Abstract
This thesis includes three studies. The first study examined how reductions in light availability and changes in soil chemistry that occur as conifers establish in aspen stands, differentially affects the regeneration success of aspen and conifers. We found that aspen were more sensitive to changes in light and soil then subalpine fir. For aspen, reduced light and conifer influenced soils significantly reduced height, biomass, photosynthesis and the production of secondary defense compounds. Subalpine fir seedlings were significantly reduced in photosynthesis, biomass and R:S under lower light conditions but showed no differences in physiology or growth when grown on the contrasting soil types. Subalpine fir seedlings were significantly reduced in photosynthesis, biomass and root:shoot ratio under lower light conditions but showed no differences in physiology or growth when grown on the contrasting soil types. Results from this study suggest that reduction in light and changes in soil chemistry associated with conifer succession place constraints on aspen growth and defense capacity, which may contribute to losses in aspen cover under longer disturbance return intervals. The second study looked at regeneration dynamics of aspen and conifers as forest stands transition from canopy gaps to aspen dominated canopies to conifer dominated canopies. We found that as overstory conifer density increases, aspen decrease in density, basal area, and seedling establishment. Conifers were shown to establish closer to aspen as the canopy increased in conifer density. As this proximity relationship extended into the canopy there is increased mortality in both aspen and subalpine fir, suggesting both facilitation and competition. Our third study looked at the physiological effects of smoke exposure on growth and primary and secondary metabolic responses of deciduous and conifer tree species. Twenty minutes of smoke exposure resulted in a greater than 50% reduction in photosynthetic capacity in five of the six species we examined. Impairment of photosynthesis in response to smoke was a function of reductions in stomatal conductance and biochemical limitations. In general, deciduous species showed greater sensitivity than conifer species. Smoke had no significant affect on growth or secondary defense compound production in any of the tree species examined.
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Claims 12
Claim · model-written summary
Aspen was more sensitive to light and soil changes than subalpine fir.
Verbatim
e0“aspen were more sensitive to changes in light and soil then subalpine fir”
Claim · model-written summary
Reduced light lowered aspen height, biomass, photosynthesis and defense compound production.
- Taxon
- aspene0
- Treatment
- reduced lighte0
- Outcome
- height, biomass, photosynthesis and the production of secondary defense compoundse0
- Direction
- reducede0
Not reportedComparator
Verbatim
e0“For aspen, reduced light and conifer influenced soils significantly reduced height, biomass, photosynthesis and the production of secondary defense compounds”
Claim · model-written summary
Conifer-influenced soil lowered aspen height, biomass, photosynthesis and defense compound production.
- Taxon
- aspene0
- Treatment
- conifer influenced soilse0
- Outcome
- height, biomass, photosynthesis and the production of secondary defense compoundse0
- Direction
- reducede0
Not reportedComparator
Verbatim
e0“For aspen, reduced light and conifer influenced soils significantly reduced height, biomass, photosynthesis and the production of secondary defense compounds”
Claim · model-written summary
Low light reduced subalpine fir photosynthesis, biomass and root:shoot ratio.
- Taxon
- Subalpine fir
Abies lasiocarpae0 - Treatment
- lower light conditionse0
- Outcome
- photosynthesis, biomass and root:shoot ratioe0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Subalpine fir seedlings were significantly reduced in photosynthesis, biomass and root:shoot ratio under lower light conditions”
Claim · model-written summary
Subalpine fir physiology and growth did not differ between soil types.
- Taxon
- Subalpine firAbies lasiocarpae0
- Treatment
- contrasting soil typese0
- Outcome
- physiology or growthe0
- Direction
- no differencese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Subalpine fir seedlings were significantly reduced in photosynthesis, biomass and root:shoot ratio under lower light conditions but showed no differences in physiology or growth when grown on the contrasting soil types”
Claim · model-written summary
Greater overstory conifer density was associated with decreased aspen density, basal area and seedling establishment.
Verbatim
e0“as overstory conifer density increases, aspen decrease in density, basal area, and seedling establishment”
Claim · model-written summary
Conifers established closer to aspen as conifer canopy density increased.
Verbatim
e0“Conifers were shown to establish closer to aspen as the canopy increased in conifer density”
Claim · model-written summary
Closer canopy proximity was associated with increased mortality of both aspen and subalpine fir.
- Taxon
- aspene0
- Interactor
- subalpine firAbies lasiocarpae0other
- Outcome
- mortalitye0
- Direction
- increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“As this proximity relationship extended into the canopy there is increased mortality in both aspen and subalpine fir”
Claim · model-written summary
Twenty minutes of smoke exposure reduced photosynthetic capacity by more than 50% in five of six tree species.
- Taxon
- tree speciese1
- Treatment
- Twenty minutes of smoke exposuree0
- Outcome
- photosynthetic capacitye0
- Direction
- reductione0
- Value
- greater than 50%e0
Not reportedComparator
Verbatim
e0“Twenty minutes of smoke exposure resulted in a greater than 50% reduction in photosynthetic capacity in five of the six species we examined”
e1“tree species examined”
Claim · model-written summary
Photosynthesis impairment under smoke reflected reduced stomatal conductance and biochemical limitations.
Verbatim
e0“Impairment of photosynthesis in response to smoke was a function of reductions in stomatal conductance and biochemical limitations”
e1“tree species examined”
Claim · model-written summary
Deciduous species generally showed greater smoke sensitivity than conifers.
Verbatim
e0“deciduous species showed greater sensitivity than conifer species”
Claim · model-written summary
Smoke did not significantly affect growth or secondary defense compound production.
- Taxon
- tree speciese0
- Treatment
- Smokee0
- Outcome
- growth or secondary defense compound productione0
- Direction
- no significant affecte0
Not reportedComparator
Verbatim
e0“Smoke had no significant affect on growth or secondary defense compound production in any of the tree species examined”
The same questions in other papers
light · physiology: photosynthesis · Abies lasiocarpa (subalpine fir)Results agree
2 papers in the same direction as this paper
- negative
- negative
Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.