The nature and origins of diester phosphates in soils: a 31 P-NMR study

Abstract

Soils of two climosequences in Russia were investigated by 31 P-NMR spectroscopy. They comprised Dystric Podzoluvisols, Haplic Greyzems, Calcic Cher- nozems, and Gypsic Kastanozems, which are located along temperature and precipitation gradients of the Russian Plain. Another sequence of soils included forest Humic Cambisols and Umbric Leptosols of subalpine and alpine meadows, which are formed in different climatic conditions along a climosequence of the Mt. Malaya Khatipara (northern Caucasus). The results showed that accumulation of DNA was high in the cold, wet, and acid soils (Dystric Podzoluvisol, alpine Umbric Leptosol), while phospholipids and teichoic acids mainly accumulated in the more microbially active soils. We performed a laboratory incubation experiment to test the relationship between microbial biomass P and P species identified in soil extracts. The proportions of P com- pounds resonating at 0.5-3.0 ppm in the NaHCO 3 and H2SO4 extracts from the incubated Humic Cambisol in- creased. The amounts of phosphate diesters resonating at 0 ppm in the same extracts and in the subsequent NaOH extracts decreased after incubation. Based on the results of 31P-NMR spectroscopy of native soils and of the labo- ratory incubation experiment we concluded that signals at 0 ppm in spectra of soil alkaline extracts belong to DNA P which is mainly stabilised in soil organic matter outside microbial cells (at least in soils with relatively low microbial activity). Phospholipids-teichoic acids P extracted with 0.5 M NaHCO 3 seems to be derived from soil microbial biomass, and its proportion can reflect the microbial activity in the soil.