Managing
British Columbia's forests requires strategically outlining
higher-level planning objectives that account for a variety of land
users (i.e. promote forest health). The resource objectives stated
in these plans are often broad in scope. Stand-level prescriptions help
link these broad objectives to operational management and
promote site-specific prescriptions that meet the requirements of
the Forest Practices Code of British Columbia Act. When higher-level
plans are not sufficient enough to formulate stand-level objectives,
consultation of guidebooks is recommended.
According to the Silvicultural Systems Guidebook[1],
determining stand structural goals is necessary to satisfy stand-level
resource objectives. Stand structural goals provide targets and a means
to measure the effectiveness of forest operations that influence stand
development. The first step to determining these structural goals is
gaining an understanding of the regeneration requirements, shade
tolerance and silvics of present and future tree
species.
Light has been shown to be the most important factor affecting tree
growth in tropical, temperate and boreal biomes. Its importance
stems from the fact that it is manipulated the most by forest
management operations[2].
A ranking system based on field observations and studies on naturally
regenerated seedlings has provided the current understanding of B.C.'s
conifer species' light, soil moisture and soil nutrient availability
tolerances[2]. The ranking system varies greatly in response to site condition and a species' genetic varaibility[3].
In the Interior Cedar Hemlock (ICH) zone, Douglas fir[4], Western Redcedar[5] and Western Hemlock[6]
are the dominant tree species. The range of Douglas-fir is vast and the
species has varied successional roles; its tolerance to shade also
ranges from very shade tolerant to very shade intolerant depending on
site characteristics[7]. This has also been found by Carter and Klinka[3],
who have shown that under different microenvironments tree
species' tolerance to environmental conditions can vary.
Silvicultural Systems that retain substantial levels of canopy trees
(retention prescriptions) create unique microenvironments for planted
seedlings[8]. Retention
prescriptions are used to meet habitat objectives, provide
shade for regenerating understory, stabliize terrain and provide
aesthetic values.
The objectives of this study are to:
(1) Understand the growth response of seedlings to retention prescriptions. This is fundamental when predicting the effects of the management prescriptions on future forest composition.
(2)
Determine if species are affected by light environments and
whether growth responses vary according to classical shade tolerance
rankings. This is important because shade
tolerance rankings are used by forest managers in achieving
stand-level objectives.
The
null hypothesis was that competition and light
levels are the same across all treatments and that neither
has an effect on species preformance (same survival and
productivity). I expect species to repond according to classical shade
tolerance rankings. The results obtained will help mitigate problems in
predicting future species compositions of Douglas-fir, Western
hemlock and Western redcedar in ICH mixed stands growing on a
substantial slope (30%).
[1] (B.C. Ministry of Forests 2007)
[2] (Vyse et al. 2006)
[3] (Carter and Klinka 1992)
[4] Fd
[5] Cw
[6] Hw
[7] (Arno 1991).
[8] (Coats and Burton 1999)
