The Community Structure and Biomass of Arbuscular Mycorrhizal Fungi in Field Soil Was Changed by Soil Depth.

Arbuscular mycorrhizal fungi (AMF) improve the uptake of phosphate from soil through symbiotic associations with plant roots. The colonization in plant roots is necessary for the proliferating and new spore formation of AMF. In generally, the amount of plant roots is different on the soil depth. Therefore, it is thought that the biomass and community structure of AMF is also different on the soil depth. Thus, the purpose of this research is to determine the accurate sampling method to assess AMF biomass and community structure in crop field A field experiment was conducted at Nihon University in Kanagawa, Japan. Replicated plots of winter sown wheat (Triticum aestivum L.), and fallow (no weeds during winter) were established in 2008. In June 2009, soil samples were collected from different soil depth (0 - 10, 10 - 20, 20 - 35, 35 - 50, 50 - 70, and 70 - 100 cm) in both plots. AM fungal biomass in soil was measured by spore density and analysis of the fatty acid biomarker C16:1cis11. AM fungal community structure was characterized on the basis of the large subunit ribosomal DNA (LSU rDNA). The AMF biomass (Concentration of C16:1cis11 and spore density in soil) decreased with increasing the soil depth in both plots. In addition, a positive correlation (r = 0.854, P < 0.05 in wheat plot, r = 0.917, P < 0.05 in fallow plot) was observed between the concentration of C16:1cis11 and the spore density in soil. Moreover, by DCA, AMF communities were different in wheat and fallow plot. AM fungal communities in the soil of sown wheat field were more diverse than that of fallow. However, there was not the distinct difference of AMF communities by soil depth in both plots. In conclusion, more detail soil sampling must be conducted to assess the AMF communities and biomass in agricultural field.