Changes in the composition and diversity of AMF communities mediated by management practices in a Mediterranean soil are related with increases in soil biological activity

A field experiment was performed in a semi-arid Mediterranean agroecosystem to assess the influence of different management practices on the composition and diversity of the arbuscular mycorrhizal fungi (AMF) present in the soil. The management practices included residual herbicide use (RH), plowing (P), plowing + oats (OP), addition of oats straw mulch (OS), and a control (land abandonment) (C). An adjacent, non-cultivated area under natural vegetation was used as a standard for local, high-quality soil, and as a reference for natural plant cover (NC). After eight years of management, soil was sampled, DNA was extracted, and the AM fungal small-subunit (SSU) rRNA genes were subjected to PCR, cloning, sequencing, and phylogenetic analyses. Thirty-five different phylotypes were identified, which were grouped in five families: the Glomeraceae, Paraglomeraceae, Diversisporaceae, Ambisporaceae, and Claroideoglomeraceae. The different agricultural management practices assayed affected both the community composition and the phylotypes richness of the AMF recovered from the soil, there being four clearly-different AMF communities (C together with OS, P together with OP, RH, and NC). The diversity of the AMF was positively correlated with soil parameters related with biological activity. The treatments involving plowing greatly altered the composition of the AMF communities but did not affect significantly the diversity and richness of the AMF with respect to treatment NC; however, the addition of herbicide gave the lowest AMF diversity found in this study. The treatment based on the addition of oats straw appears to be the most-suitable management strategy with respect to promotion of the AMF diversity and biological activity in this soil.