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Here we present results of high-resolution palaeoecological studies of the organic deposits accumulated in Lake Jaczno, located in the north-eastern Poland. Plant macrofossils and malacological analyses complimented by radiocarbon dating (AMS) were undertaken to reconstruct Early Holocene succession of the pioneer wetland plants and molluscs in the lake ecosystem. Numerous presence of charcoal pieces (>1 mm) and fungal remains (sclerotia) in the peat layer accumulated on the mineral ground document dry habitat what coincides with warm and dry climate conditions in the early Holocene recorded in this part of Europe. Change to lacustrine environment documented by accumulation of the carbonate gyttja on the highly decomposed peat layer took place ca. 10,500 cal yr BP. The current morphology of Lake Jaczno, in which several basins can be distinguished, suggests that different age of sediments accumulated at the bottom part at our sampling sites might result from different sizes of the buried dead ice blocks, and their heterochronous final melting. The first aquatic plants that appeared in Lake Jaczno were Chara sp., Ceratophyllum demersum and Nymphaea alba. The appearance of Cladium mariscus in Lake Jaczno ca. 9400 cal yr BP was synchronous with the substantial spread of this plant in this region which coincided with increased climate humidity. The first molluscan species that colonized the lake ecosystem were Gyraulus crista and Bithynia tentaculata, species living on macrophytes, and Valvata piscinalis, typical for habitats characterized by a thick layer of plant detritus.

We document the long-term development of a spring-fed fen assessing its sensivity to climate changes over the last ca. 4000 years. Our investigation is based on high-resolution, continuous plant macrofossil remains and mollusc records, complemented by pollen, geochemical analysis and radiocarbon dating of Valea Morii, located in the Feleac Hills (Transylvanian Depression) in NW Romania, Central Eastern Europe. Based on our palaeocological data we have distinguished three stages of wet habitat conditions: two stages between 4000 and 2450 cal yr BP and one in the last 800 cal yr BP, and one dry stage between ca. 2450 and 800 cal yr BP. These local habitat conditions appear to reasonably reflect regional climate characteristics. High-resolution analysis of two replicated cores documented a mostly comparable pattern of local plant and mollusc succession, and stable isotope values from ca. 500 cal yr BP. The appearance of C. mariscus during the last two centuries may be related to increased wetness and associated active CaCO3 precipitation, which allowed this plant to colonise the spring-fed fen studied. However, it can be not excluded that the occurrence and spread of a Cladium mariscus population at this site during the last two centuries might have been partly favoured by the warming of the climate after the Little Ice Age. The potential of carbonate oxygen stable isotope values as an indicator of major trends in climatic change, both temperature and humidity, in mountain spring-fed fen deposits is shown. Carbon isotopes in the carbonates were found to be useful in reconstruction of changes in vegetation, soil development and the dissolution of bedrock carbonates, primarily as a reaction to changes in climate humidity.

Leaf wax n-alkanes are often extracted from modern plant material to describe their natural occurrence and understand the factors determining their potential as biomarkers for climate reconstruction. Despite several studies on the topic no standardised approach for n-alkane extraction from leaves has been yet devised. A common issue is the necessity to work on leaf subsamples to reduce co-extraction of unwanted polar compounds (e.g. chlorophyll), as they often interfere with individual steps involved in post-extraction, wet-chemical isolation of leaf wax n-alkanes. However, subsampling can generate biases regarding n-alkane distribution, concentration, and isotopic composition due to heterogeneities along the leaf sheath. Therefore, we propose and test an optimised extraction approach. Using leaves of Cladium mariscus and Typha angustifolia, we compared the effect on n-alkane extraction of two solvent mixtures, two extraction techniques and two sample preparation modalities. We found similar results for the two modes of sample preparation (intact vs. shredded leaf), while the use of the two solvent mixes and the two extraction techniques produced significantly different results. n-Hexane/dichloromethane 9:1 was almost twice as efficient (+97%) than the more commonly used dichloromethane/methanol 9:1, producing higher n-alkane yields while reducing co-elution of highly polar compounds. The best results, both for yield, sample processing time and solvent consumption, were achieved in combination with the accelerated solvent extraction technique, averagely +49% more efficient than ultrasound assisted solvent extraction. Alongside, we investigated the distribution of n-alkanes along the leaf sheath of C. mariscus.

Here, for the first time in SE Poland, we document the long-term development of a rich fen and assess its sensitivity to climate change and human impacts over the last ca. 3500 years. Our results are based on a high-resolution, continuous plant macrofossil remains, mollusc and pollen record, complemented by geochemical, mineral magnetic and physical characterisation, and radiocarbon dating from Bagno Serebryskie rich fen located in SE Poland. Based on the palaeoecological data we distinguished five stages of wet habitat conditions: 5000–3300, 2800–2150, 1600–1100, 750–230, 150–10 cal yr BP and five dry periods at ca. 3300–2800, 2150–1600, 1100–750, 230–150, 10 to − 64 cal yr BP. The pollen and geochemistry records, particularly Pb, show that the first human activity in the study area occurred ca. 3200 cal yr BP and increased markedly from 500 cal yr BP affecting local plant development including the population size of Cladium mariscus. Our study has shown that despite human impact (drainage, fire), Bagno Serebryskie peatland has hosted rare, presently protected species, such as Cladium mariscus for hundreds of years. We conclude that, in common with ombrotrophic bogs, rich fen ecosystems can provide a reliable source of palaeoclimatic and palaeohydrological data. Our study also shows that a large peatland (376 ha) can be as sensitive a palaeohydrological archive as smaller mires.

Late Glacial and Early Holocene vegetation history and lake level fluctuations in NE Poland were described based on high-resolution plant macrofossils analyses and records of pollen, diatoms, and radiocarbon dates. The development of Lake Kojle-Perty began in the Allerod (GI-1c). Cooling during the Younger Dryas (GS-1) led to the development of communities of heliophyte herbaceous plants. Palaeobotanical and lithostratigraphical records demonstrate that abrupt climate changes at approximately 11,600 and 9450 cal. BP resulted in distinct changes in the vegetation and water level of Lake Kojle-Perty. Climate warming in the Younger Dryas–Holocene transition (11,600 cal. BP) caused the development of the terrestrial vegetation dominated by cold deciduous forest (Betula), and appearance of thermophylious aquatic plants: Typha latifolia, Najas marina, and Ceratophyllum demersum. A gradual decrease in the lake level since 11,200 cal. BP is evident from the appearance of plants from shallow lake environments (Potamogeton natans and Hippuris vulgaris). The low water levels since 10,700 cal. BP resulting from increased temperature and evaporation caused the development of peat on limnic sediments. The dry and warm climatic phase with lowest lake level in the lakes of NE Poland were coeval with the expansion of temperate deciduous forests (Corylus and Ulmus) that commenced at approximately 10,500 cal. BP. A distinctive increase in lake levels at approximately 9450 cal. BP is suggested by the development of rush plants such as Cladium mariscus and aquatic plants such as Najas marina, Chara sp., and Nuphar lutea in the shallow parts of Lake Kojle-Perty. The increased lake levels correspond with the expansion of Alnus glutinosa in North-East (NE) Poland. Our reconstructions of the vegetation development and lake level changes align with results from other studies in the region.

The aim of this study is to model, under controlled laboratory conditions, the effect of submerged aquatic vegetation (SAV) on turbulence generated in a water column by an oscillating grid turbulence (OGT). Velocity profiles have been measured by an acoustic Doppler velocimeter (MicroADV). Experimental conditions are analysed in two canopy models (rigid and semi-rigid), using nine plant-to-plant distances ( ppd ), three stem diameters ( d ), four types of natural SAV ( Cladium mariscus , Potamogeton nodosus , Myriophyllum verticillatum and Ruppia maritima ) and two oscillation grid frequencies ( f ). To quantify this response, we have developed a non-dimensional model, with a specific turbulent kinetic energy ( TKE ), f , stroke ( s ), d , ppd , distance from the virtual origin to the measurement ( z m ) and space between grid bars ( M ). The experimental data show that, at z m / z c z m , according to the well-known power law, z m ???2 , and does not depend on the vegetation characteristics. In contrast, at z m / z c > 1, TKE decreases faster with z m and scales to the model variables according to TKE 0 / ( f 2 ?? s 2 ) ??? ( d / ppd ) ??? 0.25 ?? ( z m / M ) ??? 3 . Therefore, at z m / z c > 1 the TKE is affected by the geometric characteristics of the plants (both diameter and plant-to-plant distance), an effect called sheltering. Results from semi-rigid canopies and natural SAV are found to scale with the non-dimensional model proposed for rigid canopies. We also discuss the practical implications for field conditions (wind and natural SAV).

Phragmites australis tolerates a wider range of ecological conditions than Cladium mariscus and thus may be better adapted to disturbance resulting from human manipulations. We hypothesised that the difference in ecological conditions was related to differences in photosynthetic ability under water stress. We compared the reactions of the two species to water deficit related to the summer drawdown in the Mediterranean regions that may be enhanced by drainage for human activities. Stress tolerance was evaluated in a pot experiment measuring pigment contents, chlorophyll fluorescence and gas exchanges, growth rates, living and dead biomass, for plants grown in waterlogged conditions or submitted to permanent or temporary drainage. Reed was favoured by the first days of drainage with an increase in CO2 assimilation by approximately 5 mmol m � 2 s � 1 and an increase of the elongation rates from 1 to 1.5 cm d � 1 , indicating waterlogged conditions were not optimal for this species. While pigment content showed no significant effects, growth rate, percentage live above-ground biomass, chlorophyll fluorescence and net rate of CO2 assimilation declined significantly for both species from days 5 to 7 after drying started. Assimilation rates reached 2.3 and 0.3 mmol m � 2 s � 1 on day 9 for sawsedge and reed, respectively. Sawsedge had a 50% greater assimilation rate in the waterlogged conditions, but its responses to water loss in terms of declining growth rate and CO2 assimilation started on day 5 versus 7 for reed. By contrast, the condition of PSII as indicated by chlorophyll fluorescence was affected more in reed. Both growth rates and rates of CO2 assimilation had completely recovered for both species within 3 days of re-wetting. Our results reflect the evergreen character of sawsedge leaves that are hardly damaged by stress but decrease their activity. Reed leaves die upon excessive stress and plants may shed leaf as an adjustment to stress. Sawsedge photosynthesis will be optimal in waterlogged conditions whereas that of reed will be constant within a broad range from slightly drained to mild stress. Those responses to drainage at the leaf scale may partly explain the difference in habitat where both species are usually found. # 2005 Elsevier B.V. All rights reserved.

The Nissi Fen is located in a 12 km 2 intramontane basin in northwestern Greece. Since the last glacial, limnotelmatic and pure telmatic conditions, controlled mainly by karstic springs and partly by surface waters, favoured peat formation in the basin, resulting in the accumulation of a peat deposit up to 15 m thick. The present fen occupies a large area of almost 9 km 2 . Flora cover comprises mainly Cyperaceae ( Cladium mariscus and Carex species), while Phragmites australis extend along the banks of a river flowing through the basin, as well as around a lake in the southern part of the fen. These species also contributed to the peat formation. The Nissi peatland shows many genetic similarities to the Philippi peat deposit, Eastern Macedonia, and may be considered as a recent analogue to the lignite deposits in the basins of Ptolemais, Western Macedonia and Megalopolis, the Peloponnese.