LignoStation is an "all in one system for surface preparation, high resolution assessment of tree-ring variables and wood density. The LignoStation follows a new concept: It produces high resolution digital scans, directly and automatically. The whole system is computer controlled. Thus you can focus on your scientific work, while the system does the routine work for you. Note: This product is developed in co-operation with the University of Freiburg, Germany and is in development." Details: (1) Density assessment by a high frequency probe (no x-ray source used); (2) Image resolution: <= 20 microns (=1/50 mm); (3) Optical scans with high-resolution camera; (4) Samples: increment cores or stem discs; and (5) Maximum measurement length: 500 mm.
Coupled with LignoStation is (1) LignoTrim: High resolution wood surface cutter; (2) LignoScan: High resolution, electromagnetic wood density scanner; (3) LignoScop: High resolution wood surface microscope-camera scanner; and (4) LignoVision.
LignoVision is software that represents a system for tree-ring scanning that works with any scanner and allows automatic tree-ring detection plus an easy manual editing function. Ring-width as well as early and latewood width can be separately stored. Besides surface scanning, it can also be used for analysis of x-ray images. The software also supports multiple image sources, such as optical scanner, CCD-camera, and x-ray scanner.
Yves Bégin provides a thorough description of the
densitometry system used at the Centre d'études nordiques of
(1) An increment borer of at least 7 mm diameter is needed, but we use 1.2 mm when possible or more simply entire cross-sections. (2) Cores are kept preferably in an alcohol bath for conservation.
(1) A double bladed saw (Dendrocut from Walesch Electronics) is used. Cores placed on home-made wood supports are stuck perpendicular to normal presentation for measuring ring widths. Advantage: very precise and regular. All sample thicknesses are measured afterward (average imprecision 0.02mm) with a range between 0.7 to 2.5 mm. Best: 1.5 - 2 mm thick. The machine is also easy to handle and comes with a binocular microscope allowing the measurement of the angle of the axial cells with the core axis. The same measuring system is mounted on the saw. A vacuum is needed to evacuate saw dust. Compare to other systems (Home-made most of it) - the great advantage is precision. Not much is said in the literature about precision. The use of microtome sections must be avoided because of their imprecision and they are too thin to integrate wood anatomical structures. One should mention to the readers that the range of density variations is due to the imprecision of the cut. Disadvantage (minor): the device is heavy (at least 100 kg), the potentiometers are fragile, the saw needs to be frequently sharpened, and cleaned with alcohol.
(2) A Soxhlet extractor with alcohol (96%/vol) is used to extract the resin and other substances from samples. Price: about 1000$US including a heating plate and tubes. Available from any chemistry supplier. Picea, Abies need generally 24 hrs, Larix and Pinus more. Samples are marked with China ink, insoluble in alcohol and transparent to X-ray.
(3) Samples are cut obliquely in small pieces and pressed in Bell Canada telephone directories (not expensive!) to avoid bending. How about densest populated countries? Internet directories not very useful!
dried thin sections are placed in a home-made rack made of
two layers of good quality cellophane that contracts when
heated with a hair dryer (available in home hardware stores
to insulate windows in winter). The rack is made of two
embeded wood rectangles, one applying pressure over the
other through a system of nuts. Ink numbers are placed face
down for xeroxing the montage. This sketch is very useful to
position samples afterward with the densitometer. Finally,
the montage is kept at least half an hour in the X-ray room
to equilibrate with atmosphere. According To Ernst Shär
(Birmensdorf), the equilibrium is rapidly reached (10-15
min, 50% Humidity in the air and 20°C, 8-9 % humidity in the
wood). Many details available in: Schweingruber, F.H, Schär,
E., et al., 1978. The X-ray technique as applied to
dendroclimatology. Tree-Ring Bulletin 38: 61-91.
(1) X-Ray room: We benefited from an old X-ray room from Dr. Poliquin (retired from Laval University) which is coated with lead sheets, but a concrete-walled room is sufficient to stop the rays for safety (e.g. Birmensdorf). The atmosphere is controlled into the room. T° and Humidity are kept to 20°C and 50% with an air exchanger with the exterior. A hygro-thermostat is needed. T he room is lighted with a special red-light calibrated especially for the film by Kodak (expensive: 500$ US). Finally, a rectangular plate placed over a marber plate helps place the montage under the source in the dark.
(2) X-Ray source: We fixed an old Balteau device that is generally used in a hospital. Specifications: Baryllium window of 5mm with 20mv and 12ma. A source and a sink for cold water is needed in the X-ray room. This type of device is best because it is not expensive (available in any hospital stockroom for cheap prices). Their advantage, compared to modern systems, is that the source is far from the target (2.3 m at Laval, 2.5 m at Birmensdorf). With shorter distances, the obliquity of the rays with longitudinal wood cell walls produces a shadow on the film. Some labs correct this problem by bending the extremity of their samples, but there is a risk of imprecision by doing so.
(3) Duration of film exposure: We use Kodak RPM 12 X 12 inches double-side coated. Cheap in box of 50. Irradiation duration: 45 min for 0.7 mm sections, 50 min for 1mm, 55 min for 1.5 mm and 60 min for 2 mm. The films are carried out within opaque boxes and processed in standard solution (for free) in X-O-Mat standard processing machine in hospital (90 sec).
MEASUREMENT OF DENSITY:
Laval University is one of the 5 labs having a Dendro-2003 densitometer from Walesch Electronics (see also one in Germany, China?, New York and Marseille). One word: The best machine for precision measurements. Disadvantage: expansive, extremely heavy, many mechanical parts are fragile. The operator overseas needs to develop a good knowledge of the machine with several years of use. However, Walesch gives remarkable service after purchase. Software used to handle data needs to be improved, especially with the recent developments in the definition of parameters (e.g. where do we place the limit between earlywood and latewood?).
If you're interested in the Dendrocut precision sawing device and the Dendro-2003 densitometry system, the address for Walesch Electronics is:
Phone: +41 52 326266 or +41 52 322644
Gordon Jacoby adds this about the AcuSaw and densitometry/image analysis: The AcuSaw saw works very well. The length of cut is limited to about 20 cm. Unmounted cores can be cut down to about 1 mm thickness after some adjusting of the saw. If a milling machine is available, a twin-bladed saw such as used (and described) by Fritz Schweinguber can be made for much less than the $11,000 Canadian investment for this saw.
A densitometric/image analysis system can be assembled with a frame-grabber board for a Mac (and assumably a PC), a video camera mounted on a microscope to look at xrays on a light table, and image analysis software from NIH (free). We used a similar system for several years using proprietary software based on NIH. The software was purchased from Analytical Vision Inc., 213 Merwin road, Raleigh, NC 27606, (919-85-8117). This system and an expert operator (who has unfortunately retired) produced excellent data but was slow as each frame was analyzed separately, sometimes over a hundred frames for one core. Our system is mostly described in Thetford, D'Arrigo, and Jacoby, "An image analysis system for determining densitometric and ring-width time series", Canadian Journal of Forest Research 21, 1544-1548, 1991. We have no other diagrams, schematics, or specifications drawn or compiled.
2302 West 33rd Ave.
Canada V6M 1C3
Campbell of the Canadian Forest Service reminds us that
DendroScan is software available for $99.95 + $5 shipping
Canadian from the University of British Columbia Press:
University of British Columbia
6344 Memorial Road
Canada V6T 1Z2
The book gives detailed
instructions for the assembly and use of an x-ray
densitometry lab, using stuff most universities already have
like a scanner, a darkroom, a table saw, and an x-ray
machine. It includes a pre-calibrated density wedge and a
floppy with the DendroScan program, which converts scanned
grey-scale images of x-ray negatives (or positives) into
density, identifies ring boundaries, and measures and counts
the rings. DendroScan is also able to use images scanned
directly from well-sanded wood, and will give ring
measurements and counts - but not densities. It has also
been used for other rhythmically banded objects, including
annually laminated lake sediments and growth increments in
seal teeth. If anyone has any questions, please don't
hesitate to contact:
Canadian Forest Service
5320-122 St. Edmonton