A new method to obtain good anatomical slides of heterogeneous plant parts

A new method is presented to prepare anatomical slides of plant materials including a combination of soft and hard tissues, such as stems with cambial variants, arboreal monocotyledons, and tree bark. The method integrates previous techniques aimed at softening the samples and making them thereby more homogeneous, with the use of anti-tearing polystyrene foam solution. In addition, we suggest two other alternatives to protect the sections from tearing: adhesive tape and/or Mayer’s albumin adhesive, both combined with the polystyrene foam solution. This solution is cheap and easy to make by dissolving any packaging polystyrene in butyl acetate. It is applied before each section is cut on a sliding microtome and ensures that all the tissues in the section will hold together. This novel microtechnical procedure will facilitate the study of heterogeneous plant portions, as shown in some illustrated examples

A.C.F. Barbosa, M.R. Pace, L. Witovisk & V. Angyalossy

IAWA J. 31 (4): 373-383

 

.

Wood Materials & Engineering Laboratory

 

The Wood Materials & Engineering Laboratory is now part of the Composite Materials & Engineering Center

The Wood Materials & Engineering Laboratory at Washington State University has a long and illustrious history in wood composite materials, design and construction.  Since its founding in 1949, the scope of the research, outreach and education programs of the laboratory has expanded beyond wood materials to include other natural fibers, polymers, inorganic cements, masonry and steel. In addition to materials engineering, we are extensively involved in developing standards, building codes and design methodologies for these wide-ranging composite material systems. To address this broader mission, the WMEL is now part of the Composite Materials & Engineering Center (CMEC).  This new organizational structure more accurately reflects the complete scope of our programs

 

موضوع مطالب:نوشته های مختلف - مقالات و مطالب به زبان انگلیسی

Alternative methods for nondestructively determining modulus of elasticity in young trees

Several nondestructive technologies are briefly described that can examine wood modulus of elasticity (MOE) variation in young trees. In genetic trials nondestructive sampling is often a priority; hence sampling is limited to the use of standing tree acoustic tools or increment cores whose wood properties are subsequently analyzed. If a detailed knowledge of radial variation is required, then SilviScan presents the most suitable option. If the number of trees examined is in the low thousands, then near infrared (NIR) spectroscopy or ultrasonics may be more cost effective than SilviScan. However, information regarding MOE radial variation will be of lower resolution than SilviScan and the estimation of wood properties by NIR spectroscopy relies on suitable calibrations that need to be created and maintained at some expense. If thousands of trees need to be assessed and knowledge of radial variation is not required then time-of-flight ToF acoustic instruments are the most suitable

R. Schimleck, C.R. Mora, G.F. Peter & R. Evans

IAWA J. 31 (2): 161-167

موضوع مطالب:  مقالات و مطالب به زبان انگلیسی

 

Alternative methods for nondestructively determining modulus of elasticity in young trees

Several nondestructive technologies are briefly described that can examine wood modulus of elasticity (MOE) variation in young trees. In genetic trials nondestructive sampling is often a priority; hence sampling is limited to the use of standing tree acoustic tools or increment cores whose wood properties are subsequently analyzed. If a detailed knowledge of radial variation is required, then SilviScan presents the most suitable option. If the number of trees examined is in the low thousands, then near infrared (NIR) spectroscopy or ultrasonics may be more cost effective than SilviScan. However, information regarding MOE radial variation will be of lower resolution than SilviScan and the estimation of wood properties by NIR spectroscopy relies on suitable calibrations that need to be created and maintained at some expense. If thousands of trees need to be assessed and knowledge of radial variation is not required then time-of-flight (ToF) acoustic instruments are the most suitable

L.R. Schimleck, C.R. Mora, G.F. Peter & R. Evans

IAWA J. 31 (2): 161-167

 

Effect of lignin genetic modification on wood anatomy of aspen trees

Abstracts – IAWA Journal

The directed modification of specific traits of trees through genetic engineering provides opportunities for making significant genetic improvements to wood properties in matter of years instead of extended time frames required for traditional natural selection. An attractive target of forest-tree engineering is the modification of lignin content and lignin structure. While lower lignin content improves pulping efficiency, a decrease in lignin content could affect wood characteristics that are critical for solid wood use. After one year of growth in a greenhouse, a total of forty transgenic aspen (Populus tremuloides Michx.) with reduced lignin content and increased syringyl to guaiacyl ratio were harvested and diameter growth and cell morphology were investigated using quantitative wood anatomy and fiber quality analysis techniques. Comparing genetic groups to the wild-type as the control, similar radial growth and quantitative anatomical properties were observed for the genetic group with reduced lignin content. The genetic group with increased S/G ratio had lower diameter growth, lower vessel lumen diameter, but more numerous vessels. The simultaneous change in lignin content and lignin structure had no effect on radial growth but had the most severe effect on cell morphology. The two genetic lines within this genetic group gave inconsistent results.

B. Horvath, I. Peszlen, P. Peralta, B. Kasal & L. Li

 

IAWA J. 31 (1): 29-38

 

Biomass energy from wood chips : Diesel fuel dependence

Most renewable energy sources depend to some extent on use of other, non-renewable sources. In this study we explore use of diesel fuel in producing and transporting woody biomass in the state of New Hampshire, USA. We use two methods to estimate the diesel fuel used in woody biomass production: 1) a calculation based on case studies of diesel consumption in different parts of the wood chip supply chain, and 2) to support extrapo- lating those results to a regional system, an econometric study of the variation of wood- chip prices with respect to diesel fuel prices. The econometric study relies on an assumption of fixed demand, then assesses variables impacting supply, with a focus on how the price of diesel fuel affects price of biomass supplied. The two methods yield similar results. The econometric study, representing overall regional practices, suggests that a $1.00 per liter increase in diesel fuel price is associated with a $5.59 per Mg increase in the price of wood chips. On an energy basis, the diesel fuel used directly in wood chip production and transportation appears to account for less than 2% of the potential energy in the wood chips. Thus, the dependence of woody biomass energy production on diesel fuel does not appear to be extreme

Dave Timmons*, Ce´sar ViteriMejı´a DepartmentofResourceEconomics,UniversityofMassachusetts,80CampusCenterWay,Amherst,MA01003-9246,USA

 

Available at www.sciencedirect.com

 

 

.

درباره علم گاه شناسی درخت برگرفته از دانشگاه ماساچوست

 

 

Dendrochronology is the study and comparison of tree ring growths, which can provide very accurate dates about the wood itself or artifacts found in close proximity to it. Clark Wissler of the American Museum of Natural History first recognized the potential for using tree rings as a dating method. He worked with A. E. Douglass now considered the father of dendrochronology at the University of Arizona, on Pueblo Bonito, a pre-historic Native American settlement in New Mexico.

Dendroarchaeology is the use of tree rings to date when timber has been transported, processed, felled or used in construction. Rings are made of xylem. Pith is found at the center of the tree stem followed by the xylem, which makes up the majority of the trees circumference. The cambium layer keeps the xylem separated from the rough bark. Each spring or summer a new layer of xylem is formed, producing the rings we can count. A tree ring is a layer of wood cells produced by a tree in one year, consisting of thin walled cells formed in the early growing season (called earlywood), and thicker walled cells that are produced later in the growing season (called latewood). The beginning of earlywood and the end of latewood forms on annual ring. In dendrochronology, these rings are then counted and compared. A departure of growth for any one year, as compared to average growth is known as a tree-ring chronology.

 

متن کامل 

 موضوع مطالب: آناتومی و حفاظت چوب - مقالات و مطالب به زبان انگلیسی

ادامه نوشته

MICROFIBRIL ANGLE: MEASUREMENT, VARIATION AND RELATIONSHIPS

A REVIEW

Microfibril angle (MFA) is perhaps the easiest ultrastructural variable

to measure for wood cell walls, and certainly the only such variable that

has been measured on a large scale. Because cellulose is crystalline, the

MFA of the S2 layer can be measured by X-ray diffraction. Automated

X-ray scanning devices such as SilviScan have produced large datasets

for a range of timber species using increment core samples. In conifers,

microfibril angles are large in the juvenile wood and small in the mature

wood. MFA is larger at the base of the tree for a given ring number from

the pith, and decreases with height, increasing slightly at the top tree. In

hardwoods, similar patterns occur, but with much less variation and much

smaller microfibril angles in juvenile wood. MFA has significant heritability,

but is also influenced by environmental factors as shown by its

increased values in compression wood, decreased values in tension wood

and, often, increased values following nutrient or water supplementation.

Adjacent individual tracheids can show moderate differences in MFA

that may be related to tracheid length, but not to lumen diameter or cell

wall thickness. While there has been strong interest in the MFA of the

S2 layer, which dominates the axial stiffness properties of tracheids and

fibres, there has been little attention given to the microfibril angles of S1

and S3 layers, which may influence collapse resistance and other lateral

properties. Such investigations have been limited by the much greater

difficulty of measuring angles for these wall layers. MFA, in combination

with basic density, shows a strong relationship to longitudinal modulus

of elasticity, and to longitudinal shrinkage, which are the main reasons

for interest in this cell wall property in conifers. In hardwoods, MFA is

of more interest in relation to growth stress and shrinkage behaviour

 

Key words: Microfibril angle, cellulose microfibrils, X-ray diffraction,

microscopy, wood properties.

Lloyd Donaldson

Cellwall Biotechnology Centre, Scion, Private Bag 3020, Rotorua, New Zealand

[E-mail: [e-mail]]

IAWA Journal, Vol. 29 (4), 2008: 345–386

.

Comparison of morphological and chemical properties between juvenile wood and compression wood of lo

Abstract

In conifers, juvenile wood (JW) is always associated with compression wood (CW). Due to their similar properties, there i s a common belief that JW is the same as CW. To resolve whether JW is identical to CW, 2 4 rooted cuttings of one loblolly pine clone were planted in growth cham- bers under normal, artificial bending, and windy environ- ments. The results show that the morphology of JW is significantly different from CW. Furthermore, chemical analyses revealed that JW and CW are significantly dif- ferent in chemical composition. Our results indicate that JW is different from CW, and the wood formed under a controlled windy environment is a mild type of compres- sion wood

.Keywords: C9 formula; compression wood; fiber quality analysis (FQA); juvenile wood; light microscopy; loblolly pine (Pinus taeda); nitrobenzene oxidation; ozonation; sugar analysis

Holzforschung, Vol. 59, pp. 669–674, 2005 •

.

Why Paper Money Doesn't Disintegrate In A Washing Machine?

Ordinary notebook paper is made from the intermeshed cellulose fibers of wood pulp. The cellulose fibers absorb water and come apart (dissolve) when they are soaked in water. Paper money is made from textile (rag) fibers, such as cotton and linen. Intermeshed "rag" fibers bond together more firmly and don't separate (dissolve) in water

The upper right corner (red arrow) of this U.S one dollar bill is torn off. The magnified view (right) of the torn edge shows a fringe of intermeshed textile (rag) fibers. These fibers are much more durable than the cellulose fibers from wood pulp

Plant Fibers

© W.P. Armstrong 5 March 2010

.

The Living Room Everyone Wants

 

 

 If you make the circuit of your friends regularly you know there are some living rooms that are more attractive than others. This is not a case of just decorative styles and schemes, but some are more inviting and welcoming than others. Some are living rooms you just like the ‘feel’ of and others feel cold and make you just want to go home

So, how do you make sure your home has a living room with the right feel instead of one that gives your guests cold feet

There are a number of things to take into consideration as you try to sort out this question. First, let’s look at some of the features that you can bring into play in your living room

Lounge Suite

If you want a cohesive look in your living room, you should really consider a lounge suite. This is when you purchase all the pieces of your living room together, in a matching set. There is something about everything matching that just makes them more welcoming and inviting

Comfort

While purchasing a lounge suite is a start, the next thing you need to do is make sure it is comfortable. You don’t want to have board-hard furniture that people are uncomfortable using. This is a sure-fire way to make them want to go home so they can be comfortable once again

Coziness

If you are going with a modern or contemporary decor style in your home, you may think you need to space furniture out, with fewer pieces in the room. Avoid this urge. Even if you have a massive living room space, and only one modern furniture suite, you should group the pieces together so they are an area for conversation. People are not comfortable feeling they have to yell across the room to be a part of a conversation. By grouping your furnishings closer together you will create an atmosphere of coziness and camaraderie

Bar

Nothing says relaxation like having a bar in the living room. In today’s world of great rooms the bar has often moved from a lounge area, right into the living room. This will be a space where great conversations are started, and likely finished, over a few drinks

Wall art

There is more than furniture that needs to be in place in order to create a great living room. If your guests are only looking at white walls it will feel like they are in an institution. That is not a very comfortable feeling. Utilizing wall art to dress up the room will give it a little more personality and energize the atmosphere

Fireplace

Whether you are in the cold north or in the tropical south there is something about a fireplace that says coziness. In the north, you may well want to put this in use on those cold winter days, but even in warmer climes, a fireplace is a great source of emotional warmth in a room

As you contemplate the decor in your living room, this list is a great starting point to work from. Also, take note of what makes you feel ‘at home’ in other homes. Add all this information together and use this knowledge to create a living room everyone will want to visit
Tom Matherson writes for Worldwide Tapestries which offers a wide collection of French, Italian and Belgium wall tapestries to enhance any home. See the latest range of wall decor including a wide selection of large wall tapestries to decorate any room or home setting

سینا حشمتی 

موضوع مطالب:  طراحی داخلی - مقالات و مطالب به زبان انگلیسی

AIR POLLUTION EFFECTS ON ANNUAL RING WIDTHS OF FOREST

Abstract. Annual ring widths of forest trees are affected from different ecological factors (e.g.

climate, soil, etc.) and also from air pollution. In the areas with intensive air pollution annual ring

width reductions are observed. For this reason, some methods which detect the annual ring widths,

in other words, the increase or decrease in diameter increments, are used to examine air pollution.

Industrial establishments found in the northern part of Izmir city (Aliaga region) affect air quality of

this area negatively. In this investigation, annual ring widths of 13 Pinus brutia Ten. (Calabrian pine)

and 20 Pinus nigra Arnold. (Austrian pine) from 4 mountains (Karabelen, Manisa, Kemalpasa, and

Yamanlar) with different altitudes and exposures around Izmir city were detected and the effects of

air pollution on these trees were determined. Intensive effects of air pollution have started in 1985,

for that reason, annual ring widths were examined through a reference period before this year and a

study period (1985–1998) after this year and results are statistically evaluated. Annual ring widths

of tree samples in the northern exposure were affected from air pollution, and some reductions were

observed. These reductions increased when there is a long drought period.

 

موضوع مطالب:مقالات و مطالب به زبان انگلیسی

Researchers in Austria turn wood into natural gas

استخراج گاز از چوب 

While Austria tapped into its natural gas stocks amid the recent stoppage of Russian gas supplies, engineers in the Austrian town of Guessing were busy producing an alternative: natural gas from wood. With the help of Swiss and Austrian scientists, the European Centre for Renewable Energy Guessing produced so-called synthetic natural gas for the first time outside a laboratory in December

One big advantage of this process is that this method can extract synthetic natural gas from renewable natural resources, said Christian Keglovits, the spokesperson of the centre that is located in a rural area in eastern Austria, some 10 kilometres from the Hungarian border

The process of turning trees into gas is done in two stages. First, wood chips are made into gas at a temperature of 900 degrees. In a second step, this gas is converted into methane that can be used to heat homes or fuel cars

Currently, the pilot facility in Guessing can turn 360 kilograms of wood into 120 cubic metres of gas within an hour - the energy equivalent of 120 litres of heating oil or 1,200 kilowatt hours. As the town does not have a gas heating system, the product is used for cars that run on natural gas

The Austrian 1-megawatt plant is too small to turn a profit, said Alfred Waser at the Paul Scherrer Institute in Villigen, Switzerland, which developed the technology together with scientists at the Vienna University of Technology

There is already interest from Sweden and Germany for larger facilities up to a capacity of 100 megawatts. "We assume that we enter an economically interesting range starting from 10 megawatts," Waser said

But the gas plants should not be too big, either. Scientists and engineers involved in the project want to avoid building plants that would be so big that they would cause more traffic from trucks bringing in wood from further away

In Guessing, the energy centre takes care to use only old or sick trees from the surrounding forests for its gas production, and not wood that is grown for other purposes

Synthetic gas is unlikely to become a full alternative to supplies from Russia and elsewhere, experts in Austria and Switzerland said. In Switzerland, around 10 per cent the country's primary energy could be produced with man-made gas if all available biomass such as animal waste, surplus wood or grass cuttings were used, Waser said

But Keglovits said the technology would help to make his small community of 3,800 less dependent of foreign suppliers. "It will make us independent from Russian natural gas to some extent, because we can draw on our local resources," he said

The gas crisis might also help the European Centre for Renewable Energy Guessing win additional research grants, Keglovits said. The funds might also help one of the centre's other (projects: turning wood into liquid fuel for cars. dpa)

 

موضوع مطالب:خبرها - مقالات و مطالب به زبان انگلیسی

Wood-destroying Organisms

 

Click on the links below or scroll down for pictures and descriptions of typical wood-destroying organisms

Subterrean Termites
Dampwood Termites
Drywood Termites
Anobiid Beetles
Wood Decay Fungus
Carpenter Ants

Subterranean Termites

This species is restricted to the West, ranging from British Columbia to Mexico.

These insects are swarmers. They are about 3/8" long including wings. Bodies are dark brown to almost black. Fontanelle (frontal gland pore) is present and they have front wings with two dark, hardened veins in the front portion. The wings are brownish gray with a few barely visible hairs. Their front wing scale is distinctly larger than the hind wing scale. Legs have a slightly darkened tibia and a pale tarsus.

 

Dampwood Termites

As their name implies, dampwood termites locate their colonies in damp, sometimes decaying wood. Representatives of three termite families (Kalotermitidae, Rhinotermitidae, Termopsidae) are included in this distinct habitat group. These termites vary in appearance from family to family. Almost all are larger than the eastern/western, desert subterranean termites with the nymphs being up to 3/4" (20 mm) long and the swarmers up to 1" (25 mm) long, including wings. They occur in the Pacific Coastal and adjacent states, the desert or semi-arid Southwest, and Southern Florida.

 

Drywood Termites

These insects live in wood which has a relatively low moisture content (12% or less), in the Western United States, Northwestern Mexico, and Florida. They are swarmers 7/16" to 1/2 " long including wings. Their heads and pronotums are orange brown, abdomens are dark brown, and wing membranes and hardened veins are blackened. They have Antenna with 10-11 segments. They are not hairy, their tibia exhibit no spines along their length and they have no pad between their claws.

 

Carpenter Ants

Several species of carpenter ants, Camponotus spp., are capable of damaging wood in buildings and other structures. Carpenter ants cause problems mainly in mountainous areas and in forested rural areas along the central and northern coastlines of California; they may also invade buildings in urban locations.

 

Anobiid Beetles

Anobiids Beetles are the most commonly encountered of the powderpost beetles. They are also called Deathwatch beetles because of a tapping sound they make when mating. Heard in the quiet of the night by people sitting with an ill person, this tapping was believed to indicate that death was near.

Adults are from 1/32 to 3/8" long. Their shape is variable but usually elongated and cylindrical. Their color is reddish brown to black, sometimes with lighter areas of pale hairs. Prothorax hoodlike enclosing head. Antennae are not symmetrical, last three segments lengthened and expanded. Larvae are white and C-shaped. Signs of infestation are round holes in wood with piles of powdery waste below.

 

Wood Decay Fungus

Wood Decay fungus (poria incrassata)
For a great discussion of this problem, we recommend the following web site.

More information on poria incrassata

منبع:  northwesttermite

موضوع مطالب:  آناتومی و حفاظت چوب - مقالات و مطالب به زبان انگلیسی

Ancient Ecosystem Discovered Beneath Antarctic Glacier

 

Scientists have found life in an ecosystem trapped underneath a glacier in Antarctica for nearly 2 million years. The microbes, they suggest, are surviving the dark, oxygen-free waters by drawing energy from sulfur and iron. The findings provide insight into how life may have survived "Snowball Earth"--periods when some scientists speculate that the planet was entombed in ice--and hint at the possibility of life in other inhospitable environments, such as Mars and Jupiter's icy moon Europa

Researchers have found microbial life surviving in the most unusual places: the depths of cold and dark oceans, seething geothermal vents, and the deepest layers of permafrost. And ever since scientists discovered Antarctica's dark and mysterious subglacial lakes in the late 1960s and early 1970s, they've wondered if microbes could make a life for themselves there too. But the challenges of drilling through kilometers of ice and concerns about contaminating these pristine lakes have curtailed previous efforts to find out.

Blood Falls, a small, saltwater outflow from Taylor Glacier's subglacial lake in Antarctica's Dry Valleys, offers an alternative. The lake sits beneath 400 meters of ice and trickles out at the glacier's end, painting an orange stain across the ice as its iron-rich waters rust upon contact with air. The subglacial lake was originally part of a marine fjord system that became trapped as Taylor Glacier enclosed it between 1.5 million and 2 million years ago. Its sporadic outflow allows researchers to explore the lake without drilling or risking contamination of the isolated environment.

Geomicrobiologist Jill Mikucki, now at Dartmouth College, collected water samples from Blood Falls over 6 years. A battery of tests revealed that its waters contained almost no oxygen and hosted a community of at least 17 different types of microorganisms. But how could they have survived for so long, with no light or oxygen? Mikucki and her team uncovered three main clues. First, a genetic analysis of the microbes showed that they were closely related to other microorganisms that use sulfate instead of oxygen for respiration. Second, isotopic analysis of sulfate's oxygen molecules revealed that the microbes were modifying sulfate in some form but not using it directly for respiration. Third, the water was enriched with soluble ferrous iron, which would happen only if the organisms had converted ferric iron, which is insoluble, to the soluble ferrous form. The best explanation, the team reports in tomorrow's issue of Science, is that the organisms use sulfate as a catalyst to "breathe" with ferric iron and metabolize the limited amounts of organic matter trapped with them years ago. Lab experiments have suggested this might be possible, but it has never been observed in a natural environment.

"I think this is a fantastic study," says Alan Kaufman, a biogeochemist at the University of Maryland, College Park. It presents "a spectacular new environment that we can explore to understand life on the edge," he says. "A place like this ... would be probably as close of an analog as we can find on this planet for subpermafrost life habitats on Mars," says glaciologist Slawek Tulaczyk of the University of California, Santa Cruz. Ultraviolet radiation and other  hazards would most likely lock life away beneath the surface of the Red Planet, he notes.

 

 

By Jackie Grom
ScienceNOW Daily News
16 April 2009

موضوع مطالب:  مقالات و مطالب به زبان انگلیسی- خبرها

 

True Green

True Green

Wood is the original green building material. Consider the following

Green for life - In a cradle-to-grave analysis of identically constructed wood, steel and concrete homes, the wood home was more environmentally beneficial in terms of energy consumed, air/water pollution, waste production and global warming potential.*
Demand keeps it growing - Forest growth in the U.S. has continually exceeded harvest since the 1940s. We now grow 27 percent more timber each year than is harvested.
More product, less energy - Compare the energy requirements for manufacturing one ton of wood to one ton of other building materials; it takes 5 times more energy to produce cement and 24 times more energy to produce steel.
Nature's air purifier - A 2,400 sq. ft. house locks up 28.5 tons of CO₂ - roughly 7 years of emissions from a small car.

Arm yourself with the facts. Download Wood: Sustainable Building Solutions or visit our Environmental Facts & Green Building page

 

 

Articles

Articles

Winter Rain and Summer Ozone: A Predictive Relationship

J. S. SANDBERG ¹, M. J. BASSO ¹, and B. A. OKIN ¹

¹ Bay Area Air Pollution Control District, San Francisco, California 94109

Insights from dendrochronology have provided a new seasonal predictor for air pollution meteorology. In the San Francisco Bay Area summer ozone excesses over the federal ozone standard are correlated (correlation coefficient r = .87) with precipitation for the two preceding winters, a factor related to tree-ring width in a precipitation-stressed climate. The hypothesis that reactive hydrocarbon emissions from vegetative biomass affects these ozone excesses was supported by a similar correlation between summer hydrocarbon average maximums and the two-winter precipitation factor, reaching r = .88 at suburban stations. A weak tendency for hot summers to follow wet winters (in 16 years of California data) explains only a minor part of the ozone-rain relationship in multiple correlations.

Dendrochronology

 

 

What is Dendrochronology

Dendrochronology is the dating and study of annual growth rings in trees

The word comes from these roots:

dendros =  trees; more specifically, the growth rings of trees

chronos =  time; more specifically, events and processes in the past

ology =  the study of

In other words“study of tree rings to understand past events and processes”

 

What Do Tree Rings Tell Us 

The practical uses of the study of tree rings are numerous. Dendrochronology is an interdisciplinary science, and its theory and techniques can be applied to many uses. These research interests have in

 

Dendrochronology History

Archaeological tree-ring dating began in 1917 when Andrew Ellicott Douglass, the founder of dendrochronology, first examined prehistoric wood samples. Twelve years later, the “bridging of the gap" at Show Low, Arizona joined dated living-tree and "floating" archaeological chronologies and began routine archaeological tree-ring dating

In 1937, the University of Arizona founded the Laboratory of Tree-Ring Research (LTRR) to continue Douglass' dendrochronological research. After World War II, the Laboratory collected all other Southwestern archaeological tree-ring collections - Museum of Northern Arizona, Gila Pueblo, Laboratory of Anthropology, Navajo land Claim and I. F. Flora - and the Robert E. Bell Collection of samples from the eastern United States. At the same time, LTRR's own Douglass Collection continued to grow through regular additions. As a result, the Laboratory has become the repository for all Southwestern archaeological tree-ring material and many samples from elsewhere

LTRR houses more than 360,000 archaeological samples from the Southwest, the Great Basin, the Great Plains, the Midwest, Alaska, Mexico, and the Near East. These research collections provide the ultimate certification of the dates and constitute an unmatched reservoir of materials for further archaeological and dendrochronological research

The gathering of archaeological tree-ring collections at LTRR provided the opportunity for an large-scale study of all Southwestern tree-ring material. Between 1963 and 1975, the "Dendrochronology of Southwestern United States" project organized and reanalyzed the existing collections, an exercise that quadrupled the numbers of dated samples and sites. As a result of these and subsequent analyses, the continuous regional ring chronology has been extended back to 322 B.C., and more than 60,000 dates have been produced from more than .5,000 sites

common the following goals