Arbuscular mycorrhizal fungal community structure and diversity in response to 3-year conservation tillage management in a sandy loam soil in North China

Modern agricultural science has greatly reduced the use of tillage. Monitoring conservation versus conventional tillage effects on soil microbes could improve our understanding of soil biochemical processes and thus help us to develop sound management strategies. The objective of this study was to investigate the effects of conservation tillage on the spore community structure and the diversity of soil arbuscular mycorrhizal (AM) fungi and to find out the main factors that influence these parameters. A long-term field experiment established in a sandy loam soil in Northern China has received continuous tillage management treatments for 3 years, including conventional tillage (CT), no tillage (NT), and alternating tillage (AT). Topsoil samples (0-15 cm) from four individual plots per treatment were collected for the analysis of chemical properties and fungal parameters. AM fungal spores were isolated using the wet-sieving method and identified to species level based on morphology by light microscopy. The community structure and the diversity of AM fungi were evaluated using the following parameters: spore density, relative abundance, species richness, Shannon-Wiener index ('), evenness (), and Simpson's index (). Jaccard index () of similarity was calculated to compare AM fungal species composition under different treatments. Twenty-eight species of AM fungi within four genera, , , , and , were recovered from the 12 plots within the three tillage management treatments. Higher spore density, species richness, and species diversity (', , and ) of AM fungi were observed in the two conservation tillage treatments, and the redundancy analysis showed that the species richness significantly correlated to soil organic carbon content ( < 0.05). The positive effects of NT and AT on the species richness were very close, while the AT had relatively greater beneficial impacts on the spore density and the evenness of AM fungi compared to the NT. The lowest Jaccard index () of similarity in species composition was also observed between the AT and CT treatments. Soil organic carbon, the spore density, and species richness and diversity of AM fungi increased in the two conservation tillage treatments. The species richness of AM fungi significantly correlated to soil organic carbon content ( < 0.05). Compared with the CT treatment, the AT rather than the NT significantly increased the spore density and the evenness of AM fungi ( < 0.05). Thus, alternating tillage practice may be more beneficial to agroecosystem in this region.