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Abstract:
The ecohydrological separation (EHS) paradigm, frequently compared with the translatory flow (HH), opens up a new understanding of the underlying processes of the terrestrial water cycles. However, the recent finding of deuterium offsets for cryogenic vacuum extraction (CVE) and suggested CVE-bias correction data no longer supports the EHS but goes back to HH. Here we revisited the EHS spurred by the CVE-bias correction with regard to accurate source/xylem water information. We found systematic similarities in the water line (ratio between δ18O and δ2H) of plant and soil for a global database, regardless of the suggested CVE-bias correction. This partial CVE-based data correcting from the whole dataset is only applied to correct a random error. Likewise, the correction will not change the slope of the plant water line but its intercept. Furthermore, we outline the key uncertainties that could be quantified for establishing a consistent and combined methodology to correct CVE-bias precisely, although a universal correction function might not exist. Our findings demonstrate a critical misunderstanding in the CVE-bias correction, and suggest a framework to reduce uncertainties for (dis)proving EHS and/or HH across a wide range of water isotope applications.
