Rhizosphere priming can promote mobilisation of N-rich compounds from soil organic matter |
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| Affiliation: | 1. Institute of Biological and Environmental Sciences, University of Aberdeen, Cruickshank, Building, St Machar Drive, AB24 3UU, Aberdeen, Scotland, UK;2. Teagasc; Environment, Soils and Land Use Research Department, Johnstown Castle, Wexford, Ireland;3. James Hutton Institute, Craigiebuckler, AB15 8QH, Aberdeenshire, Scotland, UK;1. School of Water, Energy & Environment, Cranfield University, Cranfield, Bedford, MK43 0AL, UK;2. The James Hutton Institute, Craigiebuckler, Aberdeen, AB15 8QH, Scotland, UK;1. Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration and Biodiversity Conservation, Chengdu Institute of Biology, Chinese Academy of Sciences, No. 9 Section 4, Renmin Nan Road, Chengdu, 610041, China;2. Department of Biology, Indiana University, 1001 E. Third St., Bloomington, IN 47403, USA;3. Key Laboratory of Ecological Forestry Engineering, Institute of Forest & Ecology, Sichuan Agricultural University, Chengdu, 611130, China;1. Center for Ecosystem Science and Society (Ecoss) and Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ 86011, USA;2. Department of Microbiology, University of Massachusetts, Amherst, MA 01003, USA;3. Geography, College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4 RJ, UK;1. Ministry of Education Key Lab for Biodiversity Science and Ecological Engineering, The Institute of Biodiversity Science, Fudan University, #2005 Songhu Road, Shanghai 200438, China;2. Hawkesbury Institute for the Environment, University of Western Sydney, Locked Bag 1797, Penrith NSW 2751, Australia |
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| Abstract: | Soil organic matter (SOM) is the dominant store of nutrients required for plant growth, but the availability of these nutrients is dependent on transformations mediated by the microbial biomass. The addition of labile C to soil is known to alter SOM turnover (priming effect, PE), but understanding of this is limited, particularly with respect to impact on gross nitrogen (N) fluxes. Here we examined relationships between C and N fluxes from SOM under primed and non-primed conditions in two soils. Stable isotopes (13C and 15N) were used to measure gross C and N fluxes from SOM and to differentiate between SOM mineralised due to priming and that from basal mineralisation. 13C-glucose was added daily to simulate the effect of addition of labile C on SOM-C and –N mineralisation within the rhizosphere. Addition of glucose increased both gross N and C mineralisation from SOM. However, the C-to-N ratio of the mineralised flux from ‘primed’ SOM was 5:1, whereas the C-to-N ratio of the basal mineralised flux was 20:1 indicating that priming acted on specific organic matter pools. This result is consistent with the concept that priming is a distinct N-mining response of the microbial biomass, as opposed to an acceleration of the basal flux. Our data suggest that C and N fluxes are not directly linked through their gross stoichiometry in SOM. This is due to the heterogeneity and overall passiveness of OM relative to the dynamic nature of mineralisation fluxes and source pools, and in primed systems the mineralisation of N-rich compounds. |
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| Keywords: | Priming Nutrient cycling Gross N mineralisation Soil organic matter Rhizodeposition Soil-microbe interactions |
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