Soil organic phosphorus (P) has been identified as a pivotal component of bioavailable P, especially in late stages of ecosystem development. Organic P turnover rate is affected by the stabilization ability of the soil (i.e. organic matter, minerals, microbial activity) and also abiotic factors (i.e. temperature, precipitation, light). However, our understanding of P transformations in the soil, especially with ecosystem development and global climate change, is complicated due to the complexity of P species. Organic P is found in a variety of forms including monoesters, diesters, and phosphonates based on the chemical arrangement. Novel approaches for identifying and quantifying organic P species include 31P nuclear magnetic resonance spectroscopy (NMR), Fourier-transformed ion cyclotron resonance mass spectrometry (FTICR-MS), and x-ray absorption near edge structure (XANES). We plan to integrate these advanced techniques to identify the soil characteristics and climatic variables that exert control over P speciation. Our research is a timely, systematic, and interdisciplinary investigation that uses state-of-the-art approaches to provide mechanistic understanding of how P cycling responds to (Mediterranean and arid) climatic gradients, and the implications for plant productivity, carbon sequestration, and other essential ecosystem services provided by the Critical Zone (the area from regolith through vegetation that supports life).