Fungal contribution to nitrous oxide emissions from cattle impacted soils.

Microscopic soil fungi isolated from arable, grassland and forest soils have been suggested as producers of nitrous oxide (N(2)O). The aim of this work was to screen the capabilities for N(2)O production of microscopic fungi originating in the pasture soils of a cattle overwintering area with three levels of cattle impact intensity. In total, 36 fungal species from 11 genera were isolated during a 2-year study, and production of N(2)O under laboratory conditions was confirmed in 23 species (64%). Species belonging to the genera Fusarium, Penicillium, Monographella, Acremonium, Gibberella, Eurotium, and Pseudallescheria were found to be the most potent N(2)O-producers. Different N(2)O production patterns and wide variations in production rates, ranging from 1 to 150 μg N(2)O-Nd(-1), were observed, resulting in the transformation of 0.2-18.4% of the initial NO(2)(-)-N present in the cultivation medium. The data revealed distinct soil fungal communities in the different sections of the cattle overwintering area, and indicate a significant effect of cattle overwintering on the composition of soil fungal consortia. These observations confirm the importance of soil fungi in total N(2)O fluxes from grazed grassland ecosystems.