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

Early expansion of mixed oak stands at 16,800–16,600 cal bp at a northern Italian glacial refugium in the Euganean Hills

Continuous sedimentary lake records covering the Last Glacial Maximum (LGM) are very rare in Europe. Here, we conducted additional palynological analyses to connect two separate radiocarbon-dated pollen sequences of Lago della Costa (AP2 and AP1) to one complete vegetation history record of the Euganean Hills (“Colli Euganei”, northern Italy) covering the past ca. 32,000 years. Previous studies on autochthonous organic lake sediments revealed that during the Last Glacial Maximum (LGM) Lago della Costa likely acted as a refugium of temperate woody taxa. Based on the new data we present the first continuous record of the vegetation history of the Euganean Hills during the past 32,000 years. Specifically, we investigate the early establishment and mass expansion of deciduous Quercus at the refugial site at ca. 16,800–16,600 cal BP. In the oak forests other temperate taxa (e.g. Corylus avellana, Abies alba, Ulmus, Fraxinus excelsior, Vitis, Hedera, Tilia, Acer, Fagus sylvatica) also established at around this time, i.e. 2,000 years prior to the onset of the Bølling/Allerød interstadial (about 14,700–12,800 cal BP). The comparison of our data with other well-dated records from the river Po catchment and refugial sites elsewhere in Italy and southern Europe suggests expansions of boreal and nemoral forests over wide areas prior to the Bølling/Allerød interstadial, i.e. 2,000 years before comparable large-scale afforestation north of the Alps or ca. 45°N. Pollen-inferred expansions of temperate tree communities (e.g. oak forests) correspond to a climatic warming as reconstructed from quantitative, pollen-independent evidence (e.g. chironomids) from the Apennines, Northern Italy, Southern Switzerland and the Swiss Plateau, suggesting that pre-Bølling afforestation processes south of the Alps were promoted by increasing (summer) temperatures during the Oldest Dryas

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

Vegetation dynamics and plant species distribution under changing climates

Quaternary climate variability strongly affected ecosystems and vegetation. Climatic oscillations became more moderate during the Holocene, and vegetation reorganizations in response to climate eventually shifted from the biome to the community level during the past 11500 years. Superimposed on climate variability, land use significantly altered European vegetation structure and composition during the mid and late Holocene. Anthropogenic alterations of vegetation during the past 8000 years included contractions and extensions of ranges and realized niches of species. Such paleo-ecological information can be used to infer measures to preserve future biodiversity and ecosystem services under global change conditions. The combination of paleoecological evidence with dynamic vegetation modeling allows investigating spatially explicit transient stages of past and future vegetation shifts under global change conditions. Specifically, dynamic modelling projections may be used to investigate open paleoecological questions or to plan paleo-validated climate-impact mitigation strategies at local to regional scale

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

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

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

Advances in fire history research and their application for ecosystem management and conservation

Paleoecology is a valuable tool for understanding the long-term ecosystem dynamics that underlie present environmental conditions.  Fire is an important form of disturbance in most terrestrial ecosystems, and increased levels of biomass burning in many parts of the world have raised concerns about the role of fire in transforming vegetation composition, extent, and function in the future.  Sedimentary charcoal records can help inform this discussion by providing fire-history information that spans a range of temporal and spatial scales.  At a regional to continental scale, climate emerges as the strong driver of past biomass burning, with warmer periods being associated with higher fire activity.  In many regions, humans have also significantly altered natural fire regimes through (1) igniting fires in places where fires were naturally rare, (2) lengthening the fire season through deliberate burning, (3) manipulating fuels through land-use activities, and (4) suppressing or eliminating natural fire