title: Eddy covariance captures four-phase crassulacean acid metabolism (CAM) gas exchange signature in Agave.
abstract: Mass and energy fluxes were measured over a field of Agave tequilana in Mexico using eddy covariance (EC) methodology. Data were gathered over 252 d, including the transition from wet to dry periods. Net ecosystem exchanges (FN,EC ) displayed a crassulacean acid metabolism (CAM) rhythm that alternated from CO2 sink at night to CO2 source during the day, and partitioned canopy fluxes (FA,EC ) showed a characteristic four-phase CO2 exchange pattern. Results were cross-validated against diel changes in titratable acidity, leaf-unfurling rates, energy exchange fluxes and reported biomass yields. Projected carbon balance (g C m(-2)  year(-1) , mean ± 95% confidence interval) indicated the site was a net sink of -333 ± 24, of which contributions from soil respiration were +692 ± 7, and FA,EC was -1025 ± 25. EC estimated biomass yield was 20.1 Mg (dry) ha(-1)  year(-1) . Average integrated daily FA,EC was -234 ± 5 mmol CO2  m(-2)  d(-1) and persisted almost unchanged after 70 d of drought conditions. Regression analyses were performed on the EC data to identify the best environmental predictors of FA . Results suggest that the carbon acquisition strategy of Agave offers productivity and drought resilience advantages over conventional semi-arid C3 and C4 bioenergy candidates.
authors.affiliation: Department of Plant Sciences, University of Cambridge, Cambridge, UK, CB2 3EA.
authors.forename: Nick A
authors.initials: NA
authors.lastname: Owen
authors.affiliation: Teagasc Environmental Research Centre, Johnstown Castle, County Wexford, Ireland.
authors.forename: Órlaith Ní
authors.initials: ÓN
authors.lastname: Choncubhair
authors.affiliation: Department of Plant Sciences, University of Cambridge, Cambridge, UK, CB2 3EA.
authors.forename: Jamie
authors.initials: J
authors.lastname: Males
authors.affiliation: Rancho el Indio, Tequila Sauza, S. de R.L. de C.V., Tequila, Jalisco, Mexico.
authors.forename: José Ignacio
authors.initials: JI
authors.lastname: Del Real Laborde
authors.affiliation: Rancho el Indio, Tequila Sauza, S. de R.L. de C.V., Tequila, Jalisco, Mexico.
authors.forename: Ramón
authors.initials: R
authors.lastname: Rubio-Cortés
authors.affiliation: Department of Plant Sciences, University of Cambridge, Cambridge, UK, CB2 3EA.
authors.forename: Howard
authors.initials: H
authors.lastname: Griffiths
authors.affiliation: Teagasc Environmental Research Centre, Johnstown Castle, County Wexford, Ireland.
authors.forename: Gary
authors.initials: G
authors.lastname: Lanigan
mesh_terms: D000143:Acids / Q000378:metabolism*; D027882:Agave / Q000378:metabolism*; D018533:Biomass; D002244:Carbon / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism; D017753:Ecosystem; D005740:Gases / Q000378:metabolism*; D008954:Models, Biological; D018515:Plant Leaves / Q000378:metabolism; D012044:Regression Analysis; D015203:Reproducibility of Results; D012119:Respiration; D012987:Soil; D013057:Spectrum Analysis; D013816:Thermodynamics; D014867:Water
chemical_list: D000143:Acids; D005740:Gases; D012987:Soil; D014867:Water; D002245:Carbon Dioxide; D002244:Carbon
keywords: Agave tequilana; CAM; bioenergy; biomass; climate change adaptation; crassulacean acid metabolism; ecophysiology; eddy covariance; eddy flux; renewable energy