Floresta natural dos Açores

O efeito da insularidade reflecte-se no número limitado de espécies arbóreas naturais dos Açores. As mais comuns são a Morella faya (Faia-da-terra), Picconia azorica (Pau-branco), Laurus azorica (Louro), Juniperus brevifolia (Cedro-do-mato), Ilex perado subsp. azorica (Azevinho), Erica azorica (Urze) e Frangula azorica (Sanguinho). Pelo contrário, Prunus azorica (Ginjeira-brava) é actualmente muito rara e Taxus bacatta (Teixo) encontra-se à beira da extinção. Dependendo das condições ambientais, particularmente de temperatura, pluviosidade e exposição ao vento, encontramos diferentes espécies a dominar a copa da floresta. […].

Adaptation and Constraint in the Plant Reproductive Phase

Conservatism is a central theme of organismic evolution. Related species share characteristics due to their common ancestry. Some concern have been raised among evolutionary biologists, whether such conservatism is an expression of natural selection or of a constrained ability to adapt. This thesis explores adaptations and constraints within the plant reproductive phase, particularly in relation to the evolution of fleshy fruit types (berries, drupes, etc.) and the seasonal timing of flowering and fruiting. The different studies were arranged along a hierarchy of scale, with general data sets sampled among seed plants at the global scale, through more specific analyses of character evolution within the genus Rhamnus s.l. L. (Rhamnaceae), to descriptive and experimental field studies in a local population of Frangula alnus (Rhamnaceae). Apart from the field study, this thesis is mainly based on comparative methods explicitly incorporating phylogenetic relationships. The comparative study of Rhamnus s.l. species included the reconstruction of phylogenetic hypotheses based on DNA sequences. Among geographically overlapping sister clades, biotic pollination was not correlated with higher species richness when compared to wind pollinated plants. Among woody plants, clades characterized by fleshy fruit types were more species rich than their dry-fruited sister clades, suggesting that the fleshy fruit is a key innovation in woody habitats. Moreover, evolution of fleshy fruits was correlated with a change to more closed (darker) habitats. An independent contrast study within Rhamnus s.l. documented allometric relations between plant and fruit size. As a phylogenetic constraint, allometric effects must be considered weak or non-existent, though, as they did not prevail among different subclades within Rhamnus s.l. Fruit size was correlated with seed size and seed number in F. alnus. This thesis suggests that frugivore selection on fleshy fruit may be important by constraining the upper limits of fruit size, when a plant lineage is colonizing (darker) habitats where larger seed size is adaptive. Phenological correlations with fruit set, dispersal, and seed size in F. alnus, suggested that the evolution of reproductive phenology is constrained by trade-offs and partial interdependences between flowering, fruiting, dispersal, and recruitment phases. Phylogenetic constraints on the evolution of phenology were indicated by a lack of correlation between flowering time and seasonal length within Rhamnus cathartica and F. alnus, respectively. On the other hand, flowering time was correlated with seasonal length among Rhamnus s.l. species. Phenological differences between biotically and wind pollinated angiosperms also suggested adaptive change in reproductive phenology.

Present-day vegetation and the Holocene and recent development of Egelsee-Moor, Salzburg province, Austria

This paper describes the present-day vegetation, stratigraphy and developmental history of the mire of Egelsee-Moor (Salzburg, Austria; 45°45′N, 13°8.5′E, 700 m a.s.l., 15 ha in area) since the early Late Glacial on the basis of 4 transects with 14 trial borings across the peatland. We present a vegetation map of the mire, a longitudinal section through the peat body based on six cores showing the peat types, overview macrofossil diagrams of six cores showing the local mire development and two pollen diagrams covering the Late Glacial and Holocene. The chronology of the diagrams depends on biostratigraphic dating for the Late Glacial and early Holocene and radiocarbon dating for the remaining Holocene. The northern part of the mire originated through terrestrialisation of nutrient-rich, mostly inundated fen and the southern part through paludification of wet soils. The very small lake of today was a reservoir until recently for providing water-power for timber rafting (‘Holztrift’). The mire vegetation today is a complex of forested parts (mainly planted Pinus sylvestris and Thuja occidentalis, but also spontaneous Picea abies, Betula pubescens and Frangula alnus), reed-lands (Phragmites) and litter meadows (Molinietum, Schoenetum, etc.). The central part has hummock-hollow complexes with regionally rare species of transitional mires (Drosera anglica, D. intermedia, Lycopodiella inundata, Scorpidium scorpioides, Sphagnum platyphyllum, S. subnitens). The results indicate that some of the mid-Holocene sediments may have been removed by the timber-rafting practices, and that water extraction from the hydrological catchment since 1967 has resulted in a partial shift of transitional mire to ombrotrophic bog. The latter potentially endangers the regionally rare species and was used as an argument to stop further water extraction.

Pollen and macroremains from sediment core Aschenhütte

The Upper Pleistocene sediments of the Aschenhütte sink-hole (west of Herzberg am Harz, Lower Saxony) enable one to make interesting correlations between palynological and geological results. The sequence is composed of limnic-telmatic deposits (Eemain to Lower Weichselian) and loess with paleosoils (Weichselian). Sedimentation started during the hornbeam-dominated phase of the Eemian interglacial period and continued throughout the Eemian, the Weichselian Brörup interstadial (sensu Andersen) and parts of the preceding and the following stadial phases, the Herning and the Rederstall stadials. As opposed to most of the known Eemian sites spruce was a major tree species during the hornbeam-dominated phase of the Eemian. The vegetational development during the interstadial phase does not show a period of climatic deterioration as is the case for the Brörup interstadial when considering regions with a more demanding vegetation or regions close to the natural boundaries of the tree species concerned. Pollen or seeds of Bruckenthalia and Picea omoricoides have not been found in the Aschenhütte cores. The limnic-telmatic sediments interlock with loess-paleosoils (Eemian soil and Lower Weichselian bleaching soils) at the lake shore. They are overlaid by loess paleosoils of the Stillfried-B interstadial (Hattorf soil and Lohne soil). Lake level fluctuations were determined by means of the facies distribution and isochrones as defined by pollen analysis. A relatively high stand of the lake level existed after the end of the Eemian interglacial and during the Brörup interstadial periods. In the course of the Herning stadial period the water level dropped, whereas during the Rederstall stadial phase the lake basin was covered by sediments and therefore dried up.

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.

Pollen records and age determination of site Bokanjacko Blato

In summary, one may conclude that human influence in the Bokanjac area started in the Eneolithic or Earlier Bronze Age - the third to second millennia Cal. BC. Traces of agriculture are weak or missing in the pollen diagram but grazing is indicated. Chestnut and walnut were introduced by humans to the area in classical times. These findings are in general agreement with the results of earlier studies at coastal sites north-west and south-east of Bokanjacko Blato.

Pollen record from Kleiner Mochowsee, Germany

A Holocene pollen diagram from Kleiner Mochowsee (northern Niederlausitz, East Germany) shows pine as an important constituent of the woodland south of the Schwielochsee. Oak woodland was widespread since the Atlantic. Betula lost its importance at the end of the Preboreal. Fagus is represented continuously in the pollen record since the Atlantic, Carpinus since the Subboreal. However, the two latter tree species remain without great importance throughout the whole pollen record. The poor sandy soils are furthermore reflected by the low values of Corylus during the Boreal, comparable to other records from Berlin and its surrounding area. The 'classical' elm decline could be shown for the Niederlausitz, radiocarbon dates assume a contemporaneous age for this event with other records from northern Germany. Only small-scaled human impact is indicated in prehistoric times, during the migration period it seems to have ceased completely. Later, in the Medieval, deforestation and tillage can be shown. Secale was cultivated since the early Medieval; an accompanying weed flora appeared at the same time. Cultivation of Fagopyrum and Linum usitatissimum could be shown for the late Medieval times.

Pollen analysis from Fiekers Busch, Rinteln, Germany

Fiekers Busch is a wet alder wood close to Rinteln (southwest of Hannover/West Germany) existing there since about 6 000 or - at the most - 7 500 radiocarbon years. The sandy layers below the peaty sequence date from about 9 000 BP. The pollen diagram shows the basic trends of the postglacial vegetational development. Low pollen frequency and poor pollen preservation do , however, strongly restrict the possibilities to explain the peculiarities of the pollendiagram, especially the high pine and linden values.

Pollen record and dating of a sediment profile from Ahlequellmoor in Germany

A pollen diagram from the Ahlequellmoor in the Solling area shows the history of vegetation and settlement over the last 7,800 years. In the early Atlantic period mixed deciduous forest with mainly Tilia together with Ulmus and Quercus grew in the area. In the late Atlantic period Quercus became most abundant. Fagus spread in the Sub-boreal period at about 2700 B.C. Since ca. 900 B.C. the Solling was covered by beech forests with some oak. In prehistoric times woodland grazing is indicated. Only in Medieval times are two settlements in the vicinity of the Ahlequellmoor reflected in the pollen diagram. The earlier one is dated to about A.D. 750-1020, and may be connected with the former Monastery of Hethis, which is thought to have existed close to the fen from A.D. 815 to 822. The second Medieval settlement dates to the 11th-12th century. The large-scale woodland destruction of late Medieval and modern times is not clearly visible. The silvicultural measures of the last 200 years are reflected by increasing values of spruce and grassland taxa.

Pollen records of 11 profiles from Wendland in northern Germany

1) Ingesamt 11 Profile aus sechs Mooren und Seen im Gebiet des Hannoverschen Wendlandes wurden pollenanalytisch untersucht. Die Ablagerungen umfassen den Zeitraum vom Beginn der Älteren Tundrenzeit bis zur Gegenwart. 2) Die Waldgeschichte des Hannoverschen Wendlandes weist teils Merkmale der atlantisch geprägten Gebiete Nordwestdeutschlands, teils solche des kontinental beeinflußten nordostdeutschen Raumes auf und nimmt damit eine Zwischenstellung ein. 3) Die Kiefer wandert zu Beginn der Allerödzeit ein, d.h. später als im mecklenburgisch-märkischen Gebiet und im mitteldeutschen Trockengebiet. Im Verlauf der Allerödzeit bildeten sich hier wie dort lichte Kiefern-Birken-Wälder aus. 4) In der Jüngeren Tundrenzeit fand zunächst nur eine geringe Auflichtung der Wälder statt, und die Kiefer überwog weiterhin. Erst im späteren Verlauf dieser stadialen Phase breitete sich die Birke aus und verdrängte die Kiefer. Der späte Rückgang der Kiefer stellt eine Parallele zu der Entwicklung in Südostmecklenburg und in der Altmark dar. Die Abgrenzung dieser Phasen in der Jüngeren Tundrenzeit ist durch eine 14C-Datierung gesichert. 5) Noch im Atlantikum ähneln die Diagramme aus dem Gartower Talsandgebiet im Osten des Wendlandes in ihren hohen Kiefernanteilen denen der Sandergebiete in Brandenburg. Die Diagramme aus dem Moränengebiet des westlichen Wendlandes schließen dagegen mehr an die der östlichen Lüneburger Heide und des Hamburger Gebietes an. Dieser Unterschied wird auf edaphische Unterschiede zurückgeführt. 6) Seit dem frühen Subboreal glich auch die Vegetation des Gartower Gebietes mehr den buchenarmen Waldgesellschaften auf sauren Sandböden, wie sie im atlantischen Westen vorkommen. Die Kiefern sind fast ganz aus dem Waldbild verschwunden, wobei der rasche Rückgang zu Beginn des Subboreals sicher zu einem wesentlichen Teil vom Menschen beeinflusst worden ist. Die anschließende kiefernarme Zeit dauerte im gesamten Wendland bis zum Beginn der Kieferaufforstungen in der Neuzeit. 7) In allen untersuchten Diagrammen ist etwa seit dem Subboreal eine Besiedlung nachzuweisen. Diese muß im Osten des Wendlandes intensiver gewesen sein als im Westen. Es lassen sich Phasen geringer und intensiver Besiedlung nachweisen. 8) Seit Beginn des Subboreals ist das Waldbild schon so stark vom Menschen beeinflusst, dass die Ausbreitungsgeschichte der Laubwaldarten nicht ohne Berücksichtigung der Siedlungsphasen diskutiert werden kann. Besonders im Westen bestand eine ausgedehnte Lindenphase, die durch eine Siedlungszeit (Bronzezeit) beendet wurde. Beim folgenden Rückgang der Siedlungsintensität breitet sich bevorzugt die Hainbuche aus, die dann bei der nächsten Besiedlungsphase (Eisenzeit) zurückging. Erst danach erfolgte die maximale Rotbuchenausbreitung, die nur im Westteil des Wendlandes bedeutende Ausmaße zeigte, während im Ostteil rot- und hainbuchenreiche Eichenwälder entstanden. 9) Seit Beginn der mittelalterlichen Besiedlung ist dann der Eingriff des Menschen so stark gewesen, dass die edaphisch bedingten Unterschiede zwischen Moränen- und Sandergebieten im Pollenspektrum verwischt wurden. Sowohl die buchenreichen Wälder des westlichen als auch die buchenarmen Wälder des mittleren und des östlichen Teilgebietes müssen zu fast reinen Eichenwäldern geworden sein. 10) Calluna-Heiden sind im östlichen Wendland schon in vorgeschichtlicher Zeit nachzuweisen. Im Mittelalter und in der Neuzeit treten sie im gesamten Wendland auf. Etwa im 18. und 19. Jahrhundert war die Ausdehnung der Heideflächen am größten. Erst danach wurden sie im Zuge der Kiefernaufforstungen bis auf geringe Reste verdrängt. 11) Während in der spätglazialen Vegetation Juniperus auftritt, ist der Wacholder sowohl in vorgeschichtlicher als auch in geschichtlicher Zeit - im Gegensatz zur Lüneburger Heide - wohl niemals ein Bestandteil der anthropogenen Calluna-Heiden gewesen.

Pollen analysis of a sediment profile from Gabelsee in Germany

The article shows that pollen analysis plays an important role in the prediction of potential settlement areas and, furthermore, can offer a crude determination of settlement duration. Especially when the archaeological data fails to offer a possibility of dating, pollen analysis in connection with 14C can importantly broaden the knowledge base. As in the present case, the results of the Archaeo-Prognosis mapping and the pollen analysis of the Gabelsee are compared and, within this vicinity, confirmend. = Der Beitrag zeigt, dass die Pollenanalyse eine wichtige Rolle für die Vorhersage von potenziellen Siedlungsflächen spielen und darüber hinaus eine grobe Berechnung der Siedlungsdauer bieten kann. Insbesondere wenn die archäologische Datenbasis keine genaue Datierung zulässt, ermöglicht die Pollenanalyse in Verbindung mit der 14C-Datierung eine wichtige Erweiterung der Kenntnisse. Im vorliegenden Fall konnten die Ergebnisse der Archäoprognosekarte mit denjenigen der Pollenanalyse des Gabelsees verglichen und für diesen lokalen Raum bestätigt werden.