Forest Ecology and Silviculture
What this domain tests
Forest ecology and silviculture questions ask you to read a stand - composition, age structure, site quality, disturbance history - and then defend a regeneration or tending treatment that fits species autecology and landowner objectives. Expect shade tolerance rankings, succession pathways, site index interpretation, and the full reproduction-method menu.
Core rules
- Shade tolerance drives method. Intolerant species (aspen, lodgepole pine, Douglas-fir on many sites) need mineral soil and full light, so clearcut, seed-tree, or patch cuts fit. Tolerant species (hemlock, sugar maple, balsam fir) regenerate under canopy, favoring selection or shelterwood.
- Shelterwood removes the overstory in two or more cuts to shelter advance regeneration. Seed-tree leaves a few scattered trees for seed only. Do not swap them.
- Selection is uneven-aged, regulated by residual basal area or BDq, and requires tolerant species plus disciplined marking to avoid high-grading.
- Site index is dominant or codominant height at a base age, commonly 50 or 100 years. It indexes site quality, not age, volume, or stocking.
- Thinning types: low (from below, removes suppressed), crown (from above, removes dominants), free (release). Precommercial versus commercial depends on product and cost recovery, not spacing alone.
Worked example
A 45-year-old Douglas-fir stand, site index 110 at base 50, carries 180 square feet per acre of basal area with a dense suppressed understory. The owner wants sawtimber. A low thinning to 110 square feet removes suppressed and intermediate trees and concentrates growth on crop trees; removed stems are small, so the cut is precommercial unless a biomass market exists. A crown thinning would cut the best dominants and reduce future value.
Traps
Mixing site index base ages; treating climax as the automatic management goal; prescribing selection for an intolerant species; forgetting that seed-tree methods require an on-site seed source and seedbed preparation.