Forestry Exam 2

Normal forest

a forest with fully stocked stands and balanced age structure

Site index

Average height of dominant and codominant trees in the stand at reference age

Silvicultural System AOR

Everything that is done between cutting cycles or throughout a rotation

Silvicultural Systems Plans

Regeneration

Tending

Harvest

Silvicultural System Naming

Based on methods that harvest the stand

A harvest method determines…

The method of regeneration which depends on the light requirement

Stand structural characteristics

Landowner objectives constraints

Forest biology
Environmental & social concerns

Economic considerations

Guidelines for Silvicultural Systems

Landowner objectives

Shade tolerance

Most important factor when choosing silvicultural system
Identify tolerance while as seedlings

Conditions should be conducive to the regeneration of the target species

Modifications of Stand Structure

Species composition
Silvical characteristics
Size structure
Age structure
Density/spacing
Health and vigor
Potential damaging agents

Longleaf Pine Restoration Objectives and Components

Open, park-like stands
Prescribed fire
Minimize disturbance to native ground cover
Secure adequate regeneration
Retain stand character
Timber production outputs relaxed
Time is important as a factor

Longleaf Pine Silvicultural System

Stoddard-Neal Approach

Stoddard-Neal Approach

Single tree selection through selective logging and prescribed burning to manage understory, centered on keystone wildlife species. Harvesting is based on aesthetics and sustained yield.

Shelterwood method

includes a preparatory cut, a seed cut, and a removal cut

Group selection drawbacks

more complicated to implement than clearcut or shelterwood. Lower yields due to increased competition between remaining trees (dense).

Even-Aged Silvicultural Systems

Clearcut

Seed tree

Shelterwood

Coppice System

Patch cut

Retention cut

Clearcut types

Alternate strip
Progressive strip

Block clearcut

Seedtree Types

Uniform

Grouped

Shelterwood Types

Uniform (strip or grouped)

Irregular (natural or nurse-tree)

Uneven-Aged Silvicultural Systems

Selective Logging (single, group, strip)

Clearcut

All trees are removed and can be modified in the way that is best to prevent erosion

Seedtree

Selected trees or tree groups are left standing to provide a seed source for national regeneration

Windfirm trees

live oak, bald cypress, beech, shumard oak, ponderosa pine, shortleaf pine

Not windfirm trees

Sweetgum, maple, loblolly pine, slash pine, ash, southern red oak, water oak

Seed tree selection

Dominants and codominant

Consistent seed producers

Good phenotypes

Windfirm

Seed trees numbers

Determines by desired number of seedlings, number of viable seeds produced per tree, chance survival of the seedling, dispersal distance, pollination considerations, cost incurred if left unharvested, receptiveness to germination

Seedtree advantages

More uniform distribution of seeds

No limitation of cut area

Logging costs are low

Early root system development

Low soil disturbance

Better aesthetics and wildlife habitat value

Maintain live roots and rhizosymbionts

Seedtree disadvantages

No control of spacing and timing

Local seed source and mixture of species

Restricted seed-bed preparation

Limited to windfirm species

Regrowth damaged by second entry

Rodents, seedbed and growing conditions hard to control

Monetary loss of seed trees

Longer rotation

Pre-commercial thinning

Silvicultural Systems with Reserves

trees retained for a defined period or indefinitely to meet objectives other than regeneration

Shelterwood Variants

Uniform, strip, grouped, irregular, natural, nurse-tree

Shelterwood Definition

mature trees removed in a series of cuts to achieve a new even-aged stand under the shelter of remaining trees

Shelterwood Objectives

Provide overstory shelter to ameliorate microclimatic

extremes or other potentially adverse conditions for

regeneration. Seed-bed moisture, frost damage Provide seeds and an environment (shelter) for natural regeneration.

Provide site occupancy and volume increments by

retaining mature trees during the regeneration phase.

Soil protection

Strip Shelterwood

Series of progressive, linear cuts in narrow successive strips

Done to minimize wind damage, control shading and accommodate terrain conditions

Group Shelterwood

Small openings are created in the stand such that

the adjacent trees shelter the new regeneration.

Group Shelterwood Process

The size or density of leave-tree groups will

decrease through one or more future stand

harvests, until the mature overstory has been

completely removed.

Regeneration methods for the final area to be

harvested may include natural or artificial

regeneration or a combination of both.

Which is easier? Uniform or strip shelterwood?

Strip shelterwood

Irregular Shelterwood

Residuals trees are left beyond the regeneration phase and initiate new age classes of regeneration, accumulate wood volume increment and achieve non-timber stand objectives

Shelterwood Advantages

Allows for best control over site conditions
Flexible for shade tolerance
Best for heavy-seeded species
Offers good soil protection
Continuous cover & root forestry
Suppress pioneer species

Wildlife benefit
Aesthetic value

Shelterwood Disadvantages

Increased logging costs
High technical skill
Requires fairly wind-firm species
Unavoidable damage to stand and reproduction
Retained overwood can limit options for establishment
Follow-up required

Shelterwood Applications

Regular choice of USDA FS on federal lands

Comparison of Reproduction Methods

With seed tree and clearcut we see more light reaching the ground than with single-tree and shelterwood but seed supply goes down. Shelterwood is a happy medium.

Uneven-aged Systems

Also known as Selection cutting
develops or maintains a mixture of three or more distinct, well-represented age classes

General characteristics of selection systems

Harvesting timber at specified intervals called cutting cycles
Harvesting single trees or small groups
Three well-represented age classes
Intermediate cuttings in immature age classes

Single Tree Selection System

New age classes created by removal of individual trees mostly uniformly

High-grading

Picking the best tree to harvest in single tree selection system
“Take the best and leave the rest”

BDq

Q-factor or Arbogast method which achieves desired diameter distribution
B: residual basal area

D: Maximum diameter

q: quotient that expresses ration between number of trees in diameter classes in stand

BDq formula

q = n_i/(n_i+1)

BDq Advantages

Simplicity
Can calculate factors and be tracked in real time

BDq Disadvantages

Real world is messier than calculations

Nutrients

elements that are required by a plant to successfully complete its life cycle

90% of Trees’ Mass

Carbon, Oxygen, Hydrogen

Macronutrients

Nitrogen, Potassium, Phosphorus

Secondary Nutrients

Calcium, Magnesium, Sulphur

Micronutrients

Necessary for some but not big impact

QCI

Quantity of nutrients present, capacity of nutrients supply rate, intensity of nutrients available

Optimum soil pH range

6.2 - 7.3

Nutrient Supply: Primary Sources

N is soil and can be controlled by organic matter
P is soil and can be controlled by pH management
K is primary and secondary minerals and can be controlled through fertilizer

Nutrient deficiencies

cause by a lack of essential elements in the soil or plants’ inability to access them which results in physical symptoms and affected critical processes.

Reasons for nutrient deficiencies 

low available capital of nutrients for a variety of reasons such as nutrient leaching or oversaturation

Liebig’s Law of the Minimum

Growth is dictated by the scarcest resource known as the limiting factor

Resource use efficiency

Yield non-uniformly increases with increasing nutrient availability

Why fertilization leads to greater growth 

Increased canopy photosynthesis due to larger leaf area

Accelerated stand/tree development

Changed allocation of photosynthate

Most Common Fertilizer Elements

Nitrogen, Phosphorus and Potassium

Common Fertilizer Sources

Diammonium Phosphate 18-46-0

Triple Superphosphate 0-44-0

Urea 45-0-0

Potassium Sulfate 0-0-48

Potassium Chloride 0-0-60

Fertilizer Calculations

Fertilizer reccomendations are made in elements amounts

Example: Urea = 45-0-0 (335 lbs Urea/ac * 0.45 = 150 lbs/ac N)

Nitrogen Fertilizers

Synthesized from N₂ gas using Haber-Bosch process

Phosphate Fertilizer

Mined and then processed

Can be mixed, often with nitrogen based fertilizers

Calcium and Magnesium Fertilizers

Come with “lime”

Sulfur Fertilizers

Used to lower soil pH and comes in elemental, calcium sulfate, and diammonium sulfate

Micronutrient Fertilizers

Rarely needed but when used it is tailored to the cite such as boron deficiency, zinc deficiency and copper as a chelate with organic molecules.

Fertilizer End Locations

Trees

Microbes
Leaching
Adsorption on mineral surfaces

Fertilization uptake efficiency

Urea is 20-25% taken up by plants

Volatilization Conditions

Relative humidity

High temp

High wind speed

Low precipitation after fertilization

Low pH buffering capacity of soil

Alternative fertilizers

Manures

Municipal Sludge
Paper mill sludge

Fly ash

Alternative Fertilizer CBA

While they may be free, they also have uneven chemistry and nutritional value, may contain toxic chemical, may have restricted use and are difficult to spread. 

Poultry Litter Fertilizer

Rich in phosphorus and micronutrients and has better results than phosphorus alone, often mixed with other waste

Phosphorus Fertilizer Running Out

Excepted to run out in 80 years, scarcity will most likely hit sometime from 2030 to 4000