A 434-year tree-ring chronology of spruce (Picea abies) with indications of Estonian precipitation

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 the non-climatic growth variations from the individual tree-ring series prior to dendroclimatic analyses to focus on the low-frequency (long-term and -period) growth variations. Previously, the chronology has been shown to correlate markedly well with Estonian precipitation history. Here we further detail this dendroclimatic connection. Correlations between the Estonian precipitation and treerings improved systematically with both the number of meteorological stations included and with the documented technical advances in the network of instrumental weather observations. The observed June precipiation explains roughly 20 percent of the tree-ring variance over the period when the network of weather observations is densest (1946–2009). On decadal and longer scales, the June precipitation explains higher portion of tree-ring variance, roughly 50 percent, over the full instrumental era (1866–2009). Comparison with previously published and similarly standardized tree-ring chronology from south-eastern Finland, based on Scots pine tree-rings, showed that the two chronologies exhibit several coinciding periods of ameliorated and deteriorated growth.