Subfossil European bog oaks: population dynamics and long-term growth depressions as indicators of changes in the Holocene hydro-regime and climate

Abstract

Some 2600 bog oaks have been dated from German, Dutch and Irish bogs covering the period 6000 bc to ad 1000. The ring patterns of these ‘bog oaks’ are characterized by recurrent, long-term growth depressions. In addition, obvious changes in the temporal distribution of the bog-oak trunks throughout the Holocene are found. Both features were probably caused by unfavourable growth conditions, which are most likely linked to changes in site hydrology. We use a new variable, ‘annual mean age’, as a tool to analyse the population dynamics of bog oaks in more detail, enabling the detection of synchronous intersite and interregional changes. It is calculated as the arithmetic mean of the age of all trees in each calendar year. We performed the calculation on regional (Germany, The Netherlands, Ireland) subsets of the bog-oak series. Abrupt changes in annual mean age are taken to indicate periods of generation change. We find good agreement for the interval from 5000 bc to 2000 bc between the continental (combined German and Dutch) and the Irish mean-age chronologies. Most changes in population dynamics correspond with contemporary changes in the associated regional tree-ring chronologies. It is concluded that the observed changes in population dynamics and growth activity are responses to common environmental forcing, most likely related to climate.

Keywords

Bog oaks Quercus spp.dendroclimatology annual mean age population dynamics germination dying-off Germany The Netherlands Ireland European climate Holocene

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References

Armstrong, W. , Brändle, R. and Jackson, M.B. 1994: Mechanisms of flood tolerance in plants . Acta Botanica Neerlandica 43, 307–358 .

Baillie, M.G.L. 1994: Dendrochronology raises questions about the nature of the ad 536 dust-veil event . The Holocene 4, 212–217 .

Baillie, M.G.L. 1995: A slice through time: dendrochronologyand precision dating. London: Batsford , 176 pp-176 pp.

Baillie, M.G.L. 1996: Extreme environmental events and the linking of the tree-ring and ice-core records. In Dean, J.S. , Meko, D.M. and Swetnam, T.W. , editors, Tree rings, environment, and humanity, Radiocarbon, Department of Geosciences, University of Arizona, Tucson , 703–711.

Baillie, M.G.L. 1999: Exodus to Arthur: catastrophic encounters with comets. London: Batsford , 272 pp-272 pp.

Baillie, M.G.L. and Brown, D.M. 1996: Dendrochronology of Irish bogtrackways. In Raftery, B. , editor, Trackway excavations in the Mountdillon Bogs, Co. Longford, Irish Archaeological Wetland Unit, Transactions Vol. 3, Dept. of Archaeology, University College, Dublin , 395–402.

Baillie, M.G.L. , Pilcher, J.R. and Pearson, G.W. 1983: Dendrochronology at Belfast as a background to high-precision calibration . Radiocarbon 25, 171–178 .

Brown, D.M. , Munro, M.A.R. , Baillie, M.G.L. and Pilcher, J.R. 1986: Dendrochronology – the absolute Irish standard . Radiocarbon 28(2A), 279–283 .

Dalfes, N.H. , Kukla, G. and Weiss, H. 1997: Third millennium bc climate change and Old World collapse. Berlin: Springer , 728 pp-728 pp.

10.

Delorme, A. and Leuschner, H.H. 1983: Dendrochronologische Befun-de zur jüngeren Flussgeschichte von Main, Fulda, Lahn und Oker . Eiszeitalter und Gegenwart 33, 45–57 .

11.

Delorme, A. , Leuschner, H.H. , Höfle, H.-Ch. and Tü xen, J. 1981: Über die Anwendung der Dendrochronologie in der Moorforschung am Beispiel subfossiler Eichenstämme aus niedersächsischen Mooren . Eiszeitalter und Gegenwart 31, 135–158 .

12.

Delorme, A. , Leuschner, H.H. , Tü xen, J. and Höfle, H.-Ch. 1983: Der subatlantische Torfeichenhorizont ‘Sieden’, erneut belegt im Toten Moor am Steinhuder Meer . TELMA 13, 33–51 .

13.

Huber, B. , Jazewitsch, W. von, John, A. and Wellenhofer, W. 1949: Jahrringchronologieder Spessarteichen. (Tree-ring chronology of Spessart oak) . Forstwissenschaftliches Centralblatt 68, 706–715 .

14.

Jansma, E. 1995: RemembeRINGs. The development and application of local and regional tree-ring chronologies of oak for the purposes of archaeological and historical research in the Netherlands. PhD dissertation, University of Amsterdam. Nederlandse Archeologische Rapporten (NAR) 19, 149 pp.

15.

Jansma, E. 1996: An 1100-year tree-ring chronology of oak for the Dutch coastal region. In Dean, J.S. , Meko, D.M. , Swetnam, T.S. , editors, Tree-rings, environment and humanity, Proceedings of the International Conference, Tucson, Arizona, 17–21 May, Tucson: Radiocarbon , 769–778.

16.

Keys, D. 1999: Catastrophe: an investigation into the origins of the modern world. London: Century , 368 pp-368 pp.

17.

Kozlowski, T.T. 1984: Flooding and plant growth. London: Academic Press , 356 pp-356 pp.

18.

Lageard, J.G.A. , Chambers, F.M. and Thomas, P.A. 1995: Recording and reconstruction of wood macrofossils three-dimensions . Journal of Archaeological Science 22, 561–567 .

19.

Leuschner, H.H. 1992: Subfossil trees . In Bartholin, T. , editor, Tree-rings and environment, Proceedings of the International Dendrochronological Symposium, Ystad, South Sweden, LUNDQUA Report 34, 193–197 .

20.

Leuschner, H.H. and Delorme, A. 1986: Dendrochronologische Befunde zu Torfeichen aus dem Kehdinger Moor bei Hammah, Kreis Stade. In Landkreis Stade, editor, Landschaftsentwicklung und Besiedlungsgeschichte im Stader Raum, Stade, 183–89.

21.

Leuschner, H.H. , Delorme, A. and Höfle, H.-C. 1987: Dendrochronological study of oak trunks found in bogs in northwest Germany . Proceedings of the International Symposium on Ecological Aspects of Tree Ring Analysis, New York, 298–318 .

22.

Leuschner, H.H. , Delorme, A. , Tüxen, J. and Höfle, H.-C. 1985: Eichenstammlagen in Mooren und Talauen und die Klimaverschlechterung im Subboreal . Flora 177, 283–295 .

23.

Leuschner, H.H. , Delorme, A. , Tü xen, J. and Höfle, H.-C. 1986: Über Eichenwaldhorizonte in küstennahen Mooren Ostfrieslands . TELMA 16, 61–82 .

24.

Leuschner, H.H. , Spurk, M. , Baillie, M. and Jansma, E. 2000: Stand dynamics of prehistoric oak forests derived from dendrochronologically dated subfossil trunks from bogs and riverine sediments in Europe . Geolines 11, 118–121 .

25.

Overbeck, F. 1975: Botanisch-geologische Moorkunde: unter besonderer Beruecksichtigung der Moore Nordwestdeutschlands als Quellen zur Vegetations-, Klima- und Siedlungsgeschichte, Neumuenster: Wachholtz, 719 pp.

26.

Pilcher, J.R , Baillie, M.G.L. , Schmidt, B. and Becker, B. 1984: A 7272-year tree-ring chronology for western Europe . Nature 312, 150–152 .

27.

Raftery, B. 1996: Trackway excavations in the Mountdillon Bogs, Co. Longford. Irish Archaeological Wetland Unit, Transactions Vol. 3. Department of Archaeology, University College, Dublin , 223–226.

28.

Riemer, T. 1994: Ueber die Varianz von Jahrringbreiten. Statistische Methoden fuer die Auswertung der jaehrlichen Dickenzuwaechse von Baeumen unter sich aendernden Lebensbedingungen (Variance of tree-ring widths. Statistical methods for evaluation of the annual increment of trees under changing living conditions). PhD dissertation, Universitaet Goettingen. Berichte des Forschundszentrums Waldekosysteme, Reihe A 121, 375 pp.

29.

Schmid, J., Bogenrieder, A. and Schweingruber, F.H. 1995: Verjuengung und Wachstum von Moorkiefern (Pinus rotundata Link) und Fichten (Picea abies (L.) Karst.) in Mooren des suedoestlichen Schwarzwaldes (Sueddeutschland) (Regeneration and growth of bog pine (Pinus rotundata Link) and spruce (Picea abies (L.) Karst.) in bogs of the southeastern Black Forest (southern Germany). Mitteilungen der Eidgenoessischen Forschunganstalt fuer Wald, Schnee und Landschaft 70(2), 174–223.

30.

Schmidt, B. 1993: Hölzerne Moorwege als Untersuchungsobjekte für die Dendrochronologie. In Fansa, F., editor, Moorarchäologie in Nordwest-Europa, Sonderdruck der Oldenburgischen Landschaft, Isensee Oldenburg, 147–60.

31.

Spurk, M. , Friedrich, M. , Hofmann, J. , Remmele, S. , Frenzel, B. , Leuschner, H.H. and Kromer, B. 1998: Revisions and extensions of the Hohenheim oak and pine chronologies – new evidence about the timing of the younger Dryas/Preboreal transition . Radiocarbon 40(3), 1–10 .

32.

Succow, M. and Joosten, H. 2001: Landschaftsökologische Moorkunde. Stuttgart: Schweizerbart'sche Verlagsbuchhandlung , 622 pp-622 pp.

33.

Wazny, T. 1994: Dendrochronology of Biskupin – absolute dating of the early Iron Age settlement . Bulletin of the Polish Academy of Sciences, Biological Sciences 42(3), 283–289 .