More info for the terms: allelopathy, basal area, competition, cover, density, shrub, tree, vine
Timber harvest: Salal commonly increases after timber harvest
[2,61,89]. Generally, if present in the understory prior to harvest, it
will also form part of the postdisturbance community [22]. Heavy
thinning can increase salal biomass by up to 2.8 times [117]. The
effects of timber harvest on salal have been examined in a number of
studies [8,30,31,57,70,71,73,79,94,112,115,131].
Competition: Salal competes vigorously with conifer regeneration in
some locations [79]. On moist sites, this shrub commonly competes with
Douglas-fir, Sitka spruce, and western hemlock, and to a lesser degree
with western redcedar [143]. In general, the nutrient-demanding Sitka
spruce is most harmed by competition with salal [89], but salal can also
significantly reduce the basal area and stocking of Douglas-fir
seedlings on some sites [16]. In some areas, salal vigorously competes
with Douglas-fir for both water and nutrients [15,41,104] resulting in
poor seedling growth [134]. In many problem areas, soil moisture
deficits are common during the growing season, and competition for
moisture may be of primary significance [109]. Competition is often
pronounced in drier low elevation forests of coastal British Columbia
where dense thickets of salal commonly form on cutover sites [24,42].
Growth of forest crop trees is commonly reduced at approximately 6 to 8
years after planting in coastal Sitka spruce-western hemlock-western
redcedar, and western hemlock forests where a dense ground cover of
salal is present [92,134]. This growth check period may be due to the
direct effects of competition with salal or allelopathy associated with
this ericaceous shrub [134]. Anderson [3] reports that a dense growth
of salal can also inhibit regeneration of maples (Acer spp.), as samaras
are physically prevented from reaching the forest floor [3].
On some sites in western Washington, salal may actually add nutrients to
the soil and apparently has no adverse effect on the growth of
Douglas-fir [45,79]. Klinka and others [79] report that the amount of
nitrogen tied up by salal is relatively small and is not likely to be
critical for tree growth except on very poor sites. In some areas,
conifer regeneration is typically better on sites dominated by salal
than on sites dominated by western swordfern or vine maple [29].
Still, much research has focused on ways to eliminate salal to improve
conifer regeneration. Recommendations for minimizing salal competition
with conifer seedlings include [89]:
(1) preventing fires on naturally regenerated clearcuts
(2) preparing seedbeds to encourage prompt natural
regeneration
(3) planting seedlings immediately after timber removal;
adding fertilizers where necessary
Successive light treatments may be preferable to a single heavy tree
removal [104]. When thinning, particular care should be taken to avoid
creating large gaps in the canopy [104]. It may be desirable to
maintain greater stand density on dry sites with salal present [104].
Competition between conifer seedling and salal occurs largely below
ground [16], and seedlings should be planted as early as possible after
timber harvest to allow seedlings a "head start" [16]. In some areas,
planting densities necessary to shade out salal quickly are
impractically high [16]. Models have been developed which explore the
effects of salal competition on the growth of various conifer seedlings
[88]. The effects of competition have been considered in detail
[16,41,88,89,92,104,135,136,142,143]. However, in many instances,
elimination of salal is difficult, uneconomical, or impractical.
Bunnell [15] reports that "...attempts to reduce salal abundance may be
unwarranted; the species appears well adapted to persist."
Chemical control: Salal is resistant to many herbicides including
2,4-D, velpar, 2,4,5-T, amitrole, picloram, and silvex [12,106,120].
Site characteristics [24,41] and season and mode of application can
greatly influence the response of salal to herbicides [121]. Repeated
application of Garlon is effective although often impractical [24] or
prohibitively expensive. Silvex can also be relatively effective in
reducing cover when properly applied [121]. Salal appears to be most
susceptible to foliage sprays in diesel oil carriers when applied at
budbreak [121]. Plants are less seriously damaged by herbicides applied
late in the growing season or by those applied in water or oil-in-water
emulsions [121]. In test applications, few of the damaged salal plants
were actually killed by herbicides, and recovery was generally rapid
[121]. However, herbicides can sometimes produce sufficient control for
conifer release [121]. Detailed information on the response of salal to
herbicides is available [12,17,21,24,45,120,121].
Mechanical removal: Various types of mechanical removal or soil
disturbance can stimulate sprouting of salal and produce increased cover
[45]. As rhizomes are broken, new plants commonly form [15]. Harvest
techniques which disrupt rhizomes, such as the use of skidders, can
produce additional management problems by fostering the spread of salal
[15]. In coastal British Columbia, spot scarification appears to be
relatively ineffective in producing long-term control of salal [24].
Pretreatment levels can be reached by the third growing season [24].
Blade scarification was more effective, reducing cover to 6 percent but
resulted in significant site degradation [24]. Details on mechanical
treatments are available [24,41,135,136].
Biomass: In general, aboveground biomass of salal appears to be
inversely proportional to the amount of overstory foliage [85]:
stand age
(years)
22 30 42 73
salal
biomass (kg/ha) 6300.6 4112.2 3394.0 1010.2
Heavy fertilizer application can decrease the aboveground biomass of
salal [117].
Wildlife: Salal fruit production may be limited beneath a closed canopy
[15]. Disturbances which eliminate portions of the overstory presumably
increase fruit production. Where management goals are aimed at
increasing winter big game forage, evidence suggests that salal will
respond favorably to thinning [15].
Research indicates that mountain lion, coyote, and wolf urine can be
used to inhibit or stop deer use of salal browse [124].
Livestock: Salal is susceptible to trampling damage [102].
Chemical composition: Evidence suggests that salal may be somewhat
allelopathic [25,136,141]. The foliage and roots of salal are resistant
to decay and can reduce decomposition and water availability [79].
