Effect of long-term conservation tillage on arbuscular mycorrhizal fungi diversity

To verify the effect of long-term conservation tillage and subsoiling on arbuscular mycorrhizal fungi (AMF) diversity in dry areas in northern China, a comparative analysis of species richness, spore density, Shannon diversity index and colonization rate of AMF among no-till with straw mulching (NTS), no-till with straw mulching after subsoiling (SNTS) and traditional tillage treatment (TT) were conducted in 2014 at a long-term (22 years) positioning test base for conservation tillage in Linfen, Shanxi Province. In the study, 9 AMF species belonging to 7 genera were isolated and identified in soil samples of NTS and SNTS treatments, including two species each of Rhizophagus and Funneliformis and one species each of Glomus, Claroideoglomus, Acaulospora, Sclerocystis and Septoglomus. Also 8 AMF species belonging to 6 genera were isolated and identified in soil samples of TT treatment. The AMF species in the TT treatment were the same with those in NTS and SNTS treatments, except that there was no Acaulospora.The dominant species of AMF in NTS, SNTS and TT treatments were the same. The dominant species of AMF in the 0-40 cm soil layer were mainly Fu. mosseae and G. versiforme, the 40-80 cm soil layer were Fu. mosseae, G. versiforme and Rh. aggregatum, and the 80-120 cm soil layer was Rh. aggregatum. Below the 120 cm soil layer, the dominant AMF species was Rh. aggregatum, which was found only under NTS and SNTS treatments. Species richness, spore density and Shannon diversity index of AMF in NTS and SNTS treatments in the same soil layers were higher than those in TT treatment, and those in SNTS treatment were higher than those in NTS treatment. Species richness, spore density and Shannon diversity index of AMF decreased with increasing of soil depth under the same treatment. The maximum species richness, spore density and Shannon diversity index of AMF were all in the 0-20 cm shallow soil layer. The colonization rate and spore density of AMF at different growth stages of wheat in NTS and SNTS treatments were all significantly higher than that in TT treatment. Colonization rate of AMF in NTS, SNTS and TT treatments was the highest at jointing stage of wheat and was respectively 14.9%, 16.1% and 10.6%. AMF spore density of soil was the highest at maturity stage of wheat and was respectively 111.7 spores·(100g)^-1, 125.0 spores·(100g)^-1 and 90.3 spores·(100g)^-1. The study showed that long-term no-till with straw mulching improved AM fungi diversity, especially under no-till with straw mulching after subsoiling. The results provided the scientific basis for the full play of AMF role and reasonable application of conservation tillage in dry farmland ecosystems in northern China.