Xiuyuan Li

Influence of water and nitrogen availability on the competition between European beech and sycamore maple for soil nitrogen sources

Nitrogen is a major growth-limiting resource in forests and plays an important role in competition between species. European beech is the most important deciduous tree species in Central Europe, and strongly promoted by forest practitioners and governments. However, its survival and growth at the seedling stage largely depends on its ability to co-exist with other competitive species. Sycamore maple is a fast growing species that shares the spectrum where beech is dominant on calcareous substrate, and is a potential competitor of beech. Previous research showed a negative effect of sycamore maple on N uptake by beech seedlings, whereas the presence of beech stimulated inorganic N uptake by maple seedlings. It is likely that active regulatory compounds are released by sycamore maple to suppress N uptake by beech seedlings. However, it still needs to be elucidated what substance is responsible for this interaction between beech and sycamore maple. Investigations include experiments in microcosms with beech and sycamore maple seedlings grown alone and in combination with different water and nitrogen supply, furthermore, a study at the research station Tuttlingen, Germany, in a beech-dominated forest with coexisting beech and maple seedlings in the understorey. In order to study the pattern and mechanism of the competition between these two species, uptake of different nitrogen sources, metabolite and protein profiles and partitioning will be determined.

Supervisors: Heinz Rennenberg; Judy Simon; Jörg-Peter Schnitzler (Head of the Department of Environmental Engineering (EUS), Institute of Biochemical   Pathology, HelmholtzZentrum München)