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ERS 234 Final > Lecture 10 - Silviculture > Flashcards

Lecture 10 - Silviculture Flashcards

1
Q

What is silviculture?

A

It is the use of sustainable management practices to establish/guide development

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2
Q

What are the objectives of silviculture?

A

Can range widely from:

  • timber production
  • wildlife management
  • biodiversity management
  • aesthetics and safety
  • stream flow volume modification (hydrology)
  • restoration of degraded forest stands/landscapes
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3
Q

What is the European history of silviculture?

A
  • shift in the approach in order to be more sustainable
  • most practiced originated in 14th-19th century Western Europe
  • forested were heavily degraded, which resulted in policy implementation to slow the exploitation rate
  • this initiated a system for trees being felled in an organized fashion rather than haphazardly
  • led to forestry being guided by science & the development of the sustained yield concept (controversial b/c not always sustainable as overharvest can still occur)
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4
Q

What is the North American history of silviculture?

A
  • a cultivated forest approach was not adopted
  • tried selective logging but mostly reverted to clear cutting b/c was more economically feasible
  • outcry over clear cutting led to silviculture - to ensure forests are managed with long term future of ecosystems in mind
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5
Q

What are the different types of forest stands?

A
  1. Even-Aged
  2. Uneven-Aged
  3. Stratified (2-aged)
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6
Q

Describe Even-Aged stands

A
  • they result from a disturbance that destroys an existing stand (sometimes naturally), which causes species to be mostly the same age and size
  • disturbance creates a void/gap that is rapidly filled by various plant species
  • in managed forests, steps are taken to ensure only desirable tree species grow (takes 70-100 years to develop this kind of stand)
  • typical in boreal forests and shade-intolerant species
  • typical harvest method is clear cutting
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7
Q

Describe Uneven-Aged stands

A
  • made up of trees of all age and size classes with considerable differences between them
  • only small scale disturbances occur (ex. tree dies and gap is created)
  • typically mixed forests (temperate and tropical) and shade tolerant species
  • the typical harvest method is selective logging
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8
Q

What are the different crown classes found in forest stands?

A

Classes are based on the differences in amt of direct sunlight going through the canopy.

  • dominant (D)
  • co-dominant (C)
  • intermediate (I)
  • suppressed (S)
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9
Q

Describe the dominant crown class

A
  • tallest, giant trees
  • extend above general level of crown cover
  • receive full light (from above and sides)
  • well-developed crown (may be crowded on sides)
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10
Q

Describe the co-dominant crown class

A
  • medium-sized crowns (crowded on sides)
  • forms general level crown covers
  • receives full sun from above but little on sides
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11
Q

Describe the intermediate crown class

A
  • shorter than D and C trees
  • crown cover slightly extends into D & C
  • receives little direct light from above and none on sides
  • small crown and crowded on sides
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12
Q

Describe the suppressed crown class

A
  • crowns entirely below general crown level
  • receives no direct light from above or sides
  • oppressed crowns (dead or dying)
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13
Q

Describe Stratified (2-aged) stands

A
  • found in managed and unmanaged forests
  • complex b/c each layer may differ in respect to species and age
  • dominant canopy may have more than one species and may be even-aged
  • subdominant canopy may consist of a single species and is uneven-aged
  • in certain cases, both layers may be the same age
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14
Q

What are intermediate treatments?

A 
Silvicultural treatments applied to stands between harvest times to help improve species composition, growth rates, and tree quality. It also helps to generate economic returns, control tree species composition and impact biodiversity.
Treatments are:
- release
- improvement cut
- thinning
- fertilization 
- pruning
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15
Q

Describe the intermediate treatment of release

A
  • frees desirable seedlings/saplings from competing species & helps growth
  • common in conifer stands b/c they’re usually outcompeted by hardwoods, so removal ensures conifer growth
  • usually achieved by using herbicides b/c hardwoods can regrow if the stem is cut
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16
Q

Describe the intermediate treatment of improvement cuts

A
  • carried out in mature stands to remove defective, diseased, poorly formed, or low value trees
  • ensures desired trees get max nutrients, H2O and light
  • can aid wildlife (ex. woodpeckers can use dead trees for food)
17
Q

Describe the intermediate treatment of thinning

A
  • reduces the density to accelerate the growth of remaining trees
  • does not increase the amt of wood produced, but trees grow larger
  • low thinning: cuts from the low/middle crown classes
  • high thinning: creates sufficient number of gaps to stimulate growth
18
Q

Describe the intermediate treatment of fertilization

A
  • addition of soil fertilizer stimulates growth

- especially in areas with a low site index

19
Q

Describe the intermediate treatment of pruning

A
  • low branches are removed in dense stands

- avoids dead knots to produce clean stems, which are of the greatest economic value

20
Q

What are the requirements of successful stand regeneration?

A
  • well conditioned/cultivated seedbeds
  • sufficient moisture and light availability
  • sufficient tree seedling density
  • minimize competition from weeds and other trees
  • ensure seedlings are derived from a resilient and robust genetic stock
21
Q

What are the best methods to approach site preparation?

A

Residual vegetation after harvest is managed to improve new seedling survival.

  • reduces fire hazard
  • prepare seedbed to maximize survival
  • slash is kept to provide nutrients for growing saplings
22
Q

How can site preparation be accomplished?

A
  • prescribed burning
  • herbicides
  • heavy machinery intervention
23
Q

Describe natural regeneration

A
  • will have a more natural species distribution
  • has higher biodiversity and tree diversity
  • may be unreliable if there are poor climate conditions or undesirable tree seedlings from the wind
24
Q

Describe artificial regeneration and its advantages

A

Occurs through direct seeding/planting, so higher survival rates are ensured.
Advantages:
- no reliance on a good seed year
- prompt regeneration of site
- greater control of diversity and composition
- greater control of tree spacing and density
- seeds are specially selected

25
Q

Describe the clear cutting silvicultural method

A
  • removes all valuable trees
  • most economical and destructive
  • likely not ecologically healthy
  • perhaps mimics a large scale disturbance
  • leaves forest floor residue, like slash
  • replanting creates even-aged forests of fast growing species
  • gives no consideration for the ecosystem
26
Q

Describe the seed tree silvicultural method

A
  • similar to CC, but leaves some high quality trees as sources of seed (trees with high regeneration)
  • no replanting occurs as it naturally regenerates and creates an even-aged forest
  • may or may not use slash management
  • gives no consideration for the ecosystem
27
Q

Describe the shelterwood silvicultural method

A
  • less impact than CC or seed tree
  • all mature trees are removed on a 3, 10 or 20 yr cycle
  • the stand is never left treeless, so reduces server erosion risk
  • creates an even-aged forest that is more desirable aesthetically and for recreational opportunities
28
Q

Describe the selective cutting silvicultural method

A
  • used in uneven-aged stands only
  • cut at regular intervals of approximately 15 yrs
  • takes trees from all diameter classes of economic and non-economic species
  • is closer to a natural disturbance
29
Q

Describe the mixedwoods silvicultural method

A
  • conifer stands or deciduous stands of several species

- typically clear cut

30
Q

What is Ecological Forest Management (EFM)?

A
  • takes what is economically valuable and uses remaining species as shade trees for seedlings
  • allows for natural regeneration, maintenance of uneven-aged stands, and mixed forest characteristics
31
Q

Describe the history of plantation forests

A
  • first established in tropics in 1680 Sri Lanka
  • 85% dominated by pines and eucalyptus
  • others include teak and rubber tree
32
Q

How is the global forestry production divided? (Where does production come from?)

A
  • 30% old growth forests in Amazon, Indonesia, Malaysia, Russia, and Canada
  • 36% secondary growth in NA, Russia, and Europe
  • 34% plantations (10% in tropics, 24% in temperate)
33
Q

What are the environmental issues with plantations?

A
  • biodiversity loss from habitat loss
  • exotic species introduced
  • soil acidification
  • changes in hydrology/water quality
  • changes in fire ecology
  • increased pest and disease attack
  • chemical use (pesticides, fertilizers, herbicides, etc.)
34
Q

In the tropics, forest plantations are increasing:

A
  • afforestation
  • rehabilitation
  • ecosystem services, like carbon sequestration, biodiversity, hydrology, biogeochemical cycles, etc.

New studies challenge negative results as it is better to have a plantation than nothing all.

35
Q

In timber harvesting operations, how is soil impacted?

A
  • harvest disturbs soil surface, ranging from severe to minimal loss of upper horizons
  • type of equipment determines degree of disturbance (ex. tractor is high but skyline is low)
  • time of year of harvest also affects degree of disturbance
36
Q

What are the main effects of harvest on soil?

A
  • decreased soil stability: area prone to severe erosion and landslides
  • loss of SOM & nutrients: causes increases in erosion
  • alteration of soil temp: loss of soil cover increases temp
  • alteration of soil physics properties: change in porosity, density, aeration, infiltration, and water retention

ERS 234 Final (9 decks)

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