Phosphorus forms in Brazilian termite nests and soils: Relevance of feeding guild and ecosystems

It is well known that termites enrich organic matter in their nests and alter its properties, but their influence on phosphorus forms is less clear. The aim of our study was to quantify and systemize phosphorus forms in different nest parts (outer wall, inner wall, and central part) of termites of varying feeding guilds and soils in seven dominant Brazilian ecosystems. Organic (P-o) and inorganic P (P-i) were analyzed after sequential extraction of six labile and stable P fractions in samples from the Amazon region (Terra firme, and Varzea and Igapo floodplains), the Pantanal, the Atlantic rain forest (Mata Atlantica), the Cerrado and the Caatinga. In addition, selected alkaline extracts were characterized by means of liquid-state P-31 NMR spectroscopy. The central part of termite nests contained between 275 and 1871 mg kg(-1) total P, dominated by P-i in nests of soil/wood interface-feeder termites, but with balanced P-o and P-i contents in nests of wood-feeding termites. All P-o fractions, and, in most nests, also labile P-i forms were enriched in termite mounds in comparison to soils. The P enrichment was most pronounced in nests of the Terra firme (enrichment factors for labile P-i forms and for P-o fractions were 1.7-36.5 and 1.1-16.8, respectively), and the Igapo (labile P-i: 4.1-34.0; P-o: 1.1-25.7) where the total P content of the soil was the lowest with 141 and 171 mg kg(-1). Nests of wood-feeding termites mainly accumulated highly labile resin-P-i (enrichment factor 10.5-36.5) and partially the stable HClconc-P-i fractions, apart from P-o, which can be all attributed to the organic food source and food digestion. The soil/wood interface-feeder termites had more variations in their nests, but in general had higher portions of P bonded to minerals. Hence. we conclude that (i) termite activity results in a gross enrichment of labile P forms in the nests, (ii) the P composition in termite nests reflects the major feeding guild, and (iii) the degree of this P enrichment is partly driven by the P stock in the soil. (C) 2009 Elsevier B.V. All rights reserved.