Paper · 2023 · Global Change Biology

When do plant hydraulics matter in terrestrial biosphere modelling?

Athanasios Paschalis; Martin G. De Kauwe; Manon Sabot; et al.

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Open access · cc-by

Abstract

The ascent of water from the soil to the leaves of vascular plants, described by the study of plant hydraulics, regulates ecosystem responses to environmental forcing and recovery from stress periods. Several approaches to model plant hydraulics have been proposed. In this study, we introduce four different versions of plant hydraulics representations in the terrestrial biosphere model T&C to understand the significance of plant hydraulics to ecosystem functioning. We tested representations of plant hydraulics, investigating plant water capacitance, and long-term xylem damages following drought. The four models we tested were a combination of representations including or neglecting capacitance and including or neglecting xylem damage legacies. Using the models at six case studies spanning semiarid to tropical ecosystems, we quantify how plant xylem flow, plant water storage and long-term xylem damage can modulate overall water and carbon dynamics across multiple time scales. We show that as drought develops, models with plant hydraulics predict a slower onset of plant water stress, and a diurnal variability of water and carbon fluxes closer to observations. Plant water storage was found to be particularly important for the diurnal dynamics of water and carbon fluxes, with models that include plant water capacitance yielding better results. Models including permanent damage to conducting plant tissues show an additional significant drought legacy effect, limiting plant productivity during the recovery phase following major droughts. However, when considering ecosystem responses to the observed climate variability, plant hydraulic modules alone cannot significantly improve the overall model performance, even though they reproduce more realistic water and carbon dynamics. This opens new avenues for model development, explicitly linking plant hydraulics with additional ecosystem processes, such as plant phenology and improved carbon allocation algorithms.

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Claims 6

Method / resourceobservedoriginal resultpositivesimulated

Claim · model-written summary

Models with plant hydraulics predict a slower onset of plant water stress as drought develops.

Outcome
plant water stresse0
Direction
slower onsete0

Not reportedComparator

Verbatim

e0

“as drought develops, models with plant hydraulics predict a slower onset of plant water stress”

✓ located verbatim in the source · abstract, characters 1003–1097 · show in text ↑
Method / resourceobservedoriginal resultpositivesimulated

Claim · model-written summary

Models with plant hydraulics produce diurnal water and carbon flux variability closer to observations.

Outcome
diurnal variability of water and carbon fluxese0
Direction
closer to observationse0

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Verbatim

e0

“a diurnal variability of water and carbon fluxes closer to observations”

✓ located verbatim in the source · abstract, characters 1103–1174 · show in text ↑
Method / resourceobservedoriginal resultpositivesimulated

Claim · model-written summary

Including plant water capacitance improves modeled diurnal water and carbon flux dynamics.

Outcome
diurnal dynamics of water and carbon fluxese0
Direction
better resultse0

Not reportedComparator

Verbatim

e0

“Plant water storage was found to be particularly important for the diurnal dynamics of water and carbon fluxes, with models that include plant water capacitance yielding better results”

✓ located verbatim in the source · abstract, characters 1176–1360 · show in text ↑
Method / resourceobservedoriginal resultnegativesignificant (as stated)simulated

Claim · model-written summary

Representing permanent xylem damage produces a significant drought legacy effect that limits plant productivity during recovery.

Outcome
plant productivitye0
Direction
limitinge0

Not reportedComparator

Verbatim

e0

“Models including permanent damage to conducting plant tissues show an additional significant drought legacy effect, limiting plant productivity during the recovery phase following major droughts”

✓ located verbatim in the source · abstract, characters 1362–1556 · show in text ↑
Method / resourceobservedoriginal resultno effectnot significant (as stated)simulated

Claim · model-written summary

Plant hydraulic modules alone do not significantly improve overall model performance under observed climate variability.

Outcome
overall model performancee0
Direction
cannot significantly improvee0

Not reportedComparator

Verbatim

e0

“when considering ecosystem responses to the observed climate variability, plant hydraulic modules alone cannot significantly improve the overall model performance”

✓ located verbatim in the source · abstract, characters 1567–1729 · show in text ↑
Method / resourceobservedoriginal resultpositivesimulated

Claim · model-written summary

Plant hydraulic modules reproduce more realistic water and carbon dynamics.

Outcome
water and carbon dynamicse0
Direction
more realistice0

Not reportedComparator

Verbatim

e0

“they reproduce more realistic water and carbon dynamics”

✓ located verbatim in the source · abstract, characters 1743–1798 · show in text ↑