Root phosphatase activity aligns with the collaboration gradient of the root economics space

The adoption of diverse resource acquisition strategies is critical for plant growth and species coexistence. Root phosphatase is of particular importance in the acquisition of soil phosphorus (P), yet it is often overlooked in studies of root trait syndromes. Here, we evaluated the role of root phosphatase activity (RPA) within the root economics space and the order-based variation of RPA, as well as the correlations between RPA and a suite of leaf traits and soil properties over a range of evergreen tree species in a subtropical forest. Root phosphatase activity exhibited a high degree of inter-specific variation. We found that there were two leading dimensions of the multidimensional root economics space, the root diameter-specific root length axis (collaboration trait gradient) and the root tissue density-root nitrogen concentration axis (classical trait gradient), and RPA aligned with the former. Root phosphatase activity is used as a 'do it yourself' strategy of soil P acquisition, and was found to be inversely correlated with mycorrhizal colonization, which suggests a trade-off in plant P acquisition strategies. Compared with soil and foliar nutrient status, root traits mattered most for the large inter-specific changes in RPA. Furthermore, RPA generally decreased from first- to third-order roots. Taken together, such diverse P-acquisition strategies are conducive to plant coexistence within local forest communities. The use of easily measurable root traits and their tight correlations with RPA could be a feasible and promising approach to estimating species-specific RPA values, which would be helpful for better understanding plant P acquisition and soil P cycling.