Responses Of Arbuscular Mycorrhizal Fungi To Long-term Chemical And Organic Nutrient Inputs In Three Distinct Soils

Arbuscular mycorrhizal fungi(AMF)form symbiotic relationships with more than 80%of terrestrial plants,and transfer nitrogen(N),phosphorus(P)and other mineral elements to host plants in exchange for carbohydrates.AMF are a group of important organisms that mediate multiple functions of terrestrial ecosystems.Studies have shown that structure and diversity of AMF communities are affected by various biotic and abiotic factors.Fertilization,as one of the important practices to increase crop yields,enhances soil nutrient availability and thus affects the composition and diversity of AMF communities.In particular,the type and duration of fertilizer applications may affect soil chemical and physical characteristics,thereby modifying AMF community structure.However,it is unclear how long-term fertilization affects the symbiotic relationship between plants and AMF.Also,little is known about how soil properties mediate the effects of long-term fertilizer inputs on the AMF communities.We examined the AMF community and diversity in plants under long-term conventional and organic managements at three locations.Soils were collected from field and maize(Z mays)or clover(T.repens)plants were used as host plants in our pot experiments.The three field locations were at Jinxian County,Jiangxi Province,Daiyue District,Shandong Province and Quzhou City,Hebei Province with a pH of 4.96,7.03 and 7.95 in their respective control.At each location three fertilization treatments were designed,included:no fertilization(CK),mineral fertilizer(NPK),organic mannue(OM),and inorganic fertilizer plus organic mannue(MNPK).The objectives of this study were to 1)quantify the effects of organic and inorganic nutrient inputs on AMF communities,and 2)determine whether similar nutrient inputs lead to similar impacts on AMF communities in different soils at three field locations.The experimental results are as follows:1.The effects of nutrient inputs on AMF communities in roots of Z.mays and T.repens in red soil ecosystem:1)Mycorrhizal colonization of roots was higher in Z.mays than T.repens.NPK and OM treatments significantly increased soil nutrient contents,plant biomass but reduced the AMF infection rate of roots in Z.mays and T.repens(P<0.05).2)AMF communities in two plants were different,indicating the host specificity.Both inorganic and organic nutrient inputs altered the AMF communities,increasing Paraglomus but reducing Glomus in both hosts(P<0.05).Also,Paraglomus abundance in Z mays roots was significantly higher under OM treatment than NPK treatment,but an opposite trend was shown in T.repens(P<0.05).3)NPK inputs significantly reduced the richness and diversity of AMF communities in both host plants(P<0.05),but OM treatment significantly reduced richness and diversity of AMF communities only in Z.mays.2.Responses of arbuscular mycorrhizal fungi to long-term chemical and organic nutrient inputs in three distinct soils:1)Nutrient inputs significantly increased shoot biomass and shoot P content of Z mays(P<0.05),and decreased mycorrhizal colonization of Z.mays in all three soils(P<0.05).2)Effects of nutrient inputs on AMF community structure were different among distinct soils.In acidic red soil of Jiangxi,fertilization significantly reduced Glomus but increased Paraglomus abundance in the roots of Z mays(P<0.05);similarly,fertilization treatments decreased Glomus abundance,but increased Claroideoglomus abundance in the neutral soil of Hebei.In contrast,both NPK and NPKM increased Glomus abundance but reduced Paraglomus abundance in the alkaline soil of Shandong.3)Effects of nutrient inputs on the richness and diversity of AMF communities were different.Both NPK and OM treatments reduced the richness of AMF communities in the acidic red soil of Jiangxi,but did not significantly affect in two other soils at Shandong and Hebei.