2.4 Statistical analyses
We performed two main analyses in this study. First, one-way ANOVA
combined with a multiple comparisons test (least significant
differences, LSD) was used to test the differences in the fraction of
total plant biomass allocated to shoots (the shoot mass fraction, SMF),
the fraction of total plant biomass allocated to roots (the root biomass
fraction, RMF), and the R/S among the different species and densities.
Second, standard major axis (SMA) regression analyses were conducted to
explore the allometric relationships of biomass between shoots and roots
at different densities. A likelihood ratio test was used to indicate the
heterogeneity of the scaling exponents at different densities and their
difference from 1 (Warton et al., 2012). The data were
log10-transformed before the SMA regression analysis.
The differences in the SMF, RMF and R/S among the six species were
analysed based on the pooled data from all five planting densities. The
pooled data were subjected to a Kolmogorov-Smirnov test to examine
whether they conformed to a normal distribution; if they did not, a
log10 transformation was performed. Before using ANOVA
to study the effect of density on the biomass allocation in each
species, the data from the individuals in each planting pot were
averaged; therefore, the data presented in the figures are averages
based on three replicates. In addition, differences in the ANPP and BNPP
fractions and ratios for the different functional groups (annualsvs perennials, C3 vs C4)
at the global scale were analysed using a mixed model and compared with
the results of this experiment. All analyses in this study were
performed in R 4.0.2 (R Core Team, 2020).