Screening of arbuscular mycorrhizal fungi for the revegetation of eroded red soils in subtropical China

Some acidic red soils in hilly regions of subtropical China were degraded as a result of slope erosion following the removal of natural vegetation, primarily for fuel. Revegetation is important for the recovery of the degraded ecosystem, but plant growth is limited by the low fertility of eroded sites. One factor contributing to the low fertility may be low inoculum density of arbuscular mycorrhizal (AM) fungi. Compared to red soils under natural vegetation or in agricultural production, substrates on eroded sites had significantly lower AM fungal propagule densities. Thus, the management and/or application of AM fungi may increase plant growth and accelerate revegetation. Thirteen species of AM fungi were identified in red soils by spore morphology. Scutellospora heterogama, Glomus manihotis, Gigaspora margarita, Glomus aggregatum and Acaulospora laevis were among the most common according to spore numbers. Pot cultures were used to isolate and propagate 14 isolates of AM fungi indigenous to red soil. The effectiveness of each fungus in promotion of growth of mungbean was evaluated in red soil. For comparison, three isolates from northern China, known to be highly effective in neutral soils, and two isolates from Australia, known to be from acidic soil were used. Effectiveness was positively related to root infection (r(2) = 0.601). For two of these isolates, Glomus caledonium (isolated from northern China) and Glomus manihotis (an isolate indigenous to red soil), the applied P concentration giving the highest infection and response to infection was approximately 17.5 mg P kg(-1) soil. In field experiments in which this concentration of P was applied, the five most effective isolates were tested on mungbean. The Glomus caledonium isolate from northern China was the most effective, followed by the indigenous Glomus manihotis isolate. The Glomus caledonium isolate was also shown to be effective on Lespedeza formosa, which is commonly used in revegetation efforts. We conclude that inoculation of plants with selected isolates of AM fungi may aid in revegetation efforts on eroded red soils in subtropical China.