Microbial community structure and residue chemistry during decomposition of shoots and roots of young and mature wheat (Triticum aestivum L.) in sand

Abstract

There is limited understanding of the relationship between carbon (C) chemistry and microbial community structure during decomposition of shoot and root residues and how plant age affects this. In this study, residues of young wheat shoots and roots, mature wheat shoots and roots or a 1:1 mix of mature shoot + root (MSR) were added to sand inoculated with a diverse microbial community. Respiration was measured over 60 days. On days 0, 15, 30 and 60, total C and nitrogen were measured, residue C chemistry was determined by 13C-NMR (nuclear magnetic resonance) spectroscopy and microbial community structure was assessed by phospholipid fatty acid (PLFA) analyses. Cumulative respiration was least in young roots and did not differ among the other residue types. In MSR, decomposition was similar to that of shoots and roots alone; shoot material appeared to be preferentially decomposed. The decomposition rate of all residues combined was not related to C chemistry. However, mineralized C (Cmin) was negatively correlated with the percentage of (aryl + O-aryl)-C in mature but not in young residues. Mineralized C of roots was positively correlated with the percentage of (di-O-alkyl + O-alkyl)-C, whereas this was not the case for shoots. Microbial community structure was influenced by time, plant organ and plant age. There was no general relationship between microbial community structure and C chemistry of the residues.