Microbial response to rhizodeposition depending on water regimes in paddy soils

• Published in: Soil biology & biochemistry 2013-10, Vol.65, p.195-203
• Main Authors: Tian, Jing, Dippold, Michaela, Pausch, Johanna, Blagodatskaya, Evgenia, Fan, Mingsheng, Li, Xiaolin, Kuzyakov, Yakov
• Format: Article
• Language: English
• Subjects: 13CO2 pulse labeling; Agronomy. Soil science and plant productions; Biochemistry and biology; Biological and medical sciences; Chemical, physicochemical, biochemical and biological properties; Fundamental and applied biological sciences. Psychology; fungi; Gram-negative bacteria; Gram-positive bacteria; microbial communities; Microbial community structure; Microbiology; Oryza sativa; Paddy soil; paddy soils; phospholipid fatty acids; Phospholipid fatty acids (PLFAs); Physics, chemistry, biochemistry and biology of agricultural and forest soils; primary energy; Rhizodeposition; rhizosphere; rice; Root exudation; roots; Soil science; upland soils; Water conservation techniques
• ISSN: 0038-0717; 1879-3428
• DOI: 10.1016/j.soilbio.2013.05.021

Rhizodeposit-carbon (rhizo-C) serves as a primary energy and C source for microorganisms in the rhizosphere. Despite important progress in understanding the fate of rhizo-C in upland soils, little is known about microbial community dynamics associated with rhizo-C in flooded soils, especially depending on water regimes in rice systems. In this study, rice grown under non-flooded, continuously flooded and alternating water regimes was pulse labeled with 13CO2 and the incorporation of rhizo-C into specific microbial groups was determined by 13C in phospholipid fatty acids (PLFAs) at day 2 and 14 after the labeling. A decreased C released from roots under continuously flooded condition was accompanied with lower total 13C incorporation into microorganisms compared to the non-flooded and alternating water regimes treatments. Continuous flooding caused a relative increase of 13C incorporation in Gram positive bacteria (i14:0, i15:0, a15:0, i16:0, i17:0, a17:0). In contrast, Gram negative bacteria (16:1ω7c, 18:1ω7c, cy17:0, cy 19:0) and fungi (18:2ω6, 9c, 18:1ω9c) showed greater rhizo-C incorporation coupled with a higher turnover under non-flooded and alternating water regimes treatments. These observations suggest that microbial groups processing rhizo-C differed among rice systems with varying water regimes. In contrast to non-flooded and alternating water regimes, there was little to no temporal 13C change in most microbial groups under continuous flooding condition between day 2 and 14 after the labeling, which may demonstrate slower microbial processing turnover. In summary, our findings indicate that belowground C input by rhizodeposition and its biological cycling was significantly influenced by water regimes in rice systems. •Continuous flooding condition resulted in lowest 13C incorporation in soil and microorganisms.•Gram negative bacteria and fungi showed greater 13C incorporation under NF and AWD conditions.•Continuous flooding caused a relative increase of 13C incorporation in Gram positive bacteria.•Microbial groups processing rhizo-C differed among rice systems with varying water regimes.