Value of Variable Retention
Variable retention is gradually becoming a popularly promoted tool for helping resolve the dilemma between demands for wood and demands to maintain habitat and ecology biodiversity and structural diversity in managed forests. What is at issue is how much a forest operation can log without adversely interfering with other ecological processes within the forest.
Variable retention is believed by some forestry experts to minimize the impact of logging operation by leaving biological legacies such as coarse woody debris(nurse logs and snags). Either few trees or many trees can be retained under the variable retention system, and trees can be retained in patches (aggregated retention) or left uniformly throughout a stand (dispersed retention); hence the name "variable retention". It is a technique for retaining trees as key structural elements of a harvested stand for at least until next harvest rotation in an effort to maintain species, habitat diversity and forest-related processes.
There are four key mechanisms through which variable retention is presumed to maintain biodiversity:
- By providing a constant supply of structural features that are at high risk to being lost due to modern forestry practices and that are known to be important to habitat availability, such as large trees, very young trees, snags, and coarse woody debris
- By providing adequate refuge for sensitive species that will colonize the surrounding managed forest environment as it develops suitable conditions
- By establishing habitat patches, Patch dynamics, that can serve as stepping stones for the dispersal of newly produced offspring, seeds, and spores
- By increasing the structural diversity of managed stands
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Famous quotes containing the words variable and/or retention:
“Walked forth to ease my pain
Along the shore of silver streaming Thames,
Whose rutty bank, the which his river hems,
Was painted all with variable flowers,”
—Edmund Spenser (1552?–1599)
“Unless a group of workers know their work is under surveillance, that they are being rated as fairly as human beings, with the fallibility that goes with human judgment, can rate them, and that at least an attempt is made to measure their worth to an organization in relative terms, they are likely to sink back on length of service as the sole reason for retention and promotion.”
—Mary Barnett Gilson (1877–?)