Pinus sylvestris, PISY, Scotch Pine is the most important specie for dendrochronology in Scandinavia, at least above the northern border of Quercus robur. A lot of chronologies are available. Pine wood is very frequently used in buildings and other constructions, which means that there is a lot of material for a dendrochronologist to work with.
Where to find samples
Pinus sylvertris is a very common specie, but in the modern forestry most trees are cut as young and not many will grow old. Pines will often reach ages of above 300 years. Exceptionally trees more than 750 years are reported (Andersson & Niklasson: Rekordgammal tall på Hornslandet i Hälsingland). Trees over 250 years is not difficult to find in central and northern Scandinavia. But in southern Scandinavia like Öland, Småland or Halland it may sometimes be difficult to find trees even older than 120-180 years.
Pine logs are common in buildings and ofter very well preserved in old buildings and other constructions. The oldest buildings of pine wood are nearly 800 years or more. In Norway from the 12'th century. In Sweden there are a few known buildings from first part of the 13'th century: Granhults kyrka and Tiondeboden i Ingatorp in Småland and Eldhuset at Zorns Gammelgård in Mora. Timber buildings from 18'th and 19'th century are very common especially in central and north Scandinavia. In such ordinary buildings annual rings from 15'th and 16'th century are often found.
In coast near areas and on lower latitudes and altitudes the sapwood often is affected by insects according to humidity, and therefore difficult to core. In such areas sometimes the splint was removed to solve this problem i houses, which means severe loss os dendrochronological data in such buildings!
Pine stumps, sometimes high ones, do sometimes persist for hundreds of years in the forest, due to high resin content. Pine wood will also persist very well in wet conditions in lakes and bogs. It is often relatively easy to collect cores from pinewood with an increment borer both from living trees and from old logs in various types of constructions.
How to recognize a dendrochronological wood sample as Pinus sylvestris?
Typical for wood from Pinus (sylvestris and other species) use to be:
- A relatively distinct change from earlywood to latewood in most of the rings.
- Often a lot of white "dots" in the late wood.
- The pitch use to be more "star shaped" than in Picea
- Often a reddish color on the heart wood in contrast to a more yellow (or blue or green according to affection) sap wood. But there are big variations from sample to sample and sometimes the border between sap wood and heart wood is almost invisible.
- Sometimes blue stain affects the sap wood.
- In microscope a thin wet preparation will show a typical pattern, different from other groups of conifers.
Observed problems according to measuring and cross dating PISY samples
Extremely thin or absent rings
An usual reason why a Pinus sample is not possible to cross date even than a good chronology is available are presence of too narrow rings or absent ones. In high resolution, rings sometimes are possible to see but not always also if the cellular structure is clearly seen.
Pines which is growing on peat bogs do often have a very weak correlation pattern towards chronologies based on samples from trees grown on firm ground. This problem is observed at least in Dalarna in central Sweden and can be tested through Petmyra (PISY-ref) (Bogg-samples) towards Swed305 (Firm ground) in the same area (Björbo. The ITRDB collections Swed314-328 by Hans Linderholm will make it possible to study the correlations between bog pines towards firm ground PISY chronologies nearby, from different parts of Sweden.