<p>The hydrogen isotope fractionation between leaf wax compounds and source water, the apparent fractionation (ε<sub>app</sub>), necessary for the reconstruction of hydrogen isotopic composition (δD) of precipitation, is mainly assessed through field and transect studies. The current ε<sub>app</sub> dataset, however, exhibit a bias toward mid-latitude regions of the Northern Hemisphere. Here we report the results of an outdoor experiment wherein four evergreen and three deciduous species were grown with water of known δD value (-1.8‰) in a tropical semi-arid monsoon region. This allowed us to estimate ε<sub>app</sub> more accurately and also quantify ε<sub>app</sub> variability within a species and among different species. Among-species ε<sub>app</sub> values varied by -119 ± 23‰ (for <em>n</em>-alkane of chain length <em>n</em>-C<sub>31</sub>) and -126 ± 27‰   (for <em>n</em>-alkanoic acid of chain length <em>n</em>-C<sub>30</sub>). The similarity of the among-species variability in ε<sub>app</sub> reported here and that observed in field and transect studies suggested the species-effect, rather than uncertainty in δD of source water, control the uncertainty in community-averaged ε<sub>app</sub>. The fractionation of  δD between <em>n</em>-C<sub>29</sub> alkane and <em>n</em>-C<sub>30</sub> alkanoic acid (ε<sub>29/30</sub>) and between <em>n</em>-C<sub>31</sub> alkane and <em>n</em>-C<sub>32</sub> alkanoic acid (ε<sub>31/32</sub>) were 7 ± 25‰ and 6 ± 15‰, respectively, suggesting minimal fractionation of hydrogen isotopes during decarboxylation. Further, as we did not observe a systematic difference between the ε<sub>app</sub> of deciduous and evergreen species; changes in the relative proportion of this vegetation in a community might not affect its ε<sub>app</sub> value.</p>

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