Estudo Químico e Biológico das Espécies Vegetais Caboverdianas Echium Hypertropicum Webb e Echium Stenosiphon Webb Subsp. Stenosiphon

Echium hypertropicum Webb e Echium stenosiphon Webb subsp. stenosiphon são arbustos endêmicos de Cabo Verde, usados na medicina popular para o tratamento de distúrbios gastrintestinais e tosse. As duas espécies tiveram suas frações alcalóidicas obtidas por extração ácido-base. A análise por CG-EM e ESI-EM/EM indicou a presença de alcaloides pirrolizidínicos (APs) e as substâncias purificadas foram analizadas por experimentos de RMN de 1D e 2D. Um total de 10 alcaloides foram isoladas e identificadas, sendo que 8 identificadas através da comparação de suas massas moleculares e padrões de fragmentação de massas, com a base de dados NIST e os dados da litratura para o género. Os diésteres hepatotóxicos equimidana e 7-(2-metilbutiril)-9-equimidinilretronecina foram identificadas em ambas as espécies. Os alcaloides 7-senecioilretronecina, 9-angeloilretronecina, licopsamina, 7-acetil-licopsamina e equihumilina foram identificados nas folhas de E. hypertropicum, enquanto que o N-óxido da 7-(2-metilbutiril)-9-equimidinilretronecina foi identificado nas folhas de E. stenosipnhon. A equimidina foi o componente majoritário na fração em éter dietílico das folhas de E. hypertropicum, enquanto a 7-(2-metilbutiril)-9-equimidinilretronecina foi o componente majoritário na fração em diclorometano das folhas de E. stenosiphon. O alcaloide 7-(2-metilbutiril)-9-equimidinilretronecina N-óxido foi identificado pela primeira vez no gênero Echium. Em adição, 22 componentes de óleo essencial foram identificadas nas flores de Echium hypertropicum, sendo trans-fitol (30,64 %), n-pentacosano (8,28 %) e n-tricosano (6,73) como componentes majoritários. O triterpeno friedelina foi também isolado das folhas de E. hypertropicum. Na avaliação da atividade antibacteriana, os extratos etanólicos das duas espécies vegetais e o alcaloide 7-(2-metilbutiril)-9-equimidinilretronecina foram capazes de inibir o crescimento de Staphylococcus aureus ATCC 29213 com CMI de 250,0 μg/mL e 25,0 μg/mL, respectivamente. A atividade anticolinesterásica foi avaliada e a equimidina foi capaz de inibir a enzima acetilcolinesterase nas concentrações testadas com o valor de P = 0,0011. O alcaloide 7-(2-metilbutiril)-9-equimidinilretronecina retardou o crescimento do fitófago Dysdercus peruvianus na concentração de 1mg/mL. Os extratos etanólicos de E. hypertropicum e E. stenosiphon (3,9 μg/mL) foram avaliados frente ao vírus HSV. O extrato etanólico de E. hypertropicum apresentou uma porcentagem de inibição (PI) de 27,5% contra HSV-1S e 43,8% contra HSV-2S. Apresentaram ainda elevada citotoxidade para as celulas Vero, utilizadas como sistema hospedeiro (CC50 de 140,10 μg/mL e 96,86 μg/mL). A composição química e as atividades biológicas de E. hypertropicum e E. stenosiphon subsp. stenosiphon foram relatadas pela primeira vez. As substâncias identificadas podem ser utilizadas no futuro como marcadores quimiotaxonômicos para o gênero Echium.

Effect of Echium oil compared with marine oils on lipid profile and inhibition of hepatic steatosis in LDLr knockout mice

Abstract Background In an effort to identify new alternatives for long-chain n-3 polyunsaturated fatty acids (LC n-3 PUFA) supplementation, the effect of three sources of omega 3 fatty acids (algae, fish and Echium oils) on lipid profile and inflammation biomarkers was evaluated in LDL receptor knockout mice. Methods The animals received a high fat diet and were supplemented by gavage with an emulsion containing water (CON), docosahexaenoic acid (DHA, 42.89%) from algae oil (ALG), eicosapentaenoic acid (EPA, 19.97%) plus DHA (11.51%) from fish oil (FIS), and alpha-linolenic acid (ALA, 26.75%) plus stearidonic acid (SDA, 11.13%) from Echium oil (ECH) for 4 weeks. Results Animals supplemented with Echium oil presented lower cholesterol total and triacylglycerol concentrations than control group (CON) and lower VLDL than all of the other groups, constituting the best lipoprotein profile observed in our study. Moreover, the Echium oil attenuated the hepatic steatosis caused by the high fat diet. However, in contrast to the marine oils, Echium oil did not affect the levels of transcription factors involved in lipid metabolism, such as Peroxisome Proliferator Activated Receptor α (PPAR α) and Liver X Receptor α (LXR α), suggesting that it exerts its beneficial effects by a mechanism other than those observed to EPA and DHA. Echium oil also reduced N-6/N-3 FA ratio in hepatic tissue, which can have been responsible for the attenuation of steatosis hepatic observed in ECH group. None of the supplemented oils reduced the inflammation biomarkers. Conclusion Our results suggest that Echium oil represents an alternative as natural ingredient to be applied in functional foods to reduce cardiovascular disease risk factors.

Island colonization and evolution of the insular woody habit in Echium L. (Boraginaceae).

Numerous island-inhabiting species of predominantly herbaceous angiosperm genera are woody shrubs or trees. Such "insular woodiness" is strongly manifested in the genus Echium, in which the continental species of circummediterranean distribution are herbaceous, whereas endemic species of islands along the Atlantic coast of north Africa are woody perennial shrubs. The history of 37 Echium species was traced with 70 kb of noncoding DNA determined from both chloroplast and nuclear genomes. In all, 239 polymorphic positions with 137 informative sites, in addition to 27 informative indels, were found. Island-dwelling Echium species are shown to descend from herbaceous continental ancestors via a single island colonization event that occurred < 20 million years ago. Founding colonization appears to have taken place on the Canary Islands, from which the Madeira and Cape Verde archipelagos were invaded. Colonization of island habitats correlates with a recent origin of perennial woodiness from herbaceous habit and was furthermore accompanied by intense speciation, which brought forth remarkable diversity of forms among contemporary island endemics. We argue that the origin of insular woodiness involved response to counter-selection of inbreeding depression in founding island colonies.

A novel approach for honey pollen profile assessment using an electronic tongue and chemometric tools

Nowadays the main honey producing countries require accurate labeling of honey before commercialization, including floral classification. Traditionally, this classification is made by melissopalynology analysis, an accurate but time-consuming task requiring laborious sample pre-treatment and high-skilled technicians. In this work the potential use of a potentiometric electronic tongue for pollinic assessment is evaluated, using monofloral and polyfloral honeys. The results showed that after splitting honeys according to color (white, amber and dark), the novel methodology enabled quantifying the relative percentage of the main pollens (Castanea sp., Echium sp., Erica sp., Eucaliptus sp., Lavandula sp., Prunus sp., Rubus sp. and Trifolium sp.). Multiple linear regression models were established for each type of pollen, based on the best sensors sub-sets selected using the simulated annealing algorithm. To minimize the overfitting risk, a repeated K-fold cross-validation procedure was implemented, ensuring that at least 10-20% of the honeys were used for internal validation. With this approach, a minimum average determination coefficient of 0.91 ± 0.15 was obtained. Also, the proposed technique enabled the correct classification of 92% and 100% of monofloral and polyfloral honeys, respectively. The quite satisfactory performance of the novel procedure for quantifying the relative pollen frequency may envisage its applicability for honey labeling and geographical origin identification. Nevertheless, this approach is not a full alternative to the traditional melissopalynologic analysis; it may be seen as a practical complementary tool for preliminary honey floral classification, leaving only problematic cases for pollinic evaluation.

Patogênese, sinais clínicos e patologia das doenças causadas por plantas hepatotóxicas em ruminantes e eqüinos no Brasil

Plantas que causam lesões hepáticas em ruminantes e eqüinos constituem um grupo importante de plantas tóxicas no Brasil. Em geral essas plantas podem ser divididas em três grandes grupos: plantas que causam necrose hepática aguda; plantas que causam fibrose hepática; e plantas que causam fotossensibilização. Em algumas dessas plantas os princípios tóxicos já foram identificados. Das plantas que causam necrose hepática aguda, os carboxiatractilosídeos estão presentes em Cestrum parqui e Xanthium cavanillesi. Os alcalóides pirrolizidínicos estão presentes nas plantas que causam fibrose hepática (Senecio spp., Echium plantagineum, Heliotropum spp. e Crotalaria spp.). Das plantas que causam fotossensibilização hepatógena são conhecidos os furanossesquiterpenos em Myoporum spp., triterpenos em Lantana spp., e saponinas esteroidais em Brachiaria spp. e Panicum spp. O quadro clínicopatológico dessas intoxicações e o mecanismo geral da insuficiência hepática, incluindo meios de diagnóstico, são descritos neste artigo de revisão.

Intoxicação por alcaloides pirrolizidínicos em ruminantes e equinos no Brasil

Casos de intoxicação por alcaloides pirrolizidínicos (APs) em ruminantes e equinos foram investigados retrospectivamente através do acesso aos arquivos de dois laboratórios de diagnóstico veterinário no Sul e Nordeste brasileiro. Os dados obtidos foram comparados com aqueles retirados da literatura concernentes a surtos dessa toxicose no Brasil, onde ela é associada com a ingestão de plantas que contêm APs dos gêneros Senecio, Crotalaria e Echium. Formas aguda e crônica da toxicose foram encontradas. A doença aguda foi observada em associação com a ingestão de Crotalaria retusa em ovinos e caprinos. C. retusa e Senecio spp. também foram responsáveis pela intoxicação crônica em bovinos, equinos e ovinos. A intoxicação por APs é uma importante causa de morte em animais pecuários no Brasil. Essa é a principal causa de morte em bovinos na região Central do Rio Grande do Sul e uma das principais causas de morte em equinos na Paraíba. A epidemiologia, os sinais clínicos, a patologia e a importância da intoxicação por APs são descritos e discutidos.

Estudo aerobiológico da cidade do Funchal: detecção bioquímica dos principais aeroalergénios polínicos

A abordagem da doença alérgica, nomeadamente da alergia respiratória, surge reforçada com o contributo da Aerobiologia no conhecimento, evolução e controlo da doença. Por seu turno, a caracterização bioquímica dos aeroalergénios de uma região pemite avaliar a sua composição e potencial alergénico, com particular interesse para espécies vegetais cuja introdução e/ou proximidade a áreas populacionais, potenciam o aparecimento ou o aumento de sensibilização a aeroalergénios. O trabalho apresentado nesta dissertação incidiu em duas vertentes de investigação distintas, porém complementares e interdependentes: numa primeira parte, no estudo da composição aerobiológica da atmosfera da cidade do Funchal no período 2002-2004 (Capítulo I), e numa segunda parte, na caracterização bioquímica dos alergénios polínicos mais frequentes detectados no referido período (Capítulo II). Assim, numa primeira parte, a monitorização aerobiológica (incluindo pólenes, esporos de fungos e demais partículas de origem biológica), foi realizada com um polinómetro do tipo volumétrico, tipo Hirst (Burkard). Os dados obtidos foram correlacionados com os parâmetros meteorológicos e avaliado o seu significado estatístico, permitindo antever a influência das variáveis ambientais em cada tipo particular de pólen e de fungo. Constataram-se algumas diferenças no conteúdo aerobiológico comparativamente ao restante território nacional. No espectro polínico dominaram as Poaceae e Urticaceae, plantas ornamentais (Asteraceae, Boraginaceae, Cupressaceae) e as representativas da faixa norte da cidade (Ericaceae, Myrtaceae e Pinaceae). Comparativamente a outras regiões do País, o espectro polínico foi no cômputo geral semelhante, embora se destaque para esta região, a expressividade do tipo Corylus no total polínico anual. A Primavera e o início de Verão, corresponderam às épocas de maior diversidade e concentração de pólenes. As diferenças encontradas no espectro polínico da cidade do Funchal são explicadas por variáveis intrínsecas desta região, tais como a composição vegetal, a localização da cidade, condições geo-climáticas inerentes, e a influência dos parâmetros meteorológicos, nomeadamente a temperatura e humidade relativa. Verificou-se a ocorrência de um maior número de pólenes quando a humidade se situa entre os 50 e 60 %, com a precipitação e a velocidade do vento a atingir valores mais baixos. A análise da variação intra-diurna observada revelou que há uma maior representação de pólenes entre as 11 e as 16 horas. Este estudo aerobiológico confere dados para o estabelecimento do primeiro calendário polínico da região e a definição de padrões de sazonalidade. Por seu turno, a fenologia dos principais tipos polínicos observados no Funchal permite definir um padrão anual de ocorrências polínicas. Relativamente à aeromicologia, verifica-se que, durante o período de estudo foram observados esporos de fungos sobretudo na Primavera (particularmente em Abril e Maio), início do Verão e no Outono. Os Deuteromicetes representaram a classe predominante, sendo Cladosporium o fungo mais abundante na atmosfera do Funchal, cujas concentrações mais elevadas ocorrem a humidades relativas de 40 a 70%. Tal como os pólenes, os esporos apresentam um dinâmica de variação intra-diurna particular: ocorreram em maior concentração entre as 13 e as 15 horas, surgindo igualmente nas primeiras horas da madrugada e da noite. O coberto vegetal do Funchal poderá afectar a aeromicologia local, na medida em que constitui um substrato importante para o crescimento de fungos, tal como as gramíneas que proliferam em quantidade e variedade ao longo de todo o ano. Constatou-se a existência de correlação entre a ocorrência de alguns esporos de fungos e taxa polínicos mais frequentes na atmosfera do Funchal. A análise de Spearman sugere a existência de correlação entre a ocorrência de Parietaria com a de Alternaria e Drechslera. Os esporos de fungos, incluindo esporos de fetos constituem uma fracção significativa das partículas na atmosfera do Funchal, sendo cerca de 11 vezes superior à dos pólenes. Na segunda parte do trabalho, o estudo bioquímico dos aeroalergénios polínicos implicou a optimização dos procedimentos de extracção, apurando-se três técnicas para a obtenção dos perfis proteicos de extractos de pólen desde a sua fonte natural. Esta análise permitiu detectar e identificar através das técnicas de SDS-PAGE-Imunoblotting, proteínas IgE específicas do pólen de plantas possivelmente relacionadas com a sensibilização alérgica. Em consonância com a monitorização aerobiológica, foram preparados extractos de pólen de 10 espécies de plantas. Os resultados em SDS-PAGE revelaram um elevado polimorfismo proteico em todos os extractos. Obtiveram-se extractos de pólen de 7 plantas acerca das quais não se conheciam estudos desta natureza: Acacia mearnsii, Avena barbata, Carduus squarrosus, Carlina salicifolia, Datura candida, Echium nervosum e Urtica membranosa. Por imunoblotting detectou-se no soro de dois pacientes IgE específica a proteínas de D. candida, com pesos moleculares entre 150,71 ± 0,05 e 58,92 ± 5,67 KDa. O soro de um deles reagiu igualmente com 5 alergénios de P. pinaster com 42,02 ± 0,05; 38,61 ± 0,46 ; 35,70 ± 7,78 ; 31,82 ± 2,11 e 27,45 ± 0,46 KDa. No soro de outro indivíduo foi detectada IgE específica para uma proteína de A. mearnsii com 66,66 ± 0,13 KDa, e outra de C. squarrosus,de 67,53 ± 0,29 KDa. É de destacar a sensibilidade e fiabilidade da técnica de Imunoblotting, e o interesse em incluila na metodologia de diagnóstico complementar da alergia respiratória. A ampla difusão de espécies como Ricinus communis, Urtica spp. ou A. mearnsii e sua proximidade à presença humana, reforçam, por um lado, a importância da vigilância aerobiológica, e por outro lado, requer uma definição do seu carácter alergénico para a população desta região.

Consequences of plant population size for pollinator visitation and plant reproductive success

Habitat loss and fragmentation have a prominent role in determining the size of plant populations, and can affect plant-pollinator interactions. It is hypothesized that in small plant populations the ability to set seeds can be reduced due to limited pollination services, since individuals in small populations can receive less quantity or quality of visits. In this study, I investigated the effect of population size on plant reproductive success and insect visitation in 8 populations of two common species in the island of Lesvos, Greece (Mediterranean Sea), Echium plantagineum and Ballota acetabulosa, and of a rare perennial shrub endemic to north-central Italy, Ononis masquillierii. All the three species depended on insect pollinators for sexual reproduction. For each species, pollen limitation was present in all or nearly all populations, but the relationship between pollen limitation and population size was only present in Ononis masquillierii. However, in Echium plantagineum, significant relationships between both open-pollinated and handcrossed-pollinated seed sets and population size were found, being small populations comparatively less productive than large ones. Additionally, for this species, livestock grazing intensity was greater for small populations and for sparse patches, and had a negative influence on productivity of the remnant plants. Both Echium plantagineum and Ballota acetabulosa attracted a great number of insects, representing a wide spectrum of pollinators, thereby can be considered as generalist species. For Ballota acetabulosa, the most important pollinators were megachilid female bees, and insect diversity didn’t decrease with decreasing plant population size. By contrast, Ononis masquillierii plants generally received few visits, with flowers specialized on small bees (Lasioglossum spp.), representing the most important insect guild. In Echium plantagineum and Ballota acetabulosa, plants in small and large populations received the same amount of visits per flower, and no differences in the number of intraplant visited flowers were detected. On the contrary, large Ononis populations supported higher amounts of pollinators than small ones. At patch level, high Echium flower density was associated with more and higher quality pollinators. My results indicate that small populations were not subject to reduced pollination services than large ones in Echium plantagineum and Ballota acetabulosa, and suggest that grazing and resource limitation could have a major impact on population fitness in Echium plantagineum. The absence of any size effects in these two species can be explained in the light of their high local abundance, wide habitat specificity, and ability to compete with other co-flowering species for pollinators. By contrast, size represents a key characteristic for both pollination and reproduction in Ononis masquillierii populations, as an increase in size could mitigate the negative effects coming from the disadvantageous reproductive traits of the species. Finally, the widespread occurrence of pollen limitation in the three species may be the result of 1) an ongoing weakening or disruption of plantpollinator interactions derived from ecological perturbations, 2) an adaptive equilibrium in response to stochastic processes, and 3) the presence of unfavourable reproductive traits (for Ononis masquillierii).

Pollen profiles from 8 sediment cores from the Degersee, Southern Germany

The discovery of a neolithic pile field in the shallow water near the eastern shore of the Degersee confirmed earlier palynological and sedimentological studies stating that early man was active in the region since more than 6000 years. The already available off-site data were freshly assessed, completed by additional data from old and new cores and the interpretations revised. A common time scale for the off-site data and the on-site data was obtained by AMS dating of terrestrial macro remains of the neolithic section of off-site core De_I+De_H. The ages can thus be parallelled with AMS ages of construction timber on-site. Pollen analyses from all cores provide a further time scale. The continuously and densely sampled pollen profile of the profundal zone embracing the entire Late glacial and Holocene serves as a reference. From the Boreal onwards the relative ages are transformed by AMS ages and varve counts into calibrated and absolute. A transect cored close to the neolithic pile field across the lake marl-platform demonstrates its geological architecture in the shallow water since the Lateglacial. Studies of the microfabric of thin sections of drilled cores and of box cores from the excavations demonstrate that neolithic settlements now at 2-3,5 m water depth had been erected on lake marl freshly fallen dry, thus indicating earlier lake levels dropped by 1.5-2 m. The neolithic section of the highly resolved off-site profile in the lake=s profundal zone has laminated and calcareous zones alternating with massive ones. Assemblages of diatoms and concentrations of trace elements changing simultaneously characterise the calcareous sections as deposits of low lake levels that lasted between some 40 and more than 300 years. The ages of discovered lake shore dwellings fall into calcareous segments with low lake levels. From the end of the Upper Atlantic period (F VII) appear Secondary Forest Cycles in the beech forest, a man-made sequence of repeated vegetational development with an identical pattern: With a decrease of beech pollen appear pollen of grasses, herbs and cultural indicators. These are suppressed by the light demanding hazel and birch, those again by ash, and finally by the shade demanding beech forming a new pollen peak. Seven main Forest Cycles are identified In the upper Neolithic period each comprising some 250, 450 or 800 years. They are subdivided into subcycles that can be broken down by very dense sampling in even shorter cycles of decadal length. Farming settlers have caused minor patchy clearances of the beech-mixed-forest with the use of fire. The phases of clearance coincide with peaks of charcoal and low stands of the lake levels. The Secondary Forest Cycles and the continuous occurrence of charcoal prove a continued occupation of the region. Together with the repeated restoration of the beech climax forest they point to pulsating occupation probably associated with dynamic demography. The synchronism of the many palynological, sedimentological and archaeological data point to an external forcing as the climate that affects comprehensively all these proxies. The fluctuations of the activity of the sun as manifested in the residual d14C go largely along with the proxies. The initial clearances at the begin of the forest cycles are linked to low lake levels and negative values of d14C that point to dry and warm phases of a more continental climate type. The subcycles exist independent from climatic changes, indicating that early man acted largely independent from external forces.

High-resolution multi-proxy record of the last interglacial period from Lake Van, eastern Anatolian high plateau, Turkey

A high-resolution multi-proxy record from Lake Van, eastern Anatolia, derived from a lacustrine sequence cored at the 357 m deep Ahlat Ridge (AR), allows a comprehensive view of paleoclimate and environmental history in the continental Near East during the last interglacial (LI). We combined paleovegetation (pollen), stable oxygen isotope (d18Obulk) and XRF data from the same sedimentary sequence, showing distinct variations during the period from 135 to 110 ka ago leading into and out of full interglacial conditions. The last interglacial plateau, as defined by the presence of thermophilous steppe-forest communities, lasted ca. 13.5 ka, from ~129.1-115.6 ka BP. The detailed palynological sequence at Lake Van documents a vegetation succession with several climatic phases: (I) the Pistacia zone (ca. 131.2-129.1 ka BP) indicates summer dryness and mild winter conditions during the initial warming, (II) the Quercus-Ulmus zone (ca. 129.1-127.2 ka BP) occurred during warm and humid climate conditions with enhanced evaporation, (III) the Carpinus zone (ca. 127.2-124.1 ka BP) suggest increasingly cooler and wetter conditions, and (IV) the expansion of Pinus at ~124.1 ka BP marks the onset of a colder/drier environment that extended into the interval of global ice growth. Pollen data suggest migration of thermophilous trees from refugial areas at the beginning of the last interglacial. Analogous to the current interglacial, the migration documents a time lag between the onset of climatic amelioration and the establishment of an oak steppe-forest, spanning 2.1 ka. Hence, the major difference between the last interglacial compared to the current interglacial (Holocene) is the abundance of Pinus as well as the decrease of deciduous broad-leaved trees, indicating higher continentality during the last interglacial. Finally, our results demonstrate intra-interglacial variability in the low mid-latitudes and suggest a close connection with the high-frequency climate variability recorded in Greenland ice cores.

Palynological investigations of profile Cergowa in Poland

The decomposition rate of organic, Compounds, following the death of a plant, is dependent on several external factors. Assimilatory pigments generally undergo a rapid degradation. In certain condition, however, their decomposition may be considerably retarded; e.g. compounds similar to chlorophyll and some carotenoids, as a and ß-carotene, lutein and others, may persist several thousand years in marine and lake Sediments (Vallentyne 1960). Derivatives of chlorophyll were also found in the surface layer of wood soil (Gorham 1959). In this connection the question arises, in what a way a still different environment, namely peat, influences the decomposition rate of pigments. The starting point in these investigations was the fact observed by one of the co-authors, that many subfossil fir needles from various depths of the peat bog in Cergowa Gora were bright yellow green pigmented. Macroscopic otoservations have already suggested that, at least, a part of the pigments did not undergo decomposition. A study was undertaken with the aim to determine the quantitative and qualitative changes in assimilatory pigments, occurring in fir needles in dependence on the pexiod of time they were lying in the peat bog.

Pollen and diatom analysis on varved sediments in Lake Jues (Harz Mountains, Germany)

Studies combining sedimentological and biological evidence to reconstruct Holocene climate beyond the major changes, and especially seasonality, are rare in Europe, and are nearly completely absent in Germany. The present study tries to reconstruct changes of seasonality from evidence of annual algal successions within the framework of well-established pollen zonation and 14C-AMS dates from terrestrial plants. Laminated Holocene sediments in Lake Jues (10°20.70' E, 51°39.30' N, 241 m a.s.l.), located at the SW margin of the Harz Mountains, central Germany, were studied for sediment characteristics, pollen, diatoms and coccal green algae. An age model is based on 21 calibrated AMS radiocarbon dates from terrestrial plants. The sedimentary record covers the entire Holocene period. Trophic status and circulation/stagnation patterns of the lake were inferred from algal assemblages, the subannual structure of varves and the physico-chemical properties of the sediment. During the Holocene, mixing conditions alternated between di-, oligo- and meromictic depending on length and variability of spring and fall periods, and the stability of winter and summer weather. The trophic state was controlled by nutrient input, circulation patterns and the temperature-dependent rates of organic production and mineralization. Climate shifts, mainly in phase with those recorded from other European regions, are inferred from changing limnological conditions and terrestrial vegetation. Significant changes occurred at 11,600 cal. yr. BP (Preboreal warming), between 10,600 and 10,100 cal. yr. BP (Boreal cooling), and between 8,400 and 4,550 cal. yr. BP (warm and dry interval of the Atlantic). Since 4,550 cal. yr. BP the climate became gradually cooler, wetter and more oceanic. This trend was interrupted by warmer and dryer phases between 3,440 and 2,850 cal. yr. BP and, likely, between 2,500 and 2,250 cal. yr. BP.

Pollen profile and age determination of sediment core Schwanengrabenrinne, Brandenburg, Germany

In der Döberitzer Heide nördlich von Potsdam wurden vegetationsgeschichtliche Untersuchungen durchgeführt. Das Untersuchungsgebiet befindet sich im östlichen Teil der Nauener Platte, die bisher vegetationsgeschichtlich weitgehend unerforscht war. In sechs verschiedenen Mooren wurden acht Bohrungen niedergebracht. Die Bohrkerne wurden stratigraphisch und pollenanalytisch untersucht und für die Radiocarbondatierung beprobt. Die Pollendiagramme ermöglichen die Rekonstruktion der Vegetationsentwicklung der terrestrischen Standorte und der Moore in der Döberitzer Heide in den letzten 14.000 Jahren. Neben einer Revision der Gliederungsprinzipien der spätglazialen Vegetationsentwicklung Brandenburgs und einer vergleichenden Betrachtung der Moorentwicklung in der Döberitzer Heide wurde besonderes Augenmerk auf die Geschichte des Döberitzer Lindenwaldes gerichtet, der einen Sonderfall in der brandenburgischen Vegetation darstellt. Die Untersuchungen boten die Möglichkeit, die Ursachen seiner Entstehung zu klären, Aussagen zu den Perspektiven seiner Entwicklung zu treffen und mögliche Entwicklungspotentiale von Lindenwäldern im Land Brandenburg aufzuzeigen.