Background and aims: Plants differ in their ability to use different nitrogen (N) forms and these differences can be related to their ecology and drive community structure. The capacity to uptake intact organic N has been observed in plants of several ecosystems. However, soil organic N uptake by Mediterranean plants is unknown despite organic N being abundant in Mediterranean ecosystems. We compare the uptake of different N forms in two widespread coexisting Mediterranean forest trees with contrasting ecophysiological characteristics: Quercus ilex and Pinus halepensis.Methods: To estimate root uptake rate of each N form we used equimolar solutions (1 mM N) of 15 NO3 -, 15 NH4 + and 15 N-13 C glycine.Results: NH4 + and glycine were taken up at a similar rate, but faster than NO3in both species. Intact dual labeled glycine was found in both species, demonstrating that both species can absorb intact organic N.Conclusions: Despite their ecological differences, both species had similar preference for N forms suggesting no niche complementarity for N uptake. The higher preference for NH4 + and glycine over NO3possibly reflects adaptation to the differing proportions of N forms in Mediterranean soils.