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Eastern Hemlock

Latin name:
Tsuga canadensis

Extracted from a waterfront pier near Wilmington, Delaware, the tree used to make this portion of the pier
actually came from a forest located in central Pennsylvania. The outermost tree ring dates to the late 1830s.

Giant Sequoia

Latin name:
Sequoiadendron giganteum

A close up of numerous fire scars on a giant sequoia cross section from Sequoia National Park in California, dating back well prior to A.D. 1000. Look closely! Can you find the sad bearded face cradled by his hands, as if he was crying?

Douglas-fir

Latin name:
Pseudotsuga menziesii

This photo shows the tree rings from a beam extracted many years ago from a pueblo in northeastern Arizona. The section shows many false rings and many micro-rings, suggesting this tree may have been growing in a marginal environment.

Ponderosa Pine

Latin name:
Pinus ponderosa

Close up of tree rings of a ponderosa pine collected at El Malpais National Monument in New Mexico, USA, showing tree rings centered around A.D. 1400. Notice the variability in ring widths indicative of sensitivity to year-to-year variation in precipitation.

Douglas-fir

Latin name:
Pseudotsuga menziesii

Perhaps my most requested image of tree rings, obtained from a small Douglas-fir growing in the Zuni Mountains of west-central New Mexico by my colleagues Rex Adams and Chris Baisan. Not very old, but has some of the most beautiful rings of all my displays!

White Oak

Latin name:
Quercus alba

Oak cores from the Hoskins House in Greensboro, North Carolina, site of a famous battle during the Revolutionary War. The house was built from trees cut in 1811 to 1813, not cut and built in the 1780s as the historical agency had hoped.

Ponderosa Pine

Latin name:
Pinus ponderosa

This ponderosa pine once grew at El Morro National Monument in New Mexico, USA, and was cut many years ago. Once you get up close to the stump, you can see a very old scar from a fire many hundreds of years ago that scarred the tree when it only about 12 years old!

Bahamian Pine

Latin name:
Pinus caribaea var. bahamensis

We collected many cross sections of Bahamian pines that had been cut for an industrial park on the island of Abaco, but the rings are very difficult to date! Many false rings, and the pine appears to terminate tree growth during the dry season.

Longleaf Pine

Latin name:
Pinus palustris

This cross section was one of many that came from an old crib dam across a creek that was exposed after a modern dam broke in Hope Mills, North Carolina in 2003. Such sections from old-growth longleaf pines are very rare and provide information on climate back to AD 1500!

White Oak

Latin name:
Quercus alba

Sometimes you don't have to look far to find beauty in wood, and sometimes it may not be a living tree! After an oak tree was cut a year or two before this section was obtained, decay fungi had already set in, beginning to break the wood down to its basic elements.

Southwestern White Pine

Latin name:
Pinus strobiformis

I collected this fire-scarred pine on Mt. Graham in southern Arizona in fall 1991, and it remains one of the best examples of how we can determine the season of fire by looking at the position of the scar within the ring.

Bristlecone Pine

Latin name:
Pinus longaeva

Bristlecone pines have become one of the best proxy records for those who study the history of volcanic eruptions because the cool temperatures caused by these eruptions create "frost rings" that form when the cells implode from the cold.

Eastern Redcedar

Latin name:
Juniperus virginiana

Many well-preserved eastern redcedar sections have been recovered from prehistoric sites in eastern Tennessee, and they have more than enough rings to date, but we don't have a long enough living-tree reference chronology to overlap with them!

Red Oak

Latin name:
Quercus rubra

Oak is by far the most common genus we find in the many historic structures we date using tree rings in the Southeastern U.S. The genus has good ring variability and rarely has problem rings. This section came from a historic tavern in Lexington, Virginia.

Sugar Maple

Latin name:
Acer saccharum

Maple, birch, beech, and basswood are all examples of hardwood species that form diffuse porous wood, meaning that the ring contains many small-diameter vessels all through the ring. Identifying the ring boundary on this wood type is a challenge to tree-ring scientists.

Live Oak

Latin name:
Quercus virginiana

Live oak is an example of an evergreen oak, which is not common within this genus. As such, the wood is semi-ring porous and the rings are very difficult to see and date. Ring growth is also very erratic, not forming the concentric around the tree that we require.

Douglas-fir

Latin name:
Pseudotsuga menziesii

These cores were collected on Mt. Graham in southern Arizona and show a major suppression event beginning in 1685 when missing rings became evident, followed by many micro-rings. This suppression was caused by a major wildfire in 1685!

Ponderosa Pine

Latin name:
Pinus ponderosa

I find it amazing what trees can record in their tree rings! Here we see a cross section of a pine that was damaged by a major flood in the year 1945 in the Chiricahua Mountains of southern Arizona. Notice the reaction wood that formed afterward.

Pignut Hickory

Latin name:
Carya glabra

Sometimes gray-scale imagery helps define tree rings when measuring. Although classified as "ring porous" species, the rather ill-defined tree rings in hickory tree species form large earlywood vessels and smaller latewoood vessels.

Subalpine Fir

Latin name:
Abies lasiocarpa

Decay has set in on the tree rings of this dead and downed subalpine fir that once grew on Apex Mountain in British Columbia, Canada, but the tree rings can still be measured and crossdated despite this!

White Fir

Latin name:
Abies concolor

We found a beautiful fire scar on this white fir that was used to build a cabin in the Valles Caldera of New Mexico. Thought to have been built in the early 1900s, we instead found the cabin was built form white fir and Douglas-fir trees cut in 1941.

Overcup Oak

Latin name:
Quercus lyrata

These oak cores were collected in northeastern Arkansas to investigate a change in the hydrologic regime of a wildlife refuge beginning in the 1990s. We found that trees at this site experienced a major disturbance event in the 1960s.

Western Juniper

Latin name:
Juniperus occidentalis

Near Frederick Butte in central Oregon, we discovered an unusual stand of western junipers that had the most unusual lobate growth forms we had ever seen. This site yielded a drought-sensitive chronology dating back to the AD 800s!

West Indies Pine

Latin name:
Pinus occidentalis

Above 3000 meters on the highest peak in the Carribean, we found an entire forest of these pines, many with fire scars, living on a steep rocky slope. The forest looked more like the dry ponderosa pine forests of the western U.S.

Whitebark Pine

Latin name:
Pinus albicaulis

Whitebark pines growing in the northern Rockies of the western U.S. can grow to be over 1,000 years old, but the species is slowly being decimated by the introduced white pine blister rust. Many of these ancient trees are now dead with ghostly white trunks.

Shagbark Hickory

Latin name:
Carya ovata

Curiously, tree-ring scientists rarely analyze some of the more common hardwood species in the eastern U.S., such as this hickory, perhaps because such forest interior trees may contain a weak climate signal necessary for crossdating.

Virginia Pine

Latin name:
Pinus virginiana

Blue stain found in many sections of dead pines (both in the western and eastern U.S.) is caused by a fungus carried by a pine beetle. The fungus spreads into the phloem and sapwood of living and dead pines, sometimes creating stunning patterns!

Pinyon Pine

Latin name:
Pinus edulis

Burned sections of pinyon pine are commonly found in archaeological sites in the southwestern U.S. These sections can be carefully broken or surfaced with a razor to reveal the ring structure inside to assist in dating the years of construction of the site.

Red Spruce

Latin name:
Picea rubens

Conifers in the highest elevations of the Appalachians of the eastern U.S., such as this red spruce, don't experience wildfires very often, but when fires do occur, they can create numerous fire scars even in this fire-intolerant species. Notice the growth release!

White Spruce

Latin name:
Picea glauca

This tree was located in the Canadian Rockies on the toe slope of an active avalanche path. The scar was created by a debris flow or snow avalanche which struck the tree, killing a section of the living tissue. The avalanche can therefore be dated to its exact year!

Engelmann Spruce

Latin name:
Picea engelmannii

I worked considerably in the spruce-fir forests of southern Arizona in my earliest years in dendrochronology, and learned that trees with limited sensitivity can provide a vast amount of information on the history of these forests.

Ponderosa Pine

Latin name:
Pinus ponderosa

The lava flows of El Malpais National Monument in New Mexico contain vast amounts of remnant wood, mostly ponderosa pines such as this sample, and the tree rings on these samples go back nearly 2000 years! Notice the year AD 1400 on this section.

Chestnut Oak

Latin name:
Quercus montana

In the southeastern U.S., hardwood species are often scarred by wildfire. Most often, this also will cause considerable decay in the sample, but this oak had several well preserved fire scars, suggesting fire was common in these drier, lower elevation sites.

Ponderosa Pine

Latin name:
Pinus ponderosa

I originally sampled this stump in 1991 for its fire scars, located in El Malpais National Monument of New Mexico. I found it again 20 years later and was happy you could still see the tree rings and fire scars clearly! It had originally been logged in the 1930s!

Lodgepole Pine

Latin name:
Pinus contorta

This pine is found at higher elevations in the Rocky Mountains of the western U.S. At this site in Montana, we had thought we found fire scars on these pines, but it turns out that these are scars caused by bark beetles stripping away portions of the bark.

Douglas-fir

Latin name:
Pseudotsuga menziesii

These cores illustrate the level of sensitivity to climate fluctuations in Douglas-fir trees growing in El Malpais National Monument in New Mexico. These rings show the common pattern of narrow marker rings between 1800 (on the left) and 1860 (on the right).

Douglas-fir

Latin name:
Pseudotsuga menziesii

This photo shows a close-up of the rings in the previous image. The very wide tree ring is the year 1816, the "Year Without a Summer." Cooler temperatures meant more soil water for the malpais Douglas-firs, causing a wide ring for that year!

Ponderosa Pine

Latin name:
Pinus ponderosa

Dating fire scars found in the annual rings is a major application of tree-ring dating. This photo shows two scars. Notice the wider rings that formed after the upper scar, perhaps caused by removal of competing vegetation or added nutrients.

Longleaf Pine

Latin name:
Pinus palustris

Longleaf pines have the greatest ages of all the eastern pines. They grow slowly in sandy soils of the Atlantic Coastal Plain, and have proven ideal for learning about past climate and disturbance events, if old-growth stands can be located!

Rocky Mountain Juniper

Latin name:
Juniperus scopulorum

The juniper species of the western U.S. have proven a challenge in tree-ring dating, but Rocky Mountain juniper has tree rings that are easily identified and can be crossdated. Just watch out for false rings and expanded latewood!

Douglas-fir

Latin name:
Pseudotsuga menziesii

A close-up photo of tree rings in Douglas-fir reveals the individual wood cells that make up the xylem. These are called "tracheids." Notice the change in cell wall thickness from the earlywood cells to the latewood cells along a radial file of cells.

Douglas-fir

Latin name:
Pseudotsuga menziesii

The best trees for learning about past climate will be those that grow to great ages and are particularly sensitive to year to year changes in climate. This Douglas-fir began growing around the year 200 BC and lived for nearly 1000 years!

Mesquite

Latin name:
Prosopis glandulosa

Some desert species from the mid-latitudes do form annual rings, but these diffuse-porous species have rings that are difficult to see. You can use black marker and white chalk dust to help bring out the rings! The dust fills the small vessels and the rings appear!

Norway Spruce

Latin name:
Picea abies

Spruce is the preferred genus for making high-quality wooden bodies on musical instruments. This photo shows the tree rings on the outer edge of the "Messiah" violin. Analysis of its tree rings helped show that the violin was contemporary with Stradivari!

Black Locust

Latin name:
Robinia pseudoacacia

In the eastern U.S., this common hardwood species has beautiful tree rings that demonstrate the ring porous wood type. The tree species, however, has some of the densest wood found in North America and is extremely difficult to core!

White Oak

Latin name:
Quercus alba

Oak is a major genus used to build log structures in the eastern U.S. Sometimes, however, we find that the individual trees experienced some major disturbances that caused very aberrant rings, making crossdating all but impossible.

Palo Verde

Latin name:
Parkinsonia florida

A common tree species in the American Southwest, palo verde is a diffuse porous species that forms very indistinct tree rings. As a result, little tree-ring research has been performed on this genus. Best to use complete cross sections, when available.

Ponderosa Pine

Latin name:
Pinus ponderosa

A major application of tree-ring research is learning about insect populations. For example, pandora moth defoliated the needles on this tree, causing some narrow rings to be produced. We can use this pattern to learn about insect populations over many centuries!

Table Mountain Pine

Latin name:
Pinus pungens

The analysis of fire scars in tree rings can also be applied to pine species growing in the eastern U.S. Table Mountain pine has proven to be the best species in the Appalachian Mountains for learning about past wildfires!

Subalpine Fir

Latin name:
Abies lasiocarpa

Subalpine fir grows in the highest elevations of the southern Rocky Mountains and forms fairly compacent ring series. Sometime between 1979 and 1980, this tree was stripped almost completely of its bark by a black bear, but it still survived in one small area!

Florida Torreya

Latin name:
Torreya taxifolia

Perhaps the rarest conifer in the U.S., this species is on the brink of extinction because its habitat is facing mounting pressure from rapid changes in its native environment. It forms very nice tree rings, but few adult individuals are left to analyze.

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Densitometry Equipment   

LignoStation and LignoVision

Image of a LignoScan TipLignoStation 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.

 


Walesch Electronics

Image of the Walesch Density SystemYves Bégin provides a thorough description of the densitometry system used at the Centre d'études nordiques of Laval University:

SAMPLING:
(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.

SAMPLE PREPARATION:
(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!

(4) The 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.

X-RAYING:
(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:

Walesch Electronics
Gestenrietstrasse 2
CH-8307 Effretikon
Switzerland
Phone: +41 52 326266 or +41 52 322644


AcuSaw Ltd.

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.

AcuSaw Ltd.
2302 West 33rd Ave.
Vancouver, B.C.
Canada V6M 1C3
Phone/Fax: 604-261-3931

 


DendroScan

The DendroScan Book is available from Amazon, too!Ian 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:

UBC Press
University of British Columbia
6344 Memorial Road
Vancouver, BC
Canada V6T 1Z2
Phone: 604-822-5959
Fax: 1-800-668-0821

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:

Ian Campbell
Canadian Forest Service
5320-122 St. Edmonton
Alberta, Canada
T6H 3S5
Phone: 403-435-7300
Fax: 403-435-7359

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