A stand of trees composed of a single age class in which the range of tree ages is usually ±20 percent of rotation (SAF, 2008) In natural an even – age stand exists in a short period of time regeneration established relatively synchronously within a short period following a major disturbance It is the stand initiation stage of forest succession
Natural Even-aged stand A stand of trees composed of a single age class in which the range of tree ages is usually ±20 percent of rotation (SAF, 2008) • • • In natural an even – age stand exists in a short period of time regeneration established relatively synchronously within a short period following a major disturbance It is the stand initiation stage of forest succession Forest succession Stand initiation stage • • • • • • • Follows major disturbances (wind, fire, clear-cut) Regeneration of open space Pioneer species occupy One cohort or age class Generally an even canopy (although even-aged species mixtures can form two- or multilayered stands) High density Artificial Even-aged stand Stands normally consist of trees at the same age • • Afforeststation Reforestation Planted forest Even-aged harvest and regeneration systems • • Clearcut Shelterwood Basal Area Clearcut Time Clearcut • A method used to regenerate a stand by the removal of most or all woody vegetation during the harvest creating a mostly or completely open area leading to the establishment of an even-aged stand • Regeneration can be from natural seed produced by adjacent stands or from felled tops of harvested trees • • Clearcuts are also used to direct seeding or replanting for artificial regeneration systems A remarkable characteristic of this method is that no trees are left in the cut area for seeding purposes Clearcut vs Seed-tree method Seed-tree: A method designed to bring about natural reproduction on clearcut harvest areas by leaving enough trees singly or in groups to naturally seed the area with adequate stocking of desired species in a reasonable period of time before the site is captured by undesirable vegetation Seed-trees may be removed after establishment or left indefinitely In Vietnam, according to Prof Pham Xuan Hoan (2013), seed – tree is also called clearcut Clearcut • • • High forest Even-aged stand structure Create open environment favorable for establishment of shade intolerant species • • • • Relatively simple Light-demanding species Creation of even-aged forest patches Intensive commercial management Clearcut • • • • Most or all trees within a unit are clear-felled at one point in time at the end of the rotation Regeneration occurs within a short period after harvest Specific regeneration strategies, such as planting, direct seddling or natural regeneration With the clearcut system, the opening size and dimensions created is generally large enough to limit significant microclimatic influence from the surrounding stand 10 CC with Artificial Regeneration – Plantation Silviculture • • • • Most efficient operationally: size & pattern of cutting areas not limited, no need to protect seedlings from hazards bypassed in nursery, no residual trees obstruct the use of fire, herbicides, machinery during site preparation Trees in rows, uniform spacing, site completely restocked Limited vertical structural diversity No large snags or additions of CWD 33 Some examples of inappropriate clearcutting 34 Some examples of inappropriate clearcutting 35 Some disadvantages of CCs • • Unsuitable for LSOG (late sucessional/old growth)-species Changes animal behavior – Black bears avoid centers of large clearcuts no escape cover, sensitive to heat stress – Deer & elk tend to primarily feed along edges of larger openings 36 Where to avoid clearcuts • • • Riparian zones Special plant & animal habitats, habitat corridors Small woodlots residual forests of adequate area Click to edit Master text styles Second level Third level Fourth level Fifth level 37 Where to avoid clearcuts • Difficult-to-regenerate sites Avalancheprone areas Steep hills 38 Where to avoid clearcuts • • • Recreation & tourist areas Aesthetically valuable areas Heritage or culturally sensitive 39 Keep clearcut edges away from… 40 Keep clearcut edges away from… • • • • Topographic features that funnel winds & accelerate the velocity saddles along ridges, ridge lines, indentations on slopes Poorly drained & shallow soils Signs of old blowdown Concentrations of unsound trees with decayed roots or trunks 41 Ecological Consequences of CC How many red spots make a white cow red? How many clearings make a forest, prairie? A score? More? A coalescing core? A threshold reached? (Landscape Ecology, Forman and Godron 1986) 42 Modifications: Altering the Configuration of Clearcuts • • • Patch cc Strip cc – – Alternate Progressive Cc with reserves (Two-aged system) 43 But… • Configurations with long edges can – – Increased probability of disturbance (wildfire & windthrow) Wildlife is highly sensitive to structural changes 44 Patch CC 45 Strip CC 46 Alternate-Strip Alternate-Patch Clearcut Width: 1-2 times the height of adjacent trees 47 ... One cohort or age class Generally an even canopy (although even- aged species mixtures can form two- or multilayered stands) High density Artificial Even- aged stand Stands normally consist of... High forest Even- aged stand structure Create open environment favorable for establishment of shade intolerant species • • • • Relatively simple Light-demanding species Creation of even- aged forest... convert the virgin lowland dipterocarp forests from the multi-species and multi -aged forest to a more or less even- aged forest which would be stocked by commercial tree species that would be harvested