Water-stress-induced breakdown of carbon–water relations: indicators from diurnal FLUXNET patterns
Understanding of terrestrial carbon and water cycles is currently hampered by an uncertainty in how to capture the large variety of plant responses to drought. In FLUXNET, the global network of CO<sub>2</sub> and H<sub>2</sub>O flux observations, many sites do not uniform...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2018-04-01
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| Series: | Biogeosciences |
| Online Access: | https://www.biogeosciences.net/15/2433/2018/bg-15-2433-2018.pdf |
| _version_ | 1819194983251443712 |
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| author | J. A. Nelson N. Carvalhais N. Carvalhais M. Migliavacca M. Reichstein M. Reichstein M. Jung |
| author_facet | J. A. Nelson N. Carvalhais N. Carvalhais M. Migliavacca M. Reichstein M. Reichstein M. Jung |
| author_sort | J. A. Nelson |
| collection | DOAJ |
| description | Understanding
of terrestrial carbon and water cycles is currently hampered by an
uncertainty in how to capture the large variety of plant responses to
drought. In FLUXNET, the global network of CO<sub>2</sub> and H<sub>2</sub>O flux
observations, many sites do not uniformly report the ancillary variables
needed to study drought response physiology. To this end, we outline two
data-driven indicators based on diurnal energy, water, and carbon flux
patterns derived directly from the eddy covariance data and based on
theorized physiological responses to hydraulic and non-stomatal limitations.
Hydraulic limitations (i.e. intra-plant limitations on water movement) are
proxied using the relative diurnal centroid (<i>C</i><sub>ET</sub>*), which
measures the degree to which the flux of evapotranspiration (ET) is shifted
toward the morning. Non-stomatal limitations (e.g. inhibitions of biochemical
reactions, RuBisCO activity, and/or mesophyll conductance) are characterized
by the Diurnal Water–Carbon Index (DWCI), which measures the degree
of coupling between ET and gross primary productivity (GPP) within each day.
As a proof of concept we show the response of the metrics at six European
sites during the 2003 heat wave event, showing a varied response of morning
shifts and decoupling. Globally, we found indications of hydraulic
limitations in the form of significantly high frequencies of morning-shifted
days in dry/Mediterranean climates and savanna/evergreen plant functional
types (PFTs), whereas high frequencies of decoupling were dominated by dry
climates and grassland/savanna PFTs indicating a prevalence of non-stomatal
limitations in these ecosystems. Overall, both the diurnal centroid and DWCI
were associated with high net radiation and low latent energy typical of
drought. Using three water use efficiency (WUE) models, we found the mean
differences between expected and observed WUE to be −0.09 to
0.44 µmol mmol<sup>−1</sup> and −0.29 to −0.40 µmol mmol<sup>−1</sup> for decoupled
and morning-shifted days, respectively, compared to mean differences −1.41
to −1.42 µmol mmol<sup>−1</sup> in dry conditions, suggesting that
morning shifts/hydraulic responses are associated with an increase in WUE,
whereas decoupling/non-stomatal limitations are not. |
| first_indexed | 2024-12-23T02:05:32Z |
| format | Article |
| id | doaj.art-f9d2c62be63e4a108844cbe2a06fe026 |
| institution | Directory Open Access Journal |
| issn | 1726-4170 1726-4189 |
| language | English |
| last_indexed | 2024-12-23T02:05:32Z |
| publishDate | 2018-04-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Biogeosciences |
| spelling | doaj.art-f9d2c62be63e4a108844cbe2a06fe0262022-12-21T18:03:53ZengCopernicus PublicationsBiogeosciences1726-41701726-41892018-04-01152433244710.5194/bg-15-2433-2018Water-stress-induced breakdown of carbon–water relations: indicators from diurnal FLUXNET patternsJ. A. Nelson0N. Carvalhais1N. Carvalhais2M. Migliavacca3M. Reichstein4M. Reichstein5M. Jung6Department of Biogeochemical Integration, Max Planck Institute for Biogeochemistry, Jena, GermanyDepartment of Biogeochemical Integration, Max Planck Institute for Biogeochemistry, Jena, GermanyFaculdade de Ciências e Tecnologia, FCT, Universidade Nova de Lisboa, Lisbon, PortugalDepartment of Biogeochemical Integration, Max Planck Institute for Biogeochemistry, Jena, GermanyDepartment of Biogeochemical Integration, Max Planck Institute for Biogeochemistry, Jena, GermanyMichael Stifel Center Jena for Data-Driven and Simulation Science, Jena, GermanyDepartment of Biogeochemical Integration, Max Planck Institute for Biogeochemistry, Jena, GermanyUnderstanding of terrestrial carbon and water cycles is currently hampered by an uncertainty in how to capture the large variety of plant responses to drought. In FLUXNET, the global network of CO<sub>2</sub> and H<sub>2</sub>O flux observations, many sites do not uniformly report the ancillary variables needed to study drought response physiology. To this end, we outline two data-driven indicators based on diurnal energy, water, and carbon flux patterns derived directly from the eddy covariance data and based on theorized physiological responses to hydraulic and non-stomatal limitations. Hydraulic limitations (i.e. intra-plant limitations on water movement) are proxied using the relative diurnal centroid (<i>C</i><sub>ET</sub>*), which measures the degree to which the flux of evapotranspiration (ET) is shifted toward the morning. Non-stomatal limitations (e.g. inhibitions of biochemical reactions, RuBisCO activity, and/or mesophyll conductance) are characterized by the Diurnal Water–Carbon Index (DWCI), which measures the degree of coupling between ET and gross primary productivity (GPP) within each day. As a proof of concept we show the response of the metrics at six European sites during the 2003 heat wave event, showing a varied response of morning shifts and decoupling. Globally, we found indications of hydraulic limitations in the form of significantly high frequencies of morning-shifted days in dry/Mediterranean climates and savanna/evergreen plant functional types (PFTs), whereas high frequencies of decoupling were dominated by dry climates and grassland/savanna PFTs indicating a prevalence of non-stomatal limitations in these ecosystems. Overall, both the diurnal centroid and DWCI were associated with high net radiation and low latent energy typical of drought. Using three water use efficiency (WUE) models, we found the mean differences between expected and observed WUE to be −0.09 to 0.44 µmol mmol<sup>−1</sup> and −0.29 to −0.40 µmol mmol<sup>−1</sup> for decoupled and morning-shifted days, respectively, compared to mean differences −1.41 to −1.42 µmol mmol<sup>−1</sup> in dry conditions, suggesting that morning shifts/hydraulic responses are associated with an increase in WUE, whereas decoupling/non-stomatal limitations are not.https://www.biogeosciences.net/15/2433/2018/bg-15-2433-2018.pdf |
| spellingShingle | J. A. Nelson N. Carvalhais N. Carvalhais M. Migliavacca M. Reichstein M. Reichstein M. Jung Water-stress-induced breakdown of carbon–water relations: indicators from diurnal FLUXNET patterns Biogeosciences |
| title | Water-stress-induced breakdown of carbon–water relations: indicators from diurnal FLUXNET patterns |
| title_full | Water-stress-induced breakdown of carbon–water relations: indicators from diurnal FLUXNET patterns |
| title_fullStr | Water-stress-induced breakdown of carbon–water relations: indicators from diurnal FLUXNET patterns |
| title_full_unstemmed | Water-stress-induced breakdown of carbon–water relations: indicators from diurnal FLUXNET patterns |
| title_short | Water-stress-induced breakdown of carbon–water relations: indicators from diurnal FLUXNET patterns |
| title_sort | water stress induced breakdown of carbon water relations indicators from diurnal fluxnet patterns |
| url | https://www.biogeosciences.net/15/2433/2018/bg-15-2433-2018.pdf |
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