ARBORICULTURE

Arboriculture  is the cultivation, management, and study of individual trees, shrubs, vines, and other perennial woody plants. The science of arboriculture studies how these plants grow and respond to cultural practices and to their environment. The practice of arboriculture includes cultural techniques such as selection, planting, training, fertilization, pest and pathogen control, pruning, shaping, and removal.

A person who practices or studies arboriculture can be termed an arborist or an arboriculturist. A tree surgeon is more typically someone who is trained in the physical maintenance and manipulation of trees and therefore more a part of the arboriculture process rather than an arborist. Risk management, legal issues, and aesthetic considerations have come to play prominent roles in the practice of arboriculture. Businesses often need to hire arboriculturists to complete “tree hazard surveys” and generally manage the trees on-site to fulfill occupational safety and health obligations.

Arboriculture is primarily focused on individual woody plants and trees maintained for permanent landscape and amenity purposes, usually in gardens, parks or other populated settings, by arborists, for the enjoyment, protection, and benefit of people.

Arboricultural matters are also considered to be within the practice of urban forestry, yet the clear and separate divisions are not distinct or discreet

Tree benefits

Tree benefits are the economic, ecological, social and aesthetic use, function purpose, or services of a tree (or group of trees), in its situational context in the landscape.

Environmental benefits

• Erosion control and soil retention
• Improved water infiltration and percolation
• Protection from exposure: windbreak, shade, impact from hail/rainfall
• Air humidification
• Modulates environmental conditions in a given microclimate: shields wind, humidifies, provides shade
• Carbon sequestration and oxygen production

Ecological benefits

• Attracting pollinators
• Increased biodiversity
• Food for decomposers, consumers, and pollinators
• Soil health: organic matter accumulation from leaf litter and root exudates (symbiotic microbes)
• Ecological habitat

Socioeconomic benefits

• Increases employment: forestry, education, tourism
• Run-off and flood control (e.g. bioswales, plantings on slopes)
• Aesthetic beauty: parks, gatherings, social events, tourism, senses (fragrance, visual), focal point
• Adds character and prestige to the landscape, creating a “natural” feel
• Climate control (e.g shade): can reduce energy consumption of buildings
• Privacy and protection: from noise, wind
• Cultural benefits: eg. memorials for a loved one
• Medical benefits: eg. Taxus chemotherapy
• Materials: wood for building, paper pulp
• Fodder for livestock
• Property value: trees can increase by 10–20%
• Increases the amount of time customers will spend in a mall, strip mall, shopping district

Tree defects

A tree defect is any feature, condition, or deformity of a tree that indicates weak structure or instability that could contribute to tree failure.

Common types of tree defects

Codominant stems

This is when two or more stems that grow upward from a single point of origin and compete with one another.

• common with decurrent growth habits
• occurs in excurrent trees only after the leader is killed and multiple leaders compete for dominance

Included bark

Bark is incorporated in the joint between two limbs, creating a weak attachment

• occurs in branch unions with a high attachment angle (i.e. v-shaped unions)
• common in many columnar/fastigiate growing deciduous trees

Dead, diseased, or broken branches

• woundwood cannot grow over stubs or dead branches to seal off decay
• symptoms/signs of disease: e.g. oozing through the bark, sunken areas in the bark, and bark with abnormal patterns or colours, stunted new growth, discolouration of the foliage

Cracks

• longitudinal cracks result from interior decay, bark rips/tears, or torsion from wind load
• transverse cracks result from buckled wood, often caused by unnatural loading on branches, such as lion’s tailing.
• Seams: bark edges meet at a crack or wound
• Ribs: bulges, indicating interior cracks

Cavity and hollows

This is when sunken or open areas wherein a tree has suffered injury followed by decay. Further indications include: fungal fruiting structures, insect or animal nests.

Lean

A lean of more than 40% from vertical presents a risk of tree failure.

Taper

A taper is a change in diameter over the length of trunks branches and roots.

Epicormic branches

These are water sprouts in canopy or suckers from root system, and often grow in response to major damage or excessive pruning.

Roots

• girdling roots compress the trunk, leading to poor trunk taper, and restrict vascular flow
• kinked roots provide poor structural support; the kink is a site of potential root failure
• circling roots occurs when roots encounter obstructions/limitations such as a small tree well or being grown too long in a nursery pot; these cannot provide adequate structural support and are limited in accessing nutrients and water
• healthy soil texture and depth, drainage, water availability, makes for healthy roots