Occasionally I found a table containing a classification for each year during the period 1683-1780 according to harvests results in Sweden, done 1783 by someone named Ekman.1 He is using seven classes, which I will replace with numbers in order to allow comparison with dendrodata:
missväxt (failure) 50
dyr (dearth) 60
ringa (small) 65
knapp (little) 70
svag (weak) 75
medelmåttlig (normal) 80
ymnig (rich) 100
After this replacement I have a "dendro-style" measurement series, for which I did an ordinary test towards all available pine ring width chronologies from Scandinavia,2 using the normalization method "proportion of last two years", i.e only the short term variation (year to year) is compared. The result of this exercise was a bit amazing: Surprisingly strong correlation values occurred towards especially a chronology from western Gästrikland3 (T-värde > 6), but rather good also towards chronologies for Dalarna and southeastern Småland. The first about 15 years, however, gives significant weaker values than the later period. This disagreement seems to be caused by the thinnest ring, the one for 1688, occurs one year after the reported crop failure 1687 - a delayed response in tree rings seems likely. Also the very last years, shows a bit lower correlation again.
It is unclear to me why the correlation towards exactly Gästrikland among all areas in Sweden, gives such a strong correlation towards Ekmans classification. It may have any of various reasons. Gästrikland may at this time have been a more prominent producer of cereals when today, according to the fertilization possible due to a strong cattle stock. So the situation in this and similar areas may have had some stronger impact on the general judgment on harvests, than we may expect? It is also possible that Ekman, about whom I do not know anything, may have been biased in favor for the situation in this particular area - maybe he lived somewhere around or he used sources from there? In any case this pine-chronology from 200 meter above sea level, seems to record the balance between temperature and precipitation in a way strongly affecting also the needs of the cereals during at least great parts of 18'th century.
A diagram showing the correlation between the pinus curve from Kungsberg in Gästrikland (green and red) and Ekmans harvest classification (blue and black). Red and black curves are normalized. The years of crop failure are marked.
Cybis CDendro, Algorithm: Proportion of last two years growth (2,0,T
Correlations between references and
SKRDekm dated to 1780 with corr >= 0.25 and with overlap >= 90
Results sorted according to decreasing correlation coefficient values.
1. Ekmans skördeomdömen 1683-1780 i Sverige, posted by Stefan Lundgren 04 jul 2005, 13:25 at http://forum.skalman.nu/viewtopic.php?f=44&t=19914&p=292484, with reference to Per-Erik Brolin in Statistisk tidskrift (Statistical review) nr 10, 1954
2. Also oak and spruce chronologies were tested but no strong correlations were found.
3. Jan-Olov Språng: Kungsberg PISY, Cybis wiki, (Pinus sylvestris ring width collection from the area around Järbo in western Gästrikland, about 200 m a s l, 60º46´N, 16º28´E.) Master compiled by CDendro NegExp-detrend function