Abstract
The Bear Brook Watershed in Maine is a paired watershed system; one watershed has been acidified bimonthly with granular ammonium sulfate ((NH4)2SO4) since 1989. The adjacent watershed is used as a reference. This acid deposition treatment presents unique opportunities to look at the long term affects of acidification on vegetation. Acidic deposition continues to be a concern for the health of sugar maple (Acer saccharum Marsh.) in northern hardwood forests. Many studies show a connection between base cation depletion induced by acid deposition and sugar maple decline. In this text we review sugar maple ecology and their response to forest acidification, we investigate the response of sugar maple saplings to chronic N and S deposition, and we compare foliar nutrients of three size classes of sugar maple at BBWM. At the Bear Brook Watershed in Maine (BBWM), we examined the effects of artificially elevated nitrogen and sulfur deposition on sugar maple sapling foliar chemistry, growth, and photosynthetic capacity. We observed a 56% increase in Al and a 25% reduction in mean foliar Ca for sugar maple sapling foliage on the treated watershed compared to reference. Foliar N (+15%), P (+10%), and K (+15%) were significantly elevated in treated saplings. Saplings on the treated watershed had significantly lower carboxylation capacity (-24%), electron transport (-15%), and tri-phosphate utilization (-11%). Net photosynthesis (Anet) was not significantly different between watersheds, respiration was significantly lower in treated saplings, and growth trends and sapling distribution do not show any clear treatment effects. We conclude that saplings, though they show depressed levels of base cations and lower photosynthetic capacity, show little sign of physical decline after 17 years of elevated nitrogen and sulfur deposition. We also investigate the variation of foliar chemistry in sugar maple of three size classes at BBWM - seedlings, saplings, and mature trees. Results showed, independent of deposition levels, mature tree foliar chemistry was at consistently lower nutrient levels relative to juvenile trees, with the exception of higher foliar carbon. Levels of base cations have been declining in mature trees since 1998, along with declines in growth. Seedlings and saplings had comparable levels of most foliar elements, with the exception that seedlings have significantly higher calcium, aluminum, and zinc compared to saplings. Treated seedlings and saplings had significantly lower levels of foliar calcium and higher levels of nitrogen, phosphorus, and potassium compared to untreated juveniles. Differences between mature trees and juveniles were attributed to declines in mature trees across both watersheds, as well as contrasts in rooting, morphology, and stress exposure across size classes. A significant ice storm in 1998 may be responsible for changes in foliar chemistry and growth.
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Claims 20
Claim · model-written summary
Sapling foliar Al increased by 56% on the acidified watershed compared with reference.
- Taxon
- sugar maple
Acer saccharume0 - Organ / stage
- sapling foliagee1
- Treatment
- artificially elevated nitrogen and sulfur depositione0
- Outcome
- Ale1
- Direction
- increasee1
- Value
- 56%e1
- Comparator
- referencee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At the Bear Brook Watershed in Maine (BBWM), we examined the effects of artificially elevated nitrogen and sulfur deposition on sugar maple sapling foliar chemistry, growth, and photosynthetic capacity”
e1“We observed a 56% increase in Al and a 25% reduction in mean foliar Ca for sugar maple sapling foliage on the treated watershed compared to reference”
Claim · model-written summary
Sapling foliar Ca was reduced by 25% on the treated watershed compared with reference.
- Taxon
- sugar mapleAcer saccharume0
- Organ / stage
- sapling foliagee1
- Treatment
- artificially elevated nitrogen and sulfur depositione0
- Outcome
- mean foliar Cae1
- Direction
- reductione1
- Value
- 25%e1
- Comparator
- referencee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At the Bear Brook Watershed in Maine (BBWM), we examined the effects of artificially elevated nitrogen and sulfur deposition on sugar maple sapling foliar chemistry, growth, and photosynthetic capacity”
e1“We observed a 56% increase in Al and a 25% reduction in mean foliar Ca for sugar maple sapling foliage on the treated watershed compared to reference”
Claim · model-written summary
Foliar N was elevated by 15% in treated saplings, significantly.
- Taxon
- sugar mapleAcer saccharume0
- Treatment
- artificially elevated nitrogen and sulfur depositione0
- Outcome
- Foliar Ne2
- Direction
- elevatede2
- Value
- +15%e2
- Comparator
- referencee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At the Bear Brook Watershed in Maine (BBWM), we examined the effects of artificially elevated nitrogen and sulfur deposition on sugar maple sapling foliar chemistry, growth, and photosynthetic capacity”
e1“We observed a 56% increase in Al and a 25% reduction in mean foliar Ca for sugar maple sapling foliage on the treated watershed compared to reference”
e2“Foliar N (+15%), P (+10%), and K (+15%) were significantly elevated in treated saplings”
Claim · model-written summary
Foliar P was elevated by 10% in treated saplings, significantly.
- Taxon
- sugar mapleAcer saccharume0
- Treatment
- artificially elevated nitrogen and sulfur depositione0
- Outcome
- Pe2
- Direction
- elevatede2
- Value
- +10%e2
- Comparator
- referencee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At the Bear Brook Watershed in Maine (BBWM), we examined the effects of artificially elevated nitrogen and sulfur deposition on sugar maple sapling foliar chemistry, growth, and photosynthetic capacity”
e1“We observed a 56% increase in Al and a 25% reduction in mean foliar Ca for sugar maple sapling foliage on the treated watershed compared to reference”
e2“Foliar N (+15%), P (+10%), and K (+15%) were significantly elevated in treated saplings”
Claim · model-written summary
Foliar K was elevated by 15% in treated saplings, significantly.
- Taxon
- sugar mapleAcer saccharume0
- Treatment
- artificially elevated nitrogen and sulfur depositione0
- Outcome
- Ke2
- Direction
- elevatede2
- Value
- +15%e2
- Comparator
- referencee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At the Bear Brook Watershed in Maine (BBWM), we examined the effects of artificially elevated nitrogen and sulfur deposition on sugar maple sapling foliar chemistry, growth, and photosynthetic capacity”
e1“We observed a 56% increase in Al and a 25% reduction in mean foliar Ca for sugar maple sapling foliage on the treated watershed compared to reference”
e2“Foliar N (+15%), P (+10%), and K (+15%) were significantly elevated in treated saplings”
Claim · model-written summary
Carboxylation capacity was significantly lower (-24%) in treated saplings.
- Taxon
- sugar mapleAcer saccharume0
- Treatment
- artificially elevated nitrogen and sulfur depositione0
- Outcome
- carboxylation capacitye3
- Direction
- lowere3
- Value
- -24%e3
- Comparator
- referencee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At the Bear Brook Watershed in Maine (BBWM), we examined the effects of artificially elevated nitrogen and sulfur deposition on sugar maple sapling foliar chemistry, growth, and photosynthetic capacity”
e1“We observed a 56% increase in Al and a 25% reduction in mean foliar Ca for sugar maple sapling foliage on the treated watershed compared to reference”
e3“Saplings on the treated watershed had significantly lower carboxylation capacity (-24%), electron transport (-15%), and tri-phosphate utilization (-11%)”
Claim · model-written summary
Electron transport was significantly lower (-15%) in treated saplings.
- Taxon
- sugar mapleAcer saccharume0
- Treatment
- artificially elevated nitrogen and sulfur depositione0
- Outcome
- electron transporte3
- Direction
- lowere3
- Value
- -15%e3
- Comparator
- referencee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At the Bear Brook Watershed in Maine (BBWM), we examined the effects of artificially elevated nitrogen and sulfur deposition on sugar maple sapling foliar chemistry, growth, and photosynthetic capacity”
e1“We observed a 56% increase in Al and a 25% reduction in mean foliar Ca for sugar maple sapling foliage on the treated watershed compared to reference”
e3“Saplings on the treated watershed had significantly lower carboxylation capacity (-24%), electron transport (-15%), and tri-phosphate utilization (-11%)”
Claim · model-written summary
Tri-phosphate utilization was significantly lower (-11%) in treated saplings.
- Taxon
- sugar mapleAcer saccharume0
- Treatment
- artificially elevated nitrogen and sulfur depositione0
- Outcome
- tri-phosphate utilizatione3
- Direction
- lowere3
- Value
- -11%e3
- Comparator
- referencee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At the Bear Brook Watershed in Maine (BBWM), we examined the effects of artificially elevated nitrogen and sulfur deposition on sugar maple sapling foliar chemistry, growth, and photosynthetic capacity”
e1“We observed a 56% increase in Al and a 25% reduction in mean foliar Ca for sugar maple sapling foliage on the treated watershed compared to reference”
e3“Saplings on the treated watershed had significantly lower carboxylation capacity (-24%), electron transport (-15%), and tri-phosphate utilization (-11%)”
Claim · model-written summary
Net photosynthesis did not differ significantly between the two watersheds.
- Taxon
- sugar mapleAcer saccharume0
- Treatment
- artificially elevated nitrogen and sulfur depositione0
- Outcome
- Net photosynthesis (Anet)e4
- Direction
- no_changeinferrede4
- Comparator
- between watershedse4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At the Bear Brook Watershed in Maine (BBWM), we examined the effects of artificially elevated nitrogen and sulfur deposition on sugar maple sapling foliar chemistry, growth, and photosynthetic capacity”
e4“Net photosynthesis (Anet) was not significantly different between watersheds”
Claim · model-written summary
Respiration was significantly lower in treated saplings.
- Taxon
- sugar mapleAcer saccharume0
- Treatment
- artificially elevated nitrogen and sulfur depositione0
- Outcome
- respiratione4
- Direction
- lowere4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At the Bear Brook Watershed in Maine (BBWM), we examined the effects of artificially elevated nitrogen and sulfur deposition on sugar maple sapling foliar chemistry, growth, and photosynthetic capacity”
e4“respiration was significantly lower in treated saplings”
Claim · model-written summary
Growth trends and sapling distribution showed no clear treatment effect.
- Taxon
- sugar mapleAcer saccharume0
- Treatment
- artificially elevated nitrogen and sulfur depositione0
- Outcome
- growth trends and sapling distributione4
- Direction
- no_changeinferrede4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At the Bear Brook Watershed in Maine (BBWM), we examined the effects of artificially elevated nitrogen and sulfur deposition on sugar maple sapling foliar chemistry, growth, and photosynthetic capacity”
e4“growth trends and sapling distribution do not show any clear treatment effects”
Claim · model-written summary
The authors conclude that saplings show little sign of physical decline after 17 years of elevated N and S deposition.
- Taxon
- sugar mapleAcer saccharume0
- Outcome
- physical declinee5
- Qualifier
- after 17 years of elevated nitrogen and sulfur depositione5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At the Bear Brook Watershed in Maine (BBWM), we examined the effects of artificially elevated nitrogen and sulfur deposition on sugar maple sapling foliar chemistry, growth, and photosynthetic capacity”
e5“show little sign of physical decline after 17 years of elevated nitrogen and sulfur deposition”
Claim · model-written summary
Mature tree foliar nutrient levels were lower than in juvenile trees, except for higher foliar carbon.
- Taxon
- sugar mapleAcer saccharume0
- Organ / stage
- mature treee6
- Outcome
- nutrient levelse6
- Direction
- lowere6
- Qualifier
- with the exception of higher foliar carbone6
- Comparator
- juvenile treese6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At the Bear Brook Watershed in Maine (BBWM), we examined the effects of artificially elevated nitrogen and sulfur deposition on sugar maple sapling foliar chemistry, growth, and photosynthetic capacity”
e6“Results showed, independent of deposition levels, mature tree foliar chemistry was at consistently lower nutrient levels relative to juvenile trees, with the exception of higher foliar carbon”
Claim · model-written summary
Base cation levels have been declining in mature trees since 1998.
- Taxon
- sugar mapleAcer saccharume0
- Organ / stage
- mature treese7
- Outcome
- Levels of base cationse7
- Direction
- declininge7
- Qualifier
- since 1998e7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At the Bear Brook Watershed in Maine (BBWM), we examined the effects of artificially elevated nitrogen and sulfur deposition on sugar maple sapling foliar chemistry, growth, and photosynthetic capacity”
e7“Levels of base cations have been declining in mature trees since 1998, along with declines in growth”
Claim · model-written summary
Growth has declined in mature trees.
- Taxon
- sugar mapleAcer saccharume0
- Organ / stage
- mature treese7
- Outcome
- growthe7
- Direction
- declinese7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At the Bear Brook Watershed in Maine (BBWM), we examined the effects of artificially elevated nitrogen and sulfur deposition on sugar maple sapling foliar chemistry, growth, and photosynthetic capacity”
e7“Levels of base cations have been declining in mature trees since 1998, along with declines in growth”
Claim · model-written summary
Seedlings and saplings had comparable levels of most foliar elements.
- Taxon
- sugar mapleAcer saccharume0
- Outcome
- levels of most foliar elementse6
- Direction
- no_changeinferrede6
- Comparator
- saplingse6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At the Bear Brook Watershed in Maine (BBWM), we examined the effects of artificially elevated nitrogen and sulfur deposition on sugar maple sapling foliar chemistry, growth, and photosynthetic capacity”
e6“Seedlings and saplings had comparable levels of most foliar elements”
Claim · model-written summary
Seedlings had significantly higher calcium, aluminum and zinc than saplings.
- Taxon
- sugar mapleAcer saccharume0
- Organ / stage
- seedlingse7
- Outcome
- calcium, aluminum, and zince7
- Direction
- highere7
- Comparator
- saplingse7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At the Bear Brook Watershed in Maine (BBWM), we examined the effects of artificially elevated nitrogen and sulfur deposition on sugar maple sapling foliar chemistry, growth, and photosynthetic capacity”
e7“seedlings have significantly higher calcium, aluminum, and zinc compared to saplings”
Claim · model-written summary
Foliar calcium was significantly lower in treated seedlings and saplings than in untreated juveniles.
- Taxon
- sugar mapleAcer saccharume0
- Organ / stage
- seedlings and saplingse5
- Treatment
- artificially elevated nitrogen and sulfur depositione0
- Outcome
- foliar calciume5
- Direction
- lowere5
- Comparator
- untreated juvenilese5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At the Bear Brook Watershed in Maine (BBWM), we examined the effects of artificially elevated nitrogen and sulfur deposition on sugar maple sapling foliar chemistry, growth, and photosynthetic capacity”
e5“Treated seedlings and saplings had significantly lower levels of foliar calcium and higher levels of nitrogen, phosphorus, and potassium compared to untreated juveniles”
Claim · model-written summary
Foliar nitrogen, phosphorus and potassium were significantly higher in treated seedlings and saplings than in untreated juveniles.
- Taxon
- sugar mapleAcer saccharume0
- Organ / stage
- seedlings and saplingse5
- Treatment
- artificially elevated nitrogen and sulfur depositione0
- Outcome
- nitrogen, phosphorus, and potassiume5
- Direction
- highere5
- Comparator
- untreated juvenilese5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At the Bear Brook Watershed in Maine (BBWM), we examined the effects of artificially elevated nitrogen and sulfur deposition on sugar maple sapling foliar chemistry, growth, and photosynthetic capacity”
e5“Treated seedlings and saplings had significantly lower levels of foliar calcium and higher levels of nitrogen, phosphorus, and potassium compared to untreated juveniles”
Claim · model-written summary
The authors attribute differences between mature trees and juveniles to declines in mature trees and to contrasts in rooting, morphology and stress exposure.
- Taxon
- sugar mapleAcer saccharume0
- Outcome
- Differences between mature trees and juvenilese4
- Qualifier
- contrasts in rooting, morphology, and stress exposure across size classese4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At the Bear Brook Watershed in Maine (BBWM), we examined the effects of artificially elevated nitrogen and sulfur deposition on sugar maple sapling foliar chemistry, growth, and photosynthetic capacity”
e4“Differences between mature trees and juveniles were attributed to declines in mature trees across both watersheds, as well as contrasts in rooting, morphology, and stress exposure across size classes”
The same questions in other papers
nitrogen · growth · Acer saccharum (sugar maple)Positive and negative results
1 paper in the same direction as this paper · 1 in the opposite direction
- positive
- no effect
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.