Sample analyses
Soil available N and P may alter AM fungal impacts on plant fitness in native grassland (Johnson, 2010; G. Yang et al., 2016). Therefore, soil available P and inorganic N in each experimental plot were measured annually; soil available P was measured through the Olsen method (Bélanger & Rees, 2007), while soil inorganic N (NH4+-N and NO3-N) was determined by a flow injection autoanalyser (Flowsys; Ecotech, Germany). Mycorrhizal root colonisation was assessed using the method described by Trouvelot (1986)(Trouvelot, 1986). The extra-radical biomass of AM fungi was measured by soil neutral lipid fatty acid (NLFA) analysis (Andrino, Guggenberger, Sauheitl, Burkart, & Boy, 2021; Cozzolino, Di Meo, Monda, Spaccini, & Piccolo, 2016; Stevens et al., 2020).