Relevance of organic vs. inorganic nitrogen in intra- and interspecific competition of seven central European tree species

Abstract

Key message: When competing for nitrogen with other treespecies, organic N is more important than inorganic N for most species Abstract: Competition for nitrogen (N) in the rhizosphereis a key process regulating a seedling´s chances for growth and survival.However, only few studies have investigated this at the individual species´level when using a community approach. In this study, 15N incubationexperiments were conducted to quantify inorganic (i.e. ammonium and nitrate)and organic (i.e. glutamine-N and arginine-N) net N-uptake capacity of seventemperate woody species co-occurring on calcareous substrate and to investigatethe consequences of intra- vs. interspecific competition in a woody seedlingcommunity. The results showed that short-term net inorganic and organic Nuptake capacity was unrelated to a seedling´s fast or slow growth. Furthermore,competition with other tree species did not change a seedlings´ overallcapacity to take up inorganic and organic N sources. Organic N was preferredover inorganic N for most species and the preferences for specific N sourceshifted with competition regime and tree species. Overall, this study indicatesthe importance of organic N sources for N uptake in woody seedlings.