3.5 Relationship between changes in environmental factors and
herb diversity under N addition conditions
Long-term N addition reduced the diversity of understory herbaceous
plants. The correlation between the α diversity index of herbs and
biochemical factors was analyzed by Pearson correlation.
The diversity of understory
herbaceous plants was significantly and positively correlated with the
diversity of AM fungi (P <0.05; Fig.6), and the
colonization rate of AM fungi (R2 =0.66). The
diversity of herbs was significantly and positively correlated with
total nitrogen content (P <0.05), significantly and
negatively correlated with NH4+-N
content (P <0.01), and significantly and positively
correlated with pH (R2 =0.67). Additionally,
herbaceous plant fine root biomass was significantly and positively
correlated with diversity (P <0.01).
A structural equation model (SEM) was developed to illustrate the effect
of each factor on herb diversity under N addition conditions (Fig. 7),
The P-value of χ2 was higher than 0.05 indicated that the model
structure was reasonable. The SEM throughput analysis largely
(R2 > 90%) explained the effects of
biotic as well as abiotic factors on herb diversity. N addition
indirectly affected AM fungal diversity and plant diversity though soil
pH value, ammonium N, and AP content. Among them, AM fungal diversity
was the strongest pathway affecting plant diversity.