17O-excess of grass leaf phytoliths across the North American prairies records late-growing season daytime relative humidity
Bibliographic record
Abstract
Because it is an important climate parameter, an accurate proxy is required for the reconstruction of past Relative Humidity (RH). Triple oxygen isotopes of grass-leaf phytoliths have a high potential for this purpose. A strong correlation between RH and 17 O-excess of grass leaf phytoliths has been previously demonstrated from calibration experiments in growth chambers and at natural Sub-Saharan African and Mediterranean sites. Here we focus on the potential of 17 O-excess of grass leaf phytoliths as a proxy of RH across the North American Great Plains. We tested the relationship between the 17 O-excess of naturally grown Calamovilfa longifolia phytoliths and RH for different periods of the grass growing season. The results show that 17 O-excess of leaf phytoliths has a strong correlation with late-growing season (July–August) daytime RH, which varies from 29 to 72 % across North America. The correlation can be expressed as: 17 O-excess leaf phytoliths = 4.14(±0.47) × RH (%) – 497(±26) (R 2 = 0.85, p -value<0.0001). To use the 17 O-excess of bulk phytoliths buried in soils and sediments as a quantitative proxy of past RH, future calibration studies on soil phytoliths are needed to evaluate the contribution of non-transpiring phytoliths. The 17 O-excess of stem water, which was determined by 17 O-excess of stem phytoliths, shows similar values to the 17 O-excess of precipitation in North America without evaporation, which therefore does not affect the 17 O-excess of leaf phytoliths in North America. These results demonstrate that the 17 O-excess of phytoliths is a promising proxy for regional growing season RH. • Grass leaf phytolith 17 O-excess is a direct proxy of Relative Humidity (RH). • North American grass leaf phytoliths record late-growing season daytime RH. • 17 O-excess leaf phytolith = 4.14 × RH (%) – 497 (R 2 = 0.85), RH ranges from 29 to 72 %. • Soil water evaporation does not imprint on the estimated 17 O-excess stem water. • The contribution of non-transpiring phytolith to soil assemblages must be evaluated.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".