The effect of plant species on soil nitrogen mineralization.

1 To ascertain the influence of different plant species on nitrogen (N) cycling, we performed a long-term garden experiment with six grasses and five dicots with different potential growth rates, that are adapted to habitats with different nutrient supplies. We measured N mineralization and nitrification of the soil under monocultures of each species during the fourth year of the experiment.2 We focused on the effects of the different species on (i) annual net N mineralization; (ii) the seasonal pattern of N mineralization; and (iii) the fraction of the total N mineralization that is nitrified. Our hypothesis was that plant species of nutrient-rich habitats would enhance the N mineralization compared with species of nutrient-poor habitats.3 The results demonstrate a strong influence of the species on net N mineralization and net nitrification, both of which fluctuated strongly during the year. Overall, species from high fertility habitats increased N mineralization and nitrification more than species from low fertility habitats. About 90% of the mineralized ammonium was oxidized to nitrate. There was no significant difference in this proportion in the plots of species from nutrient-rich, moderate and nutrient-poor habitats.