NBFRAC - WILDLIFE TECHNICAL COMMITTEE

DWAMU HARVEST AND SILVICULTURE GUIDE WORKING GROUP

SPECIALIZED HARVESTING: As defined by Fraser Inc. refers to harvesting in a fashion other than clearcutting for the purpose of extracting wood products and leaving a standing residual voulume to gain some silvicultural advantage in a stand.

STAND DENSITY:  A quantitative measurement of a stand in terms of Basal Area (BA in m2/ha), number of trees, or volume per hectare.  (Husch, et al, see stocking)

STAND MATURITY: Related to FDS descriptions of stand development stage.

SITE QUALITY: Relates to the (1) development of the existing stand condition (ie. growth, vigour, longevity, etc.) and (2) the potential for coniferous regeneration and the establishment of other types competition.  In the Spruce/Fir Guide, it pertains to the stand as a primary (pure) or secondary (mixed) softwood site.

SPECIES COMPOSITION: Is the relative distribution of the amount (#'s, BA, vol., etc.) of the various species present.  Used as an indicator of the stands suitability as deer winter habitat or various silvicultural techniques.

STOCKING:  Stocking is a relative term used to describe the distribution of the density of trees per unit area.  Stocking is also related to the utilization of a given stand density in meeting a management objective.  Thus a stand with a density of 18 m2/ha of BA, may be classified as overstocked or understocked depending on what density is considered desirable. (Husch, et al)

STOCKING CHARTS:  Stocking charts are graphical representations of the degree or stocking percent, relative to the mean stand diameter (tree size), the number of trees/hectare, and the basal area (BA) within the stand. (Vermont guide)  The three standard curves are the A, B, & C Level.  Above the A line, the stand is overstocked.  Between the A & B lines, the stand is stocked.  Below the B line, between the B & C line is considered slightly understocked, as the stand will grow into a stocked condition within 10 years.  Below the C line is definitely understocked.

   For example;    Thinning a young stand to 400 trees/ac is preferred over thinning it to B-level stocking.  At 400 trees/ac a stand will be at B-level when the Mean Stand Diameter (MSD) reaches 6 inches, and will not be overstocked until it reaches 11 inches MSD.  This stand will approach functional shelter (35 ft tall, 70% crown closure) at 30 years of age, and will afford shelter for the rest off the rotation without becoming stagnant.  It should then be scheduled for regeneration.

 *TRAVEL CORRIDORS: Areas or strips which provide uninterrupted cover to unharvested blocks thus ensuring mobility.  These travel lanes could coexist with riparian buffer strips and maintained as permanently as possible.  (Vermont)

 TWO-PASS HARVESTING: A term which is recently in vogue, it seems  to refer to a grouping of various partial cutting activities with no regeneration objective, confined to buffers, DWAs, and blocks adjacent to recent clearcuts.  Hence, by definition partial cuttings must be considered intermediate cuts.  However, two pass harvesting has a beginning and an end, and should deliver more in terms of the management objectives.  In the context of a reproduction cutting, this term should imply either a shelterwood or a seed tree system, assumming complete overstory removal occurrs in two cuttings.  (The exception would be to leave reserves to achieve other objectives.)  While the seed tree system is fairly straight forward, the shelterwood system is suitable for considerable variation.  However, both cuts must be economically and biologically viable.  Under normal circumstances, this would involve a 30 to 50 % by volume, low grade first cut, followed shortly (once regeneration has become established) by a complete overstory removal, release cut.

 UNEVENAGED MANAGEMENT:     Is characterized by the presence of trees from at least three distinct age classes, irregularly mixed in the same stand.  Uneven-aged stands are irregular in height and there is a great variation in tree size.  An uneven-aged stand is maintained through regular selection harvests throughout the rotation.  The diameter distribution in a balanced uneven-aged stand, plots as a characteristically inversed J-shaped curve.

VARIABLE RETENTION Variable retention presciptions remove almost all mechantable stems of all species in a single teatment. This prescription is generally applied to even-aged mature or over-mature stands, leading to an even aged regeneration through natural processes or tree planting. In some variable situations, a "Seed Tree" harvest presciption will be utilized (typically used in white pine conditions). Within the harvested area attention is paid to maintain sufficient vertical structure and biodiversity by leaving residual trees, clumps or islands of uncut trees and advanced natural regeneration. This variable retention is imporatant for wildlife and to maintain natural disturbance and biodiversity patterns. We have assumed that approximately 3% of the pretreatment volume will remain as residual stand component following this presciption (source: JD Irving)

WINDTHROW HAZARD: The susceptibility  of trees being blown over by normal winds.  Determined by stand and species characteristics such as spacing, rooting habit and soil, tree size and vigour, and landscape position. (DNR Field Guides)