Segregation of nitrogen use between ammonium and nitrate of ectomycorrhizas and beech trees.

Here, we characterized nitrogen (N) uptake of beech (Fagus sylvatica) and their associated ectomycorrhizal (EM) communities from NH and NO . We hypothesized that a proportional fraction of ectomycorrhizal N uptake is transferred to the host, thereby resulting in the same uptake patterns of plants and their associated mycorrhizal communities. N uptake was studied under various field conditions after short-term and long-term exposure to a pulse of equimolar NH and NO concentrations, where one compound was replaced by N. In native EM assemblages, long-term and short-term N uptake from NH was higher than that from NO , regardless of season, water availability and site exposure, whereas in beech long-term N uptake from NO was higher than that from NH . The transfer rates from the EM to beech were lower for N from NH than from NO . N content in EM was correlated with N uptake of the host for NH , but not for NO -derived N. These findings suggest stronger control of the EM assemblage on N provision to the host from NH than from NO . Different host and EM accumulation patterns for inorganic N will result in complementary resource use, which might be advantageous in forest ecosystems with limited N availability.