Abstract
Summary Plant responses to elevated atmospheric CO 2 have been characterized generally by stomatal closure and enhanced growth rates. These responses are being increasingly incorporated into global climate models that quantify interactions between the biosphere and atmosphere, altering climate predictions from simpler physically based models. However, current information on CO 2 responses has been gathered primarily from studies of crop and temperate forest species. In order to apply responses of vegetation to global predictions, CO 2 responses in other commonly occurring biomes must be studied. A Free Air CO 2 Enrichment (FACE) study is currently underway to examine plant responses to high CO 2 in a natural, undisturbed Mojave Desert ecosystem in Nevada, USA. Here we present findings from this study, and its companion glasshouse experiment, demonstrating that field‐grown Ephedra nevadensis and glasshouse‐grown Larrea tridentata responded to high CO 2 with reductions in the ratio of transpirational surface area to sapwood area (LSR) of 33% and 60%, respectively. Thus, leaf‐specific hydraulic conductivity increased and stomatal conductance remained constant or was increased under elevated CO 2 . Field‐grown Larrea did not show a reduced LSR under high CO 2 , and stomatal conductance was reduced in the high CO 2 treatment, although the effect was apparent only under conditions of unusually high soil moisture. Both findings suggest that the common paradigm of 20–50% reductions in stomatal conductance under high CO 2 may not be applicable to arid ecosystems under most conditions.
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Claims 6
Claim · model-written summary
High CO2 reduced leaf to sapwood area ratio by 33% in field grown Ephedra nevadensis.
- Taxon
- Ephedra nevadensis
Ephedra nevadensise0 - Treatment
- high CO 2e0
- Outcome
- ratio of transpirational surface area to sapwood area (LSR)e0
- Direction
- reductionse0
- Value
- 33%e0
- Setting
- field‐growne0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“field‐grown Ephedra nevadensis and glasshouse‐grown Larrea tridentata responded to high CO 2 with reductions in the ratio of transpirational surface area to sapwood area (LSR) of 33% and 60%, respectively”
Claim · model-written summary
High CO2 reduced leaf to sapwood area ratio by 60% in glasshouse grown Larrea tridentata.
- Taxon
- Larrea tridentata
Larrea tridentatae0 - Treatment
- high CO 2e0
- Outcome
- ratio of transpirational surface area to sapwood area (LSR)e0
- Direction
- reductionse0
- Value
- 60%e0
- Setting
- glasshouse‐growne0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“field‐grown Ephedra nevadensis and glasshouse‐grown Larrea tridentata responded to high CO 2 with reductions in the ratio of transpirational surface area to sapwood area (LSR) of 33% and 60%, respectively”
Claim · model-written summary
Leaf specific hydraulic conductivity increased under elevated CO2.
Not reportedTaxonComparator
Verbatim
e0“leaf‐specific hydraulic conductivity increased and stomatal conductance remained constant or was increased under elevated CO 2”
Claim · model-written summary
Stomatal conductance stayed constant or increased under elevated CO2 in the responsive shrubs.
Not reportedTaxonComparator
Verbatim
e0“stomatal conductance remained constant or was increased under elevated CO 2”
Claim · model-written summary
Field grown Larrea did not show reduced leaf to sapwood area ratio under high CO2.
LarreaNot reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Field‐grown Larrea did not show a reduced LSR under high CO 2”
Claim · model-written summary
High CO2 reduced stomatal conductance in field grown Larrea only with unusually high soil moisture.
- Treatment
- high CO 2 treatmente0
- Outcome
- stomatal conductancee0
- Direction
- reducede0
- Qualifier
- unusually high soil moisturee0
Not reportedTaxonComparator
Verbatim
e0“stomatal conductance was reduced in the high CO 2 treatment, although the effect was apparent only under conditions of unusually high soil moisture”