2.4 Statistical analyses
To evaluate the impacts of inter-annual precipitation fluctuation and
experimental treatments on plant, soil and AM fungal parameters,
repeated measures analysis of variance (ANOVA) was used with N, P and
fungicide application as between-subject factors, and year as a
within-subject factor. In addition, three-way ANOVA (N, P and fungicide
application) was used to test the impacts of experimental treatments on
these parameters. Statistical analyses were conducted via SPSS software
(version 21.0; IBM, Armonk, NY, USA).
To evaluate the direct and indirect impacts of the experimental
treatments on ANPP, we performed structural equation modelling (SEM) in
Amos (version 18.0, IBM, USA). In our SEM model, we supposed that
precipitation, N and P addition and AM fungi can impact ANPP both
directly and indirectly by altering the aboveground biomass of main
plant species. We examined the model’s fitness using the
χ2 test,
root
mean square error of approximation and Akaike information
criterion.χ2 values and P -values >
0.05 suggested that the covariance of the chosen data was no
significantly differ with which we expected (Grace, 2006).