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Temperature‐sensitive biochemical $^{18}$O‐fractionation and humidity‐dependent attenuation factor are needed to predict δ $^{18}$O of cellulose from leaf water in a grassland ecosystem

Hirl, Regina T.; Ogée, Jérôme; Ostler, Ulrike; Schäufele, Rudi; Baca Cabrera, Juan C.; Zhu, Jianjun; Schleip, Inga; Wingate, Lisa; Schnyder, Hans

Abstract:
We explore here our mechanistic understanding of the environmental and physiological processes that determine the oxygen isotope composition of leaf cellulose (δ$^{18}$O$_{cellulose}$) in a drought‐prone, temperate grassland ecosystem.
A new allocation‐and‐growth model was designed and added to an $^{18}$O‐enabled soil–vegetation–atmosphere transfer model (MuSICA) to predict seasonal (April–October) and multi‐annual (2007–2012) variation of δ$^{18}$O$_{cellulose}$ and $^{18}$O‐enrichment of leaf cellulose (Δ$^{18}$O$_{cellulose}$) based on the Barbour–Farquhar model.
Modelled δ$^{18}$O$_{cellulose}$ agreed best with observations when integrated over c. 400 growing‐degree‐days, similar to the average leaf lifespan observed at the site. Over the integration time, air temperature ranged from 7 to 22°C and midday relative humidity from 47 to 73%. Model agreement with observations of δ$^{18}$O$_{cellulose}$ (R$^{2}$ = 0.57) and Δ$^{18}$O$_{cellulose}$ (R$^{2}$ = 0.74), and their negative relationship with canopy conductance, was improved significantly when both the biochemical $^{18}$O‐fractionation between water and substrate for cellulose synthesis (ε$_{bio}$, range 26–30‰) was temperature‐sensitive, as previously reported for aquatic plants and heterotrophically grown wheat seedlings, and the proportion of oxygen in cellulose reflecting leaf water $^{18}$O‐enrichment (1 – p$_{ex}$p$_{x}$, range 0.23–0.63) was dependent on air relative humidity, as observed in independent controlled experiments with grasses.
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Verlagsausgabe §
DOI: 10.5445/IR/1000129335
Veröffentlicht am 05.02.2021
Cover der Publikation
Zugehörige Institution(en) am KIT Institut für Meteorologie und Klimaforschung - Atmosphärische Umweltforschung (IMK-IFU)
Publikationstyp Zeitschriftenaufsatz
Publikationsmonat/-jahr 03.2021
Sprache Englisch
Identifikator ISSN: 0028-646X, 1469-8137
KITopen-ID: 1000129335
HGF-Programm 12.02.01 (POF III, LK 01) Effects of land use and climate change
Erschienen in The new phytologist
Verlag Wiley
Band 229
Heft 6
Seiten 3156-3171
Vorab online veröffentlicht am 30.12.2020
Schlagwörter canopy conductance; grassland; isotope‐enabled soil–vegetation–atmosphere transfer model (MuSICA); 18O‐enrichment of cellulose oxygen isotope composition of cellulose; perennial ryegrass (Lolium perenne); relative humidity temperature
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