ANOVA results indicated significant seasonal differences for 19 different carbon substrates including 3 amino acids (L-phenylalanine, L-serine, and glycyl-L-glutamic acid), 9 carbohydrates ([alpha]-D-lactose, [beta]-methyl D-glucoside, D-cellobiose, D-mannitol, i-erythritol, glucose-1-phosphate, D-galacturonic acid
[gamma]-lactone, N-acetyl-D-glucosamine, and D-xylose), 4 carboxylic acids ([alpha]-ketobutyric acid, [gamma]-hydroxybutyric acid, pyruvic acid methyl ester, and D-galacturonic acid
), 2 polymers ([alpha]-cyclodextrin and 2-hydroxybenzoic acid), and 1 phenolic compound (2-hydroxybenzoic acid).
Pectin is a polymer of partially methoxylated alpha, 1,4 linked D-galacturonic acid
that is interrupted by dispersed or alternating 1,2 linked L-rhamnose units that are linked to neutral sugars such as L-galactose and L-arabinose.
Of these, 2 types of carbon sources (D-galacturonic acid
and a-D-lactose) were positively correlated with the principal component and soil microbes showed the most efficient utilisation of these carbon sources under calcium cyanamide treatment; the other 3 carbon sources (a-cyclodextrin, 2-hydroxy benzoic acid and L- asparagine) were negatively correlated with the principal component and soil microbes showed the most efficient utilisation of a-cyclodextrin and 2-hydroxy benzoic acid in the CK treatment (Table 5).