Tree rings are one of the most important indicators for reconstructing past history of climate variability as well as anthropogenic and ecological processes. The climatic signal for the past centuries recorded on tree rings is well known in regions of Europe for Scots pine growing in dry conditions, but little knowledge is available regarding pines growing on peatlands. Extreme changes of environmental conditions limit the radial increment of trees and influence the formation of very wide or very thin tree rings. Usually, these extreme events (pointer years) are best explained by climatic factors. The study was carried out on five bogs with variable evidence of past human disturbance. A large number of pointer years common between study sites were identified (positive 1913, 1916, 1917, 1934–1939, 1957, 1967, 1968, 1972 and negative 1865–1867, 1926, 1928–1931, 1947–1949, 1951, 1990, 2000, 2002). Correlation analysis between climatic variables (maximal, minimal, and mean air temperature and precipitation sum) and pointer years indicated that the response to precipitation sum was mainly local and low compared to the response to air temperature. The main climatic variables influencing the development of pointer years were the mean air temperature in the growing season (May–September) and minimal air temperature in February, as well as the precipitation sum in February (positive response) and in the growing season (negative response). However, pointer year development of Scots pine on bogs is mainly determined by local factors.
Ågren, J. & Zackrisson, O. 1990. Age and size structure of Pinus sylvestris population on mires in central and northern Sweden. J. Ecol., 79, 1049–1062.
Boggie, R. 1972. Effect of water-table height on root development of Pinus contorta on deep peat in Scotland. Oikos, 23, 304–312.
http://dx.doi.org/10.2307/3543168
Bridge, M. C., Haggart, B. A. & Lowe, J. J. 1990. The history and paleoclimatic significance of subfossil remains of Pinus sylvestris in blanket peats from Scotland. J. Ecol., 78, 77–99.
http://dx.doi.org/10.2307/2261038
Cedro, A. 2001. Dependence of radial growth of Pinus sylvestris L. from western Pomerania on the rainfall and temperature conditions. Geochronometria, 20, 69–74.
Čejková, A. & Kolář, T. 2009. Extreme radial growth reaction of Norway spruce along an altitudinal gradient in the Šumava Mountains. Geochronometria, 33, 41–47.
Desplanque, C., Rolland, C. & Schweingruber, F. H. 1999. Influence of species and abiotic factors on extreme tree ring modulation: Picea abies and Abies alba in Tarentaise and Maurienne (French Alps). Trees, 13, 218–227.
http://dx.doi.org/10.1007/s004680050236
Elferts, D. 2007. Scots pine pointer-years in northwestern Latvia and their relationship with climatic factors. Acta Univ. Latviensis, 723, 163–170.
Glebov, F. Z. & Litvinenko, V. I. 1976. On the relationship of many years dynamics of tree rings width to climatic factors in various swampy forests. Lesovedenie, 4, 56–62 (in Russian).
Havranek, M. & Tranquillini, W. 1995. Physiological processes during their winter dormancy and their ecological significance. In Ecophysiology of Coniferous Forest (Smith, W. K. & Hinkley, T. M., eds), pp. 95–124. Academic Press, New York.
Hökkä, H. & Ojansuu, R. 2004. Height development of Scots pine on peatlands: describing change in site productivity with a site index model. Can. J. For. Res., 34, 1081–1092.
Holmes, R. L. 1983. Computer-assisted quality control in tree-ring dating and measurement. Tree-Ring Bull., 43, 69–78.
Hordo, M., Metslaid, S. & Kiviste, A. 2009. Response of Scots pine (Pinus sylvestris L.) radial growth to climate factors in Estonia. Baltic Forestry, 15(2), 195–205.
Jātnieks, J. 1987. Parastās priedes ekoloģiskais profils Krustkalnu rezervātā. Mežsaimniecība un mežrūpniecība, 2, 51–52.
Kaennel, M. & Schweingruber, F. H. 1995. Multilingual Glossary of Dendrochronology. Terms and Definitions in English, German, French, Spanish, Italian, Portuguese and Russian. Berne, Stuttgart, Vienna.
Kilian, M. R., van der Plicht, J. & van Geel, B. 1995. Dating raised bogs: new aspects of AMS 14C wiggle matching, a reservoir effect and climatic change. Quaternary Sci. Rev., 14, 959–966.
http://dx.doi.org/10.1016/0277-3791(95)00081-X
Kozlowski, T. T. 1997. Responses of woody plants to flooding and salinity. Tree Physiol. Monogr., 1, 1–29.
Läänelaid, A. & Eckstein, D. 2003. Development of a tree-ring chronology of Scots pine (Pinus sylvestris L.) for Estonia as a dating tool and climatic proxy. Baltic Forestry, 9(2), 76–82.
Lebourgeois, F., Bréda, N., Ulrich, E. & Granier, A. 2005. Climate–tree-growth relationships of European beech (Fagus sylvatica L.) in the French Permanent Plot Network (RENECOFOR). Trees, 19, 385–401.
http://dx.doi.org/10.1007/s00468-004-0397-9
Linderholm, H. W. 2001. Climatic influence on Scots pine growth on dry and wet soils in the central Scandinavian Mountains, interpreted from tree-ring widths. Silva Fenn., 35, 415–424.
Linderholm, H. W. & Leine, M. 2004. An assessment of twentieth century tree-cover changes on a southern Swedish peatland combining dendrochronology and areal photograph analysis. Wetlands, 24, 357–363.
http://dx.doi.org/10.1672/0277-5212(2004)024[0357:AAOTCT]2.0.CO;2
Linderholm, H. W., Moberg, A. & Grudd, H. 2002. Peatland pine as a climate indicator? A regional comparison of the climatic influence on Scots pine growth in Sweden. Can. J. For. Res., 32, 1400–1410.
http://dx.doi.org/10.1139/x02-071
MacDonald, S. E. & Yin, F. 1999. Factors influencing size inequality in peatland black spruce and tamarack: evidence from post-drainage release growth. J. Ecol., 87, 404–412.
http://dx.doi.org/10.1046/j.1365-2745.1999.00370.x
Mannerkoski, H. 1991. Relation between tree roots and soil aeration on drained peatlands. In Proceedings, Peat and Peatlands – Diversification and Innovation, 6–10 Aug. 1989, Quebec City, Que (Jeglum, J. K. & Overend, R. P., eds), pp. 109–114. Canadian Society for Peat and Peatlands, Darnouth, N.S.
Neuwirth, B., Esper, J., Schweingruber, F. H. & Winiger, M. 2004. Site ecological differences
to the climatic forcing of spruce pointer years from the Lötschental, Switzerland. Dendrochronologia, 21(1), 69–78.
http://dx.doi.org/10.1078/1125-7865-00040
Oberhuber, W., Stumböck, M. & Kofler, W. 1998. Climate–tree-growth relationships of Scots pine stands (Pinus sylvestris L.) exposed to soil dryness. Trees, 13, 19–27.
http://dx.doi.org/10.1007/PL00009734
Ohlson, M. 1995. Growth and nutrient characteristics in bog and fen populations of Scots pine (Pinus sylvestris). Plant Soil, 172, 235–245.
http://dx.doi.org/10.1007/BF00011326
Ohlson, M. & Zackrisson, O. 1992. Tree habitat establishment and microhabitat relationships in north Swedish peatlands. Can. J. For. Res., 22, 1869–1877.
Pärn, H. 2009. Temporal history of relationships between Scots pine (Pinus sylvestris L.) growth and mean monthly temperatures. Baltic Forestry, 15(1), 48–57.
Pederson, N., Cook., E. R., Jacoby, J. C., Peteet, D. M. & Griffin, K. L. 2004. The influence of winter temperatures on the annual radial growth of six northern range margin tree species. Dendrochronologia, 22, 7–29.
http://dx.doi.org/10.1016/j.dendro.2004.09.005
Pilcher, J. R., Baillie, M. G. L., Brown, D. M., McCormac, F. G., MacSweeny, P. B. & McLawrence, A. S. 1995. Dendrochronology of subfossil pine in the north of Ireland. J. Ecol., 83, 665–671.
http://dx.doi.org/10.2307/2261634
Prieditis, N. 1999. Status of wetland forests and their structural richness in Latvia. Environ. Conserv., 26, 332–346.
http://dx.doi.org/10.1017/S0376892999000442
Richardson, D. M. & Rundel, P. W. 2000. Ecology and biogeography of Pinus, an introduction. In Ecology and Biogeography of Pinus (Richardson, D. M., ed.), pp. 3–46. Cambridge University Press, Cambridge.
Rinn, F. 1996. TSAP – Reference Manual. Frank Rinn, Heidelberg, Germany.
Rolland, C., Desplanque, C., Michalet, R. & Schweingruber, F. H. 2000. Extreme tree rings in spruce (Picea abies (L.) Karst.) and fir (Abies alba Mill.) stands in relation to climate, site, and space in the southern French and Italian Alps. Arct. Antarc. Alp. Res., 32, 1–13.
http://dx.doi.org/10.2307/1552404
Rydin, H. & Jeglum, J. 2006. The Biology of Peatlands. Oxford University Press, Oxford.
http://dx.doi.org/10.1093/acprof:oso/9780198528722.001.0001
Sarkkola, S., Hökkä, H. & Penttilä, T. 2004. Natural development of stand structure in peatland Scots pine following drainage, results based on long-term monitoring of permanent sample plots. Silva Fenn., 38, 405–412.
Schweingruber, F. H. 1988. Tree Rings: Basics and Applications of Dendrochronology. D. Reidel Publishing Company, Dordrecht, Netherlands.
Schweingruber, F. H. 1996. Tree Rings and Environment: Dendroecology. Birmensdorf, Swiss Federal Institute for Forest, Snow and Landscape Research, Berne, Stuttgart, Vienna.
Schweingruber, F. H. 2007. Wood Structure and Environment. Springer-Verlag, Berlin.
Schweingruber, F. H., Eckstein, D., Serre-Bachet, F. & Bräker, O. U. 1990. Identification, presentation and interpretation of event years and pointer years in dendrochronology. Dendrochronologia, 8, 8–38.
Schweingruber, F. H., Börner, A. & Schulze, E.-D. 2006. Atlas of Woody Plant Stems. Evolution, Structure, and Environmental Modifications. Springer-Verlag, Berlin.
Stravinskiene, V. & Juknys, R. 1998. The climatic signal in radial growth variations of Pinus sylvestris L. trees growing in raised bog habitat. In Proceeding of the International Conference ‘Dendrochronology and Environmental Trends’. Kaunas, Lithuania.
Vaganov, E. A. & Kachaev, A. V. 1992. Dendroclimatic analysis of pine growth in forest-bog phytocenoses of Tomsk province. Lesovedenie, 6, 3–10 (in Russian).
Vitas, A. 2004a. Tree rings of Norway spruce (Picea abies (L.) Karsten) in Lithuania as drought indicators: dendroecological approach. Pol. J. Ecol., 52, 201–210.
Vitas, A. 2004b. Dendroclimatological research of Scots pine (Pinus sylvestris L.) in the Baltic coastal zone of Lithuania. Baltic Forestry, 10(1), 65–71.
Vitas, A. & Erlickytė, R. 2007. Influence of drought to the radial growth of Scots pine (Pinus sylvestris L.) in different site conditions. Baltic Forestry, 13(1), 10–16.
Zālītis, P. & Bambe, B. 1991. Priežu augšanas gaitas dendrohronoloģiskā analīze Teiču rezervāta meža un purva saskares zonā. Teiču rezervāts (Rīgā), 1, 48–63.
Zunde, M., Briede, A. & Elferts, D. 2008. The influence of climatic factors on the radial growth of Scots pine (Pinus sylvestris) in Western Latvia. Proc. Latv. Acad. Sci., 62, 120–128.
