Silviculture is the technique of regulating a forest’s development, composition/ structure, and quality to satisfy goals and demands, particularly the necessity for wood output.
Shelterwood System is one of the Silvicultural systems defined as “A method of securing natural tree reproduction under the shelter of old trees which are removed by successive cutting and results in an even-aged stand structure ”.
The central theme to shelter woods is that the over story leave-trees are left on site to protect the regenerating under-storey until the under-storey no longer requires the protection.
Criteria to leave trees in shelterwood stems
- Larger, dominant, genetically superior
- wind firm trees
- desirable species
- desirable physical characteristics
STAGES OF SHELTERWOOD SYSTEM
|1. Preparatory Felling|
|•Felling made with the objective of creating favorable conditions for seed production. |
•Done towards the end of rotation ( when the trees are 60 – 80 year old)
I. Less valuable species
II. Trees not putting the increment
III. Dead, dying, diseased trees
|2. Seeding Felling|
|•Felling made with the objective of opening the canopy (to about 50 %) to secure the regeneration of seed from tree. •Felling perform when the trees are 80 – 100 years old. •Retain good seed tree •Remove over wood.|
|3. Secondary Felling|
|•Felling made with the objective of opening the canopy to remove the shelter and allow more light for the regenerated crops. •This condition favors seedling development.|
|4. Final Felling|
|•Felling made with the objective of removing the last Shelter trees and seed trees. •By giving the saplings full sunlight, the removal cut encourages the rapid growth of a new forest.|
Types of Shelterwood System
A. Uniform shelterwood system
The shelterwood system with a uniformly opened canopy over the whole compartment supporting Uniform regeneration under the shelterwood is a uniform shelterwood system.
B. Group shelterwood system
The shelterwood system in which Small gaps(patches) are created in the stand where adjacent trees can shelter the new regeneration growing in the gaps.
C. Strip shelterwood system
The shelterwood system in which silvicultural operations are undertaken in uniformly spaced linear strips.
D. Irregular shelterwood system
The shelterwood system undertakes Successive cuttings in a long regeneration period, with flexibility in generating spatial and vertical heterogeneity in stands. This system is widely used in SFM in Nepal.
Advantages and Disadvantages
- Regeneration is protected from extreme climate( cold, frost etc)
- Soil not completely denuded, (least soil deterioration.)
- less risk of invasion to regeneration(Shelter trees)
- Seed tree-superior new crop
- More natural condition, low immature felling and avoidance of loss during felling
- suitable for light demander and shade bearer
- Planning and prediction of yield and growth is uncertain
- Difficult in practical field(irregular growth)
- Increased harvesting cost due to successive harvesting
- Desiccation of soil (Hot, exposed),
- Heavy mortality (Poor soil condition),