Four thousand years of vegetation and fire history in the spruce forests of northern Kyrgyzstan (Kungey Alatau, Central Asia)

Analyses of pollen, macrofossils and microscopic charcoal in the sediment of a small sub-alpine lake (Karakol, Kyrgyzstan) provide new data to reconstruct the vegetation history of the Kungey Alatau spruce forest during the late-Holocene, i.e. the past 4,000years. The pollen data suggest that Picea schrenkiana F. and M. was the dominant tree in this region from the beginning of the record. The pollen record of pronounced die-backs of the forests, along with lithostratigraphical evidence, points to possible climatic cooling (and/or drying) around 3,800 cal year b.p. and between 3,350 and 2,520 cal year b.p., with a culmination at 2,800-2,600 cal b.p., although stable climatic conditions are reported for this region for the past 3,000-4,000years in previous studies. From 2,500 to 190 cal year b.p. high pollen values of P. schrenkiana suggest rather closed and dense forests under the environmental conditions of that time. A marked decline in spruce forests occurred with the onset of modern human activities in the region from 190 cal year b.p. These results show that the present forests are anthropogenically reduced and represent only about half of their potential natural extent. As P. schrenkiana is a species endemic to the western Tien Shan, it is most likely that its refugium was confined to this region. However, our palaeoecological record is too recent to address this hypothesis thoroughl

Ein paläoökologischer Beitrag zum besseren Verständnis der natürlichen Vegetation der Schweiz

Zusammenfassung: Wie natürlich oder naturnah ist eine Pflanzengemeinschaft oder eine Landschaft? Diese Frage ist von Interesse, wenn wir verstehen wollen, wie unsere heutigen Landschaften entstanden sind. Noch wichtiger ist sie aber, wenn abgeschätzt werden muss, welche Massnahmen zum Schutz und zur Bewahrung der Funktionen eines bestimmten Vegetations-, Umwelt- oder Landschaftstyps notwendig sind. Wir fassen hier die Erkenntnisse aus über 30 paläoökologischen Untersuchen zur postglazialen Vegetationsgeschichte in der Schweiz zusammen. Die Kombination von Pollen- und Makrorestauswertungen sowie die Untersuchung von mikro- und makroskopischen Holzkohle-Partikeln und der Vergleich mit Klimaindikatoren ermöglicht es, die Vegetationsentwicklung mit hoher zeitlicher und räumlicher Auflösung zu rekonstruieren. Gemeinsame Trends bei der Vegetationsentwicklung gehen vorwiegend auf die Klimadynamik zurück, es gibt aber nennenswerte Unterschiede in Abhängigkeit vom Bodentyp, der menschlichen Aktivität (besonders unter Einsatz des Feuers) oder der Höhenlage. Verschiedene Waldtypen, die bis anhin unter den jeweiligen Klimabedingungen als natürlich betrachtet wurden, sind das Resultat menschlicher Landnutzung über die Jahrtausende, insbesondere ist die Dominanz einzelner weniger Baumarten in den Wäldern der Schweiz anthropogen bedingt. Umgekehrt wurden lokale, isolierte Bestände nicht als Relikte natürlicher Wälder betrachtet. Die Vielfalt der Waldvegetation hat also stark abgenommen, während dem die gesamte Biodiversität stark zugenommen hat, vorwiegend als Folge der Ausbreitung von Offenlandarten durch landwirtschaftliche Tätigkeiten. Die Paläoökologie hat also dazu beigetragen, die Natürlichkeit von Pflanzengesellschaften neu einzuschätzen und die Reaktionsweisen auf Störungen besser zu verstehen. In diesem Sinne stellen wir neue Projekte vor, in denen die Paläoökologie eingesetzt wird, um Kenntnisse zu gewinnen, die für Naturschutz, Waldbau und die Planung von Nationalparks unentbehrlich sin

Zur Langzeitökologie des Lärchen-Arvengürtels in den südlichen Walliser Alpen

Abstract.: Kaltenrieder P., Tinner W. and Ammann B. 2005. Long-term vegetation history at timberline in the Swiss Alps (Alpe d'Essertse, VS). Bot. Helv. 115: 137-154. Palaeoecological studies in the "Alpe d'Essertse” area have provided much information about vegetation changes and timberline fluctuations during the Holocene. In this study we repeated previous biostratigraphic investigations using plant macrofossils to improve their temporal and taxonomic resolution and to test their reliability. By analyzing 0.5-cm layers of a lake sediment we reached a temporal resolution of 44years, and we were able to reconstruct vegetation changes in the surrounding area at species level. The sedimentary record analyzed extends from the Late-Glacial to the late Holocene. Alpine grasslands (12'000-11'000cal. BP) were afforested by Larix decidua, Juniperus nana, and Pinus cembra (11,000-9'600cal. B.P.). Stable subalpine larch-stone pine-forests (9'600-4'900cal. BP) were followed by shrublands and meadows as a consequence of the climatically and anthropogenically induced destruction of forest vegetation (4'900-2'600cal. BP). Changes in the abundance of P. cembra and L. decidua needles as well as changes of the other taxa were consistent with those found in previous studies from the same lake. Our results demonstrate that plant-macrofossil records can be reproduced spatially and temporally on separate cores with independent 14C chronologie

The importance of microscopic examinations of eggshells: Discrimination of bioalteration and diagenetic overprints from biological features

Although fossilization usually favors the preservation of calcium carbonate biominerals, diagenetic alterations might still produce erratic patterns that overprint the original biological structures. This investigation tries to discriminate in the fossil record “pathological” eggshells from diagenetic induced features as well as determine their origin, and aims, when possible, to provide alternative parsimonious interpretations to the origin of some of these rare and erratic features. In the past, most dinosaur eggshell studies failed to combine cathodoluminescence, scanning electron microscopy, transmitted and polarized light microscopic observations and were limited to only one or several of these examinations, which might have contributed to misinterpretations by lack of thorough observations. Sauropod eggshells from Faidella (Spain) and Auca Mahuevo (Argentina) provide ideal proxies to perform this research, as they display aberrant crystallographic features that have been or could be considered pathological. Under cathodoluminescence, the specimens fluoresce tremendously, indicating a strong diagenetic component in their make up. Guide by this information, further transmitted and polarized light microscopic examinations reveal microscopic dissolution fronts, which otherwise would have been left unnoted. The proposed hypothesis for the Faidella specimens in that organic filaments, which represent up to 2% of the shell composition, were exposed on the internal wall surfaces of pore canals where the calcium carbonate had been dissolved during a first diagenetic event. As such, the exposed extremities of the organic filaments likely triggered the formation of pseudo cores that mimic those in the membrana testacea during oogenesis. Observations based on the Argentinean specimens indicate that an added extra external structural layer is also separated from the original biological eggshell by a dissolution and recrystallization front. In addition to this abiotic process, artifact formations induced by bacterial mediation, a topic treated in an earlier publication, was also common at Auca Mahuevo. Without combined microscopic and cathodoluminiscence observations, the Faidella and Auca Mahuevo megaloolithid eggshells could be easily considered pathological eggshells. This would bias ensuing phylogenetic, paleobiological, and paleoenvironmental interpretations.A pesar de que la fosilizacion favorece la conservacion de los biominerales de carbonato calcico, las alteraciones diageneticas pueden llegar a producir patrones erraticos que se sobrepongan a las estructuras biologicas originales. Esta investigacion intenta discriminar en el registro fosil cascaras “patologicas” con rasgos diageneticamente inducidos, determinando su origen y procura, en la medida de lo posible, dar una interpretacion parsimoniosa alternativa al origen de algunos de estos rasgos extranos y erraticos. En el pasado, la mayoria de los estudios en cascaras de dinosaurios se vieron limitados al uso de uno o dos de estos procedimientos (catodoluminiscencia, microscopia electronica, observaciones con microscopio de luz transmitida y polarizada), lo que puede haber contribuido a interpretaciones erroneas debido a observaciones incompletas. Las cascaras de huevos de sauropodos del yacimiento de Faidella (Espana) y de Auca Mahuevo (Argentina) muestran condiciones ideales para realizar esta investigacion, ya que denotan rasgos critalográficos aberrantes que habían sido o podrían ser considerados como patológicos. Mediante catodoluminiscencia, los ejemplares muestran una violenta fluorescencia, lo que indica un fuerte componente diagenético en su composición. Guiados por esta informacion, los analisis posteriores con microscopia de transmision y luz polarizada revelan frentes de disoluciones microscópicas, que de otro modo no habrían sido apreciadas. La hipótesis que se propone para los ejemplares de Faidella es que filamentos orgánicos, que representan hasta el 2% de la composición de las cáscaras, estaban expuestos en las superficies de las paredes internas de los canales de los poros donde el carbonato calcico se hubo disuelto durante el primer evento diagetico. Dada esta condicion, los extremos de los filamentos orgánicos expuestos, muy probablemente dispararon la formación de pseudo núcleos que imitan los de la membrana testacea durante la oogenesis. Las observaciones basadas en los ejemplares argentinos indican que una capa externa extra esta separada de la cascara biologica original por una disolucion y recristalizacion. Ademas de este proceso abiotico, en Auca Mahuevo son tambien frecuentes rasgos inducidos por bacterias, asunto tratado en una publicacion anterior. Sin la combinacion de la combinacion de estos metodos, las cascaras de huevo de Faidella y Auca Mahuevo podrian haber sido fácilmente consideradas como patológicas, lo que sesgaría otras interpretaciones como las filogenéticas, paleobiológicas y paleoambientales

A new Late-glacial and Holocene record of vegetation and fire history from Lago del Greppo, northern Apennines, Italy

Detailed Late-glacial and Holocene palaeoenvironmental records from the northern Apennines with a robust chronology are still rare, though the region has been regarded as a main area of potential refugia of important trees such as Picea abies and Abies alba. We present a new high-resolution pollen and stomata record from Lago del Greppo (1,442m a.s.l., Pistoia, northern Apennines) that has been dated relying on 12 terrestrial plant macrofossils. Late-glacial woodlands became established before 13000cal b.p. and were dominated by Pinus and Betula, although more thermophilous taxa such as Quercus, Tilia and Ulmus were already present in the Greppo area, probably at lower altitudes. Abies and Picea expanded locally at the onset of the Holocene at ca. 11500cal b.p. Fagus sylvatica was the last important tree to expand at ca. 6500cal b.p., following the decline of Abies. Human impact was generally low throughout the Holocene, and the local woods remained rather closed until the most recent time, ca. a.d. 1700-1800. The vegetational history of Lago del Greppo appears consistent with that of previous investigations in the study region. Late-glacial and Holocene vegetation dynamics in the northern Apennines are very similar to those in the Insubrian southern Alps bordering Switzerland and Italy, across the Po Plain. Similarities between the two areas include the Late-glacial presence of Abies alba, its strong dominance during the Holocene across different vegetation belts from the lowlands to high elevations, as well as its final fire and human-triggered reduction during the mid Holocene. Our new data suggest that isolated and minor Picea abies populations survived the Late-glacial in the foothills of the northern Apennines and that at the onset of the Holocene they moved upwards, reaching the site of Lago del Greppo. Today stands of Picea abies occur only in two small areas in the highest part of the northern Apennines, and they have become extinct elsewhere. Given the forecast global warming, these relict Picea abies stands of the northern Apennines, which have a history of at least 13,000years, appear severely endangere

Human impact during the Bronze Age on the vegetation at Lago Lucone (northern Italy)

Lake-sediment records were used to reconstruct human impact on the landscape around Lago Lucone (45°33′N, 10°29′E, 249ma.s.l.), a former lake in the western amphitheatre system of the Lago di Garda. Presence of prehistoric human populations is attested by pile-dwelling settlements from the Early-Middle Bronze Age, with one settlement at a distance of only 100m from the coring site. Pollen, plant-macrofossil and microscopic charcoal analyses were applied to a 250cm sediment core with four dates providing the time control. A mixed oak forest that was important during the Early-Middle Holocene was cleared and replaced by open vegetation during the Bronze Age (∼2000-1100 b.c.) when open lands were estimated to have covered more than 60% of the total relevant pollen-source area. During a phase of high human impact, independent climatic proxies suggest warm and dry climatic conditions. Later, ca. 1100 b.c., palaeobotanical evidence indicates a sharp decrease in human pressure in the Lago Lucone area. The comparison with other sedimentary palaeocultural records shows that the period 1300-1100 b.c. was characterised by general declines of agricultural activities both south and north of the Alps. These declines have been previously attributed to a change towards wetter and colder climatic conditions in and around the Alps. However, the decline in human impact around Lago Lucone cannot be exclusively attributed to climatic variation. Therefore other forcing factors independent of climatic changes, such as cultural crises or changes in spatial organisation of the habitats, cannot be ruled out under the present state of knowledg

Rates of palaeoecological change can inform ecosystem restoration

Accelerations of ecosystem transformation raise concerns, to the extent that high rates of ecological change may be regarded amongst the most important ongoing imbalances in the Earth system. Here, we used high-resolution pollen and diatom assemblages and associated ecological indicators (the sum of tree and shrub pollen and diatom-inferred total phosphorus concentrations as proxies for tree cover and lake-water eutrophication, respectively) spanning the past 150 years to emphasise that rate-of-change records based on compositional data may document transformations having substantially different causes and outcomes. To characterize rates of change also in terms of other key ecosystem features, we quantified for both ecological indicators (i) the percentage of change per-unit-time, (ii) the percentage of change relative to a baseline level, and (iii) the rate of percentage change per-unit-time relative to a baseline level, taking into account the irregular spacing of palaeoecological data. These measures document how quickly specific facets of nature changed, their trajectory, as well as their status in terms of palaeoecological indicators. Ultimately, some past accelerations of community transformation may document the potential of ecosystems to rapidly recover important ecological attributes and functions. In this context, insights from palaeoecological records may be useful to accelerate ecosystem restoration

Early to late Holocene vegetation and fire dynamics at the treeline in the Maritime Alps

We used pollen, plant macrofossil, and charcoal records to investigate local long-term timberline shifts and changes in vegetation composition in relation to fire activity at the modern upper forest limit (ca. 2,000 m a.s.l.) in the Mont Bégo area, Maritime Alps of France and Italy. The area is an important place for Alpine archaeology because it has thousands rock-art carvings whose age cannot be directly assessed. Our new record confirms the occurrence of distinct land use phases (7,450–7,150, 6,200–4,900, and 4,250–3,700 cal bp), as suggested by earlier studies of rock art typology. Moreover, the vegetation reconstruction from macrofossils, with co-dominance of Pinus and Betula, suggests that early Holocene conditions were moister than in drier inner Alpine valleys, where Larix decidua played a more important role, both in the past as well as in modern timberline forests. After 8,000 cal bp, the timberline shifted upwards and mixed Abies alba and Pinus cembra stands established around the study site. These fire sensitive trees were finally replaced during the Bronze Age (around 4,000 cal bp) by L. decidua, which still dominates the subalpine woodlands in the area today. Our study supports the notion that while the range of A. alba has been reduced at the colder end of its natural distribution, that of L. decidua has been widened by land use changes and fire disturbances to create high alpine wood pastures