Substrate origin controls phosphorus availability in globally distributed long-term chronosequences

Phosphorus (P) is one of the most important elements for soil biology and biogeochemistry worldwide. Yet, despite decades of research, important uncertainties persist about the drivers and changes in soil P forms during long-term soil formation. Here, we analyzed topsoils from nine globally distributed retrogressive soil chronosequences aiming to evaluate the relative contribution of key environmental factors (that is, soil age, substrate origin, climate, soil attributes, and vegetation) in explaining the long-term dynamics of primary, occluded, non-occluded, organic, and total P across different terrestrial ecosystems. We found that, rather than soil age, substrate origin was the main driver controlling the fate of different P fractions across contrasting environmental conditions. Moreover, our findings suggest that temporal patterns governing the long-term dynamics of different P forms as soils develop are not consistent among soil chronosequences, which is a result of contrasting environmental conditions, especially substrate origin. We further showed that topsoil total P was the greatest at intermediate soil development stage across the globe. Lastly, our results showed that P fractions were highly correlated with multiple surrogates of ecosystem services, such as carbon sequestration, plant productivity, and biodiversity. Together, our work provides new insights into the natural history of P availability, and further highlights that substrate origin, rather than soil age, is essential to predict changes in P availability in response to physical perturbation and climate change.