Fungal denitrification potential in vertical flow microcosm wetlands as impacted by depth stratification and plant species

• Fungal denitrification dominantly occurred in the 0–30 cm substrate of vertical flow microcosms.
• Plant species greatly impacted the fungal denitrification, which only occurred in the top layer.
• Fungal and plant biomass parameters were the determinants of the fungal denitrification.

Fungal denitrification potential (FDP) was investigated in vertical flow microcosm wetlands (VFMWs) unplanted and mono-cultured with different plant species using the depth stratification and plant species as the fixed factors. Through two sampling layers of the VFMWs, the FDP was greater in the first sampling layers than in the second sampling layers in all treatments (P < 0.05), and positively related to the fungal biomass. Besides, through two sampling layers, the FDP was also related positively to the capacities of fungal communities to utilize polymers or miscellaneous compounds in the VFMWs mono-cultured with Iris pseudacorus, and also related to the capacities of fungal communities to utilize amino acids in the VFMWs mono-cultured with Canna glauca. Plant species significantly impacted the FDP pattern in the VFMWs, with the greater FDP only occurring in the VFMWs mono-cultured with C. glauca and I. pseudacorus (P < 0.05), but the plant species effect only occurred in the first sampling layers of the VFMWs. Across the VFMWs mono-cultured with different species, the fungal and plant biomass parameters as well as the capacities of fungal communities to utilize carboxylic acids, polymers and amino acids were positively related to the FDP. Overall, both depth stratification and plant species are the important factors in mediating the FDP pattern of the VFMWs.