Phosphorus-acquisition strategies of native plant species of campo natural grasslands of southern South America

Abstract

The role of plant functional traits associated with phosphorus acquisition in shaping the structure andfunctioning of plant communities is receiving increasing attention. Two biodiversity hotspots in the southernhemisphere have been studied, identifying the diversity in plant phosphorus-acquisition strategies and theirlinks with soil properties. We focus on the diversity of plant phosphorus-acquisition traits of species from theCampo natural grasslands, to test the relationships between them and the effect of variation in soil attributesamong communities. We sampled 110 plant species in seven herbaceous communities associated with differentsoil geomorphology, and quantified root arbuscular mycorrhizal colonization and extracellular rootphosphomonoesterase and phosphodiesterase activity. Readily available soil phosphorus was closelyassociated with variation in phosphorus-acquisition strategy. Cyperaceae, Asteraceae and Poaceae, the mostcommon families of these communities, had low levels of arbuscular mycorrhizal fungi colonization; 80 %, 53% and 34 % of total observations, respectively, had arbuscular mycorrhizal colonization values below 2 %, while92 % of the plant species had colonization levels below 10 %. Cyperaceae had the highest values of rootphosphomonoesterase and phosphodiesterase activity (27.8 and 8.5 mg phosphorus g-1 root hour-1,respectively), followed by Poaceae (25.3 and 6.0 mg phosphorus g-1 root hour-1 respectively) and Asteraceae(15.5 and 6.0 mg phosphorus g-1 root hour-1 respectively). Community-weighted values of arbuscularmycorrhizal fungi colonization increased with increasing readily-available soil phosphorus. The opposite wasfound for community-weighted root phosphomonoesterase and phosphodiesterase activity values. Notably,these community-level responses were not observed at an individual species level. These results suggest thatsoil phosphorus availability strongly modulates the dominant phosphorus-acquisition strategies, and thus plantfunctioning, in species-rich Campo natural grasslands of South America.