Incorporation of 13C-labelled rice rhizodeposition carbon into soil microbial communities under different water status |
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| Institution: | 1. International Center for Ecology, Meteorology and Environment (IceMe), Nanjing University of Information Sciences & Technology, No. 219 Ningliu Road, Nanjing 210044, China;2. National Observation Station of Hailun Agro-ecology System, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Harbin 150081, China;3. Department of Animal, Plant & Soil Sciences, Centre for AgriBioscience, La Trobe University (Melbourne Campus), Bundoora, Vic 3086, Australia |
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| Abstract: | The overall processes by which carbon is fixed by plants in photosynthesis then released into the soil by rhizodeposition and subsequently utilized by soil micro-organisms, links the atmospheric and soil carbon pools. The objective of this study was to determine the plant derived 13C incorporated into the phospholipid fatty acid (PLFA) pattern in paddy soil, to test whether utilization of rice rhizodeposition carbon by soil micro-organisms is affected by soil water status. This is essential to understand the importance of flooded conditions in regulating soil microbial community structure and activity in wetland rice systems. Rice plants were grown in soil derived from a paddy system under controlled irrigation (CI), or with continuous waterlogging (CW). Most of the 13C-labelled rice rhizodeposition carbon was distributed into the PLFAs 16:0, 18:1ω7 and 18:1ω9 in both the CW and CI treatments. The bacterial PLFAs i15:0 and a15:0, both indicative of gram positive bacteria, were relatively more abundant in the treatments without rice plants. When rice plants were present rates of 13C-incorporation into i15:0 and a15:0 was slow; the microbes containing these PLFAs may derive most of their carbon from more recalcitrant C (soil organic matter). PLFAs, 18:1ω7 and 16:1ω7c, indicative of gram negative bacteria showed a greater amount incorporation of labelled plant derived carbon in the CW treatment. In contrast, 18:2ω6,9 indicative of fungi and 18:1ω9 indicative of aerobes but also potentially fungi and plant roots had greater incorporation in the CI treatment. The greater root mass concomitant with lower incorporation of 13C into the total PLFA pool in the CW treatment suggests that the microbial communities in wetland rice soil are limited by factors other than substrate availability in flooded conditions. In this study differing soil microbial communities were established through manipulating the water status of paddy soils. Steady state 13C labelling enabled us to determine that the microbial community utilizing plant derived carbon was also affected by water status. |
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