Forestry Science and Silviculture
Forestry Science and Silviculture tests forest ecology, tree growth, regeneration and stand treatment, using Nepal's Terai, Hill and Mountain forests as the setting. The exam expects you to select and justify a silvicultural system, not merely define it.
Core rules and concepts
- Succession moves a site from pioneer to climax vegetation; silviculture imitates natural disturbance to favour desired species.
- Even-aged systems include clear felling, seed-tree and shelterwood; uneven-aged systems include single-tree and group selection; coppice suits species that sprout well, such as Sal and Khair.
- In Nepal, Sal (Shorea robusta) regenerates from seed and coppice; Chir pine is light-demanding; oak and rhododendron need protection from grazing and fire.
- A silvicultural system is a planned sequence: regeneration felling, tending, thinning, pruning and final harvest. Thinning removes competition and is not a regeneration felling.
- Nursery and planting practice: collect seed from phenotypically superior trees, prepare pits, weed and protect young plants.
Worked example
A 20 ha Sal stand is managed on a 100-year rotation with area regulation. Annual coupe = 20/100 = 0.2 ha. If the regeneration period is 5 years under shelterwood, the regeneration block is 5 x 0.2 = 1.0 ha. The reasoning: divide total area by rotation to get the annual felling area; multiply by the regeneration period to find the area kept open for regeneration at one time. If the stand carries 1,200 trees/ha and a thinning removes 30%, retained trees = 1,200 x 0.70 = 840/ha.
Traps that cost marks
Do not confuse a silvicultural system with a harvesting method. Do not claim clear felling is always illegal in Nepal; it is restricted, not universally banned. Do not prescribe selection felling for light-demanding Chir pine. Do not ignore grazing, fire and invasive species when explaining regeneration failure.