Lecture #8 - Wood Flashcards
What are the five major certification systems for wood?
Sustainable Forestry Initiative (SFI), Forest Stewardship Council (FSC), American Tree Farm System (ATFS), Canadian Standards Association (CSA), Programme for the Endorsement of Forest Certification (PEFC)
What does endogenous mean?
Growing or originating from within an organism. Grow with intertwined fibres
What does exogenous mean?
Growing or originating from outside an organism, grow from the center out by adding concentric layers of wood around the central core
What are conifers? What is another name for conifers? Name 4 conifer trees.
Soft wood, needlelike leaves that do not shed, grow continuously through the crown (homogenous), used for construction, economical and renewable because grow fast and in large stands. Fir, pine, larch, spruce
What are deciduous trees?
Hard wood, exogenous, shed their leaves at the end of each growing season, used for furniture, expensive, hard to cut.
What kind of forest do we have in Nova Scotia?
Acadian Forest
What is the most prevalent kind of forest in Canada?
Boreal
How is lumber produced?
Cut down, brought to sawmill, cut in half, cut to size, may or may not be cut again into planks, dried using air or kiln seasoning
Explain growth rings.
Wood produced in one growing season is a single growth ring. Composed of early wood produced by rapid spring growth and late wood from summer growthZ
What is bark?
The exterior covering of the tree. Has an inner and outer layer.
What are the properties of barks outer layer?
Dead, corky, great variability in thickness
What is barks inner layer?
Growth layer for bark, not part of wood section of tree
What is cambium?
Thin layer of cells situated between wood and bark and location of all wood growth
What is sapwood?
Storehouse for starches and pipeline to transport sap.
What kind of species have thick sapwood regions?
Fast growing
What is heartwood?
Darker coloured occurs at centre of cross section and surrounded by sapwood. Not a living part of tree, provides structural strength
What is pith?
Central core of tree, varies a lot between species
What does anisotropic mean? What are the 3 directions for wood?
Different and unique properties in each direction. Longitudinal, radial, tangential
What percentage of wood is cellulose?
50%
What percentage of wood is lignin (for hardwood and softwood)?
23-33% for hardwood, 16-25% for softwood
What percentage of wood is hemicellulose?
20-30%
What percentage of wood is extractive?
5-30%
What percentage of wood is ash-producing minerals?
0.1-30%
What is woods glue? What wood property does it limit?
Lignin, limits longitudinal shear strength of wood
What is moisture content?
Weight of water in wood/oven dry weight of wood in percentage form
What is bound water?
Water held within the cell wall by absorption forcws
What is free water?
Condensed water or water vapor in the cell cavities
What is the FSP saturation point?
Level of saturation at which cell walls completely saturated by no free water in cell cavities (21-32%)
Why is FSP important?
Above FSP, wood properties independent of moisture content. Below FSP, moisture content has large effect on all wood properties
What causes shrinkage?
Loss of moisture from cell walls
What causes swelling?
Gain of moisture in the cell walls
What causes structural performance problems in wood?
Anisotropy of dimensional changes
Order of magnitude of dimensional changes for all directions. (least to most)
longitudinal, radial, tangential
What does EMC stand for? What is this?
Equilibrium Moisture Content, moisture content for average atmospheric conditions
