在自然条件下,生态系统中的矿物质循环是一个大闭合圈。被树木吸收的矿物质以有机物的形态归回土壤,土壤中的这些有机物又被矿化并再次被根吸收。有机物一点也不耗损地保留在生态系统中,耗尽的营养物必须予以补充。在一般性施肥和给树木特别的营养方面,意见分歧很大(Himelick等,1965;Murphy and Meyer,1969;Neely等, Under natural conditions, the mineral cycle in ecosystems is a large closed loop. The minerals absorbed by the trees return to the soil in the form of organic matter, which in turn is mineralized and again absorbed by the roots. Organic matter remains intact in the ecosystem at all, and depleted nutrients must be replenished. Opinions vary widely in terms of general fertilization and special nutrition for trees (Himelick et al., 1965; Murphy and Meyer, 1969; Neely et al.