Abstract
ABSTRACT The growth rates of woody plants depend on both the rate of photosynthetic carbon gain and the availability of essential nutrients. Instantaneous carbon gain is known to increase in response to increasing atmospheric CO 2 concentration, but it is uncertain whether this will translate into increased growth in the longer term under nutrient‐limited conditions. An analytical model to address this question was developed by Comins & McMurtrie (1993, Ecological Applications 3, 666–681). Their model was further tested and analysed. Manipulation of various assumptions in the model revealed its key assumptions and allowed a more confident prediction of expected growth responses to CO 2 enrichment under nutrient‐limited conditions. The analysis indicated that conclusions about the CO 2 sensitivity of production were strongly influenced by assumptions about the relationship between foliar and heartwood nitrogen concentrations. With heartwood nitrogen concentration proportional to foliar nitrogen concentration, the model predicted a strong response of plant productivity to increasing CO 2 concentration, whereas with heartwood nitrogen concentration set constant, the model predicted only a very slight growth response to changing CO 2 concentration. On the other hand, predictions were only slightly affected by: (1) assumptions about the extent of nitrogen retranslocation out of senescing roots and foliage or wood during heartwood formation; (2) the effects of nitrogen status on specific leaf area or (3) leaf longevity; (4) carbon allocation between different plant parts; or (5) changes in the N:C ratio of organic matter sequestered in the passive pool of soil organic matter. Modification of the effect of foliar nitrogen concentration on the light utilization coefficient had only a small effect on the CO 2 sensitivity for pines. However, this conclusion was strongly dependent on the chosen relationship between single‐leaf photosynthesis and leaf nitrogen concentration. Overall, the analysis suggested that trees growing under nitrogen‐limited conditions can respond to increasing atmospheric CO 2 concentration with considerable increases in growth.
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Claims 10
Claim · model-written summary
Predicted CO2 sensitivity of production depended strongly on the assumed relationship between foliar and heartwood nitrogen.
- Taxon
- treese1
- Organ / stage
- foliar and heartwoode0
- Compound
- nitrogene0
- Outcome
- CO 2 sensitivity of productione0
Not reportedDirection
Verbatim
e0“conclusions about the CO 2 sensitivity of production were strongly influenced by assumptions about the relationship between foliar and heartwood nitrogen concentrations”
e1“trees growing under nitrogen‐limited conditions”
Claim · model-written summary
With proportional heartwood and foliar nitrogen, increasing CO2 strongly increased predicted productivity.
- Taxon
- treese1
- Treatment
- increasing CO 2 concentratione0
- Outcome
- plant productivitye0
- Qualifier
- heartwood nitrogen concentration proportional to foliar nitrogen concentratione0
Not reportedComparatorDirection
Verbatim
e0“With heartwood nitrogen concentration proportional to foliar nitrogen concentration, the model predicted a strong response of plant productivity to increasing CO 2 concentration”
e1“trees growing under nitrogen‐limited conditions”
Claim · model-written summary
With constant heartwood nitrogen, changing CO2 produced only a slight predicted growth response.
- Taxon
- treese1
- Treatment
- changing CO 2 concentratione0
- Outcome
- growth responsee0
- Qualifier
- heartwood nitrogen concentration set constante0
Not reportedComparatorDirection
Verbatim
e0“with heartwood nitrogen concentration set constant, the model predicted only a very slight growth response to changing CO 2 concentration”
e1“trees growing under nitrogen‐limited conditions”
Claim · model-written summary
Predictions were only slightly affected by assumptions about nitrogen retranslocation.
Not reportedDirection
Verbatim
e0“predictions were only slightly affected by: (1) assumptions about the extent of nitrogen retranslocation out of senescing roots and foliage or wood during heartwood formation”
e1“trees growing under nitrogen‐limited conditions”
Claim · model-written summary
Predictions were only slightly affected by assumed nitrogen effects on specific leaf area and leaf longevity.
Not reportedDirection
Verbatim
e0“(2) the effects of nitrogen status on specific leaf area or (3) leaf longevity”
e1“trees growing under nitrogen‐limited conditions”
Claim · model-written summary
Predictions were only slightly affected by carbon allocation among plant parts.
Not reportedDirection
Verbatim
e0“(4) carbon allocation between different plant parts”
e1“trees growing under nitrogen‐limited conditions”
Claim · model-written summary
Predictions were only slightly affected by changes in the N:C ratio of passive soil organic matter.
Not reportedDirection
Verbatim
e0“(5) changes in the N:C ratio of organic matter sequestered in the passive pool of soil organic matter”
e1“trees growing under nitrogen‐limited conditions”
Claim · model-written summary
Changing the foliar nitrogen effect on light utilization had only a small effect on pine CO2 sensitivity.
PinusNot reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Modification of the effect of foliar nitrogen concentration on the light utilization coefficient had only a small effect on the CO 2 sensitivity for pines”
Claim · model-written summary
The pine prediction depended strongly on the assumed relationship between leaf photosynthesis and leaf nitrogen.
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“this conclusion was strongly dependent on the chosen relationship between single‐leaf photosynthesis and leaf nitrogen concentration”
e1“CO 2 sensitivity for pines”
Claim · model-written summary
The analysis suggested substantial growth increases in nitrogen limited trees under rising atmospheric CO2.
- Taxon
- treese0
- Treatment
- increasing atmospheric CO 2 concentratione0
- Outcome
- growthe0
- Direction
- increasese0
- Qualifier
- nitrogen‐limited conditionse0
Not reportedComparator
Verbatim
e0“trees growing under nitrogen‐limited conditions can respond to increasing atmospheric CO 2 concentration with considerable increases in growth”
The same questions in other papers
co2 · yield · PinusPositive and negative results
2 papers in the same direction as this paper · 1 in the opposite direction
- no effect
- positive
- positive
co2 · growth · PinusPositive and negative results
6 papers in the same direction as this paper · 4 in the opposite direction
- no effect
- no effect
- no effect
7 papers more in this group
See all 11 papers →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.