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| Titel |
Hysteresis response of daytime net ecosystem exchange during drought |
| VerfasserIn |
N. Pingintha, M. Y. Leclerc, J. P. Beasley, D. Durden, G. Zhang, C. Senthong, D. Rowland |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 7, no. 3 ; Nr. 7, no. 3 (2010-03-31), S.1159-1170 |
| Datensatznummer |
250004601
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| Publikation (Nr.) |
 copernicus.org/bg-7-1159-2010.pdf |
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| Zusammenfassung |
| Continuous measurements of net ecosystem CO2 exchange (NEE) using the
eddy-covariance method were made over an agricultural ecosystem in the
southeastern US. During optimum environmental conditions, photosynthetically
active radiation (PAR) was the primary driver controlling daytime NEE,
accounting for as much as 67 to 89% of the variation in NEE. However,
soil water content became the dominant factor limiting the NEE-PAR response
during the peak growth stage. NEE was significantly depressed when high PAR
values coincided with very low soil water content. The presence of a
counter-clockwise hysteresis of daytime NEE with PAR was observed during
periods of water stress. This is a result of the stomatal closure control of
photosynthesis at high vapor pressure deficit and enhanced respiration at
high temperature. This result is significant since this hysteresis effect
limits the range of applicability of the Michaelis-Menten equation and other
related expressions in the determination of daytime NEE as a function of
PAR. The systematic presence of hysteresis in the response of NEE to PAR
suggests that the gap-filling technique based on a non-linear regression
approach should take into account the presence of water-limited field
conditions. Including this step is therefore likely to improve current
evaluation of ecosystem response to increased precipitation variability
arising from climatic changes. |
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