The mechanisms shown below are still under development and are not yet integrated with the other crossdating methods in CDendro |
Blue intensity measurements on latewood may be an inexpensive way to rapidly access paleoclimatic information, i.e. temperature in earlier years.
Density data is known to be related to temperature, though density is very difficult and expensive to measure.
Recent studies indicate that blue intensity measurements could be used as kind of a poor mans substitute for density measurements.
It sounds great, though a requirement for useful blue channel measurements require chemical treatment of thin wood laths to first remove resin, i.e. "cooking the wood in alcohol" (Soxhlet extraction).
Mechanisms are now available in CooRecorder to measure blue channel data from scanned wood samples.
My own measurements have been done on Norway Spruce (PCAB) certainly without as much resin as Scots pine. These samples were not chemically treated at all.
My measurements show that the color of the latewood is related to the ring width variations for Norway spruce growing on the island of Nämdö East of Stockholm, Sweden. *)
This is an indication that the CooRecorder color measurements are correct.
Though the case may be that useful data for climate analysis can best be retrieved from "alcohol cooked" wood of Scots pines and not from Norway spruce.
Recent work behind these studies are reported in:
Blue Reflectance Provides a Surrogate for Latewood Density of High-latitude Pine Tree Rings
by D. McCarroll, E. Pettigrew and A. Luckman, Arctic, Antarctic, and Alpine Research, Vol. 34, No. 4, 2002, pp. 450-453
Blue intensity in Pinus sylvestris tree rings: developing a new paleoclimate proxy
by Rochelle Campbell, Danny McCarroll, Neil J. Loader, Håkan Grudd, Iain Robertson and Risto Jalkanen. The Holocene 17,6 (2007) pp. 821-828
*) N.B. What I state is that their is a signal in the yearly variations of latewood minimum blue color that is also present (=quite high correlation) in the yearly variations of ring widths for these trees.
How to measure blue channel data with CooRecorder
The measurment rectangels (or frames) can be layed out in various ways across the latewood rings.
A number of parameters control how the frames are layed out.
My measurements on Norway spruce indicate that the latewood has different blue channel characteristics in various parts of the ring.
So it may be reasonable to experiment with various settings. But do not forget to write down your different settings used.
(When blue values are saved in a file, these settings are also written to the file as a comment.)
If this box is not checked all other blue channel settings are ignored! So this is the way to turn on or off this blue channel mechanism!
Frame placement:
A positive (f)-value means that the frame starts in the earlywood in front of the (distinct) latewood border.
This will guarantee that CooRecorder measures across both earlywood and latewood areas which makes it more easy to discern the latewood areas.
The 30% setting above means that 30% of the darkest latewood areas are used to calculate the minimum blue channel value.
With a negative (f)-value, the start of the frames will be inside the latewood ring with a a distance of (f) pixels to the (distinct) latewood border as shown in the lower part of the picture above.
This means that you avoid to measure over those pixels which are close to the latewood border.
Note that the percentage value is set to 100% above. This means that the blue channel value is calculated over the whole latewood areas found, which are accordingly marked as dark-blue!
This is probably not what you want to measure, though the values may be of interest when compared to a measurement series from the first example above.
If you place the frames so there is normally no earlywood inside the frames, then CooRecorder will anyhow divide the frames into light and dark areas. And then calculate the minimum blue channel values from the dark areas. Though the extent of the dark areas may be a matter of chance. So settings are best when there is both earlywood and latewood inside the frames!
After you have changed blue channel setting parameters, you have to recalculate the blue channel values! Click the lb-button!
Then write out the collection in decadal format, i.e. containing blue channel data series from several samples.
Faked width-data from blue channel measurements
The simplest method is to subtract the blue channel numbers from a constant number which is a bit higher than any of the blue channel numbers.
That created series of numbers can be handled as a ring width file in CDendro and be found to correlate quite well to ring width data from the sample.
To get such a file, see that you have the setting as shown above!
Not all faked width series match as well as that shown above!