Bioavailability of phosphorus in oak forests in Scotland was studied mainly by examining theeffects of activities of microbials and phosphates in forested soil. The results indicated that therewas a close correlation between activity of soilmicrobials and that of phosphates. Both activitiesshowed gradient changes in range of distances from fine roots. The activity of phosphates reachedpeak in summer as trees grew into the most vital period. Through a fractionation scheme of ex-tracting phosphorus ranged from labile to stable pools in soil, an attempt was made to explore therelationship between bioavailability of phosphorus and activities presented by soilmicrobials andphosphates. After adding organic matter into soil as energy for microbials, it was found that vari-ous fractions had corresponding change in contents of available P. 0. 1 M NaOH was used as ex-tractant to identify size of available P. A fresh design of pressing down tube cutting into soil wasput on trial for determination f difference in takeup-P between parts of soil inside and outside oftube. Based on the method, bioavailable P was determined to be about 36%, compared to totalavailable P in oak forest soil.