Specific Nmin uptake patterns of two widely applied poplar and willow clones for short rotation coppices – Implications for management practices

Short rotation coppices (SRCs) are a promising alternative for environmental-friendly biomass production. However, profound understanding of nitrogen (N) uptake and allocation dynamics and their interaction with biomass production of individual tree species is required for their sustainable management. In-situ 15N soil pulse labeling of the widely applied willow cv. Tordis and poplar cv. Max 1 allowed tracing their uptake of Nmin and to evaluate the effect of N nutrition on their growth. A pulse of either 15NH4NO3 or NH4 15NO3 was applied to the soil of four replicate trees of each species in a pot experiment. Leaf, twigs, stem, root were analyzed to quantify the uptake and allocation of 15N after labeling. Summarizing all compartments of poplar, almost all of 15NO3 − (97%) from the N soil pool could be recovered, but only a third of the 15NH4 + (34%). In contrast, willow incorporated exactly the same amount of 15N (49%) from both tracers i.e. showing no preference for a certain Nmin species. Poplar did not only have the higher Nmin uptake but also showed a higher total biomass (12.2 g·tree−1) production than willow (10.2 g·tree−1) in first 56 days, which goes along which its higher allocation of N into leaves. We conclude that the poplar cv. Max 1 might be a better choice for biomass production, especially at arable sites with high N contents as well as for protecting from all negative impacts of non-closed N cycles as typical for classical agricultural managed sites (e.g. nitrate leaching or N2O emissions).