Recognizing Important Tree Species and Their Products HOW MANY tree species are there? When asked, most people respond by saying they don t know or they never really thought about trees being different. Yet, there is a great diversity of tree species with different characteristics that lend themselves to different uses. Objective: Identify important forest tree species. Key Terms: angiosperms dehiscent fruits dichotomous venation dioecious gymnosperms hardiness indehiscent fruits inflorescence leaf venation monoecious palmate venation parallel venation pinnate venation taxonomy Important Tree Species There are many tree species. Forests in one part of the country have different tree species than forests in other parts of the country. Recognizing that trees are different and that each type of tree has unique characteristics is important in forestry. TREE TAXONOMY Taxonomy is the classification of plants according to natural relationships. Trees are members of the plant kingdom and are placed into divisions, classes, subclasses, orders, families, Page 1 www.mycaert.com
genera, and species. Carl von Linné (Linnaeus), a Swedish botanist, proposed this system of classifying plants. There are two divisions: Pinophyta and Magnoliophyta. Coniferous species make up the Pinophyta, and the trees in this division are called gymnosperms. Gymnosperms are plants that bear naked seeds without an ovary. Broad-leaved species make up the Magnoliophyta, and the trees in this division are called angiosperms. Angiosperms are plants having seeds borne within a pericarp. HARDINESS Hardiness is a plant s ability to withstand cold temperatures. Hardiness is one of many factors that affect plant survival in a specific area. Large bodies of water, well-drained soil, wind protection, and adequate moisture increase plant hardiness. 2 4 3 5 6 7 1 8 9 10 11 Zone 1 Below -50 F Zone 7 0 to10 F Zone 2-50 to -40 F Zone 8 10 to 20 F 11 Zone 3-40 to -30 F Zone 9 20 to 30 F Zone 4-30 to -20 F Zone 10 30 to 40 F Zone 5-20 to -10 F Zone 11 Above 40 F Zone 6-10 to 0 F FIGURE 1. A typical hardiness map. Page 2 www.mycaert.com
A hardiness map is useful in determining the average low temperatures in a given area. Both the Arnold Arboretum and the U.S. Department of Agriculture publish hardiness maps. Hardiness ratings are meant only as guides and should not be looked upon as limiting factors in plant use. TREE IDENTIFICATION To identify woody plants successfully requires a working knowledge of taxonomic terminology and concise mental pictures of leaf, bud, stem, flower, and fruit morphology. The leaf, twig, bark, and fruit are the most commonly used characteristics for tree identification. Each kind of tree, whether broad leaved or coniferous, has certain characteristics that make it distinctive from other species. Leaf Morphology Most trees can be identified by the type, size, shape, color, texture, and arrangement of leaves. Angiosperms have broad leaves, while gymnosperms have needlelike leaves. Broad Leaves A broad leaf consists of one or more leaf blades and a petiole, or leaf stem. A bud is located where FIGURE 2. This pine tree is classified as a gymnosperm. the leaf and the stem meet. Broad leaves may be simple or compound. A simple leaf has a single leaf blade. A compound leaf has multiple leaf blades, known as leaflets. A palmately compound leaf has each leaflet attached at a common point. A pinnately compound leaf can have either an odd or even number of leaflets along an extension of the petiole, called a rachis. The arrangement of leaves and buds can be used as a basis for identification. Leaves are typically arranged in an alternate, opposite, subopposite, or whorled fashion. The arrangement in which leaves are spaced in alternating fashion along the stem is known as alternate. An opposite leaf arrangement is characterized by leaves directly across from each other on the stem. Subopposite refers to a condition in which the leaves are not spaced sufficiently far apart to be considered alternate, nor are they perfectly opposite. Whorled refers to a condition in which three or more leaves are present at a node. The pattern of veins in a leaf is called leaf venation. If the leaf has a prominent central vein, or midrib, that extends from the base where the petiole attaches to the blade to the apex of the leaf, the pattern is known as pinnate venation. If several main veins of approximately equal size extend from the base of the leaf to the apex of the lobes or the margins of the leaf, the leaf has palmate venation.indichotomous venation, the basal veins extend for a Page 3 www.mycaert.com
Pinnate Venation Palmate Venation FIGURE 3. Vein patterns in various leaves. Parallel Venation distance and then branch to form a Y -type pattern. In parallel venation, the veins run essentially parallel to each other along the long axis of the leaf. A tremendous amount of terminology is related to leaf shapes, bases, margins, and apices. Needle-like Leaves Needle-like leaves can be of different shapes. Three common shapes are scale-like, awl shaped, and needle-like. Scale-like foliage overlaps like the shingles on a roof or the scales on a fish. This type of foliage is relatively soft to the touch. Needles shaped like awls are usually very sharp to the touch. Needle-like foliage can be born singly or in clusters along the stem. The needles may be relatively flat (two sided) or angular in cross section. Twig Morphology During autumn and winter, tree identification is based on bud, stem, and bark characteristics. Buds and stems are the principal means of identification. The shape, size, color, and texture of buds offer interesting identification characteristics. Leaf scars often provide distinguishing features. The shape of leaf scars and the vascular bundle arrangement are often used to identify plants. Lenticels, lip-shaped structures composed of corky cells, are produced through the action of the cork cambium. They are beneficial for identification because of their different colors and sizes. Bud scales, by their size, color, shape, or markings, offer good characteristics for identification. The terminal bud scale scar is the place where the previous year s bud scales were attached. As the buds open and expand in spring, the scales abscise and leave a distinct scar around the stem. This scar can be useful for gauging the linear growth in a particular season or over a number of seasons. Page 4 www.mycaert.com
Pith is a very valuable plant tissue for differentiating closely related plants. Pith is derived from a primary meristem. The color and texture of pith can often be used for separating similar plant types. Bark On deciduous trees, bark is the most important identification feature in the dormant winter period. Bark varies in thickness, roughness, type of fissures, and color. Each year the cambium lays down an annual ring of new cork cells (bark), forcing the old bark outward. Since the outer bark cannot stretch, it fissures or cracks into plates, ridges, and scales, forming the bark characteristic of each species. Flowers Flowers are important components of positive tree identification. The flowering periods of most woody plants average 7 to 14 days. There are numerous variations in flower shape, but the reproductive parts stamens and pistils are essentially similar. A flower that has all the parts (sepals, petals, stamens, and one or more pistils) is called complete. Incomplete flowers lack one or more whorls of floral parts. Imperfect flowers lack either stamens or pistils. Perfect flowers have both stamens and pistils. FIGURE 4. Each species of tree has its own pattern of bark. Petal Anther Filament Stamen Stigma Pistil Style Sepal Ovary Receptacle Pedicel FIGURE 5. Diagram of a perfect flower. Page 5 www.mycaert.com
Trees may be monecious or dioecious. Monoecious means that staminate and pistillate flowers are present on the same plant but in different structures. Dioecious means the staminate and pistillate flowers are borne on different plants. Some trees have solitary flowers, and others have flowers borne on structures called inflorescences. An inflorescence is a collection of individual flowers arranged in some specific fashion. Fruit Fruit offers positive identification features. The longitudinal section of the typical flower presents a representative view of the ovary. The ovary is the forerunner of the fruit and is defined as an unripened fruit. The ovary is composed of one or more carpels. A carpel is a highly modified leaf-like structure that encloses ovules (forerunners of seeds). A simple fruit consists of a single enlarged ovary composed of one carpel. Simple fruits can be divided into two major groups: dry and fleshy. Dry fruits can be divided into indehiscent and dehiscent. Indehiscent fruits are fruits that do not split open at maturity. There are several types, including achene, samara, and nut. An achene is a one-seeded fruit with the seed attached at only one place to the pericarp. The pericarp is very close fitting and does not split open, at least along regular established lines. A samara is usually one seeded, with a membranous wing that develops from the pericarp. A nut is a bony, hard, one-seeded fruit. The pericarp is bony throughout. Dehiscent fruits split open when mature. There are several types, including legume, follicle, and capsule. A legume (pod) is composed on one carpel and opens along two sutures. A follicle is composed of one carpel but splits open at maturity along one suture, exposing several seeds. A capsule is a many-seeded fruit formed from more than one carpel. The carpels are united. Several types of fleshy fruits are common with forest trees, including berry, drupe, and pome. When the entire pericarp is fleshy, the fruit is called a berry. With a drupe, the pericarp is clearly differentiated into three layers: the exocarp, the mesocarp, and the endocarp. With a pome, the pericarp is surrounded by the floral tube, which becomes fleshy and tasty. Two types of compound fruit are aggregate fruit and multiple fruit. An aggregate fruit consists of two or more carpels. It develops from a single flower that contains many pistils. Several fruitlets are massed on one receptacle. A multiple fruit consists of several flowers that are more or less united into one mass. MAJOR FOREST TREE SPECIES There are many forest tree species with economic importance. The term southern pine is applied in the lumber trade to shortleaf pine, loblolly pine, slash pine, and longleaf pine. The term yellow pine, derived from the yellowish color of the wood, is equally common for these species. Southern pine lumber has a variety of uses. These include heavy structural and light framing, interior finish, flooring, sheathing, crates, boxes, railcars, Page 6 www.mycaert.com
and many other industrial uses. Southern pine wood readily takes preservative treatment. When treated, it is used extensively for poles, piling, fence posts, crossties, foundation timbers, and other construction materials. Ash is slightly lighter in color than oak, straight grained, and similar in appearance to plainsawn oak, with the exception of having no visible medullary rays. Ash wood possesses highstrength properties. Ash wood is used to make baseball bats, polo and hockey sticks, playground equipment, skis, tennis rackets, handles for shovels and rakes, trim, doors, and other woodwork. Ash wood has extensive use in bent wood parts, as it responds to steam bending. American beech is known for its slow growth. The beech wood is hard, dense, and light in color. It has a diffuse-porous structure and numerous medullary rays. Flooring is the most important product made from beech. Products of the furniture and brush industries, truck body parts, toys, woodenware, and novelties are other uses for beech. Cottonwood is a rapid-growing tree. The wood of cottonwood is soft textured and lightweight. It has especially long fiber that makes it strong and tough in proportion to its weight. Principal uses of cottonwood include shipping containers, paper production, furniture, agricultural implements, and veneer. Baldcypress is a deciduous conifer, and its wood is soft. Baldcypress does not warp or check and may be depended on to stay in place. It holds paint well. Principal uses of baldcypress include interior and exterior trim, paneling, sash, doors, and fencing. Elms are divided into two groups, soft elm and hard elm. Elm is difficult to split. Soft elm is an excellent bending wood and is used extensively for boats and bent parts. Furniture and truck body parts are some other uses. Sweetgum is the most important southern hardwood. Many industries use the sapwood of sweetgum for all their needs. The sapwood of sweetgum is used in furniture, cabinets, containers, and general millwork. FIGURE 6. Among the uses for wood from cottonwood trees are shipping containers, furniture, and agricultural implements. Black tupelo grows slowly and has a uniform appearance, indistinct annual rings, and an interlocking grain. It is a tough wood that is difficult to split. Hackberry wood is creamy white, ring-porous, and uniform in texture. It has a high resistance to warping and shrinkage. The wood is used extensively in the furniture industry and in the making of veneer. No wood compares to hickory for strength, toughness, and elasticity. Hickory is used to make tool handles, skis, veneer, and rungs on ladders. Page 7 www.mycaert.com
The wood of pecan hickories has a pleasing grain pattern and is not as hard as the wood of true hickories. Pecan wood is used to make furniture, flooring, decking in railroad cars, trailer parts, and expensive cabinets. The wood of magnolia is soft, fine textured, and straight grained. The wood is excellent for interior trim, paneling, furniture, veneer, and doors. Soft maple is used for furniture, paneling, toys, shipping containers, and specialty kitchen cabinets. No hardwood is more widely known or used than oak. Two groups of oak are the white oak group and red oak group. Oak is a universal wood, used for many purposes. Oak wood is well adapted to any finishing treatment. Its strength is ideal for structural use. It is unequaled for flooring and makes the best railroad ties. White oak is used for barrels and casts for liquids. Other uses for oak include decking for railroad cars, furniture, millwork, and novelties. The wood of the sycamore is fairly hard, stiff, and strong. Sycamore is used in furniture and furniture parts, millwork, and novelties. Yellow poplar is known for its ability to resist warping and to take a smooth, lasting paint or enamel finish. Yellow poplar is used in furniture, as core stock in veneer, and for wood boxes, exterior trim, piano parts, fixtures, toys, and novelties. Black willow is one of the lightest and softest woods in North America, yet it is a strong wood. Black willow uses include paneling, furniture, caskets, shipping containers, interior trim, veneer, and toys. FIGURE 7. Oak trees produce the most common hardwood. Honeylocust wood is used in the manufacture of furniture, pallets, and skis. Sassafras wood is a very durable, hard-textured wood used in manufacturing furniture. It is also used in boat construction, oars, exterior trim, and general millwork. Eastern redcedar is most commonly used in the making of cedar chests and in the lining of closets. Atlantic white cedar is used for boat planks, tank stock, shingles, millwork, and lumber for crating. Red mulberry is used in the manufacture of caskets. At one time, red bay was in demand for use in shipbuilding. Black walnut is used in quality furniture, gunstocks, caskets, and specialty items. American holly is used for making piano keys, cabinets, veneer, and fancy inlays. Southern catalpa is used to make fence posts. Black cheery is used in quality furniture, interior trim, paneling, and cabinet making. Page 8 www.mycaert.com
Persimmon wood is hard and strong and is in demand for golf club heads and weaving loom shuttle blocks. Basswood does not significantly warp and is used for molding, Venetian blinds, core stock for veneer paneling, excelsior, food containers, pulpwood fruit containers, and tongue depressors. Douglas-fir is the most important commercial tree species in the United States. The wood is primarily used for dimensional lumber and plywood veneer. Red alder wood is lightweight and has low shrinkage. It is used for furniture, doors, sash, panel stock, and millwork. Aspen wood is straight grained and easily worked. It is used for lumber, pulpwood, veneer, excelsior, matches, pallets, boxes, crating, and particleboard. Paper birch is used for turned products, while yellow and sweet birch are primarily used for furniture, crates, barrels and casks, interior finish, baskets, and woodenware. Alaska cedar is used for furniture, small boats, and novelties. Balsam fir wood is lightweight and is mainly used for pulpwood. Western fir wood is lightweight but strong. It is primarily used for lumber and general millwork. Eastern hemlock is coarse, lightweight, and low in strength. It is primarily used for lumber and pulpwood and in the manufacture of boxes and crates. Western hemlock is a lightweight wood of moderate strength. The wood is principally used for pulpwood, lumber, plywood, and the manufacture of boxes, crates, flooring, and pallets. Incense cedar wood is lightweight, is moderately low in strength, and has a spicy odor. The wood is used principally for lumber and fence posts. Eastern white pine wood is lightweight and moderately soft. It is mainly used for lumber. Ponderosa pine wood is used mainly for lumber and to a lesser extent for poles, posts, veneer, ties, and piles. Sugar pine wood is easy to work and is used almost entirely for lumber products. Western white pine wood is lightweight and moderately low in strength. It is used for lumber and in building construction. Redwood, or sequoia wood, is easy to work and is resistant to decay. The wood is used for building, cooling towers, tanks, house siding, shingles, and hot tubs. Eastern spruce wood is moderately lightweight and easily worked. It is primarily used for pulpwood. Sitka spruce wood is a desirable wood for musical instruments because of its resonance qualities. The wood is also used for lumber, pulpwood, cooperage, furniture, millwork, and boats. FIGURE 8. Ponderosa pine trees. Page 9 www.mycaert.com
Summary: Coniferous tree species are called gymnosperms. Broad-leaved species are called angiosperms. Hardiness is a plant s ability to withstand cold temperatures. The leaf, bud, stem, flower, and fruit of a tree are useful in identifying the species. Most trees can be identified by the type, size, shape, color, texture, and arrangement of leaves. Angiosperms have broad leaves, while gymnosperms have needle-like leaves. During autumn and winter, tree identification is based on stem, bud and bark characteristics. Some trees have solitary flowers, and others have flowers borne on structures called inflorescences. Simple fruits can be divided into two major groups: dry and fleshy. Dry fruit types include achene, samara, nut, legume, follicle, and capsule. Types of fleshy fruits are berry, drupe, and pome. Two types of compound fruit are aggregate fruit and multiple fruit. There are numerous tree species with economic importance. Checking Your Knowledge: 1. How do gymnosperms and angiosperms differ? 2. What is hardiness? 3. What are the different types of leaf structures and shapes? 4. What features of a leaf, bud, stem, flower, and fruit are used in plant identification? 5. What are some economically important tree species? Expanding Your Knowledge: Identify tree species in your area using a key or knowledge of leaf, bud, stem, flower, and fruit morphology. Web Links: 680 Tree Fact Sheets http://hort.ufl.edu/trees/ United States Forest Service Tree List http://www.fs.fed.us/database/feis/plants/tree/ Arborday.org Tree Guide http://www.arborday.org/treeguide/ Page 10 www.mycaert.com