Dating ring

Useful Tree Species for Tree-Ring Dating

This is a cross-section of a Douglas-fir ( Pseudotsuga menziesii ) from the Catalina Mountains north of Tucson, Arizona. The sample shows excellent ring-width variability from one ring to the next. The inner ring on this sample has been dated to 1928, and the outer ring dated to 1965.

Douglas-fir is one of the preferred species for dendrochronology in the western portions of North America. The species has exceptional circuit uniformity, meaning that the rings are usually concentric around the middle. The rings are also well defined - in other words, there is a sharp definition between the earlywood (wood formed early in the growing season) and latewood (wood formed later in the growing season). In addition, Douglas-fir is well distributed from Canada all the way down to northern Mexico, making this an ideal species for large-scale climate reconstructions.

The cross-section above is a white fir ( Abies concolor ) from California cut in 1981. Note the very narrow ring in 1977 reflecting a dry year.

The cross-section below is a Douglas-fir from the Jemez Mountains in northern New Mexico, showing darker bands of reaction wood(toward the top right corner). Reaction wood forms when a tree tilts. There are many elements that may cause a tree to tilt, like wind and snow. The sample also shows a branch growing from the center of the tree outward (dark spot toward the bottom right corner).

Comparing the two samples, which are about the same size around, we see that growth conditions were more favorable for the white fir than for the Douglas-fir, because of the wider rings. The Douglas-fir was growing in a closed canopy (a forest overshadowed by bigger trees), while the white fir was growing in a relatively open area exposed to more sun and water.

This image shows a closeup of ponderosa pine ( Pinus ponderosa ) tree rings. Growth is from the left to right. Earlywood is marked by lighter colored cells, while latewood is marked by the dark bands. Together, they make up one annual tree ring.

Note the subtle false rings in the fourth ring from the left and in the fifth ring from the right. These two examples are not so obvious, but sometimes in certain tree species growing in certain environments, false rings can look just like true rings. Without training in crossdating, false rings can be problematic when attempting to crossdate tree ring patterns. False rings can usually be identified during the crossdating process. Sometimes, they can actually aid in the crossdating process if the false rings occur in numerous trees sampled from a site.

This is a cross-section of post oak ( Quercus stellata ) showing its tree rings. Growth is from left to right.

Note the difference in growth patterns between the four younger rings to the left and the older rings to the right. During the year in which the fourth ring from the left formed, some disturbance occurred which greatly reduced the growth rate of this tree. Perhaps a wind storm damaged the crown of the tree, thus reducing its ability to photosynthesize and produce more wood.

Oak is a highly preferred species to use in dendrochronology - in fact, the longest continuous tree-ring chronology anywhere in the world was developed in Europe and is currently about 10,000 year in length. This chronology is providing scientists new insights on climate over the past 10,000 years, especially at the end of the last Glacial Maximum.

This is a microphotograph of two red oak ( Quercus rubra ) tree rings. Growth is from the left to the right. The large vessels in the earlywood indicate this is a ring-porous angiosperm tree species.

The large earlywood vessels are formed early in the spring during the initial flush of growth that occurs when the tree breaks dormancy after the winter. The vessels help transport water and nutrients up to the crown of the tree.

Because ring-porous species almost always begin annual growth with this initial flush, missing rings are rare in such species as oak and elm. In fact, the only recorded instance of a missing ring in oak trees occurred in the year 1816, also known as the Year Without a Summer. A volcanic eruption in the year 1815 caused much cooler temperatures globally, thus causing oak trees to remain dormant. Therefore, no clear annual ring was formed in 1816 for certain locations in Europe.

This is another closeup of post oak with a ray cutting across the tree rings, offsetting the rings between the ray. The earlywood is marked by large vessels used in conducting water. Latewood appears darker, marked by smaller vessels. Occasionally, offsets in oak tree rings can be problematic when trying to crossdate the rings. Dendrochronologists therefore must be careful when working with oak species, as these rays can cause a misdate of one year.

A closeup of tree rings from a sugar maple ( Acer saccharum ). Growth is from the left to the right. The small vessels throughout the entire tree ring indicates this is a diffuse-porous angiosperm species.

In general, diffuse-porous trees are difficult to crossdate because the rings are not so well defined as they are with conifer and ring-porous species. The maples and birches ( Betula spp.) are examples of diffuse-porous species that can be easily dated, however. The aspens and other poplars ( Populus spp.) are more difficult to work with. With careful sample collection and preparation techniques, tree-ring dating can be applied to practically all diffuse-porous species.

A ll graphics and text on these pages © 1996 by Lori Martinez, Laboratory of Tree-Ring Research, and The University of Arizona. Last updated October, 2001. All rights reserved.

Tree-Ring Dating

A tree was felled in 1982 giving rise to Stump A which dates back to 1906. The 1906 ring pattern in wood Sample A (which was cut from Stump A) correlates with a 1906 ring pattern in Sample B which was cut from an older, undated Stump B. Wood Sample B dates back to the year 1840. By matching up similar spaced rings in Samples B, C and D, the ages of ancient timbers can be determined. As long as the wood samples being compared have some ring patterns that coincide, time may be extended back through an unbroken succession of growth rings. In this example, wood Sample D dates back to the year 1691. This represents an unbroken succession of 291 annual rings, almost three centuries of time recorded in four small pieces of wood. Today, scientists have painstakingly established an unbroken succession of rings extending back in time over 80 centuries (8,000 years). Cross-dating is a valuable tool in dendrochronology and archaeology.

Lack Of Visible Annual Rings In Tropical Trees?

In the tropical rain forest, relatively few species of trees, such as teak, have visible annual rings. The difference between wet and dry seasons for most trees is too subtle to make noticeable differences in the cell size and density between wet and dry seasonal growth. According to Pascale Poussart, geochemist at Princeton University, tropical hardwoods have "invisible rings." She and her colleagues studied the apparently ringless tree ( Miliusa velutina ) of Thailand. Their team used X-ray beams at the Brookhaven National Synchrotron Light Source to look at calcium taken up by cells during the growing season. There is clearly a difference between the calcium content of wood during the wet and dry seasons that compares favorably with carbon isotope measurements. The calcium record can be determined in one afternoon at the synchrotron lab compared with four months in an isotope lab.

IAC Putting A Ring On Dating Site HowAboutWe

The Rise Of The “Social Professional” Networks

Looks like IAC is adding Brooklyn-based HowAboutWe as another notch in its dating site acquisition belt. It already owns Match. com. OkCupid and a majority stake in Tinder .

According to a letter obtained by Business Insider, founder Brian Schechter addressed employees about the acquisition, confirming that many HowAboutWe employees would be losing their jobs:

Indeed, we are still finalizing a deal and zero final decisions have been made. That a deal is even a possibility should remain completely confidential. I know this is a bumpy – and let’s face it – a weird moment but we should proceed in a manner that is really smart, graceful, and empowering for everyone.

A weird moment, indeed. HowAboutWe snatched up Nerve. com earlier this year to take on competition from IAC. However, some key employees had already started to leave earlier this month.

According to a staffer, Schechter and co-founder Aaron Schildkrout pulled aside a number of employees in closed door meetings on Thursday and Friday to let them know they could be let go. However, the founders also texted 3 employees that they were definitely keeping their jobs. That is until one of the three got a text asking them what their current salary was. Schechter allegedly recanted the offer to let that particular employee stay when the staffer reminded Schechter they’d recently received a raise.

Many were reportedly upset at the way the news has been handled thus far. Here’s the full email sent to Business Insider :

Subject: Quick touch base

Hi Everyone,

I got an email from someone in the media industry asking about “What’s happening with layoffs at HowAboutWe?” They specifically asked about the edit team.

If you get this question, it should be denied. It’s inaccurate. We have not laid anyone off.

Indeed, we are still finalizing a deal and zero final decisions have been made. That a deal is even a possibility should remain completely confidential, as well.

The company being in control of the message is the best thing for everyone to be well set up for next steps, and that means keeping things truly in confidence and not telling anyone about this exciting next step may at HowAboutWe, etc. [sic]

I know this is a bumpy — and let’s face it — a weird moment, but we should be sure that we proceed in a manner that is really smart, graceful and empowering for everyone

Thank you. Please don’t hesitate to reach to me with any questions or concerns. I’m available.

Dendrochronology

The growth rings of a tree at Bristol Zoo. England. Each ring represents one year; the outside rings, near the bark, are the youngest.

Dendrochronology (from ???????. dendron . "tree limb"; ??????. khronos . "time"; and -?????. - logia ) or tree-ring dating . is the scientific method of dating based on the analysis of patterns of tree rings . also known as growth rings . Dendrochronology can date the time at which tree rings were formed, in many types of wood, to the exact calendar year. This has three main areas of application: paleoecology. where it is used to determine certain aspects of past ecologies (most prominently climate); archaeology and the history of art and architecture, where it is used to date old panel paintings on wood, buildings, etc.; and radiocarbon dating. where it is used to calibrate radiocarbon ages (see below).

Contents

History [ edit ]

Growth rings [ edit ]

The inner portion of a growth ring is formed early in the growing season, when growth is comparatively rapid (hence the wood is less dense) and is known as "early wood" or "spring wood" or "late-spring wood". The outer portion is the "late wood" (and has sometimes been termed "summer wood", often being produced in the summer, though sometimes in the autumn) and is denser. [ 2 ] "Early wood" is used in preference to "spring wood", as the latter term may not correspond to that time of year in climates where early wood is formed in the early summer (e. g. Canada ) or in autumn, as in some Mediterranean species.

Many trees in temperate zones make one growth ring each year, with the newest adjacent to the bark. For the entire period of a tree's life, a year-by-year record or ring pattern is formed that reflects the climatic conditions in which the tree grew. Adequate moisture and a long growing season result in a wide ring. A drought year may result in a very narrow one. Alternating poor and favorable conditions, such as mid summer droughts, can result in several rings forming in a given year. Missing rings are rare in oak and elm trees—the only recorded instance of a missing ring in oak trees occurred in the year 1816, also known as the Year Without a Summer. [ 3 ] Trees from the same region will tend to develop the same patterns of ring widths for a given period. These patterns can be compared and matched ring for ring with trees growing in the same geographical zone and under similar climatic conditions. Following these tree-ring patterns from living trees back through time, chronologies can be built up, both for entire regions, and for sub-regions of the world. Thus wood from ancient structures can be matched to known chronologies (a technique called cross-dating ) and the age of the wood determined precisely. Cross-dating was originally done by visual inspection, until computers were harnessed to do the statistical matching.

To eliminate individual variations in tree-ring growth, dendrochronologists take the smoothed average of the tree-ring widths of multiple tree samples to build up a ring history. This process is termed replication. A tree-ring history whose beginning and end dates are not known is called a floating chronology . It can be anchored by cross-matching a section against another chronology (tree-ring history) whose dates are known. Fully anchored chronologies which extend back more than 11,000 years exist for river oak trees from South Germany (from the Main and Rhine rivers) and pine from Northern Ireland. [ 1 ] [ 4 ] [ 5 ] Furthermore, the mutual consistency of these two independent dendrochronological sequences has been confirmed by comparing their radiocarbon and dendrochronological ages. [ 6 ] Another fully anchored chronology which extends back 8500 years exists for the bristlecone pine in the Southwest US (White Mountains of California). [ 7 ] In 2004 a new calibration curve INTCAL04 was internationally ratified for calibrated dates back to 26,000 Before Present (BP) based on an agreed worldwide data set of trees and marine sediments. [ 8 ] The part of the new calibration curves that relies on tree-ring evidence (IntCal04) dates back to 12,410 calendar (cal) yr B. P. Beyond that and back to 14,700 cal yr B. P. IntCal04 is mainly constructed from 14C dates of foraminifera from Venezuela's Cariaco basin that are corrected for a constant reservoir age of 405 years. [ 9 ]

Sampling and dating [ edit ]

Timber core samples measure the width of annual growth rings. By taking samples from different sites and different strata within a particular region, researchers can build a comprehensive historical sequence that becomes a part of the scientific record; for example, ancient timbers found in buildings can be dated to give an indication of when the source tree was alive and growing, setting an upper limit on the age of the wood. Some genera of trees are more suitable than others for this type of analysis. Likewise, in areas where trees grew in marginal conditions such as aridity or semi-aridity, the techniques of dendrochronology are more consistent than in humid areas. These tools have been important in archaeological dating of timbers of the cliff dwellings of Native Americans in the arid Southwest.

A benefit of dendrochronology is that it makes available specimens of once-living material accurately dated to a specific year to be used as a calibration and check of radiocarbon dating. through the estimation of a date range formed through the interception of radiocarbon (B. P.. or ' B 'efore ' P 'resent, where present equals 1950-01-01) and calendar years. [ 10 ] The bristlecone pine. being exceptionally long-lived and slow growing, has been used for this purpose, with still-living and dead specimens providing tree-ring patterns going back thousands of years. In some regions dating sequences of more than 10,000 years are available. [ 11 ]

The dendrochronologist faces many obstacles, however, including some species of ant which inhabit trees and extend their galleries into the wood, thus destroying ring structure.

Similar seasonal patterns also occur in ice cores and in varves (layers of sediment deposition in a lake, river, or sea bed). The deposition pattern in the core will vary for a frozen-over lake versus an ice-free lake, and with the fineness of the sediment. Some columnar cactus also exhibit similar seasonal patterns in the isotopes of carbon and oxygen in their spines (acanthochronology ). These are used for dating in a manner similar to dendrochronology, and such techniques are used in combination with dendrochronology, to plug gaps and to extend the range of the seasonal data available to archaeologists and paleoclimatologists.

A similar technique is also used to analyse fish stocks through the analysis of similar growth rings in the otolith bones of fish.

While archaeologists can use the technique to date the piece of wood and when it was felled, it may be difficult to definitively determine the age of a building or structure that the wood is in. The wood could have been reused from an older structure, may have been felled and left for many years before use, or could have been used to replace a damaged piece of wood.

Reference sequences [ edit ]

European chronologies derived from wooden structures initially found it difficult to bridge the gap in the 14th century when there was a building hiatus which coincided with the Black Death. [ 12 ] however there do exist unbroken chronologies dating back to prehistoric times, for example the Danish chronology dating back to 352 BC. [ 13 ]

Given a sample of wood, the variation of the tree-ring growths provides not only a match by year, it can also match location because the climate across a continent is not consistent. This makes it possible to determine the source of ships as well as smaller artifacts made from wood but which were transported long distances, such as panels for paintings and ship timbers.

Applications [ edit ]

Climatology [ edit ]

In areas where the climate is reasonably predictable, trees develop annual rings of different properties depending on weather. rain. temperature. soil pH. plant nutrition. CO

2 concentration, etc. in different years. These variations are used in dendroclimatology to infer past climate variations.

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The Private Man

A Potential Online Dating Profile Photo Experiment

UPDATE – This photo is now the primary photo of my Plenty of Fish online dating profile (link in the blog post). Expect updates. This could get interesting.

I do not own that gun. This photo of me holding the assault rifle (FN-FAL) was the result of a visiting friend who brought over the fearsome firearm so as to show it to me. That was the first time I’ve ever held such a weapon and the big smile was the result of the sheer novelty.

Yes, I’ve fired guns in the past – on a gun range – but I am not an owner of such hardware. I would rather spend my money on other things. As well, I have little opinion about the politics surrounding firearms but I do understand the passion that both sides have regarding gun control legislation. My own enthusiasm will always be that of providing men and women with truthful advice about attraction and dating.

What some folks might notice – aside from the large assault rifle I’m clutching – is the ring on the fourth finger of my left hand, the traditional position for a wedding ring. The ring is the result of my trip to DragonCon last year where I helped a friend with her exhibitor booth as she sold jewelry and those ultra-cool stainless steel rings (photos at the end of this blog post). I helped with the ring sales by putting in words and numbers on the outside of the ring by using a hammer and punch. I felt like Thor but on a much smaller scale. I have lots of those rings now and I wear them on any particular finger when my mood suits me, I sometimes wear several rings at once (pea-cocking?).

That very spur-of-the-moment photo provides a very unique opportunity for an online dating profile experiment. I have a mostly inactive online dating account on Plenty of Fish (PoF). I’ve not done any recent online dating mostly because of events related to health and pavement. But the profile is still out there. Wow, I just made that profile public.

I have the option to make the gun photo my primary profile photo and see what the response will be. Should I do this, here are my predictions:

PoF receives complaints and my account is banned because, you know, assault rifle. Again, I’m not political about this issue but I’m curious how a photo with this type of weapon will be received.

PoF receives complaints and my account is banned because, you know, “wedding” ring.

Women respond favorably to the gun photo and their attraction for me goes way up yet they don’t notice the ring. Because, you know, assault rifle.

Women respond favorably to the gun photo and their attraction for me goes way up but they do notice the ring. Because, you know, “wedding” ring.

So, readers, what say you? Should I make the infamous gun and ring photo my primary online dating profile photo? Perhaps hilarity would ensue. Granted, I am a shockingly handsome fellow so the girlies will, of course, respond to that. I am just wondering how these “accessories” will impact my online dating experience.

This is me in my friend’s DragonCon exhibitor booth. I am definitely looking awesome in that fine kilt and sporran.

This is the ring set up where I pretended to be Thor. We sold a shitload of those things and I got to work out my aggressions. Danny would be proud.

[If you want to buy a ring, let me know. I can have any combination of words and letters punched on the outside of the ring. The number of characters is limited by the ring size and there is only one font. There are four different styles available. Contact me for more details. Seriously, these are cool rings and only $20 a pop plus shipping and handling.]

Online dating is the crucible of real attraction ‘twixt the sexes and it’s away from the prying eyes of political correctness. It is the behind the scenes action that reveals the true motivations of men and women alike. Read online dating profiles and be informed.

P. S. – Don’t forget to donate. Thanks!