Abstract
1 Ecological and physiological characteristics of vascular plants may facilitate or constrain hydraulic lift. Studies of hydraulic lift typically include only one or few species, but in species-rich ecosystems a larger number of representative species needs to be studied. 2 Measurements of sap flow in tap roots, lateral roots and stems, as well as stable isotope labelling techniques were used to determine the occurrence and relative magnitude of hydraulic lift in several individuals of nine co-occurring Brazilian savanna (Cerrado) tree species differing in life-history traits, and to assess physical and biological determinants of this process at the tree and ecosystem level. 3 The occurrence of reverse sap flow observed in deciduous and brevideciduous species during the dry season was consistent with hydraulic lift. The evergreen species did not exhibit reverse flow. Consistent with their ability to carry out hydraulic lift, the brevideciduous and deciduous species had both shallow and tap roots (dimorphic root systems), whereas the evergreen species had mostly deep roots (monomorphic root systems). 4 In the deciduous and brevideciduous species, the contribution of tap roots to transpiration increased substantially as the dry season progressed. Seasonal changes in the contribution of tap roots to transpiration were not observed in the evergreen species. 5 There was an inverse relationship between rates of reverse sap flow and seasonal loss of hydraulic conductivity in lateral roots, suggesting that hydraulic lift in Cerrado woody plants may help maintain the functionality of the lateral roots in exploring dry and nutrient rich superficial soil layers without directly enhancing the amount of water uptake. 6 Reverse sap flow in lateral roots of the deciduous and brevideciduous species increased asymptotically as the driving force for water movement from roots to the soil increased. This nonlinear relationship implies that additional sinks for water such as nocturnal transpiration and refilling of internal water storage tissues may compete for internal water resources during the dry season. 7 There appears to be a trade-off between greater year-round access to nutrients in the upper soil layers (deciduous and brevideciduous species) and a greater access to deep and more reliable water sources during the dry season (evergreen species), which has implications for whole-ecosystem water, carbon and nutrient balance in Neotropical savannas.
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Claims 16
Claim · model-written summary
Deciduous species exhibited dry-season reverse sap flow consistent with hydraulic lift.
- Taxon
- Neotropical savanna treest0
- Material
- deciduouse0
- Outcome
- occurrence of reverse sap flowe0
- Qualifier
- during the dry seasone0
Not reportedDirection
Verbatim
e0“The occurrence of reverse sap flow observed in deciduous and brevideciduous species during the dry season was consistent with hydraulic lift.”
t0“Neotropical savanna trees”
Claim · model-written summary
Brevi-deciduous species exhibited dry-season reverse sap flow consistent with hydraulic lift.
- Taxon
- Neotropical savanna treest0
- Material
- brevideciduouse0
- Outcome
- occurrence of reverse sap flowe0
- Qualifier
- during the dry seasone0
Not reportedDirection
Verbatim
e0“The occurrence of reverse sap flow observed in deciduous and brevideciduous species during the dry season was consistent with hydraulic lift.”
t0“Neotropical savanna trees”
Claim · model-written summary
Evergreen species did not exhibit reverse flow.
Not reportedDirection
Verbatim
e0“The evergreen species did not exhibit reverse flow.”
t0“Neotropical savanna trees”
Claim · model-written summary
Brevi-deciduous species had dimorphic shallow and tap-root systems.
- Taxon
- Neotropical savanna treest0
- Material
- brevideciduouse0
- Outcome
- both shallow and tap roots (dimorphic root systems)e0
Not reportedDirection
Verbatim
e0“the brevideciduous and deciduous species had both shallow and tap roots (dimorphic root systems), whereas the evergreen species had mostly deep roots (monomorphic root systems).”
t0“Neotropical savanna trees”
Claim · model-written summary
Deciduous species had dimorphic shallow and tap-root systems.
- Taxon
- Neotropical savanna treest0
- Material
- deciduouse0
- Outcome
- both shallow and tap roots (dimorphic root systems)e0
Not reportedDirection
Verbatim
e0“the brevideciduous and deciduous species had both shallow and tap roots (dimorphic root systems), whereas the evergreen species had mostly deep roots (monomorphic root systems).”
t0“Neotropical savanna trees”
Claim · model-written summary
Evergreen species had mostly deep monomorphic root systems.
- Taxon
- Neotropical savanna treest0
- Material
- evergreen speciese0
- Outcome
- mostly deep roots (monomorphic root systems)e0
Not reportedDirection
Verbatim
e0“whereas the evergreen species had mostly deep roots (monomorphic root systems).”
t0“Neotropical savanna trees”
Claim · model-written summary
Tap-root contribution to transpiration increased as the dry season progressed in deciduous species.
Verbatim
e0“In the deciduous and brevideciduous species, the contribution of tap roots to transpiration increased substantially as the dry season progressed.”
t0“Neotropical savanna trees”
Claim · model-written summary
Tap-root contribution to transpiration increased as the dry season progressed in brevi-deciduous species.
Verbatim
e0“In the deciduous and brevideciduous species, the contribution of tap roots to transpiration increased substantially as the dry season progressed.”
t0“Neotropical savanna trees”
Claim · model-written summary
Evergreen species showed no seasonal changes in tap-root contribution to transpiration.
Verbatim
e0“Seasonal changes in the contribution of tap roots to transpiration were not observed in the evergreen species.”
t0“Neotropical savanna trees”
Claim · model-written summary
Reverse sap-flow rates were inversely related to seasonal loss of lateral-root hydraulic conductivity.
Verbatim
e0“There was an inverse relationship between rates of reverse sap flow and seasonal loss of hydraulic conductivity in lateral roots”
t0“Neotropical savanna trees”
Claim · model-written summary
Hydraulic lift may maintain lateral-root functionality in dry nutrient-rich superficial soil without directly increasing water uptake.
Verbatim
e0“suggesting that hydraulic lift in Cerrado woody plants may help maintain the functionality of the lateral roots in exploring dry and nutrient rich superficial soil layers without directly enhancing the amount of water uptake.”
Claim · model-written summary
Deciduous lateral-root reverse sap flow increased asymptotically with the driving force for root-to-soil water movement.
Verbatim
e0“Reverse sap flow in lateral roots of the deciduous and brevideciduous species increased asymptotically as the driving force for water movement from roots to the soil increased.”
t0“Neotropical savanna trees”
Claim · model-written summary
Brevi-deciduous lateral-root reverse sap flow increased asymptotically with the driving force for root-to-soil water movement.
Verbatim
e0“Reverse sap flow in lateral roots of the deciduous and brevideciduous species increased asymptotically as the driving force for water movement from roots to the soil increased.”
t0“Neotropical savanna trees”
Claim · model-written summary
The nonlinear relationship implies nocturnal transpiration and storage refilling may compete for internal water during the dry season.
Verbatim
e0“This nonlinear relationship implies that additional sinks for water such as nocturnal transpiration and refilling of internal water storage tissues may compete for internal water resources during the dry season.”
t0“Neotropical savanna trees”
Claim · model-written summary
The authors infer a trade-off between upper-soil nutrient access by deciduous species and reliable deep-water access by evergreens.
Verbatim
e0“There appears to be a trade-off between greater year-round access to nutrients in the upper soil layers (deciduous and brevideciduous species) and a greater access to deep and more reliable water sources during the dry season (evergreen species)”
t0“Neotropical savanna trees”
Claim · model-written summary
The authors infer a trade-off between upper-soil nutrient access by brevi-deciduous species and reliable deep-water access by evergreens.
Verbatim
e0“There appears to be a trade-off between greater year-round access to nutrients in the upper soil layers (deciduous and brevideciduous species) and a greater access to deep and more reliable water sources during the dry season (evergreen species)”
t0“Neotropical savanna trees”