Relationship between the chemical structure of straw and composition of main microbial groups during the decomposition of wheat and maize straws as affected by soil texture

摘要

Field decomposition of wheat and maize straws was monitored for 20 months using litterbag method in Calcaric Fluvisol soils with three different textures (sand, sandy loam, and silty clay). Residual straw samples were collected at 0 or after 4, 6, 10, and 20 months of decomposition. The chemical structure of straw was analyzed by solid-state C-13 nuclear magnetic resonance (C-13-NMR) spectroscopy, and the composition of main microbial groups was evaluated by phospholipid fatty acid analysis. Regardless of the straw type and soil texture, the straw biomass and C loss increased steadily in the first 10 months and then leveled off in the following 10 months; both the chemical structure of straw and the composition of main microbial groups differed during incubation. During the first 4 months of wheat straw degradation, the decrease in di-O-alkyl and O-alkyl C and the increase in alkyl and N-alkyl/methoxyl C contents were related to the enrichment of fungi (18:1 omega 9c) and Gram-negative bacteria (18:1 omega 7c and 16:1 omega 7c), while the degradation of maize straw was associated with the decrease in the fungal (18:1 omega 9c) abundance and the increase in the abundance of Gram-negative (18:1 omega 7c and 16:1 omega 7c) and Gram-positive (a15:0) bacteria. During the 6-10-month period, the decrease in di-O-alkyl and O-alkyl C and the increase in alkyl, aryl, and carboxyl/amide C contents were related to the enrichment of arbuscular mycorrhizal fungi (AMF) (16:1 omega 5c) and Gram-negative (cy19:0 omega 8c) bacteria and the decrease in fungal (18:2 omega 6,9c) abundance, with AMF playing an important role in the degradation of both straw types. The altered chemical structure of wheat and maize straws had opposite links with fungal abundance during the first 4 months, while alterations occurring during the 6-10-month period mainly depended on the variation in the AMF abundance.