romikgosai/squad_modified huggingface dataset:
If a tree grows all its life in the open and the conditions of soil and site remain unchanged, it will make its most rapid growth in youth, and gradually decline. The annual rings of growth are for many years quite wide, but later they become narrower and narrower. Since each succeeding ring is laid down on the outside of the wood previously formed, it follows that unless a tree materially increases its production of wood from year to year, the rings must necessarily become thinner as the trunk gets wider. As a tree reaches maturity its crown becomes more open and the annual wood production is lessened, thereby reducing still more the width of the growth rings. In the case of forest-grown trees so much depends upon the competition of the trees in their struggle for light and nourishment that periods of rapid and slow growth may alternate. Some trees, such as southern oaks, maintain the same width of ring for hundreds of years. Upon the whole, however, as a tree gets larger in diameter the width of the growth rings decreases.

Questions and answers:
['
Q: In what stage of its life does a tree usually grow the fastest?
A: youth', '
Q: As a tree ages, do its growth rings usually get wider or narrower?
A: narrower', '
Q: What part of a tree opens and spreads out more as it matures?
A: crown', '
Q: Is wood production of a tree lessened or increased as it ages?
A: lessened', '
Q: Along with nutrients, what do trees growing in forests have to compete for?
A: light']
Different pieces of wood cut from a large tree may differ decidedly, particularly if the tree is big and mature. In some trees, the wood laid on late in the life of a tree is softer, lighter, weaker, and more even-textured than that produced earlier, but in other trees, the reverse applies. This may or may not correspond to heartwood and sapwood. In a large log the sapwood, because of the time in the life of the tree when it was grown, may be inferior in hardness, strength, and toughness to equally sound heartwood from the same log. In a smaller tree, the reverse may be true.

Questions and answers:
['
Q: When a big tree is cut up, will the pieces of wood differ or all be the same?
A: differ', '
Q: In a large log, will the heartwood or sapwood usually be stronger and tougher?
A: heartwood', '
Q: If you need really hard, strong wood from a small tree, would it likely be better to use the heartwood or sapwood?
A: sapwood', '
Q: Besides big trees, what trees are more likely to have a range of different kinds of wood?
A: mature']
In species which show a distinct difference between heartwood and sapwood the natural color of heartwood is usually darker than that of the sapwood, and very frequently the contrast is conspicuous (see section of yew log above). This is produced by deposits in the heartwood of chemical substances, so that a dramatic color difference does not mean a dramatic difference in the mechanical properties of heartwood and sapwood, although there may be a dramatic chemical difference.

Questions and answers:
['
Q: When trees have a visible difference in color between sapwood and heartwood, which is darker?
A: heartwood', '
Q: What is deposited naturally in heartwood that changes its color?
A: chemical substances', '
Q: Is the color difference between heartwood and sapwood usually very subtle or conspicuous?
A: conspicuous', '
Q: What type of properties of heartwood and sapwood is often the same even if their colors are very different?
A: mechanical', '
Q: Although heartwood and sapwood might be similar mechanically, if their colors are very different, what other type of difference would they have?
A: chemical']
Some experiments on very resinous Longleaf Pine specimens indicate an increase in strength, due to the resin which increases the strength when dry. Such resin-saturated heartwood is called "fat lighter". Structures built of fat lighter are almost impervious to rot and termites; however they are very flammable. Stumps of old longleaf pines are often dug, split into small pieces and sold as kindling for fires. Stumps thus dug may actually remain a century or more since being cut. Spruce impregnated with crude resin and dried is also greatly increased in strength thereby.

Questions and answers:
['
Q: What type of tree has resin that makes it stronger when it dries?
A: Longleaf Pine', "
Q: What's the funny name for resin-saturated heartwood?
A: fat lighter", '
Q: What is fat lighter practically impervious to in addition to termites?
A: rot', '
Q: If spruce is shot full of crude resin and dried, which of its properties is increased?
A: strength', "
Q: Since it's highly flammable, what do people often use little pieces of longleaf pine tree stumps for?
A: kindling"]
Since the latewood of a growth ring is usually darker in color than the earlywood, this fact may be used in judging the density, and therefore the hardness and strength of the material. This is particularly the case with coniferous woods. In ring-porous woods the vessels of the early wood not infrequently appear on a finished surface as darker than the denser latewood, though on cross sections of heartwood the reverse is commonly true. Except in the manner just stated the color of wood is no indication of strength.

Questions and answers:
['
Q: Which of the wood in a growth ring is usually darker?
A: latewood', "
Q: Which property of a tree's wood that gives clues about its strength and hardness can be judged by it's color?
A: density", '
Q: What category of trees show this difference greatly?
A: coniferous', '
Q: What type of woods might sometimes appear to have darker earlywood on a finished surface?
A: ring-porous', "
Q: With the exception of earlywood/latewood difference in some types of trees, how much of an indication of strength is a wood's color?
A: no indication"]
Abnormal discoloration of wood often denotes a diseased condition, indicating unsoundness. The black check in western hemlock is the result of insect attacks. The reddish-brown streaks so common in hickory and certain other woods are mostly the result of injury by birds. The discoloration is merely an indication of an injury, and in all probability does not of itself affect the properties of the wood. Certain rot-producing fungi impart to wood characteristic colors which thus become symptomatic of weakness; however an attractive effect known as spalting produced by this process is often considered a desirable characteristic. Ordinary sap-staining is due to fungal growth, but does not necessarily produce a weakening effect.

Questions and answers:
['
Q: What condition does an abnormal color usually indicate in wood?
A: diseased', '
Q: What other property can you assume of wood that is diseased?
A: unsoundness', '
Q: What causes the black checked pattern in the wood of western hemlocks?
A: insect attacks', '
Q: What animals cause the reddish-brown streaks of color in hickory wood?
A: birds', "
Q: What's the name for the pretty coloring effect caused in some wood by rot-producing fungi?
A: spalting"]
In heartwood it occurs only in the first and last forms. Wood that is thoroughly air-dried retains 8–16% of the water in the cell walls, and none, or practically none, in the other forms. Even oven-dried wood retains a small percentage of moisture, but for all except chemical purposes, may be considered absolutely dry.

Questions and answers:
['
Q: What does wood retain in its cell walls despite being air-dried?
A: water', '
Q: Air-dried wood keeps up to what percentage of the water in its cell walls?
A: 16', '
Q: What kind of dried wood retains a small quantity of water but is considered absolutely dry?
A: oven-dried']
The general effect of the water content upon the wood substance is to render it softer and more pliable. A similar effect of common observation is in the softening action of water on rawhide, paper, or cloth. Within certain limits, the greater the water content, the greater its softening effect.

Questions and answers:
['
Q: Often the water in wood makes it more pliable and what else?
A: softer', '
Q: What material sometimes used for dog chews reacts similarly to wood because of its water content?
A: rawhide', '
Q: What material we use to write or print on, like wood, becomes softer and more pliable when wet?
A: paper', '
Q: When water content increases within certain limits in wood, does is have a less or greater softening effect?
A: greater', '
Q: What type of action does water create in cloth?
A: softening']
Drying produces a decided increase in the strength of wood, particularly in small specimens. An extreme example is the case of a completely dry spruce block 5 cm in section, which will sustain a permanent load four times as great as a green (undried) block of the same size will.

Questions and answers:
['
Q: What will drying often increase in wood?
A: strength', '
Q: What color is also used interchangeably with "undried" for wood?
A: green', '
Q: What type of wood can hold four times as much of a load when dried?
A: spruce']
The greatest strength increase due to drying is in the ultimate crushing strength, and strength at elastic limit in endwise compression; these are followed by the modulus of rupture, and stress at elastic limit in cross-bending, while the modulus of elasticity is least affected.

Questions and answers:
['
Q: What type of "ultimate" strength is one of the two types increased the most by drying wood?
A: crushing', '
Q: What property of wood is least affected by drying?
A: elasticity', '
Q: Is strength at elastic limit in endwise compression or stress at elastic limit in cross-bending increased more by drying wood?
A: strength at elastic limit in endwise compression', '
Q: Is the strength of the modulus of rupture or elasticity increased more when wood is dried?
A: modulus of rupture']
Wood is a heterogeneous, hygroscopic, cellular and anisotropic material. It consists of cells, and the cell walls are composed of micro-fibrils of cellulose (40% – 50%) and hemicellulose (15% – 25%) impregnated with lignin (15% – 30%).

Questions and answers:
['
Q: Along with hygroscopic, cellular, and anisotropic, how is the material of wood described?
A: heterogeneous', '
Q: What does wood consist of?
A: cells', "
Q: What part of wood's cells are composed of cellulose and hemicellulose?
A: walls", '
Q: What makes up 40-50% of the cell walls in wood?
A: cellulose', '
Q: What substance is hemicellulose impregnated with?
A: lignin']
In coniferous or softwood species the wood cells are mostly of one kind, tracheids, and as a result the material is much more uniform in structure than that of most hardwoods. There are no vessels ("pores") in coniferous wood such as one sees so prominently in oak and ash, for example.

Questions and answers:
['
Q: What type of cells makes up most wood cells in coniferous trees?
A: tracheids', '
Q: Are hardwood or softwood species more uniform in structure?
A: softwood', '
Q: What are the visible vessels in hardwoods commonly called?
A: pores', '
Q: What hardwood that starts with the letter "O" would have pores?
A: oak', "
Q: Besides oak, what's an example of a hardwood with prominent pores?
A: ash"]
The structure of hardwoods is more complex. The water conducting capability is mostly taken care of by vessels: in some cases (oak, chestnut, ash) these are quite large and distinct, in others (buckeye, poplar, willow) too small to be seen without a hand lens. In discussing such woods it is customary to divide them into two large classes, ring-porous and diffuse-porous.

Questions and answers:
['
Q: Is the structure of hardwood simple or complex?
A: complex', '
Q: What handles most of the water conduction in hardwoods?
A: vessels', '
Q: Are the vessels in chestnut wood large or small?
A: large', '
Q: In wood from a willow tree, what would you need to use to see the tiny vessels?
A: a hand lens', "
Q: Besides ring-porous, what's the other class hardwoods are often divided into?
A: diffuse-porous"]
In ring-porous species, such as ash, black locust, catalpa, chestnut, elm, hickory, mulberry, and oak, the larger vessels or pores (as cross sections of vessels are called) are localised in the part of the growth ring formed in spring, thus forming a region of more or less open and porous tissue. The rest of the ring, produced in summer, is made up of smaller vessels and a much greater proportion of wood fibers. These fibers are the elements which give strength and toughness to wood, while the vessels are a source of weakness.[citation needed]

Questions and answers:
['
Q: What species of hardwood are hickory and mulberry trees?
A: ring-porous', '
Q: In what season do the growth-rings of ring-porous species form with larger vessels localized?
A: spring', '
Q: In what season does the part of the growth-ring with smaller vessels form in ring-porous species?
A: summer', "
Q: What fibers does the summer's section of growth-ring have more of?
A: wood fibers", '
Q: Along with strength, what property do wood fibers lend to wood?
A: toughness']
In diffuse-porous woods the pores are evenly sized so that the water conducting capability is scattered throughout the growth ring instead of being collected in a band or row. Examples of this kind of wood are alder, basswood,[citation needed] birch, buckeye, maple, willow,and the Populus species such as aspen, cottonwood and poplar. Some species, such as walnut and cherry, are on the border between the two classes, forming an intermediate group.[citation needed]

Questions and answers:
['
Q: What kind of woods have pores that are uniformly sized?
A: diffuse-porous', '
Q: What species do aspen, cottonwood, and poplar trees belong to?
A: Populus', "
Q: With walnut, what's another tree in the intermediate group?
A: cherry", '
Q: What capability is spread through the growth ring in ring-porous species?
A: water conducting', '
Q: Is maple wood diffuse-porous or ring-porous?
A: diffuse-porous']
In temperate softwoods there often is a marked difference between latewood and earlywood. The latewood will be denser than that formed early in the season. When examined under a microscope the cells of dense latewood are seen to be very thick-walled and with very small cell cavities, while those formed first in the season have thin walls and large cell cavities. The strength is in the walls, not the cavities. Hence the greater the proportion of latewood the greater the density and strength. In choosing a piece of pine where strength or stiffness is the important consideration, the principal thing to observe is the comparative amounts of earlywood and latewood. The width of ring is not nearly so important as the proportion and nature of the latewood in the ring.

Questions and answers:
['
Q: What kind of softwoods often have significant differences in their earlywood and latewood?
A: temperate', '
Q: Is latewood denser or less dense than earlywood?
A: denser', '
Q: Does strength come from the walls or cavities of wood cells?
A: walls', '
Q: Are the cell walls of earlywood thick or thin?
A: thin', '
Q: What general size are the cavities in the cells of very dense latewood?
A: very small']
If a heavy piece of pine is compared with a lightweight piece it will be seen at once that the heavier one contains a larger proportion of latewood than the other, and is therefore showing more clearly demarcated growth rings. In white pines there is not much contrast between the different parts of the ring, and as a result the wood is very uniform in texture and is easy to work. In hard pines, on the other hand, the latewood is very dense and is deep-colored, presenting a very decided contrast to the soft, straw-colored earlywood.

Questions and answers:
['
Q: Comparing a heavy and a lightweight piece of wood from a pine, which would have a greater proportion of latewood?
A: heavy', '
Q: What feature of a piece of pine with more latewood would be more clear and pronounced?
A: growth rings', '
Q: What type of tree has very little contrast between parts of its growth rings?
A: white pines', '
Q: Is white pine easy or difficult to work with because of its texture?
A: easy', '
Q: What kind of pines have very deep, darkly colored hardwood that stands out against the light earlywood?
A: hard pines']
It is not only the proportion of latewood, but also its quality, that counts. In specimens that show a very large proportion of latewood it may be noticeably more porous and weigh considerably less than the latewood in pieces that contain but little. One can judge comparative density, and therefore to some extent strength, by visual inspection.

Questions and answers:
["
Q: Having a high proportion of latewood isn't all that matters; what else is important?
A: quality", '
Q: What can we judge in wood just by looking at it?
A: comparative density', '
Q: What property of wood could we project some indication of by looking at its density?
A: strength', '
Q: What could we call some specimens with a high proportion of latewood that explains why they weigh less than specimens with much less latewood?
A: porous']
No satisfactory explanation can as yet be given for the exact mechanisms determining the formation of earlywood and latewood. Several factors may be involved. In conifers, at least, rate of growth alone does not determine the proportion of the two portions of the ring, for in some cases the wood of slow growth is very hard and heavy, while in others the opposite is true. The quality of the site where the tree grows undoubtedly affects the character of the wood formed, though it is not possible to formulate a rule governing it. In general, however, it may be said that where strength or ease of working is essential, woods of moderate to slow growth should be chosen.

Questions and answers:
['
Q: What facet of wood is affected to some degree by the place where the tree grows?
A: character', "
Q: If you want wood that's easy to work with, what kind of growth would you want the tree to have?
A: moderate to slow", "
Q: What species of tree can be said to growth ring proportions that aren't determined just by their rate of growth?
A: conifers", '
Q: What counterpart of earlywood are scientists still trying to explain the formation of?
A: latewood', "
Q: While there is some relationship between where and how a tree grows, what can't anyone formulate to govern it?
A: a rule"]
In ring-porous woods each season's growth is always well defined, because the large pores formed early in the season abut on the denser tissue of the year before.

Questions and answers:
['
Q: What kind of woods always have very clearly marked seasonal growth?
A: ring-porous', "
Q: What size pores form early in ring-porous woods' growing season?
A: large", '
Q: When does the denser tissue the new pores abut come from?
A: the year before']
In the case of the ring-porous hardwoods there seems to exist a pretty definite relation between the rate of growth of timber and its properties. This may be briefly summed up in the general statement that the more rapid the growth or the wider the rings of growth, the heavier, harder, stronger, and stiffer the wood. This, it must be remembered, applies only to ring-porous woods such as oak, ash, hickory, and others of the same group, and is, of course, subject to some exceptions and limitations.

Questions and answers:
['
Q: Ring-porous hardwoods have a clear relationship between their properties and what other factor?
A: rate of growth', '
Q: Is harder, heavier wood indicated by narrower or wider growth rings?
A: wider', '
Q: What kind of wood with a name that starts with "H" is a ring-porous hardwood?
A: hickory', '
Q: If the growth rings are wider, was the growth of the tree slower or more rapid?
A: more rapid', '
Q: What is the only kind of wood that will definitely be harder and stronger when it grows faster?
A: ring-porous']
In ring-porous woods of good growth it is usually the latewood in which the thick-walled, strength-giving fibers are most abundant. As the breadth of ring diminishes, this latewood is reduced so that very slow growth produces comparatively light, porous wood composed of thin-walled vessels and wood parenchyma. In good oak these large vessels of the earlywood occupy from 6 to 10 percent of the volume of the log, while in inferior material they may make up 25% or more. The latewood of good oak is dark colored and firm, and consists mostly of thick-walled fibers which form one-half or more of the wood. In inferior oak, this latewood is much reduced both in quantity and quality. Such variation is very largely the result of rate of growth.

Questions and answers:
['
Q: Which specific type of wood within ring-porous woods have more fibers to make it strong?
A: latewood', '
Q: When there is less latewood, what is diminishing?
A: breadth of ring', '
Q: Does slow or rapid growth make relatively porous, light wood?
A: slow', '
Q: What kind of oak has just 6-10% volume of large vessels in the log?
A: good', '
Q: What kind of fibers are in the latewood of good oak, making it very firm?
A: thick-walled']
Wide-ringed wood is often called "second-growth", because the growth of the young timber in open stands after the old trees have been removed is more rapid than in trees in a closed forest, and in the manufacture of articles where strength is an important consideration such "second-growth" hardwood material is preferred. This is particularly the case in the choice of hickory for handles and spokes. Here not only strength, but toughness and resilience are important. The results of a series of tests on hickory by the U.S. Forest Service show that:

Questions and answers:
['
Q: What term is sometimes used for wood with wide rings?
A: second-growth', '
Q: Do young trees grow more quickly in open stands or in a closed forest?
A: open stands', '
Q: What property is important to manufacturers who use "second-growth" hardwood?
A: strength', '
Q: What specific kind of "second-growth" hardwood is often used to make handles and spokes? 
A: hickory', '
Q: What organization tested hickory to find out about its properties?
A: U.S. Forest Service']
In the diffuse-porous woods, the demarcation between rings is not always so clear and in some cases is almost (if not entirely) invisible to the unaided eye. Conversely, when there is a clear demarcation there may not be a noticeable difference in structure within the growth ring.

Questions and answers:
["
Q: What kind of wood often has ring divisions that can't even be seen by looking at it?
A: diffuse-porous", '
Q: In diffuse-porous woods, if the demarcation between rings is obvious, what type of difference within the ring might not be?
A: structure', '
Q: What adjective describes how our eyes function without a tool like a microscope to help?
A: unaided']
In diffuse-porous woods, as has been stated, the vessels or pores are even-sized, so that the water conducting capability is scattered throughout the ring instead of collected in the earlywood. The effect of rate of growth is, therefore, not the same as in the ring-porous woods, approaching more nearly the conditions in the conifers. In general it may be stated that such woods of medium growth afford stronger material than when very rapidly or very slowly grown. In many uses of wood, total strength is not the main consideration. If ease of working is prized, wood should be chosen with regard to its uniformity of texture and straightness of grain, which will in most cases occur when there is little contrast between the latewood of one season's growth and the earlywood of the next.

Questions and answers:
['
Q: What kind of wood has all similarly sized vessels?
A: diffuse-porous', '
Q: What rate of growth in a tree will make the wood from it stronger than trees that grow very slowly or very quickly?
A: medium', '
Q: The capability of diffuse-porous woods to carry what substance is spread out in the growth ring?
A: water', '
Q: What division of trees are diffuse-porous woods more similar in growth rate to than ring-porous woods?
A: conifers', '
Q: Does uniformity of the texture and grain of wood usually result from much or little contrast between earlywood and latewood?
A: little']