Understanding how variations in the hydrogen isotope composition of leaf-wax lipids (dD) relate to environmental and plant physiological conditions is especially important for sedimentary n-alkane based paleoclimate reconstructions. Currently it is unclear which water pool regulates dD for different plant functional types. A number of studies have indicated that the dD of soil water, leaf water and atmospheric water vapour are extremely important in determining the dD of leaf wax nalkanes to varying degrees, yet none of the published studies have measured all possible source water pools in the same experiment over several growing seasons. This study presents the results from a 2-yr field experiment (2007-2008) conducted in a Maritime pine forest located in the south west of France. Every month waters were collected from every ecosystem compartment: needles, twigs, soil and atmosphere and analysed for their oxygen (d18O) and hydrogen (dD) isotope composition. In addition, during the same time interval, pine needles were collected at a monthly resolution for n-alkane dD analysis. We observed dynamic variations in the dD of n-C29 alkane and needle water over the two growing seasons with occasional large shifts of >25‰ observed from one month to the next. These results were compared to state-of-the-art isotope enabled soil and leaf water models in order to elucidate the primary control on leaf wax dD signals.