black spruce regeneration in kalmia dominated sites : effects of mycorrhizal inoculation and forest floor mixing
abstract
study area : terra nova national park, 90 km southeast of gander, newfoundland. there can be a shift in vegetation from black spruce (picea mariana mill.)
forests with the ericaceous shrub kalmia angustifolia l. (kalmia) in the
understory to ericaceous dominated heath in some areas of newfoundland.
this occurs on low to medium fertility sites after forest fire, insect defoliation, or
clear-cut harvesting. kalmia spreads rapidly with the concomitant failure of black
spruce regeneration. this is a serious and widespread problem for the forest
industry, and for protected area management when human interventions to
natural disturbance cause the formation of kalmia heath. the objective of this
thesis was to test two alternate methods of enhancing black spruce regeneration
in kalmia dominated sites. i examined the growth response and foliar nutrient
concentration of black spruce seedlings inoculated with the ectomycorrhiza (em)
paxillus involutus (batsch. ex fr.) fr, planted in mechanically-mixed forest floors
dominated by kalmia. changes in soil physical and chemical properties following
mechanical mixing (tilling) of the forest floor horizon were also studied. the
experiment was conducted over two growing seasons in kalmia dominated sites
resulting from heavy insect defoliation by spruce budworm and natural fires in
terra nova national park, newfoundland.
i found that inoculated seedlings had higher levels of em formation, but
lower growth than control seedlings, suggesting that the effect of em on host
performance is likely related to the physiological performance of the specific em
isolate under the prevailing soil conditions. control seedlings that were exposed
to nutrient stress in the greenhouse had better growth than the commercial nursery
grown seedlings that were cultured using standard levels of fertilization.
this suggests that black spruce growth might be closely related to adaptations to
tolerate nutrient stress. seedlings in insect defoliated sites in general had higher
growth and foliar nutrient concentrations than those in burned sites. this was
likely due to increased decomposition. seedlings in all of the mixed forest floors
had higher foliar nutrient concentrations than those in non-mixed forest floors,
likely due to decreased acidity and competition, and increased decomposition.
however, my results did not explain why forest floor mixing resulted in increased
growth of black spruce seedlings in insect defoliated sites, but not in burned
sites. most theories of the growth of black spruce in kalmia dominated sites
include only below ground effects, but above ground effects may also be
important. one possibility is that partial canopy cover is an important factor due
to its effects on extremes of soil temperature and moisture, decomposition, litter
quality, light levels, and near ground microclimate. my results indicate that it is
possible to restore black spruce forest in insect defoliated sites with partial
canopy cover that are dominated by kalmia by mixing the forest floor and
planting seedlings grown at low soil nutrient levels. however, further research is
required to establish a method for restoring black spruce forest in open canopy
burned sites.
collections
- retrospective theses [1604]