Plant-microbe competition for nitrogen and phosphorous affected by drought
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Date
2014-08-05
Journal Title
Journal ISSN
Volume Title
Publisher
The University of Western Australia
Abstract
Competition for nutrients between plants and microbes is an important determinant for plant
growth, biodiversity and carbon cycling. Perturbations such as drought affect plant-microbe
competition for nitrogen (N) and phosphorus (P). Despite the importance of these nutrients in most
ecosystems, plant-microbe competition for N and P remains poorly understood. We used a novel
dual isotope labelling technique (15N and 32P) to assess plant-microbe competition for N and P
affected by drought in two different plant-soil systems.
Mesocosms were extracted from a grassland site where plants were strongly limited by N
(N-limiting system) and from a grassland site that showed strong soil P adsorption (P-adsorbing
system). Half of the mesocosms were subjected to drought one week prior to injection of the
tracers. Stable 15N (as KNO3) and radio-labelled 32P (as H3PO4) were injected, and measured in the
plant and microbial biomass 72 hrs later. Microbial uptake of 32P was strongly reduced by drought (on average by 89%), while
microbial 15N uptake was not. In contrast, drought reduced plant uptake of 15N (by 28%), but not of
32P. Microbial 15N uptake was much larger in the N-limiting system than in the P-adsorbing
system (by 491%), while plant 32P uptake was much larger in the P-adsorbing system than in the Nlimiting
system (by 703%). Both plants and microbes showed large flexibility in taking up 15N and
32P with the largest uptake of the nutrient that was in greatest demand.
Our results suggest that under drought conditions, plants lose in terms of N uptake, but win
in terms of P uptake when competing for these nutrients with microbes. These different
sensitivities to drought by plants and microbes may enhance decoupling of the N and P cycle with
increased drought conditions, depending on if plants and microbes are N or P limited.
Description
Keywords
Microbial EOR, Plants, Nutrients, Nitrogen, Species diversity
Citation
Dijkstra, F. A., He, M., Johansen, M. P., Harrison, J. J., & Keitel, C. (2014). Plant-microbe competition for nitrogen and phosphorous affected by drought. Paper presented at the 9th International IsoEcol Conference, Applications of Stable Isotope Techniques to Ecological Studies, 3rd-8th August 2014, Perth, Australia.