Fire is one of the incorporate vegetation management practices for grasslands and semi-arid rangelands. It may affect symbiotic relationship between range plants and mycorrhiza. Accordingly, this research was aimed to investigate the effects of a spring prescribed fire on the symbiotic relationships between mycorrhiza and 6 plant species. The study was conducted in a semi-arid steppe rangeland called Dehbar, Torghabeh in Mashhad, Iran. A prescribed fire was applied on 20th April 2015. Soil and plant samples were taken one month later. Colonisation and spore density were measured on the root of 6 different species. Spring fires significantly increased fungi spores in the rhizosphere of all plant species with the highest and lowest frequencies (42 and 24 per gram dry soil) obtained for Pimpinella tragium and Artemisia aucheri, respectively. Fire effects on colonization varied from high to no effect ranges. The increases in the mycorrhiza propagules after a prescribed burning during the growth season might be due to a sudden increase of nutrients from plant ashes. Although the studied plant species were different in terms of morphology (canopy and root type), phenology and life form (geophyte, perennial grasses and shrubs), the spring fire increased the colonization rate for plant species that had just started vegetative plant growth (Stipa barbata, Artemisia aucheri and Pimpinella tragium) but it had no effects regarding the plant species (Poa bulbosa, Agropyron trichophorum and Astragalus gossypinus) that were fully grown at the time of burning and/or had terminated seasonal growth period at the time of soil sampling. Therefore, in terms of plant-mycorrhizal symbiosis, a prescribed spring fire might increase the competitive advantage of perennial late season species as compared to annual early season species which are mostly ephemeral or invasive plants.

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