Rule of organic phosphorous and microbial on phosphorous supply for vegetation in forest soil

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Phosphorus fractions by Hedley method and microbial biomass P (MBP) have been investigated in general Japanese forest, tropical forest and karst region forest soils to clarify the characteristics of P and P supply to forest vegetation. The results are summarized as follows.1. Available-P (Ion fraction-P + Bicarb-P) concentrations were remarkable low (under 30 μg P/g), and their values were lower than the annual uptake P by forest vegetation.2. Mineralizable-P is much in general Japanese forest. Phosphorus mineralization rate from organic P is important for P supply to forest vegetation.3. In tropical forest soil with strong weathering in East Kalimantan in Indonesia, total-P amount, available-P ratio and mineralizable-P ratio decreased with decreases of forest vegetation.4. MBP concentrations were greater than labile-P (available plus mineralizable-P) concentrations, so MBP pool is important for P supply to tropical forest.5. In forest soils in a karst region of the upper Yangtze River in China, both available-P and mineralizable-P have strong positive correlation with soil pH and total-C.6. Available-P concentrations by Hedley method have positive correlation with P concentrations by Bray II and Olsen methods. Available-P by Hedley is nearly equal to Bray II-P.7. MBP concentrations were nearly equal as labile-P concentrations, so MBP is index of P supply evaluation in karst region forest.8. In the region of the thick and very hard volcanic ash sedimentation in Miyake Island, Alnus sieboldiana grew a lot with their root nodule because of poor N supply in the ash layer.9. The tropical natural forest and Kanto region forest in Japan, which have rich N supply, had P limit condition compared to N condition.10. We discuss that P supply to root noble is the key to forest recovery in tropical degradation forest and in acid soil on Miyake Island.