Ndiaye D., Lepage Michel, Sall C.E., Brauman Alain. (2004). Nitrogen transformations associated with termite biogenic structures in a dry savanna ecosystem. Plant and Soil, 265 (1-2), p. 189-196. ISSN 0032-079X.
Titre du document
Nitrogen transformations associated with termite biogenic structures in a dry savanna ecosystem
Ndiaye D., Lepage Michel, Sall C.E., Brauman Alain
Source
Plant and Soil, 2004,
265 (1-2), p. 189-196 ISSN 0032-079X
Soil structures built by litter-feeding termites are one of the main soil translocation processes in dry tropical savanna. Runways (soil sheeting) made of soil particles cemented with salivary secretions covering the dead plant pieces collected on the ground surface represent the main soil structures. The aim of this study was to determine the impact of this soil engineering activity on the microbially-mediated N transformations (nitrification and denitrification) associated with termite sheeting. We investigated the hypothesis that the physicochemical and microbial properties of termite soil sheeting depend on (i) the termite species and (ii) the type of organic substrate consumed. Soil sheeting built by two of the main savanna species, Macrotermes subhyalinus and Odontotermes nilensis, were sampled on field plots treated with three different types of litter (Acacia leaves, millet straw, both whole and ground (< 500 mum), and cattle manure). The soil's organic C, total N, inorganic N, microbial biomass, potential CO2 respiration, nitrification and denitrification were measured. For both termite species and all types of litter, the soil sheeting was enriched in organic C and inorganic N, resulting in an increase in soil respiration, whereas the microbial biomass was unchanged with respect to the reference soil. With the exception of the soil nitrification potential, the type of organic substrate did not significantly affect the properties of the soil sheeting measured. However, the nitrogen cycle was affected differently by the two termite species. In O. nilensis sheeting, the denitrification potential was reduced with respect to the reference soil, whereas the nitrification potential was inhibited in M. subhyalinus sheeting. The changes in the nitrogen cycle processes resulted in an increase in NH4+ and NO3- in the termite soil sheeting, increasing the availability of nitrogen to plants. This study reinforces the importance of termites as a keystone savanna group whose building activities have an effect on tropical soil mineralization.
