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| Titel |
Water use efficiency and functional traits of a semiarid shrubland |
| VerfasserIn |
Oscar Perez-Priego, Ana Lopez-Ballesteros, Enrique P. Sánchez-Cañete, Penelope Serrano-Ortíz, Arnaud Carrara, Agustí Palomares-Palacio, Cecilio Oyonarte, Francisco Domingo, Andrew S. Kowalski |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250071938
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| Zusammenfassung |
| In semiarid climates, water is the fundamental factor determining ecosystem productivity
and thereby the capacity for carbon sequestration. Increased water use efficiency
(WUE), the ratio of carbon dioxide assimilation (canopy photosynthesis, Pc) to
water transpired (canopy evaporation, Ec), is assumed to be an adaptive strategy for
sclerophyll shrublands to improve productivity and stress resistance in water-limited
environments. However, the real complexity of WUE lies in its dependence on both plant
physiological traits (e.g. stomatal resistance, photosynthetic capacity, leaf chemical
composition, structure) and on environmental conditions (e.g. atmospheric CO2
concentration, vapour pressure deficit, temperature, light, soil water availability).
We used a transient-state closed canopy-chamber to characterise CO2 and water
vapour exchanges at the whole plant scale under different environmental conditions
and phenological stages. Diurnal and seasonal variations in Pc, Ec and WUE were
explained by both physiological and environmental variables. All species showed
symmetric patterns in both Pc and Ec when not water limited, but asymmetry during
summer drought when leaf water potential was low. During drought, grasses (Festuca
sp.) showed a marked decline in functioning (Pc and Ec), whereas shrubs (Genista
sp., Hormathophylla sp.) maintained spring-like assimilation rates all morning
until stomatal controls shut down gas exchanges. While grasses showed the highest
WUE when not water limited, their near senescence during summer drought yielded
the lowest WUE. Shrubs showed reduced WUE under moderate drought stress, in
contradiction to the assumptions made in global ecosystem models. The importance of the
appropriate time-scale for calculating WUE (daily versus hourly), together with water use
strategies and ecological functions of individual species, will be further discussed. |
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