3.5.Principal component analysis (PCA) of carbon source
metabolization
The differences in metabolic characteristics of the intercropping system
were directly reflected by the position of the points in the principal
vector space. As shown in Figure 3, the multivariate vectors were
transformed into two uncorrelated principal component vectors; PC1
accounted for 55.64% of the total variability and PC2 for 13.24%. For
the intercropping system, the point positions of MN0, MNE, M0, ME, AN0,
ANE, AE, and A0 were significantly different.
The sample distribution along the PC axis was relevant to the carbon
source use. Based on the results of the PCA, 17 carbon sources
constituted PC1, including six amino acids, three carbohydrates, three
carboxylic acids, two polymers, two miscellaneous substances, and one
amide. Only four carbon sources accounted for PC2, including two
carboxyl acids, one polymer, and one carbohydrate. The carbon sources
used by mulberry microbes were greatly related to PC1, including amino
acids, carbohydrates, and carboxylic acid, while the alfalfa community
mainly used carbon sources related to PC2.