Partitioning of soil phosphorus regulates competition between Vaccinium vitis-idaea and Deschampsia cespitosa

Abstract

It has been hypothesized that the wide range of forms and complexities ofphosphorus (P) in soil may result in resource partitioning that contributes tothe maintenance of plant species diversity. Here, we test whether the graminoid,Deschampsia cespitosa, and the ericaceous shrub, Vaccinium vitis-idaea, whichoften coexist, display preferences in utilization of P forms, and differ in theirproduction of extracellular P-degrading enzymes. We provided plants with noadditional P, or P forms with decreasing lability, namely sodium phosphate(SP), D-glucose 6 phosphate (DG6P), sodium phytate (PASS), and a combinationof SP, DG6P, and PASS. We also tested if preferences for P forms affectedthe competitive outcomes between the two species compared between conspecifics,as indicated by shoot biomass and acquisition of nitrogen (N) and P.Both D. cespitosa and V. vitis-idaea produced the greatest biomass when suppliedwith a mix of all three forms of P. Of the three forms of P tested alone,shoot biomass produced by both species was least when supplied with SP.D. cespitosa performed better when grown with PASS or a mix of all P formscompared with the performance of V. vitis-idaea on these substrates. This wasreflected by substantially greater phytase activity on the surface of its rootscompared with V. vitis-idaea. In contrast, V. vitis-idaea produced more phosphomonoesteraseto hydrolyze the simple organic P form, DG6P. Although Nwas kept constant in the treatments, the ability of plants to acquire it wasdependent on species identity, competition, and P supply. These findings providedirect evidence for preferences toward specific forms of P and indicate akey role played by organic forms of P. The results support the idea that partitioningfor soil P is one factor regulating plant competition, and ultimately,community composition. Our data also highlight the importance of theinterplay between P supply and N acquisition. © 2013 The Authors.