Abstract
The gas exchange of an oak stand in the southeastern forest steppe was examined under variable moisture availability and ambient temperature. For several years the CO2 exchange was measured concurrently on leafy shoots and nonphotosynthesizing organs (trunks, branches, and roots) of oak trees (Quercus robur L.). The root respiration was found to decrease upon moisture limitation. The trunk respiration was promoted by the increase in moisture deficiency until the predawn leaf water potential (PLWP) reduced to −1.5 MPa, and respiration declined gradually upon further reduction in moisture availability. The proportion between net and gross primary productivities (NPP/GPP) also depended on moisture availability. The NPP/GPP ratio was 0.49 under optimal conditions at PLWP of −0.5 MPa, but it approached zero when PLWP lowered to −1.5 MPa. Upon drought conditions, which are typical of southeastern steppe in the second half of summer, the oak stand lost its CO2 sink capacity and became the CO2 source.
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Claims 7
Claim · model-written summary
Root respiration of oak decreased under moisture limitation
- Taxon
- Quercus robur L.
Quercus robure2 - Treatment
- moisture limitatione3
- Outcome
- root respiratione3
- Direction
- decreasee3
- Setting
- southeastern forest steppee1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“The gas exchange of an oak stand in the southeastern forest steppe was examined under variable moisture availability and ambient temperature”
e2“oak trees (Quercus robur L.)”
e3“The root respiration was found to decrease upon moisture limitation”
Claim · model-written summary
Trunk respiration of oak increased with moisture deficiency until predawn leaf water potential fell to −1.5 MPa
- Taxon
- Quercus robur L.Quercus robure2
- Treatment
- moisture deficiencye4
- Outcome
- trunk respiratione4
- Direction
- promotede4
- Qualifier
- predawn leaf water potential (PLWP) reduced to −1.5 MPae4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e2“oak trees (Quercus robur L.)”
e4“The trunk respiration was promoted by the increase in moisture deficiency until the predawn leaf water potential (PLWP) reduced to −1.5 MPa”
Claim · model-written summary
Trunk respiration declined gradually with further reduction in moisture availability beyond −1.5 MPa
- Taxon
- Quercus robur L.Quercus robure2
- Treatment
- further reduction in moisture availabilitye5
- Direction
- declined graduallye5
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e2“oak trees (Quercus robur L.)”
e4“The trunk respiration was promoted by the increase in moisture deficiency until the predawn leaf water potential (PLWP) reduced to −1.5 MPa”
e5“respiration declined gradually upon further reduction in moisture availability”
Claim · model-written summary
NPP/GPP ratio of the oak stand was 0.49 under optimal conditions at PLWP of −0.5 MPa
- Taxon
- Quercus robur L.Quercus robure2
- Outcome
- NPP/GPP ratioe7
- Value
- 0.49e7
- Qualifier
- under optimal conditions at PLWP of −0.5 MPae7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e2“oak trees (Quercus robur L.)”
e7“The NPP/GPP ratio was 0.49 under optimal conditions at PLWP of −0.5 MPa, but it approached zero when PLWP lowered to −1.5 MPa”
Claim · model-written summary
NPP/GPP ratio depended on moisture availability
- Taxon
- Quercus robur L.Quercus robure2
- Treatment
- moisture availabilitye6
- Outcome
- NPP/GPPe6
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e2“oak trees (Quercus robur L.)”
e6“The proportion between net and gross primary productivities (NPP/GPP) also depended on moisture availability”
Claim · model-written summary
NPP/GPP ratio approached zero when PLWP was lowered to −1.5 MPa
- Taxon
- Quercus robur L.Quercus robure2
- Treatment
- PLWP lowered to −1.5 MPae7
- Outcome
- NPP/GPP ratioe7
- Direction
- approached zeroe7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e2“oak trees (Quercus robur L.)”
e7“The NPP/GPP ratio was 0.49 under optimal conditions at PLWP of −0.5 MPa, but it approached zero when PLWP lowered to −1.5 MPa”
Claim · model-written summary
Under drought the oak stand lost its CO2 sink capacity and became a CO2 source
- Taxon
- Quercus robur L.Quercus robure2
- Treatment
- drought conditionse0
- Outcome
- CO2 sink capacitye0
- Direction
- loste0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e2“oak trees (Quercus robur L.)”
e0“Upon drought conditions, which are typical of southeastern steppe in the second half of summer, the oak stand lost its CO2 sink capacity and became the CO2 source”