Nitrogen losses from perennial grasses species.

Nitrogen losses from plants may occur through a variety of pathways, but so far, most studies have only quantified losses ofnutrient by above-ground litter production. We used 15N pulse labelling to quantify total nitrogen losses from above-and belowground plant parts. Using this method we were able to inelude also pathways other than above-ground litter production. To test the hypothesis that species from nutrientpoor habitats lose less nitrogen than species from more fertile soils six perennial grasses from habitats with a wide range ofnutrient availability were investigated: Lolium perenne, Arrhenatherum elatius, Anthoxanthum odoratum, Festuca rubra" Festuca ovina and Molinia caerulea. The results ofan experiment carried out in pots in a greenhouse at two fertility treatments show that statistically significant losses occur through pathways other than litter production. In the low fertility treatment, most (70010) losses from L. perenne occurred by litter production, but in A. elatius, F. rubra, F. ovina and M. caerulea. more than 50% oflabelled N losses took place by root tumover, leaching or exudation from roots. When nutrient supply increased, the 15N losses in above-ground dead material increased in all species and in A. elatius, A. odoratum and F. rubra the 15N losses vía other pathways decreased. Ranked according to decreasing tumover coefficient the sequence of species was: L. perenne, A. odoratum F. rubra. F. ovina" A. elatius, M. caerulea These results show that species adapted to sites with low availability ofnutrients lose less nitrogen (incIuding above-and belowground losses) than species adapted to more fertile soils.