Impact of waterlogging on the N-metabolism of flood tolerant and non-tolerant tree species

The present study was conducted to characterize the N‐metabolism of important European tree species with different degrees of flooding tolerance. The roots of Fagus sylvatica (sensitive to flooding), Quercus robur (moderately flood tolerant) and Populus tremula × P. alba (flood tolerant) saplings were exposed to different flooding regimes and N uptake, amino acid, protein and chlorophyll concentrations as well as gas exchange were measured. The effects of these treatments on the tree species varied distinctly. In general, the N metabolism of beech was severely affected whereas less impacts were observed on oaks and almost no effects on poplars. The concentrations of amino compounds, particularly of Asp, Asn, Glu and Gln, were lower in the roots of flooded trees than in controls. By contrast, γ‐amino butyric acid concentrations increased. Root protein concentrations remained unaffected in oak and poplar but decreased in beech in response to flooding. The concentrations of pigments remained unaffected by flooding in all tree species investigated. However, photosynthesis and transpiration were severely affected in beech but much less in oak and poplar. The data obtained show a clear correlation between the different flooding tolerances of the trees investigated and the impacts of flooding on N uptake and N metabolism.