Silviculture FNR 338/439 Exam 1

Not comprehensive

cover type

dominant tree species in overstory

silvicultural system

a planned process by which a stand is established, tended, harvested, and re-established

a silvicultural system is named based on

age structure maintained within the stand and the regen method

stand development

competitive process of tree initiation, growth, senescence, and death

stand dynamics

the study of changes in forest stand structure with time, including stand behavior during and after disturbance

four reasons strata form

height growth patterns, shade tolerance, lifespan, age

3 reasons crown classes form

genetics, microsites, physical damage

What happens to tree crowns during stand initiation?

Expand until branches begin to interlock (crown closure)

What does this point signify?

Stem exclusion starts

Why are stems excluded?

Trees develop enough foliage to intercept all the available light

What happens to tree crowns in stem exclusion?

Lower branches become so shaded that they cannot continue to photosynthesize, and they begin to die

Maximum leaf biomass occurs when

lower branches start to die

Does the stand stay at maximum leaf biomass forever?

no

Foliage Shells

Crowns expand upward by adding a new “shell” of foliage each growing season

Branch elongation is strongly related to

height growth (at least in conifers)

Important principle

Crowns can expand outward and become larger only by gaining new foliage faster than the lowest branches die off

How can we control crown expansion?

Cut/kill competitors that would shade out lower branches or manipulate crown directly

Why do we want to control crown expansion?

Wood production and wood quality are both directly related to crown size

What does LCR stand for?

Live Crown Ratio

Define LCR

Crown length as a percentage of the total tree height

Nutritional Theory

downward transfer of photosynthate from a leaf nourishes all cambial cells equally

Pipe-model Theory

each leaf has its own “pipe” of xylem extending to the roots for water conductance

Mechanical Theory

trees act like cantilevered beams of uniform resistance to bending in the wind

Both the nutritional and pipe-model theories lead to

a “constant area” (Pressler’s Law) pattern below the crown base

Which theory doesn’t explain pressler’s law?

mechanical

Which theory does explain differences in stem taper low on the bole?

mechanical theory

Juvenile

Wood formed near pith by young, juvenile

meristems. Found in all trees

Crown

Wood formed in close proximity to the live

crown. Found in all trees

Reaction

Wood formed to counteract leaning

stresses on the tree stem on some trees

Hardwood reaction wood

tension wood forms on side away from lean

Softwood reaction wood

compression wood forms on side of lean

Pros of branches

Branches hold the foliage, more foliage means more wood production and a healthier tree

Cons of branches

Branches can increase taper, branches produce knots, a defect in most timber

Live (red, tight) knots

Formed where branch was still

living within the live crown

Dead (black, loose) knots

Formed in tree after branch died

but was not yet shed, below the base of the live crown usually

Branch tradeoff for wood quality

smaller crown-better quality

Branch tradeoff for branch size

smaller crown-smaller branch size

Branch tradeoff for stem form

Smaller crown-smaller stem taper

Branch tradeoff for tree growth

Smaller crown-smaller growth

Two types of pruning

Pathological and normal (green or dry)

Pathological pruning is used to

combat prevalent lethal rust pathogens in early development, remove infected tissues before they spread and girdle main stem

Pathological pruning is done in how many stages to what LCR?

2-3, 40-50%

Pathological pruning is

expensive

3 reasons to prune

poor natural branch shedding, fast growth, premium material

What affects branch retention?

Species characteristics, and size of branch

Branch collar

Xylem and callus forms protection during branch shedding

Epicormic branches

Develop from dormant buds in the cambium after tree is exposed or stressed

4 ways to prevent epicormics

Favor vigorous dominants and avoid releasing low

vigor trees, Avoid trees that are branchy or have epicormic

structures, Leave some nearby trees in the lower stratum to

shade the boles of the crop trees, Prune only “low-risk” species

When does sunscald occur?

when bole is heated enough to kill cambium underneath

4 ways to prevent hardwood stain

prevent logging damage to lower bole, encourage rapid early branch shedding, do not allow branches in butt log to become large then die, grow trees to larger diameters

knotty core

crown (juvenile) wood zone plus the time required for branches to be shed and occlude

thinning

A cultural treatment made to reduce stand density primarily to improve growth, enhance forest health, and/or to recover potential mortality

four kinds of primary thinning

low, crown, dominant, geometric/mechanical/row

other kinds of thinning

free form, variable density

low thinning is also known as

thinning from below

low thinning removes

lower crown classes

in low thinning, most of gross growth becomes

net growth

low thinning tries to

maintain full stand stocking

species that gets low thinned

scots pine

crown thinning

favors high quality dominants and codominants by removing competing trees from the upper crown classes only

primary focus of crown thinning

releasing high quality crop trees

if I were to draw crown thinning, which crown classes would I release, cut, and ignore?

release D and C crop trees, cut D and C competitors, and ignore O and most I

crown thinning divides the stand

into two distinct vertical strata

what crown classes accidentally get released during crown thinning?

O and I

what methods are there for crown thinning?

crown touching method

three comparisons of crown vs low thinning

crown thinning increases structural diversity but low thinning reduces it, crown thinning focuses on making crop trees grow faster and low thinning focuses on higher stand yields, crown thinning cuts larger trees than low thinning

dominant thinning favors which crown classes?

high quality codominants and intermediates

dominant thinning removes

poorly formed or low value dominants

dominant thinning has limited applications. give a few examples.

old field stands with low density origins, white pine subjected to weevil attacks, stratified stands with dominant low value species

how many times should you do dominant thinning?

ONLY ONCE

what is the application of geometric thinning?

facilitating the thinning operation before differentiation, early spacing operations, precommercial thinnings, strip thinning in aspen

what does row and low thinning do

provides access for later thins, low thinning salvages mortality

what is variable density thinning for?

creating areas of low to very high density for wildlife and biodiversity values

what are trainers

trees in lower strata that shade the boles of crop trees to reduce epicormic branching