Popular Science Monthly/Volume 24/December 1883/Concentric Rings of Trees
By A. L. CHILD, M.D.
IN the December number (1882) of the "Monthly," you published an article prepared by me, on the "Annual Growth of Trees," which has been somewhat largely commented upon, in the periodicals and press of the day, as also by the "American Congress of Forestry" at St. Paul. I am glad to note this interest in the subject, as it will cause more accurate observation of the facts in the case. As many of my critics have apparently read only extracts from the article, and have accordingly drawn very incorrect inferences as to my views, I wish to restate some of the more important points, and the evidence sustaining them.
In June of 1871 I planted a quantity of seed as it ripened and fell from some red-maple trees. In 1873 I transplanted some of the trees from these seeds, placing them on my city lots in Plattsmouth, Nebraska. In August, 1882, finding them too much crowded, I cut some out, and, the concentric rings being very plain and distinct, I counted them. From the day of planting the seed to the day of cutting the trees was two months over eleven years.
On one, more distinctly marked (although there was but little difference between them), I counted on one side of the heart forty rings. Other sides were not so distinct; but in no part were there fewer than thirty-five. There was no guess-work about the age of this tree. A daily record of meteorological events for the Smithsonian Institution and Signal-Office for over twenty years, and a life-long habit of daily record of all important events, had led to much care and caution in such matters. Hence, from my own record, I knew the tree had but twelve years of growth; and yet, as counted by myself and many others, it had forty clear concentric rings.
Here permit me to quote a few lines from the original article, which, so far as I have seen, have been entirely ignored or overlooked by all commentators: "I could select twelve more distinct ones (rings) between which fainter and narrower, or sub-rings, appeared. Nine of these apparently annual rings on one section were peculiarly distinct; much more than the sub-rings. But, of the remaining, it was difficult to decide which were annual and which were not." When first cut, and while the wood was green and the cells filled with sap, these rings were very clear and plain; but, as the water evaporated and the wood contracted, they showed less plainly. I have a section of it now before me, and I can not make out clearly over twenty-four, where, when green, forty were clearly visible. This section was not at first so distinctly marked as a section forwarded to Professor Cleveland Abbe, of the Signal-Office, at his request; although that, when forwarded, showed the rings much less conspicuously than when fresh and green.
Mr. P. C. Smith, in the August (1883) "Monthly," supporting the commonly received reliability of the rings, as an index to the age of the tree, refers to certain disputed corners and lines marked by hacks on trees, and the agreement of the number of the subsequent rings with the record of the surveyor. This indicates an uncertainty in the matter which is hardly receivable as scientific proof. If the record was reliable, why question the hack? If only for confirmatory evidence, how identify the one hack among the many which on old lines invariably accumulate in the vicinity of disputed lines by many resurveys? Is it not a mere assumption that the rings do indicate a like number of years; and that, as the record agreed with these rings, therefore, that hack was the one? Mr. Smith says, "It will be very difficult to convince an old surveyor, or an old lawyer, who has tried many of these land cases, that each concentric ring on an oak-tree, at least, does not indicate a year's growth only of such tree." Well, I am an old surveyor, having followed the business more or less for upward of fifty years, and the evidence before me admits of but the one possible conclusion; and, had Mr. Smith or any other intelligent man the same evidence, I am sure there could be no disagreement between us on the subject.
The Hon. James J. Wilson, of Bethel, Vermont, an "old lawyer" and late Senator in the State Legislature, writes me, under date of August 15th, that at a trial in the District Court at Woodstock, Vermont, on a disputed line based upon a cut on a hemlock-tree, a section of the tree embracing the cut was produced in court, and the rings outside the cut counted up from forty to fifty, while those on the opposite side were only nine or ten! The verdict of the court was, that "the rings were not a sure indication of the age of the tree."
Hon. Robert W. Furness, late Governor of Nebraska, so well known as a practical forester, has kindly furnished me with several sections of trees of known age, from which I select the following: A pig-hickory eleven years old, with sixteen distinct rings; a green-ash eight years old, with eleven very plain rings; a Kentucky coffee-tree ten years old, with fourteen very distinct rings, and, in addition to these, twenty-one sub-rings; a burr-oak ten years old, with twenty-four equally distinct rings; a black-walnut five years old, with twelve rings. Governor Furness adds that he has a chestnut of four years, with seven rings; a peach of eight years, with six rings; and a chestnut-oak of twenty-four years, with eighteen rings. He attended the recent meeting of the American Association for the Advancement of Science, at Minneapolis, Minnesota, and presented this question and his specimens to the section on forestry. He reports that Professor Budd, of the Iowa Agricultural College, presented also a specimen spruce from Puget's Sound, of known age, or nearly fifteen years old. The section was twelve inches in length, and on one end had eighteen rings and on the other end had only twelve. Commissioner Loring expresses the opinion that "this settled the question, that rings at all times could not be relied upon as an index of the age of trees."
Hon. J. T. Allan, of Omaha, superintendent of tree-planting for the Union Pacific Railroad Company, in a recent letter says: "Any intelligent man, who has given any attention to this matter of yearly tree-growth, knows that the rings are no index of a tree's age. H. P. Child, superintendent of the Kansas City stock-yards, shows me a section of pine eight years old, with nineteen rings, and a soft maple of nearly fourteen years, with sixteen very distinct rings, in addition to which there are forty-seven less distinct sub-rings."
In conclusion, that the more distinct concentric rings of a tree approximate, or in some cases exactly agree, in number with the years of the tree, no one, I presume, will deny; but that in most and probably nearly all trees, intermediate rings or sub-rings, generally less conspicuous, yet often more distinct than the annual rings, exist, is equally certain: and I think the foregoing evidence is sufficient to induce those who prefer truth to error to examine the facts of the case.These sub-rings or additional rings are easily accounted for by sudden and more or less frequent changes of weather and requisite conditions of growth each check tending to solidify the newly-deposited cambium, or forming layer; and, as long intervals occur of extreme drought or cold, or other unfavorable cause, the condensation produces a more pronounced and distinct ring than the annual one. Query: Has a tree grown in a conservatory, or place of unchanged conditions of heat and moisture, any concentric rings?