Abstract
Because of difficulties in directly assessing root responses of mature forest trees exposed to atmospheric pollutants, we have used the model TREGRO to analyze the effects of a 3- and a 10-year exposure to ozone (O(3)) on root dynamics of a simulated 160-year-old sugar maple (Acer saccharum Marsh.) tree. We used existing phenological, allometric, and growth data to parameterize TREGRO to produce a simulated 160-year-old tree. Simulations were based on literature values for sugar maple fine root production and senescence and the photosynthetic responses of sugar maple seedlings exposed to O(3) in open-top chambers. In the simulated 3-year exposure to O(3), 2 x ambient atmospheric O(3) concentrations reduced net carbon (C) gain of the 160-year-old tree. This reduction occurred in the C storage pools (total nonstructural carbohydrate, TNC), with most of the reduction occurring in coarse (woody) roots. Total fine root production and senescence were unaffected by the simulated 3-year exposure to O(3). However, extending the simulated O(3) exposure period to 10 years depleted the TNC pools of the coarse roots and reduced total fine root production. Similar reductions in TNC pools have been observed in forest-grown sugar maple trees exhibiting symptoms of stress. We conclude that modeling can aid in evaluating the belowground response of mature forest trees to atmospheric pollution stress and could indicate the potential for gradual deterioration of tree health under conditions of long-term stress, a situation similar to that underlying the decline of sugar maple trees.
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Claims 6
Claim · model-written summary
Three years at twice ambient ozone reduced net carbon gain.
- Taxon
- sugar maple
Acer saccharumt0 - Treatment
- 2 x ambient atmospheric O(3) concentrationse0
- Outcome
- net carbon (C) gaine0
- Direction
- reducede0
- Comparator
- ambient atmospheric O(3) concentrationse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“2 x ambient atmospheric O(3) concentrations reduced net carbon (C) gain of the 160-year-old tree”
t0“sugar maple (Acer saccharum Marsh.)”
Claim · model-written summary
Ozone reduced nonstructural carbohydrate storage mainly in coarse roots.
- Taxon
- sugar mapleAcer saccharumt0
- Organ / stage
- coarse (woody) rootse0
- Treatment
- ozonet0
- Outcome
- C storage pools (total nonstructural carbohydrate, TNC)e0
- Direction
- reductione0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This reduction occurred in the C storage pools (total nonstructural carbohydrate, TNC), with most of the reduction occurring in coarse (woody) roots”
t0“Simulated root dynamics of a 160-year-old sugar maple (Acer saccharum Marsh.) tree with and without ozone exposure using the TREGRO model”
Claim · model-written summary
Three years of simulated ozone exposure left total fine root production and senescence unaffected.
- Taxon
- sugar mapleAcer saccharumt0
- Treatment
- simulated 3-year exposure to O(3)e0
- Outcome
- Total fine root production and senescencee0
- Direction
- unaffectede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Total fine root production and senescence were unaffected by the simulated 3-year exposure to O(3)”
t0“sugar maple (Acer saccharum Marsh.)”
Claim · model-written summary
Ten years of ozone exposure depleted coarse-root TNC pools.
- Taxon
- sugar mapleAcer saccharumt0
- Treatment
- simulated O(3) exposure period to 10 yearse0
- Outcome
- TNC pools of the coarse rootse0
- Direction
- depletede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“extending the simulated O(3) exposure period to 10 years depleted the TNC pools of the coarse roots and reduced total fine root production”
t0“sugar maple (Acer saccharum Marsh.)”
Claim · model-written summary
Ten years of ozone exposure reduced total fine root production.
- Taxon
- sugar mapleAcer saccharumt0
- Treatment
- simulated O(3) exposure period to 10 yearse0
- Outcome
- total fine root productione0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“extending the simulated O(3) exposure period to 10 years depleted the TNC pools of the coarse roots and reduced total fine root production”
t0“sugar maple (Acer saccharum Marsh.)”
Claim · model-written summary
The authors conclude modeling can aid evaluation of mature-tree belowground responses to pollution.
- Taxon
- sugar mapleAcer saccharumt0
- Outcome
- modeling can aid in evaluating the belowground responsee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“modeling can aid in evaluating the belowground response of mature forest trees to atmospheric pollution stress”
t0“sugar maple (Acer saccharum Marsh.)”
The same questions in other papers
ozone · quality: sugar starch · Acer saccharum (sugar maple)Results agree
1 paper in the same direction as this paper
- negative
ozone · molecular: metabolites · Acer saccharum (sugar maple)Results agree
2 papers in the same direction as this paper
- no effect
- no effect
ozone · quality: postharvest · Acer saccharum (sugar maple)Results agree
2 papers in the same direction as this paper
- no effect
- 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.