@article{fdi:010077454,
  title = {{E}ffects of leaf length and development stage on the triple oxygen isotope signature of grass leaf water and phytoliths : insights for a proxy of continental atmospheric humidity},
  author = {{A}lexandre, {A}. and {W}ebb, {E}. and {L}andais, {A}. and {P}iel, {C}. and {D}evidal, {S}. and {S}onzogni, {C}. and {C}ouapel, {M}artine and {M}azur, {J}. {C}. and {P}ierre, {M}. and {P}rie, {F}. and {V}allet-{C}oulomb, {C}. and {O}utrequin, {C}. and {R}oy, {J}.},
  editor = {},
  language = {{ENG}},
  abstract = {{C}ontinental relative humidity ({RH}) is a key climate parameter, but there is a lack of quantitative {RH} proxies suitable for climate model-data comparisons. {R}ecently, a combination of climate chamber and natural transect calibrations have laid the groundwork for examining the robustness of the triple oxygen isotope composition (delta {O}-'18 and {O}-17-excess) of phytoliths, that can preserve in sediments, as a new proxy for past changes in {RH}. {H}owever, it was recommended that besides {RH}, additional factors that may impact delta'{O}-18 and {O}-17-excess of plant water and phytoliths be examined. {H}ere, the effects of grass leaf length, leaf development stage and day-night alternations are addressed from growth chamber experiments. {T}he triple oxygen isotope compositions of leaf water and phytoliths of the grass species {F}. arundinacea are analysed. {E}volution of the leaf water delta'{O}-18 and {O}-17-excess along the leaf length can be modelled using a string-of-lakes approach to which an unevaporated-evaporated mixing equation must be added. {W}e show that for phytoliths to record this evolution, a kinetic fractionation between leaf water and silica, increasing from the base to the apex, must be assumed. {D}espite the isotope heterogeneity of leaf water along the leaf length, the bulk leaf phytolith delta'{O}-18 and {O}-17-excess values can be estimated from the {C}raig and {G}ordon model and a mean leaf water-phytolith fractionation exponent (lambda({P}hyto-{LW})) of 0.521. {I}n addition to not being leaf length dependent, delta'{O}-18 and {O}-17-excess of grass phytoliths are expected to be impacted only very slightly by the stem vs. leaf biomass ratio. {O}ur experiment additionally shows that because a lot of silica polymerises in grasses when the leaf reaches senescence (58 % of leaf phytoliths in mass), {RH} prevailing during the start of senescence should be considered in addition to {RH} prevailing during leaf growth when interpreting the {O}-17-excess of grass bulk phytoliths. {A}lthough under the study conditions {O}-17-excess({P}hyto) do not vary significantly from constant day to day-night conditions, additional monitoring at low {RH} conditions should be done before drawing any generalisable conclusions. {O}verall, this study strengthens the reliability of the {O}-17-excess of phytoliths to be used as a proxy of {RH}. {I}f future studies show that the mean value of 0.521 used for the grass leaf water-phytolith fractionation exponent lambda({P}hyto-{LW}) is not climate dependent, then grassland leaf water {O}-17-excess obtained from grassland phytolith {O}-17-excess would inform on isotope signals of several soil-plant-atmosphere processes.},
  keywords = {},
  booktitle = {},
  journal = {{B}iogeosciences},
  volume = {16},
  numero = {23},
  pages = {4613--4625},
  ISSN = {1726-4170},
  year = {2019},
  DOI = {10.5194/bg-16-4613-2019},
  URL = {https://www.documentation.ird.fr/hor/fdi:010077454},
}