Chapter 1: Tree Biology and Pruning Flashcards
trees
woody, compartmentalizing, long-lived perennial plants that grow to heights of a few to many feet (meters) on a single stem; the stem may divide low down, but it must do so above ground level; dominant vegetation over large areas of the world
arboriculture
the care of individual trees; an art and a science; combines skill and craft with knowledge and fact; propagation, planting, and management of trees so that people can coexist in sustainable environments
What is the foundation for the practice of arboriculture?
a thorough understanding of how trees grow and defend themselves and how people interact with them
tree biology
the study of structure and function and the relationship between them
sections of trees
- a crown with leaves and branches
- roots
- a trunk (sometimes called a bole or stem) that connects the crown and the roots
roots
the portion of a woody plant found below ground that provides stability, water, and nutrients to a woody plant; anchor the tree in the ground, absorb water and essential nutrients from the soil, transport those materials toward the trunk, and store starch reserves
xylem
water and nutrient-conducting tissue of the stem
leaves
the organs that make food for the tree via photosynthesis
photosynthesis
the process in green plants (and in some bacteria) by which light energy is used to form organic compounds from water and carbon dioxide; “putting together with light”
chloroplasts
cells where photosynthesis takes place; contain molecules of green, light-absorbing pigment chlorophyll
chlorophyll
traps light energy from sunlight and combines it with carbon dioxide from the air and water transported from the roots and produces carbohydrates in the form of sugars
What is a byproduct of photosynthesis?
oxygen; released into the atmosphere through stomata
photosynthate
general term for the products of photosynthesis; sugar product; carbohydrate
What is the energy source for plant respiration?
photosynthates or carbohydrates
sources
the leaves where photosynthates are produced
sinks
tree parts that use and/or store more photosynthate than they produce
phloem
plant vascular tissue that conducts photosynthates; situated to the inside of the bark; inner bark; outside of the xylem
wood rays
tissues that extend radially across the xylem and phloem of a tree; (outward to in = phloem to xylem)
energy reserves
form of starch or sugar; released and used as required by tree during normal biological functions; equivalent of animal fat
essential elements
nitrogen, potassium, sulfur, and iron
How do water, mineral elements, and micronutrients enter the tree?
osmosis via the absorbing roots
osmosis
diffusion of water throughout a semi-permeable membrane from a region of higher water potential to a region of lower water potential; passive process
pure water
highest potential
transpiration
the evaporation of water from plants; pulls water through the xylem to the leaves, where it is lost to the atmosphere through the stomata
axial transport
longitudinal movement of water in the xylem and photosynthates in the phloem
radial transport
horizontal movement in and out of wood and cells of different ages
ray cells
tissues that extend radially across the xylem and the phloem of a tree
rays
living channels of cells through which water, nutrients, and carbohydrates move laterally
reaction zone
a natural boundary formed by a tree to separate wood infected by disease organisms from healthy wood; important in the process of compartmentalization; limits the spread of decay following an injury or pruning event
Compartmentalization of Decay in Trees
CODIT; process whereby trees limit the spread of discoloration and decay; forms four barrier “walls” that limit the spread of decay in different planes within the tree; Wall 1 is formed when the tree responds to wounding by “plugging” the upper and lower vascular elements to limit vertical spread of decay; Wall 2 is formed by the last cells of the growth ring, limiting inward spread; Wall 3 is composed of ray cells that compartmentalize decay by limiting lateral spread; Wall 4 is the new growth ring that forms after the injury, the strongest wall
vertical wall
a layer of cells formed to resist upward and downward spread through the tree by plugging xylem vessels or tracheids; Wall 1 of CODIT; resists the spread up and down through the tree by plugging xylem vessels (in angiosperms) or tracheids (in gymnosperms)
horizontal wall
a layer of cells, formed by the last cells of the growth ring, that resists inward horizontal spread of decay; Wall 2 of CODIT; resists inward horizontal spread through the more compact summerwood cells and by depositing chemicals in active xylem cells
lateral/radial wall
a layer of cells composed of ray cells, that compartmentalizes decay by limiting lateral spread; Wall 3 of CODIT; inhibits lateral spread around the rings by activating ray cells to resist decay
barrier zone
a layer of wood formed immediately after injury, which resists the spread of microorganisms into new wood formed to the outside of the existing annual ring; Wall 4 of CODIT
strength of walls of CODIT
Wall 1 is the weakest barrier
Wall 4 is the strongest barrier; rarely fails; decay is kept out of new wood
Walls 1, 2, and 3 may fail sequentially if the tree cannot resist the spread of aggressive pathogens
pruning
cutting away unwanted parts of a plant; removing branches for defined reasons; the most common tree maintenance procedure; desirable and necessary for safety
common pruning goals
- improve tree structure or health
- accommodate human needs such as clearance pruning or hazard mitigation
- to increase light penetration
- to provide a view
- to correct or prevent a problem
line clearance
the process of removing vegetation around power lines; shape(s) may not always be aesthetically pleasing or appear natural
A300-2001
industry-developed standards of practice for tree care, approved by the American National Standards Institute; American National Standard for Tree Care Operations - Tree, Shrub and other Woody Plant Maintenance - Standard Practice (Pruning)
BS3998
British Standards Institute Recommendations for Tree Work; pruning guidelines in Britain