Abstract: [Objective] Arbuscular mycorrhizal (AM) fungi, forming the symbiosis with the majority of terrestrial plants, can facilitate host plants to absorb nutrients from soils and thus improve plant growth. This study aimed to investigate the relationships among AM fungi, plants and soil physical-chemical properties, and to determine the factors affecting the different-aged black locust (Robinia pseudoacacia) growth on the Loess Plateau of China. These result could provide a scientific basis for managing black locust plantation and further reveal their important role in environmental protection.[Method] This study was conducted in Wangdonggou watershed region at Changwu County, Shaanxi Province, China. Soil, shoot and root samples were collected in a chronosequence of black locust plantations including stands 0 (grassland), 11, 23, 35 and 46 years old stands. Soil physical-chemical properties, shoot and root nutrient contents, easily extracted glomalin contents, arbuscular mycorrhizal (AM) fungal colonization rate and spore density were measured.[Result] 1) Along the chronosequence, AM fungal colonization rate firstly increased and then maintained stability, and AM fungal spore density increased linearly; 2) Stand age was significantly correlated with the nutrients status of black locust roots and shoots such as contents of K, Zn, Fe, Mn in roots and N, Cu, Zn, K, Mn, Ca, Mg in shoots; 3) With the increasing stand age, soil available K increased, soil NO₃^--N firstly increased, then decreased and finally increased, and easily extracted glomalin content decreased linearly; 4) In general, black locust growth was synthetically affected by soil physical-chemical properties, AM fungi and plant nutrient status, whereas the factors positively affecting black locust growth varied with stand age. Specially, the growth of 11 and 23 years old black locust was positively correlated with contents of shoot K, Mn, Ca, Mg, Fe and Zn; the 35 years old black locust was positively correlated with contents of soil available K, shoot N and Cu, AM fungal colonization rate and spore density; the 46 years old black locust was positively correlated with AM fungal spore density and contents of root K and Fe, soil available K and NO₃^--N.[Conclusion] 1) Soil physical-chemical properties, AM fungal attributes and plant nutrients varied along the chronosequence of black locust. 2) The influencing factors of black locust growth changed as black locust aged. More specially, the growth of young black locust (11-23 years) mainly depended on shoot nutrient status, while, the growth of mature black locust (35-46 years) was synthetically affected by shoot and root nutrient status, AM fungal attributes and soil N and K content.

Key words: Robinia pseudoacacia, soil properties, AM fungi, plant nutrient