Abstract
Elevated CO₂ increases intrinsic water use efficiency (WUE(i) ) of forests, but the magnitude of this effect and its interaction with climate is still poorly understood. We combined tree ring analysis with isotope measurements at three Free Air CO₂ Enrichment (FACE, POP-EUROFACE, in Italy; Duke FACE in North Carolina and ORNL in Tennessee, USA) sites, to cover the entire life of the trees. We used δ¹³C to assess carbon isotope discrimination and changes in water-use efficiency, while direct CO₂ effects on stomatal conductance were explored using δ¹⁸O as a proxy. Across all the sites, elevated CO₂ increased ¹³C-derived water-use efficiency on average by 73% for Liquidambar styraciflua, 77% for Pinus taeda and 75% for Populus sp., but through different ecophysiological mechanisms. Our findings provide a robust means of predicting water-use efficiency responses from a variety of tree species exposed to variable environmental conditions over time, and species-specific relationships that can help modelling elevated CO₂ and climate impacts on forest productivity, carbon and water balances.
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Claims 3
Claim · model-written summary
Liquidambar styraciflua had increased carbon-derived water-use efficiency under elevated CO2 by 73%.
- Taxon
- Liquidambar styraciflua
Liquidambar styracifluae0 - Treatment
- elevated CO₂e0
- Outcome
- ¹³C-derived water-use efficiencye0
- Direction
- increasede0
- Value
- 73%e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Across all the sites, elevated CO₂ increased ¹³C-derived water-use efficiency on average by 73% for Liquidambar styraciflua, 77% for Pinus taeda and 75% for Populus sp.”
Claim · model-written summary
Pinus taeda had increased carbon-derived water-use efficiency under elevated CO2 by 77%.
- Taxon
- Pinus taeda
Pinus taedae0 - Treatment
- elevated CO₂e0
- Outcome
- ¹³C-derived water-use efficiencye0
- Direction
- increasede0
- Value
- 77%e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Across all the sites, elevated CO₂ increased ¹³C-derived water-use efficiency on average by 73% for Liquidambar styraciflua, 77% for Pinus taeda and 75% for Populus sp.”
Claim · model-written summary
Populus sp. had increased carbon-derived water-use efficiency under elevated CO2 by 75%.
PopulusNot reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Across all the sites, elevated CO₂ increased ¹³C-derived water-use efficiency on average by 73% for Liquidambar styraciflua, 77% for Pinus taeda and 75% for Populus sp.”
The same questions in other papers
co2 · physiology: water · Populus (poplar)Positive and negative results
1 paper in the same direction as this paper · 1 in the opposite direction
- no effect
- positive
co2 · physiology: water · Pinus taeda (loblolly pine)Positive and negative results
2 in the opposite direction · 1 reporting no difference from an alternative
- no effect
- negative
- no effect
co2 · physiology: water · Liquidambar styraciflua (sweet gum)Results agree
1 paper in the same direction as this paper
- positive
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.