place for the establishment of seedlings. We conclude that hummocky microtopography and abundant seed rain in the mire enable the establishment of Japanese alder seedlings.     

Effects of above-ground browsing by mammals on mycorrhizal infection in an early successional taiga ecosystem

Using an exclosure experiment in the willow stage of primary succession on the floodplain of the Tanana River, we tested the hypothesis that browsing can reduce mycorrhizal infection. We measured the effects winter browsing by moose (Alcesalces) and snowshoe hare (Lepusamericanus) had on mycorrhizal infection and fine root biomass of willow (Salix spp.) and balsam poplar (Populusbalsamifera). We found that protection from winter browsing increased ectomycorrhizal infection by 10% in the top 5 cm of the soil profile, by 23% at 5–10 cm, and by 42% at the 10–15 cm depth. Mammal browsing in taiga forests is now recognized as a major cause of the shift from palatable deciduous species such as willow and balsam poplar to less palatable species such as alder and spruce. We suggest that browsing-induced reduction in ectomycorrhizal infection of salicaceous species plays a central role in this shift in plant community composition. Received: 26 March 1996 / Accepted: 26 September 1996     

Late pleistocene deposits at Wretton, Norfolk. I. Ipswichian interglacial deposits

Interglacial deposits found in the low terrace at Wretton, Norfolk, were formed in the zones II and III of the Ipswichian interglacial. The variety of sediments found is associated with the fluviatile environments of a meandering river. During zone II there was a regional mixed oak forest, with the local development of alder carr, fen, reedswamp and open water communities. During zone III the regional vegetation was more open and Carpinus became an important woodland tree. Locally, fen, reedswamp and open-water communities persisted, but alder carr was absent. The plants give some indication that the climate may have been more continental than at present, a number of species occurring which are not native to the British post-glacial flora but which have a wide distribution on the Continent. A brief comparison of the vegetational history is made with that of other Ipswichian interglacial sites in England and with the correlative Eemian interglacial on the Continent. The interglacial sections at Wretton form one of the richest Ipswichian sites for non-marine Mollusca so far found in England. The presence of a few more southern or more continental species, not now living in England, confirms that the climate was probably slightly warmer than at present, at least in summer. Numbers are large enough for satisfactory analysis in almost all sections, so that the environmental conclusion they suggest can be checked against those deduced from the plants. In general, these conclusions match and indicate a series of deposits laid down by a plant-rich Fenland river, a true ancestor of the present river Wissey, in its channel and neighbouring parts of its floodplain. The occurrence of brackish water species of Mollusca allows levels of marine influence to be clearly integrated with the vegetational history. Brackish horizons occur between - 1.95 m and +0.45 m O.D. in zone II b deposits, giving an indication of sea-level at this stage. The zone III deposits, although at a lower level, show no trace of brackish influences and a possible oscillation of sea-level is inferred.     

Restoration of an abandoned species-rich fen-meadow in Denmark changes in species richness and dynamics of plant groups during 12 years

A period without management had transformed the vegetation of a species-rich fenmeadow, with no external change in the hydrological regime, into three communities: alder thicket (unmanaged 15 years), tall herb and sedge dominated communities (unmanaged 11 years). Following reintroduction of management (felling of alder thicket, mowing and grazing) the vegetation development was monitored and species cover was measured along a permanent transect before and during 12 years of restoration succession. Management increased the density of fen- meadow species and made the three communities more similar. The appearance of new fen species and the increase in species density followed immediately after the introduction of management. Thereafter, only a few new species appeared and the turnover index stabilised. Management by mowing and grazing both increased species density of herbs and promoted establishment of biennials and hemicryptophytes. Other plant groups responded differently to management: mowing increased total cover, the cover of grasses, and promoted phanerophytes and chamaephytes; grazing reduced the influence of these groups and promoted 'sedge & rush' and geophytes. Restoration was particularly successful in the felled alder thicket, but the success was caused by spreading of species from the pool of species within the site and establishment of species having persistent seed bank, i.e. inherent good potential for restoration. The results are discussed in relation to use of functional plant groups and Ellenberg N- and L-indices as response indicators for monitoring restoration progress.