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| Titel |
Eddy covariance measurements of net C exchange in the CAM bioenergy crop,
\textit{Agave tequiliana} |
| VerfasserIn |
Nick A. Owen, Órlaith Ní Choncubhair, Jamie Males, José Ignacio Del Real Laborde, Ramón Rubio-Cortés, Howard Griffiths, Gary Lanigan |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250135785
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| Publikation (Nr.) |
 EGU/EGU2016-16690.pdf |
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| Zusammenfassung |
| Bioenergy crop cultivation may focus more on low grade and marginal lands in order to avoid
competition with food production for land and water resources. However, in many
regions, this would require improvements in plant water-use efficiency that are
beyond the physiological capacity of most C3 and C4 bioenergy crop candidates.
Crassulacean acid metabolism (CAM) plants, such as Agave tequiliana, can combine high
above-ground productivity with as little as 20% of the water demand of C3 and
C4 crops. This is achieved through temporal separation of carboxylase activities,
with stomata opening at night to allow gas exchange and minimise transpirational
losses.
Previous studies have employed ‘bottom-up’ methodologies to investigate carbon (C)
accumulation and productivity in Agave, by scaling leaf-level gas exchange and titratable
acidity (TA) with leaf area index or maximum productivity. We used the eddy covariance
(EC) technique to quantify ecosystem-scale gas exchange over an Agave plantation in Mexico
(‘top-down’ approach). Measurements were made over 252 days, including the
transition from wet to dry periods. Results were cross-validated against diel changes in
titratable acidity, leaf-unfurling rates, energy exchange fluxes and reported biomass
yields.
Net ecosystem exchange of CO2 displayed a CAM rhythm that alternated from a net C
sink at night to a net C source during the day and partitioned canopy fluxes (gross C
assimilation, FA,EC) showed a characteristic four-phase CO2 exchange pattern. The
projected ecosystem C balance indicated that the site was a net sink of -333 ± 24 g C m−2
y−1, comprising cumulative soil respiration of 692 ± 7 g C m−2 y−1 and FA,EC of
-1025 ± 25 g C m−2 y−1. EC-estimated biomass yield was 20.1 Mg ha−1 y−1.
Average integrated daily FA,EC was -234 ± 5 mmol CO2 m−2 d−1 and persisted
almost unchanged after 70 days of drought conditions. Our results suggest that the
carbon acquisition strategy of drought avoidance employed by Agave and other
CAM plants could offer significant yield advantages over conventional arid and
semi-arid C3 and C4 bioenergy crops. Furthermore, their capacity for high productivity
on marginal land and drought resilience suggest that CAM plants could play an
important role in addressing conflicting land and water resource allocation issues. |
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