『Abstract
　Estimating phosphorus (P) availability is difficult - particularly in infertile soils such as those exposed after glacial recession - because standard P extraction methods may not mimic biological acquisition pathways. We developed an approach, based on microbial CO2 production kinetics and conserved carbon:phosphorus (C:P) ratios, to estimate the mount of P available for microbial growth in soils and compared this method to traditional, operationally-defined indicators of P availability. Along a primary succession gradient in the High Andes of Peru（uの頭に´）, P additions simulated the growth-related (logistic) kinetics of glutamate mineralization in soils that had been deglaciated from 0 to 5 years suggesting that microbial growth was limited by soil P availability. We then used a logistic model to estimate the amount of C incorporated into biomass in P-limited soils, allowing us to estimate total microbial P uptake based on a conservative C:P ratio of 28:1 (mass;mass). Using this approach, we estimated that there was＜1μg/g of microbial-available P in recently de-glaciated soils in both years of this study. These estimates fell well below estimates of available soil P obtained using traditional extraction procedures. Our results give both theoretical and practical insights into the kinetics of C and P utilization in young soils, as well as show changes in microbial P availability during early stages of soil development.

Keywords: Biological weathering; Phosphorus limitation』

1. Introduction
2. Methods
　2.1. Study sites
　2.2. Soil P fractions
　2.3. Microbial kinetics
　2.4. Estimating soil P using microbial kinetics
　2.5. Estimating microbial growth rates
　2.6. Statistics
3. Results
4. Discussion
5. Conclusion
Acknowledgements
References