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Plant species identity and arbuscular mycorrhizal status modulate potential nitrification rates in nitrogenâlimited grassland soils
- Veresoglou, Stavros D., Sen, Robin, Mamolos, Andreas P., Veresoglou, Demetrios S.
- journal of ecology 2011 v.99 no.6 pp. 1339-1349
- Agrostis capillaris, Fragaria vesca, Prunella vulgaris, allelopathy, ammonia, ecosystems, grassland soils, mycorrhizal fungi, nitrification, nitrogen, oxidation, vesicular arbuscular mycorrhizae
- 1.âArbuscular mycorrhizal (AM) fungi and ammonia oxidizers (AO) represent key soil microbial groups regulating nitrogen (N) cycling in terrestrial ecosystems. Both utilize soil ammoniumâN reserves for N assimilation, whilst the latter, through autotrophic nitrification, drive ammonia oxidation to highly mobile nitrateâN. 2.âAn incompatible interaction between root symbiotic AM fungi and AO was hypothesized and evaluated in plantâspeciesârich, Nâlimited Mediterranean grassland soils. Such an outcome would be manifested in a negative relationship between plant mycotrophy and local soil potential nitrification rates (PNR), a standard functional measure of ammoniaâoxidizing activity in soils. 3.âIn three independent mesocosm experiments, grassland soils that supported monocultures of mycotrophic, as opposed to weakly and nonâmycotrophic, plants exhibited significantly lower PNR. Under field conditions in a fourth experiment, we verified that soils from stands of weakly mycotrophic Agrostis capillaris sustained higher PNR than counterparts supporting highly mycorrhizal Prunella vulgaris and Fragaria vesca. 4.âDiscussion of mycotrophyârelated modulation of AO activity centres on whether the observed relationships highlight evidence for either direct competition or a functionally important example of plantâmicrobial allelopathy. 5.âSynthesis. Substantial evidence has been presented confirming (i) plant species identityârelated regulation of PNR and (ii) negative relationships between plant mycotrophy and plant speciesâmediated impact on PNR in Nâlimited Mediterranean grassland soils. Likely mechanisms (i.e. competition and/or allelopathy) that underpin this functionally significant plantâmicrobeâsoil relationship controlling the fate of ammoniumâN require urgent elucidation in Nâdeficient ecosystems.