A Silvicultural System for sustain management consists of three key elements: Regeneration, Tending and Harvesting. Regeneration may be established by artificial or natural means. Once established trees are subject of a series of tending treatments to nurture their growth and development, following landowner’s objectives (Nyland, 2002). Through tending, foresters intend to control stand and tree growth by regulating stand density, and reducing inter-tree competition. They keep stands healthy through thinning, pruning, release and intermediate treatments. Tending enhances growth of the trees, improves their quality and shortens the rotation of an even-aged stand. By concentrating the growth potential on trees of desire species.
Harvesting implements the silvicultural objective of sustaining a forest’s commodity and non-market values (Nyland, 2002). When an age class reaches a predetermined stage of maturity, silviculturists make use of harvesting operations to regenerate the stands. To regenerate Uneven-aged stand the reproduction methods applied are single-tree, group selection and hybrid methods. In the case of even-aged stands, the methods applied include Clearcutting, Shelter wood and Seed-tree variants. Harvesting serves to control forest stand and age class establishment (across stands for even aged) by periodically altering conditions of the physical environment in a particular stand. Harvesting allows to reduce the overstory and consequently that light reaches the ground in forested areas. It induces and enhancement of soil conditions for timely germination and optimal growth of a new cohort (Nyland, 2002). The continuous and interdependence of the Silvicultural System components ensures the long term success of getting the desired ecologic and economic conditions to satisfy landowner’s objectives.
In even-aged silviculture, the stands are comprised of a single age class and foresters normally tend it as a unit, applying a single treatment to the whole stand throughout the rotation. During the early stages of the stand various tending treatments are executed. Foresters may harvest trees to help tend the immature classes or harvest the mature trees to regenerate the community. Tending and harvesting occur at very different times within even-aged silviculture. Characteristics of importance in stands under even-aged silviculture include the determination of the rotation age by the time it takes the stands to reach sexual maturity; the long period it takes for many species to produce seeds and the homogeneity within stands after crown closure.
In uneven-aged silviculture however, tending occurs concurrently. It is applied periodically to immature classes to foster their growth and development and requiring different techniques for each class. Common advantages of selection systems are the appropriateness of the array of age classes in correct proportions, the acceptable mixture of species, good growth rates on residual trees of all ages and the periodic upgrading of stand quality through judicious tending (Nyland, 2002). Shortcomings include the need to periodically conduct forest inventories to secure timely data each cutting cycle, damages to residual trees and the establishment of shade intolerant species if that is desired.
In general, uneven-aged silvicultural systems provide for the concurrent regeneration and tending of the stand. The growing stock is manipulated by thinning, pruning, release treatments and that contributes to periodically improve its quality. Mostly shade tolerant species regenerate in uneven-aged stands and the spread of ages will exceed 25% among size classes. In even-aged silviculture within a stand, harvesting operations used to regenerate the mature trees are done using reproduction methods such as clearcutting, shelterwood and seed-tree. Shade intolerant species grow rapidly due to increased amounts of light. The age of trees in even-aged stand differs by less than 20%.
Both systems keep sufficient numbers of well distributed trees to ensure full site utilization. They also address non-commodity values and reflect the economic interest of the landowner.
FEATURES OF UNEVEN-AGED SYSTEMS
Trees influenced by older trees, or have dominating positions
Depending on age
Early slow growth due to partial shading
Heterogeneous competition across stand that changes as trees mature
Ecological conditions never change
Branching influenced by spacing & tree age
Special felling & skidding needed to protect residual growing stock
No complete removal
Regeneration mostly shade-tolerant species
Continued selectivity should upgrade growing stock through time
High vertical structural diversity
Micro horizontal diversity
FEATURES OF EVEN-AGED SYSTEMS
1. Trees influenced by others of same age
Fast early growth due to full sunlight
Even competition across the stand
Changing ecological conditions as stand matures
Branching influenced by crowding
Special thinning programs needed to maintain vigor
Complete removal at end of rotation
New regeneration may contain many shade-intolerant trees
Repeated selectivity in thinning should upgrade growing stock quality through time
Low vertical structural diversity
No horizontal diversity
References
1. Nyland, R.D., 2002. Silvicultural Concepts and Applications. 2nd edition. McGraw-Hill Series in Forest Resources. N.Y. USA.
2. Nyland, R.D., 2005. FOR 534-Silvicultural Practice Class Notes.Faculty of Forest and Natural Resources Management. SUNY College of Environmental Science and Forestry. Syracuse, NY 13210.
Harvesting implements the silvicultural objective of sustaining a forest’s commodity and non-market values (Nyland, 2002). When an age class reaches a predetermined stage of maturity, silviculturists make use of harvesting operations to regenerate the stands. To regenerate Uneven-aged stand the reproduction methods applied are single-tree, group selection and hybrid methods. In the case of even-aged stands, the methods applied include Clearcutting, Shelter wood and Seed-tree variants. Harvesting serves to control forest stand and age class establishment (across stands for even aged) by periodically altering conditions of the physical environment in a particular stand. Harvesting allows to reduce the overstory and consequently that light reaches the ground in forested areas. It induces and enhancement of soil conditions for timely germination and optimal growth of a new cohort (Nyland, 2002). The continuous and interdependence of the Silvicultural System components ensures the long term success of getting the desired ecologic and economic conditions to satisfy landowner’s objectives.
In even-aged silviculture, the stands are comprised of a single age class and foresters normally tend it as a unit, applying a single treatment to the whole stand throughout the rotation. During the early stages of the stand various tending treatments are executed. Foresters may harvest trees to help tend the immature classes or harvest the mature trees to regenerate the community. Tending and harvesting occur at very different times within even-aged silviculture. Characteristics of importance in stands under even-aged silviculture include the determination of the rotation age by the time it takes the stands to reach sexual maturity; the long period it takes for many species to produce seeds and the homogeneity within stands after crown closure.
In uneven-aged silviculture however, tending occurs concurrently. It is applied periodically to immature classes to foster their growth and development and requiring different techniques for each class. Common advantages of selection systems are the appropriateness of the array of age classes in correct proportions, the acceptable mixture of species, good growth rates on residual trees of all ages and the periodic upgrading of stand quality through judicious tending (Nyland, 2002). Shortcomings include the need to periodically conduct forest inventories to secure timely data each cutting cycle, damages to residual trees and the establishment of shade intolerant species if that is desired.
In general, uneven-aged silvicultural systems provide for the concurrent regeneration and tending of the stand. The growing stock is manipulated by thinning, pruning, release treatments and that contributes to periodically improve its quality. Mostly shade tolerant species regenerate in uneven-aged stands and the spread of ages will exceed 25% among size classes. In even-aged silviculture within a stand, harvesting operations used to regenerate the mature trees are done using reproduction methods such as clearcutting, shelterwood and seed-tree. Shade intolerant species grow rapidly due to increased amounts of light. The age of trees in even-aged stand differs by less than 20%.
Both systems keep sufficient numbers of well distributed trees to ensure full site utilization. They also address non-commodity values and reflect the economic interest of the landowner.
FEATURES OF UNEVEN-AGED SYSTEMS
Trees influenced by older trees, or have dominating positions
Depending on age
Early slow growth due to partial shading
Heterogeneous competition across stand that changes as trees mature
Ecological conditions never change
Branching influenced by spacing & tree age
Special felling & skidding needed to protect residual growing stock
No complete removal
Regeneration mostly shade-tolerant species
Continued selectivity should upgrade growing stock through time
High vertical structural diversity
Micro horizontal diversity
FEATURES OF EVEN-AGED SYSTEMS
1. Trees influenced by others of same age
Fast early growth due to full sunlight
Even competition across the stand
Changing ecological conditions as stand matures
Branching influenced by crowding
Special thinning programs needed to maintain vigor
Complete removal at end of rotation
New regeneration may contain many shade-intolerant trees
Repeated selectivity in thinning should upgrade growing stock quality through time
Low vertical structural diversity
No horizontal diversity
References
1. Nyland, R.D., 2002. Silvicultural Concepts and Applications. 2nd edition. McGraw-Hill Series in Forest Resources. N.Y. USA.
2. Nyland, R.D., 2005. FOR 534-Silvicultural Practice Class Notes.Faculty of Forest and Natural Resources Management. SUNY College of Environmental Science and Forestry. Syracuse, NY 13210.
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