Contributing factors in foliar uptake of dissolved inorganic nitrogen at leaf level
Faculty of Sciences. Bioscience Engineering
The science of the total environment. - Amsterdam
, p. 992-1002
University of Antwerp
We investigated the influence of leaf traits, rainwater chemistry, and pedospheric nitrogen (N) fertilisation on the aqueous uptake of inorganic N by physiologically active tree leaves. Leaves of juvenile silver birch and European beech trees, supplied with NH4NO3 to the soil at rates from 0 to 200 kg N ha(-1) y(-1), were individually exposed to 100 mu l of artificial rainwater containing (NH4+)-N-15 or (NO3-)-N-15 at two concentration levels for one hour. In the next vegetative period, the experiment was repeated with NH4+ at the highest concentration only. The N form and the N concentration in the applied rainwater and, to a lesser extent, the pedospheric N treatment and the leaf traits affected the aqueous foliar N uptake. The foliar uptake of NH4+ by birch increased when leaves were more wettable. High leaf N concentration and leaf mass per area enhanced the foliar N uptake, and NO; uptake in particular, by birch. Variation in the foliar N uptake by the beech trees could not be explained by the leaf traits considered. In the first experiment, N fertilisation stimulated the foliar N uptake in both species, which was on average 1.42-1.78 times higher at the highest soil N dose than at the zero dose. However, data variability was high and the effect was not appreciable in the second experiment. Our data suggest that next to rainwater chemistry (N form and concentration) also forest N status could play a role in the partitioning of N entering the ecosystem through the soil and the canopy. Models of canopy uptake of aqueous N at the leaf level should take account of leaf traits such as wettability and N concentration. (C) 2014 Elsevier B.V. All rights reserved.