Fig. 4.
Mean xylem hydraulic properties of Potentilla diversifolia plants growing on the drier windward and moister lee side of a snow fence at Niwot Ridge (CO, USA): (A, B) relative frequency distribution of vessel size classes (simply termed ‘vessel size distribution’ in the text; note the logarithmic scale); (C, D) contribution of each vessel size class to overall hydraulic conductivity (denoted as Kh); (E, F) relative cumulative conductivity curves derived from vessel size distribution. (A), (C) and (E) are for pre-snow fence years; (B), (D) and (F) for post-snow-fence years. Dotted lines in (F) illustrate the remaining xylem conductivity that would be expected if embolisms rendered vessels greater than a specific size non-functional. See text for further explanations. A three-value simple moving average was used to smooth out curves for representation purposes, but not when statistical testing. n = number of individual plants; ns, not significant; **, P < 0·01; ***, P < 0·001.