Abstract: To uncover the effects of arbuscular mycorrhizal fungi (AMF) on reseeding species at different growth period,a microcosm experiment was carried out using Bromus inermis, Agropyron cristatum,Leymus chinensis,and Poa pratensis as test material. This experiment was set up as a factorial design containing two AMF inoculation treatments (with AMF,without AMF) and three growth period (seedling,jointing,jointing after mowing). We measured above-ground and below-ground biomass,root colonization,soil hyphal density,mycorrhizal growth response,and plant-available phosphorus. Our results showed that AMF inoculation increased the above biomass and below biomass of B. inermis and L. chinensis,compared with none inoculation. However,AMF inoculation did not affect the above biomass and below biomass of A. cristatum and P. pratensis at jointing after mowing period,compared with none inoculation. Mycorrhizal growth response (MGR) of four species was positive at each period,and the lowest MGR of A. cristatum,L. chinensis,and P. pratensis was at jointing period after mowing. From seedling to jointing period,AMF root colonization of these four species significantly increased. Soil hyphal density in B. inermis, A. cristatum,and L. chinensis reached the maximum level at jointing period after mowing. Therefore,the symbiotic relationships between AMF and plants depend on growth periods of plants and were species specific. Overall,from seedlings to adults,the abundance of AMF in roots and outside roots increased,while the response of MGR showed a decreasing trend. This indicated that AMF had a strong growth-promoting effect on plant seedlings,and this growth-promoting effect was not related to AMF abundance.

Key words: AMF, Degraded grassland, Grassland restoration, Bromus inermis, Agropyron cristatum, Leymus chinensis, Poa pratensis

摘要： 为探究接种丛枝菌根真菌(Arbuscular mycorrhizal fungi,AMF)对不同生育期牧草生长的影响，本研究选取无芒雀麦(Bromus inermis)、冰草(Agropyron cristatum)、羊草(Leymus chinensis)和草地早熟禾(Poa pratensis)4种牧草进行盆栽试验，分别在苗期、拔节期和刈割后拔节期进行取样，测定植物生物量、菌根侵染率和菌丝密度等指标。结果表明：与不接种AMF相比，接种AMF显著提高了无芒雀麦和羊草的地上与地下生物量，但对刈割后拔节期冰草和草地早熟禾的地上和地下生物量无显著影响；4种牧草在不同生育期下菌根响应均为正效应，但是刈割后拔节期冰草、羊草和早熟禾菌根生长响应显著降低；4种牧草根系的菌根侵染率随生育期均呈增加趋势；刈割后拔节期土壤菌丝密度达到最高。因此，AMF与植物的共生关系具有物种特异性，共生作用随着生育期发生改变，随着生育期根内和根外AMF丰度增加，但菌根生长响应下降，说明AMF对植物幼苗有更强的促生作用，而这种促生作用与AMF丰度无关。

关键词: 丛枝菌根真菌, 退化草地, 草地修复, 无芒雀麦, 冰草, 羊草, 草地早熟禾