Importance of the ectomycorrhizal network for seedling survival and ectomycorrhiza formation in rain forests of south Cameroon.

An investigation was undertaken at two sites south Cameroon to assess the importance of living roots of adult trees as sources of inoculum for survival, ectomycorrhizal colonisation and growth of seedlings of Paraberlinia bifoliolata. One-month-old seedlings of Paraberlinia bifoliolata, isolated from or in contact with roots of adult target trees, were transplanted in concentric circles 5, 10, 15, and 30 m away from the stem bases of four adult tree species (Afzelia bipindensis, Brachystegia cynometroides, Paraberlinia bifoliolata and Tetraberlinia bifoliolata). After 4 and 8 months, survival, ectomycorrhiza formation and seedling height were observed; plant biomass was determined after 8 months. After 4 months, there was no difference in seedling survival between seedlings in contact with roots of adult trees and isolated seedlings. The number of ectomycorrhizal seedlings was higher among seedlings in contact with adult trees than among isolated seedlings. After 8 months, both seedling survival and ectomycorrhiza formation were higher in seedlings in contact with roots than in isolated seedlings. Seedling survival and ectomycorrhiza formation were highest under Brachystegia. The fraction of surviving seedlings that had formed ectomycorrhizas was lowest under Afzelia. The fraction of surviving seedlings that were ectomycorrhizal declined monotonically towards the edge of the crown projection. Biomass of seedlings in contact with adult trees was significantly higher than that of isolated seedlings. This difference was consistent for all four tree species. The height of seedlings did not vary with the treatment.