A branch attachment is where a branch is attached to the trunk of a tree. Three types of branch attachment are recognized due to differences in the anatomical position of buds that form them. Two key components contribute to the mechanical strength and toughness of the attachment: interlocking wood grain at the top of the attachment and an embedded knot that often lies within the attachment. A common malformation of a branch attachment is the inclusion of bark within the join, which can weaken the attachment.
Initially branches are mechanically attached to the trunks of trees by forming interlocking wood grain patterns at the top of the joint, within what is known as 'axillary wood' (Fig. 1). [1] The axillary wood (or xylem) formed in this location is denser than in surrounding tissues of the tree's stem or branch, the wood grain pattern formed is tortuous and in these tissues there is typically a reduction in vessel length, diameter and frequency of occurrence (i.e. more of the xylem consists of fibre cells). [2] This specialized xylem tissue (axillary wood), formed under the branch bark ridge, provides unique mechanical properties to the union of the branch to the trunk, requiring that wood fibres are stretched along their length (the axial strength of the wood) in order to rupture the attachment apart. [1]
As the typical lateral branch of a tree and its trunk expand in diameter at different rates, the base of the smaller branch becomes occluded in the larger trunk of the tree which is producing a larger increment of growth, and this occluded part of the branch forms a knot that provides substantial additional mechanical support to the attachment as it develops (Fig. 2). This is not the case in tree forks, where the growth rate of both branches is approximately equal, and no occluded knot is formed.[ citation needed ]
The combination of the interlocking axillary wood patterns at the junction apex and the occluded knot embedded into the tree's trunk make mature branch attachments in trees very strong components of a tree's crown. From static testing, branch attachments have been found to be far stronger than attachments made at forks in trees. [3]
Botanists commonly differentiate between branches that originate from the initial extension growth and those that have developed epicormically from the growth of latent buds or adventitious buds that developed later on the tree's trunk surface. [4] A clear anatomical difference can be found on dissection between these branch attachments, in that the former has an initial knot that originates near to the stem's pith, those developing from latent buds will have a bud trace that originates near the stem's pith, and adventitious epicormic branches will exhibit neither of these internal features.[ citation needed ]
A common malformation of a branch attachment in a tree is the inclusion of bark within the join, commonly referred to as a 'bark inclusion' or 'included bark'. This malformation is known to weaken the connection of the branch to the rest of the tree's structure, as it acts to block the formation of the axillary wood at the branch attachment's apex. [5] [6] [7]
Bark included branch junctions are commonly found in a wide range of tree species, and are primarily caused by the effects of natural bracing within the crowns of the trees. In amenity trees, it is common practice for arborists to prune out young branches with such malformed attachments, subordinate the branch by reducing its length or brace the weakened branch to the rest of the tree, ideally using a flexible brace. [8]
In 1985, the researcher Dr. Alex Shigo published an anatomical model of branch attachment [9] based on analysis of extensive tree cross-sections and which came to be widely utilised in the arboricultural industry. However, the research this article is based on considers this model of branch attachment to be illogical and anatomically incorrect. [10]
The basis of Shigo's model was that the branch base grew first, then the branch's base was overlapped by the growth of the trunk, and the further development of overlapping layers of these two distinct xylem tissues resulted in the development of a strong connection (Fig. 3). The research by Slater has argued that this model does not take into account the anatomy of tree forks, nor when tree growth is continuous (such as in tropical trees) and it requires contortions of the vascular cambium that are infeasible. [10] However, others have argued Slater fundamentally misunderstood Shigo's model and the language he used to describe it. [11]
Prior to the development of Shigo's model of branch attachment, it was commonly thought that wood grain traversed directly from the top of the branch into the trunk of the tree, ascending to the tree's crown. Such a wood grain arrangement would result in sap travelling from the foliage at the end of the branch to other foliage in the tree's crown, which is contrary to the 'source-to-sink' model widely accepted for sap distribution in all woody plants, [12] and can clearly be seen not to be the case by dissections of junctions formed in trees.
Wood is a structural tissue found in the stems and roots of trees and other woody plants. It is an organic material – a natural composite of cellulose fibers that are strong in tension and embedded in a matrix of lignin that resists compression. Wood is sometimes defined as only the secondary xylem in the stems of trees, or it is defined more broadly to include the same type of tissue elsewhere such as in the roots of trees or shrubs. In a living tree it performs a support function, enabling woody plants to grow large or to stand up by themselves. It also conveys water and nutrients between the leaves, other growing tissues, and the roots. Wood may also refer to other plant materials with comparable properties, and to material engineered from wood, or woodchips or fiber.
In botany, a bud is an undeveloped or embryonic shoot and normally occurs in the axil of a leaf or at the tip of a stem. Once formed, a bud may remain for some time in a dormant condition, or it may form a shoot immediately. Buds may be specialized to develop flowers or short shoots or may have the potential for general shoot development. The term bud is also used in zoology, where it refers to an outgrowth from the body which can develop into a new individual.
Fruit tree pruning is the cutting and removing of selected parts of a fruit tree. It spans a number of horticultural techniques. Pruning often means cutting branches back, sometimes removing smaller limbs entirely. It may also mean removal of young shoots, buds, and leaves.
An arborist, tree surgeon, or arboriculturist, is a professional in the practice of arboriculture, which is the cultivation, management, and study of individual trees, shrubs, vines, and other perennial woody plants in dendrology and horticulture.
The hazel (Corylus) is a genus of deciduous trees and large shrubs native to the temperate Northern Hemisphere. The genus is usually placed in the birch family Betulaceae, though some botanists split the hazels into a separate family Corylaceae. The fruit of the hazel is the hazelnut.
Betula nigra, the black birch, river birch or water birch, is a species of birch native to the Eastern United States from New Hampshire west to southern Minnesota, and south to northern Florida and west to Texas. It is one of the few heat-tolerant birches in a family of mostly cold-weather trees which do not thrive in USDA Zone 6 and up. B. nigra commonly occurs in floodplains and swamps.
Pruning is a horticultural, arboricultural, and silvicultural practice involving the selective removal of certain parts of a plant, such as branches, buds, or roots.
Lepidodendron is an extinct genus of primitive vascular plants belonging to order Lepidodendrales, part of a group of Lycopodiopsida known as scale trees or arborescent lycophytes, related to quillworts and lycopsids. They were part of the coal forest flora. They sometimes reached heights of 50 metres, and the trunks were often over 1 m (3.3 ft) in diameter. They thrived during the Carboniferous Period. Sometimes erroneously called "giant club mosses", the genus was actually more closely related to modern quillworts than to modern club mosses. Within the form classification system used within paleobotany, Lepidodendron is both used for the whole plant as well as specifically the stems and leaves.
A burl or burr is a tree growth in which the grain has grown in a deformed manner. It is commonly found in the form of a rounded outgrowth on a tree trunk or branch that is filled with small knots from dormant buds. Burl formation is typically a result of some form of stress such as an injury or a viral or fungal infection.
Girdling, also called ring-barking, is the complete removal of the bark from around the entire circumference of either a branch or trunk of a woody plant. Girdling results in the death of the area above the girdle over time. A branch completely girdled will fail and when the main trunk of a tree is girdled, the entire tree will die, if it cannot regrow from above to bridge the wound. Human practices of girdling include forestry, horticulture, and vandalism. Foresters use the practice of girdling to thin forests. Animals such as rodents will girdle trees by feeding on outer bark, often during winter under snow. Girdling can also be caused by herbivorous mammals feeding on plant bark and by birds and insects, both of which can effectively girdle a tree by boring rows of adjacent holes.
Wood grain is the longitudinal arrangement of wood fibers or the pattern resulting from such an arrangement.
This glossary of woodworking lists a number of specialized terms and concepts used in woodworking, carpentry, and related disciplines.
Ulmus davidianavar.japonica 'Thomson' is a hardy, cold-resistant cultivar of the Japanese Elm assessed by the Prairie Farm Rehabilitation Administration (PFRA) Nursery at Indian Head, Saskatchewan, in the 1970s as part of its shelterbelt tree research..
A branch collar is the "shoulder" between the branch and trunk of woody plants; the inflammation formed at the base of the branch is caused by annually overlapping trunk tissue. The shape of the branch collar is due to two separate growth patterns, initially the branch grows basipetally, followed by seasonal trunk growth which envelops the branch.
A woody plant is a plant that produces wood as its structural tissue and thus has a hard stem. In cold climates, woody plants further survive winter or dry season above ground, as opposite to herbaceous plants that die back to the ground until spring.
A stem is one of two main structural axes of a vascular plant, the other being the root. It supports leaves, flowers and fruits, transports water and dissolved substances between the roots and the shoots in the xylem and phloem, stores nutrients, and produces new living tissue. The stem can also be called halm or haulm.
In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are usable as lumber or plants above a specified height. In wider definitions, the taller palms, tree ferns, bananas, and bamboos are also trees. Trees are not a taxonomic group but include a variety of plant species that have independently evolved a trunk and branches as a way to tower above other plants to compete for sunlight. The majority of tree species are angiosperms or hardwoods; of the rest, many are gymnosperms or softwoods. Trees tend to be long-lived, some reaching several thousand years old. Trees have been in existence for 370 million years. It is estimated that there are around three trillion mature trees in the world.
An epicormic shoot is a shoot growing from an epicormic bud, which lies underneath the bark of a trunk, stem, or branch of a plant.
Water sprouts or water shoots are shoots that arise from the trunk of a tree or from branches that are several years old, from latent buds. The latent buds might be visible on the bark of the tree, or submerged under the bark as epicormic buds. They are sometimes called suckers, although that term is more correctly applied to shoots that arise from below ground, from the roots, and a distance from the trunk. Vigorous upright water sprouts often develop in response to damage or pruning.
A tree fork is a bifurcation in the trunk of a tree giving rise to two roughly equal diameter branches. These forks are a common feature of tree crowns. The wood grain orientation at the top of a tree fork is such that the wood's grain pattern most often interlocks to provide sufficient mechanical support. A common "malformation" of a tree fork is where bark has formed within the join, often caused by natural bracing occurring higher up in the crown of the tree, and these bark-included junctions often have a heightened risk of failure, especially when bracing branches are pruned out or are shaded out from the tree's crown.