LAUSR

Aims Ingrowth bags are widely used to estimate mycorrhizal growth and dynamics. However, it remains unclear to what extent they reflect the surrounding soil, and how this varies with environmental conditions. Methods We used a fertilization experiment to investigate if carbon-free mesh bags were representative of their surrounding soil. We determined AMF hyphal length density (HLD), phospholipid fatty acids (PLFA 16:1ω5) and neutral lipid fatty acids (NLFA 16:1ω5). Results When AMF abundance in surrounding soil was high, HLD and both fatty acids were underestimated by the mesh bags. The PLFA 16:1ω5 in surrounding soil included bacterial PLFA, complicating the comparison of PLFA 16:1ω5 between mesh bags and surrounding soil. Both NLFA 16:1ω5 and HLD showed a significantly positive correlation, and fertilization effects were mostly similar for mesh bags and surrounding soil. Conclusions Although carbon-free mesh bags can underestimate AMF abundance in soils, they represent a useful method to compare patterns in AMF abundance across environmental gradients and can be particularly useful in combination with the use of stable isotope tracers for unraveling patterns in AMF growth. NLFA 16:1ω5 appeared a more accurate measure for AMF than PLFA 16:1ω5 because the latter included bacterial PLFA.