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| Titel |
Hydrologic control of the oxygen isotope ratio of ecosystem respiration in a semi-arid woodland |
| VerfasserIn |
J. H. Shim, H. H. Powers, C. W. Meyer, A. Knohl, T. E. Dawson, W. J. Riley, W. T. Pockman, N. McDowell |
| 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 ; 10, no. 7 ; Nr. 10, no. 7 (2013-07-23), S.4937-4956 |
| Datensatznummer |
250018354
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| Publikation (Nr.) |
 copernicus.org/bg-10-4937-2013.pdf |
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| Zusammenfassung |
| We conducted high frequency measurements of the δ18O value of
atmospheric CO2 from a juniper (Juniperus monosperma) woodland in New Mexico, USA,
over a four-year period to investigate climatic and physiological
regulation of the δ18O value of ecosystem respiration (δR). Rain pulses reset δR with the dominant water source
isotope composition, followed by progressive enrichment of δR.
Transpiration (ET) was significantly related to post-pulse δR enrichment because the leaf water δ18O value showed strong
enrichment with increasing vapor pressure deficit that occurs following
rain. Post-pulse δR enrichment was correlated with both
ET and the ratio of ET to soil evaporation (ET/ES). In
contrast, the soil water δ18O value was relatively stable and
δR enrichment was not correlated with ES. Model
simulations captured the large post-pulse δR enrichments only
when the offset between xylem and leaf water δ18O value was
modeled explicitly and when a gross flux model for CO2 retro-diffusion
was included. Drought impacts δR through the balance between
evaporative demand, which enriches δR, and low soil moisture
availability, which attenuates δR enrichment through reduced
ET. The net result, observed throughout all four years of our study, was
a negative correlation of post-precipitation δR enrichment with
increasing drought. |
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