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Blue intensity and density from Northern Fennoscandian tree rings, exploring the potential to improve summer temperature reconstructions with earlywood information

Björklund, Jesper; Gunnarson, Björn; Seftigen, Kristina; Esper, Jan and Linderholm, Hans (2014) In Climate of the Past 10. p.877-885
Abstract
Here we explore two new tree-ring parameters, derivedfrom measurements of wood density and blue intensity(BI). The new proxies show an increase in the interannualsummer temperature signal compared to establishedproxies, and present the potential to improve long-term performance.At high latitudes, where tree growth is mainlylimited by low temperatures, radiodensitometric measurementsof wood density, specifically maximum latewood density(MXD), provides a temperature proxy that is superior tothat of tree-ring widths. The high cost of developing MXDhas led to experimentation with a less expensive method usingoptical flatbed scanners to produce a new proxy, hereinreferred to as maximum latewood blue absorption intensity(abbreviated MXBI). MXBI... (More)
Here we explore two new tree-ring parameters, derivedfrom measurements of wood density and blue intensity(BI). The new proxies show an increase in the interannualsummer temperature signal compared to establishedproxies, and present the potential to improve long-term performance.At high latitudes, where tree growth is mainlylimited by low temperatures, radiodensitometric measurementsof wood density, specifically maximum latewood density(MXD), provides a temperature proxy that is superior tothat of tree-ring widths. The high cost of developing MXDhas led to experimentation with a less expensive method usingoptical flatbed scanners to produce a new proxy, hereinreferred to as maximum latewood blue absorption intensity(abbreviated MXBI). MXBI is shown to be very similar toMXD on annual timescales but less accurate on centennialtimescales. This is due to the fact that extractives, such asresin, stain the wood differentially from tree to tree and fromheartwood to sapwood. To overcome this problem, and to addresssimilar potential problems in radiodensitometric measurements,the new parameters 1blue intensity (1BI) and1density are designed by subtracting the ambient BI/densityin the earlywood, as a background value, from the latewoodmeasurements. As a case-study, based on Scots pine treesfrom Northern Sweden, we show that 1density can be usedas a quality control of MXD values and that the reconstructiveperformance of warm-season mean temperatures is morefocused towards the summer months (JJA – June, July, August),with an increase by roughly 20% when also utilisingthe interannual information from the earlywood. However,even though the new parameter 1BI experiences an improvementas well, there are still puzzling dissimilarities between1density and 1BI on multicentennial timescales. As aconsequence, temperature reconstructions based on 1BI willpresently only be able to resolve information on decadalto-centennial timescales. The possibility of trying to calibrateBI into a measure of lignin content or density, similarlyto how radiographic measurements are calibrated into density,could be a solution. If this works, only then can 1BIbe used as a reliable proxy in multicentennial-scale climatereconstructions. (Less)
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author
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Scots pine, Blue Intensity, Temperature reconstructions, Fennoscandia
in
Climate of the Past
volume
10
pages
877 - 885
publisher
Copernicus Gesellschaft Mbh
external identifiers
  • scopus:84899689529
ISSN
1814-9332
DOI
10.5194/cp-10-877-2014
project
BECC
MERGE
language
English
LU publication?
no
id
c8277672-ba54-483d-961f-8857f2616977 (old id 7515786)
date added to LUP
2014-11-28 12:26:25
date last changed
2017-11-12 04:06:14
@article{c8277672-ba54-483d-961f-8857f2616977,
  abstract     = {Here we explore two new tree-ring parameters, derivedfrom measurements of wood density and blue intensity(BI). The new proxies show an increase in the interannualsummer temperature signal compared to establishedproxies, and present the potential to improve long-term performance.At high latitudes, where tree growth is mainlylimited by low temperatures, radiodensitometric measurementsof wood density, specifically maximum latewood density(MXD), provides a temperature proxy that is superior tothat of tree-ring widths. The high cost of developing MXDhas led to experimentation with a less expensive method usingoptical flatbed scanners to produce a new proxy, hereinreferred to as maximum latewood blue absorption intensity(abbreviated MXBI). MXBI is shown to be very similar toMXD on annual timescales but less accurate on centennialtimescales. This is due to the fact that extractives, such asresin, stain the wood differentially from tree to tree and fromheartwood to sapwood. To overcome this problem, and to addresssimilar potential problems in radiodensitometric measurements,the new parameters 1blue intensity (1BI) and1density are designed by subtracting the ambient BI/densityin the earlywood, as a background value, from the latewoodmeasurements. As a case-study, based on Scots pine treesfrom Northern Sweden, we show that 1density can be usedas a quality control of MXD values and that the reconstructiveperformance of warm-season mean temperatures is morefocused towards the summer months (JJA – June, July, August),with an increase by roughly 20% when also utilisingthe interannual information from the earlywood. However,even though the new parameter 1BI experiences an improvementas well, there are still puzzling dissimilarities between1density and 1BI on multicentennial timescales. As aconsequence, temperature reconstructions based on 1BI willpresently only be able to resolve information on decadalto-centennial timescales. The possibility of trying to calibrateBI into a measure of lignin content or density, similarlyto how radiographic measurements are calibrated into density,could be a solution. If this works, only then can 1BIbe used as a reliable proxy in multicentennial-scale climatereconstructions.},
  author       = {Björklund, Jesper and Gunnarson, Björn and Seftigen, Kristina and Esper, Jan and Linderholm, Hans},
  issn         = {1814-9332},
  keyword      = {Scots pine,Blue Intensity,Temperature reconstructions,Fennoscandia},
  language     = {eng},
  pages        = {877--885},
  publisher    = {Copernicus Gesellschaft Mbh},
  series       = {Climate of the Past},
  title        = {Blue intensity and density from Northern Fennoscandian tree rings, exploring the potential to improve summer temperature reconstructions with earlywood information},
  url          = {http://dx.doi.org/10.5194/cp-10-877-2014},
  volume       = {10},
  year         = {2014},
}