4.3 Effect of N addition on understory herb plants
Cases of nitrogen deposition-induced soil acidification leading to
reduced plant diversity have been reported (Kimmel et al., 2020).In this
study, we found that the diversity of understory herb plants in the
forest also decreased with decreasing soil pH value. In addition, excess
N can also cause nutrient imbalance. Large-scale input of exogenous N
can break the original stable stoichiometry, thus causing a nutrient
imbalance in the soil and plants, which can also lead to the loss of
some species of plants. N deposition indirectly affected plant species
diversity by altering the composition of soil microbial communities
(Bobbink et al., 2010). In the present study, it was also found that the
varies of understory plant diversity was linearly and positively
correlated with AM fungal diversity and AM fungal colonization rate
(Fig.6), this also verified that the function of AM fungi in maintaining
the stability of ecosystems and preserving biodiversity should not be
underestimated. In addition, plant fine root biomass was also
significantly reduced by long-term N addition, and a small amount of N
input increased plant root biomass (Frew, 2022), In contrast, excessive
N addition decreased the fine root biomass with increasing time of N
application. The SEM clearly shows that AM fungal diversity is the
strongest influence pathway affecting herb diversity under N addition
conditions (Fig. 7), which is further evidence of the ability of AM
fungi in maintaining understory herb diversity.