Phosphorus-Acquisition Strategies of Plant Species ofthe Pampas Biome

Abstract

Phosphorus (P) is found in several chemical compounds in soil, yet it is typically poorly available for plant uptake (Condron et al., 2005).The diversity of P forms in soil may determine “niche differences” in terms of plant P-uptake specializations through resource partitioning (Turner, 2008), promoting the coexistence of plant species (Chesson, 2000). There is scarce information on uptake specialization of different soil P forms by different plant species. Among land plants and ecosystems exists several different plant-P uptake strategies. The relative importance of these different strategies on a community depends on its soil P level, and it changes across communities due to variations of soil P levels (Lambers et al., 2008). Along a wide range of soil P levels plant species associate with mycorrhizal fungi for acquiring P. But in soil with very low levels of total P (<100 mg P kg-1) and available P (<1 mg P kg-1, resin P), the nutrient-uptake strategies of plants are mainly based on the release of exudates to mobilize nutrients; this has been observed along soil P gradients (Hayes et al., 2014, Oliveira et al., 2015). For the Pampas biome, studies are needed to test the relationship between soil P resources and the specializations of plants for acquiring this nutrient, and how different specializations can coexist in environments with P as a severely limiting resource. We hypothesise that in grasslands of the Pampas biome, highly diverse in plants and soils but understudied ecologically, total P and the different soil P forms explain differences in the proportion of plant species with different plant nutrient-acquisition strategies, i.e. 1) arbuscular mycorrhizal species, 2) non-mycorrhizal (NM) organic-acid-exuding species, 3) phosphatase-exuding species: 3a) monoesterase-, 3b) diesterase-, and 3c) phytase-exuding species.