Abstract
Abstract Changes in evapotranspiration ( ET ) from terrestrial ecosystems affect their water yield ( WY ), with considerable ecological and economic consequences. Increases in surface runoff observed over the past century have been attributed to increasing atmospheric CO 2 concentrations resulting in reduced ET by terrestrial ecosystems. Here, we evaluate the water balance of a Pinus taeda (L.) forest with a broadleaf component that was exposed to atmospheric [CO 2 ] enrichment (ECO 2 ; +200 ppm) for over 17 years and fertilization for 6 years, monitored with hundreds of environmental and sap flux sensors on a half‐hourly basis. These measurements were synthesized using a one‐dimensional Richard's equation model to evaluate treatment differences in transpiration ( T ), evaporation ( E ), ET , and WY . We found that ECO 2 did not create significant differences in stand T, ET , or WY under either native or enhanced soil fertility, despite a 20% and 13% increase in leaf area index, respectively. While T , ET , and WY responded to fertilization, this response was weak (<3% of mean annual precipitation). Likewise, while E responded to ECO 2 in the first 7 years of the study, this effect was of negligible magnitude (<1% mean annual precipitation). Given the global range of conifers similar to P. taeda , our results imply that recent observations of increased global streamflow cannot be attributed to decreases in ET across all ecosystems, demonstrating a great need for model–data synthesis activities to incorporate our current understanding of terrestrial vegetation in global water cycle models.
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Claims 6
Claim · model-written summary
Elevated CO2 did not produce significant differences in stand transpiration under either fertility condition.
- Taxon
- Pinus taeda
Pinus taedae1 - Treatment
- ECO 2e0
- Outcome
- stand Te0
- Direction
- did not create significant differencese0
- Comparator
- native or enhanced soil fertilitye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ECO 2 did not create significant differences in stand T, ET , or WY under either native or enhanced soil fertility”
t0“Evapotranspiration and water yield of a pine‐broadleaf forest are not altered by long‐term atmospheric [CO2] enrichment under native or enhanced soil fertility”
e1“Pinus taeda (L.) forest”
Claim · model-written summary
Elevated CO2 did not produce significant differences in evapotranspiration under either fertility condition.
- Taxon
- Pinus taedaPinus taedae1
- Treatment
- ECO 2e0
- Outcome
- ETe0
- Direction
- did not create significant differencese0
- Comparator
- native or enhanced soil fertilitye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ECO 2 did not create significant differences in stand T, ET , or WY under either native or enhanced soil fertility”
t0“Evapotranspiration and water yield of a pine‐broadleaf forest are not altered by long‐term atmospheric [CO2] enrichment under native or enhanced soil fertility”
e1“Pinus taeda (L.) forest”
Claim · model-written summary
Elevated CO2 did not produce significant differences in water yield under either fertility condition.
- Taxon
- Pinus taedaPinus taedae1
- Treatment
- ECO 2e0
- Outcome
- WYe0
- Direction
- did not create significant differencese0
- Comparator
- native or enhanced soil fertilitye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ECO 2 did not create significant differences in stand T, ET , or WY under either native or enhanced soil fertility”
t0“Evapotranspiration and water yield of a pine‐broadleaf forest are not altered by long‐term atmospheric [CO2] enrichment under native or enhanced soil fertility”
e1“Pinus taeda (L.) forest”
Claim · model-written summary
Leaf area index increased by 20% and 13% under native and enhanced fertility, respectively.
- Taxon
- Pinus taedaPinus taedae1
- Treatment
- atmospheric [CO2] enrichmentt0
- Outcome
- leaf area indexe0
- Direction
- increasee0
- Value
- 20% and 13%e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“despite a 20% and 13% increase in leaf area index, respectively”
t0“Evapotranspiration and water yield of a pine‐broadleaf forest are not altered by long‐term atmospheric [CO2] enrichment under native or enhanced soil fertility”
e1“Pinus taeda (L.) forest”
Claim · model-written summary
Fertilization had a weak response in transpiration, evapotranspiration and water yield, less than 3% of mean annual precipitation.
- Taxon
- Pinus taedaPinus taedae1
- Treatment
- fertilizatione0
- Outcome
- T , ET , and WYe0
- Value
- <3% of mean annual precipitatione0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“While T , ET , and WY responded to fertilization, this response was weak (<3% of mean annual precipitation)”
t0“Evapotranspiration and water yield of a pine‐broadleaf forest are not altered by long‐term atmospheric [CO2] enrichment under native or enhanced soil fertility”
e1“Pinus taeda (L.) forest”
Claim · model-written summary
Evaporation responded to elevated CO2 during the first seven years, by less than 1% of mean annual precipitation.
- Taxon
- Pinus taedaPinus taedae1
- Treatment
- ECO 2e0
- Outcome
- Ee0
- Value
- <1% mean annual precipitatione0
- Qualifier
- first 7 years of the studye0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“while E responded to ECO 2 in the first 7 years of the study, this effect was of negligible magnitude (<1% mean annual precipitation)”
t0“Evapotranspiration and water yield of a pine‐broadleaf forest are not altered by long‐term atmospheric [CO2] enrichment under native or enhanced soil fertility”
e1“Pinus taeda (L.) forest”
The same questions in other papers
co2 · growth · Pinus taeda (loblolly pine)Results differ
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- positive
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co2 · yield · Pinus taeda (loblolly pine)Positive and negative results
2 papers in the same direction as this paper · 7 reporting no difference from an alternative
- positive
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See all 10 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.