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Holocene forest dynamics in north-western Romania
Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
2005 (English)In: The Holocene, ISSN 0959-6836, E-ISSN 1477-0911, Vol. 15, no 3, 435-446 p.Article in journal (Refereed) Published
Abstract [en]

Pollen analyses and AMS radiocarbon measurements were carried out on peat deposits from the former crater lake Preluca Tiganului, located in a mid-altitude area of the Gutaiului Mountains (NW Romania), in order to reconstruct the postglacial vegetation history. At the Lateglacial/Holocene transition the open vegetation was replaced by forest, suggesting a fast response to climatic warming. The rapid expansion of Pinus, Betula and later Picea may be due to their existence in the area during the Lateglacial. At approximately 11 250 cal. yr BP, the dense forest was composed primarily of Ulmus and some Picea, Betula and Pinus. A small population of Ulmus might also have survived in the area during the Lateglacial. At 10 750 cal. yr BP, Quercus, Tilia and Fraxinus, followed by Corylus at c. 10 200 cal. yr BP, expanded significantly in the forest. The delay of approximately 550 years in their establishment, as compared to the expansion of Ulmus, was probably due to their immigration from more distant localities. Between 9300 and 5750 cal. yr BP, the forest became denser and was composed of Corylus (dominating), Ulmus, Quercus, Tilia, Fraxinus and Picea. At 5750 cal. yr BP Carpinus became established and expanded, possibly as a response to higher temperatures. At 5200 cal. yr BP, Fagus became locally established, and expanded from about 4800 cal. yr BP, possibly as a result of moist climatic conditions, although human activities cannot be excluded. From 4000 cal. yr BP to the present, Fagus dominated the woodlands, and all other deciduous trees (except for Carpinus and Quercus) became greatly reduced. Evidence of human influence on the local vegetation is low for this time period, but becomes more evident in the pollen stratigraphy around 2300 cal. yr BP. This is reflected by a decrease in forest diversity and an increase in pasture and forest grazing.

Place, publisher, year, edition, pages
2005. Vol. 15, no 3, 435-446 p.
URN: urn:nbn:se:su:diva-22757DOI: 10.1191/0959683605hl803rpOAI: diva2:189379
Part of urn:nbn:se:su:diva-108Available from: 2004-04-15 Created: 2004-04-15 Last updated: 2010-08-02Bibliographically approved
In thesis
1. Palaeoenvironment in North-Western Romania during the last 15 000 years
Open this publication in new window or tab >>Palaeoenvironment in North-Western Romania during the last 15 000 years
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The objectives of this thesis are to establish a chronological framework for environmental changes during the last 15,000 years in northwest Romania, to reconstruct the vegetation development, and to evaluate the underlying processes for forest dynamics. Furthermore, an overview of earlier and ongoing pollenstratigraphic work in Romania is provided.

Sediments from two former crater lakes, Preluca Tiganului and Steregoiu, situated in the Gutaiului Mountains, on the western extremity of the Eastern Carpathians at 730 m and 790 m a.s.l., respectively were obtained and analysed for high-resolution pollen, macrofossils, charcoal, mineral magnetic parameters and organic matter. The chronostratigraphic framework was provided by dense AMS 14C measurements.

Cold and dry climatic conditions are indicated by the occurrence of open vegetation with shrubs and herbs, and cold lake water prior to 14,700 cal. yr BP. The climatic improvement at the beginning of the Lateglacial interstadial (around 14,700 cal. yr BP) is seen by the development of open forests. These were dominated by Pinus and Betula, but contained also new arriving tree taxa, such as Populus, Alnus and Prunus. The gradual establishment of forests may have led to a stabilization of the soils in the catchment. Between ca. 14,100 and 13,800 cal. yr BP the forest density became reduced to stands of Pinus, Betula, Alnus, Larix and Populus trees and grassland expanded, suggesting colder climatic conditions. Picea arrived as a new taxon at around 13,800 cal. yr BP, and between 13,800 and 12,900 cal. yr BP, the surroundings of the sites were predominantly covered by Picea forest. This forest included Betula, Pinus, Alnus, Larix and Populus and, from 13,200 cal. yr BP onwards also Ulmus. At ca. 12,900 cal. yr BP, the forest became significantly reduced and at 12,600 cal. yr BP, a recurrence of open vegetation with stands of Larix, Pinus, Betula, Salix and Alnus is documented, lasting until 11,500 cal. yr BP. This distinct change in vegetation may by taken as a strong decline in temperature and moisture availability.

At the transition to the Holocene, at ca. 11,500 cal. yr BP, Pinus, Betula and Larix quickly expanded (from small local stands) and formed open forests, probably as a response to warmer and more humid climatic conditions. At 11,250 cal. yr BP Ulmus and Picea expanded and the landscape became completely forested. The rapid increase of Ulmus and Picea after 11,500 cal. yr BP may suggest the existence of small residual populations close to the study sites during the preceding cold interval. Ulmus was the first and most prominent deciduous taxa in the early Holocene in the Gutaiului Mountains. From ca. 10,750 cal. yr BP onwards Quercus, Tilia, Fraxinus and Acer expanded and Corylus arrived. A highly diverse, predominantly deciduous forest with Ulmus, Quercus, Tilia, Fraxinus, Acer, Corylus and Picea developed between 10,700 and 8200 cal. yr BP, which possibly signifies more continental climatic conditions. The development of a Picea-Corylus dominated forest between 8200 and 5700 cal. yr BP is likely connected to a more humid and cooler climate. The establishment of Carpinus and Fagus was dated to 5750 cal. yr BP and 5200 cal. yr BP, respectively. The dominance of Fagus during the late Holocene, from 4000 cal. yr BP onwards, may have been related to cooler and more humid climatic conditions. First signs of human activities are recorded around 2300 cal. yr BP, but only during the last 300 years did local human impact become significant.

The vegetation development recorded in the Gutaiului Mountains during the Lateglacial is very similar to reconstructions based on lowland sites, whereas higher elevation sites seem not to have always experienced visible vegetation changes. The time of tree arrival and expansion during the past 11,500 cal. yr BP seems to have occurred almost synchronously across Romania. The composition of the forests during the Holocene in the Gutaiului Mountains is consistent with that reconstructed at mid-elevation sites, but differs from the forest composition at higher elevations. Important differences between the Gutaiului Mountains and other studied sites in Romania are a low representation of Carpinus and a late and weak human impact.

The available data sets for Romania give evidence for the presence of coniferous and cold-tolerant deciduous trees before 14,700 cal. yr BP. Glacial refugia for Ulmus may have occurred in different parts of Romania, whereas the existence of Quercus, Tilia, Corylus and Fraxinus has not been corroborated.

Place, publisher, year, edition, pages
Stockholm: Institutionen för naturgeografi och kvartärgeologi, 2004. 47 p.
Avhandling i kvartärgeologi, ISSN 1651-3940 ; 3
Northwest Romania, Gutaiului Mountains, pollenstratigraphy, macrofossil remains, Lateglacial, Holocene, tree refugia, tree dynamics, past climate, human influence
urn:nbn:se:su:diva-108 (URN)91-7265-837-8 (ISBN)
Public defence
2004-05-06, De Geersalen, Geovetenskapens hus, Svante Arrhenius väg 8 A, Stockholm, 13:00
Available from: 2004-04-15 Created: 2004-04-15Bibliographically approved

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