Proxy data forms natural time series used to lengthen instrumental climatic records, and may contain a significant portion of autocorrelation. Increased serial correlation limits the number of independent observations, not satisfying the assumptions of conventional statistical methods. We estimate...
Author(s)
Macias-Fauria, M.; Grinsted, A.; Helama, S.; Holopainen, J.
Publisher
Elsevier GmbH, München, Germany
Citation
Dendrochronologia, 2012, 30, 2, pp 179-187
Cross-dating is considered one of the most important principles of dendrochronology. The first known cross-dating attempts, conducted between the years 1737 and 1783 by independent researchers in France, Germany, and Sweden, were related to the identification of growth rings believed to have formed ...
Author(s)
Norrgård, S.; Helama, S.
Publisher
NRC Research Press, Ottawa, Canada
Citation
Canadian Journal of Forest Research, 2020, 51, 2, pp 267-273
The common growth signal and spatial synchrony of nine chronologies of tree rings (Pinus sylvestris L.) from the Baltic Sea region were studied using moving correlations with time windows of 50 and 100 years. Drifts from synchrony to asynchrony and again back to synchrony across several centuries...
Author(s)
Läänelaid, A.; Helama, S.; Kull, A.; Timonen, M.; Jaagus, J.
Publisher
Elsevier GmbH, München, Germany
Citation
Dendrochronologia, 2012, 30, 2, pp 147-155
This proceedings comprises 14 papers presenting the usefulness of dendrochronology in providing information on scientific questions about the past and to help prepare for the future. These papers focused on growth ring chronology of different trees, indicators of mid-Holocene climate variability,...
Author(s)
Helama, S.; Devall, M. S.
Publisher
Elsevier GmbH, München, Germany
Citation
Dendrochronologia, 2012, 30, 2, pp 67-194
Tree-line ecotones are strongly climatically limited and serve as potential monitors of climate change. We employed annual growth increment from tree-rings, and tree density and age structure data derived from two Juniperus przewalskii tree-line sites in the eastern part of the Qilian Mountains,...
Author(s)
Gou XiaoHua; Zhang Fen; Deng Yang; Ettl, G. J.; Yang MeiXue; Gao LinLin; Fang KeYan
Publisher
Elsevier GmbH, München, Germany
Citation
Dendrochronologia, 2012, 30, 2, pp 121-126
Tree rings are commonly used proxy data for past climate variability. Probably the simplest practical solution for transforming raw tree-ring data into proxy estimates and retaining information on low-frequency tree-growth forcing is the regional curve standardization (RCS). This paper reviews the...
Author(s)
Helama, S.; Melvin, T. M.; Briffa, K. R.
Publisher
Sage Publications Ltd, London, UK
Citation
Holocene, 2017, 27, 1, pp 172-177
Urban trees growing in roadside locations encounter stressful impacts in terms of atmospheric and soil conditions and mechanical damage. Here, a set of lime trees from a roadside location in Helsinki was analysed for their radial growth and tree-ring width variability in relation to climate...
Author(s)
Helama, S.; Läänelaid, A.; Raisio, J.; Sohar, K.; Mäkelä, A.
Publisher
Elsevier GmbH, Munich, Germany
Citation
Urban Forestry & Urban Greening, 2020, 53,
Three tree-ring chronologies of white pine (Pinus strobus), a species which are non-native to Europe, were constructed for Suuremõisa, Jädivere and Järvselja sites in Estonia. These chronologies were related to instrumental climate records and Scots pine (P. sylvestris) chronologies from nearby...
Author(s)
Läänelaid, A.; Helama, S.
Publisher
Lithuanian Forest Research Institute (Lietuvos Misku Institutas), Kaunas, Lithuania
Citation
Baltic Forestry, 2020, 26, 2,
In this study, an Estonian tree-ring network of Norway spruce (Picea abies (L.) H.Karst.), originating from both living trees and dead wood of construction wood, was used for determining the growth variations over the past 350 years (AD 1657-2009). Regional curve standardization was used to remove...
Author(s)
Läänelaid, A.; Helama, S.; Eckstein, D.
Publisher
Institute of Dendrology, Polish Academy of Sciences, Kórnik, Poland
Citation
Dendrobiology, 2015, 73, pp 145-152
Tree-ring data of individual trees show lifelong biological trends as a function of cambial age. The compilation of a tree-ring chronology entails standardization (detrending) of the series. Tree-ring standardization commonly derives detrended series of dimensionless tree-ring data that are devoid...
Publisher
Society of American Foresters, Bethesda, USA
Citation
Forest Science, 2015, 61, 5, pp 817-828