3.3.1 Morphological identification of AM fungi
There were 4461 AM fungal spores isolated from all soil samples, and 9 genera and 20 species were identified morphologically. Among them, 7 species belonging to Acaulospora are the most diverse, accounting for 35% of the total number of species, followed by the genusGlomus with four species, accounting for 20% of the total number of species.
The relative abundance (RA) and importance values (I) of AM fungal spores under the N application treatment were analyzed (Table 4). The soil samples from the CK had the most abundant spore species, with 17 AM fungal species identified, whileAcaulospora spinosa and Claroideoglomus lamellosum only appeared in CK and not found in other treatment. Gradual reduction of spore species in soil samples with increasing N addition concentration, and 14 species of AM fungi were isolated and identified in the LN treatment. There were also 14 species in the MN treatment, in whichSclerocystis sinuosa was unique and never found in other treatments. It was found that HN treatment reached the least AM fungal species of 10. In summary, the increasing of N addition concentration gradually reduced the spore species.