Litter decomposition and soil organisms within and outside of Camponotus punctulatus nests insown pasture in Northeastern Argentina

PARIS, C. I.; GONZALEZ-POLO, M.; GARBAGNOLI, C.; MARTINEZ, P.; SOMMA DE FERRÉ, G.; FOLGARAIT, P. J.

APPLIED SOIL ECOLOGY

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2008 vol. 40 p. 271 - 282

0929-1393

Camponotus punctulatus builds big nests, up to 1.20 m high and 2 m in diameter, containingmore organic matter and nutrients than the surrounding soil. The aim of this study was torelate litter decomposition in C. punctulatus nests with soil organisms. We expected a greaterlevel of decomposition and more soil organisms within than outside the nests. The studysite was a field of Setaria sphacelata, a common sown pasture in Northeastern Argentina, with180 nests of C. punctulatus per hectare. To estimate decomposition rates we buried litterbagswithin and outside the nest (microsite type) at the beginning of each season and recoveredthose from the previous season. We used litterbags of different mesh size (7 mm, 2 mm,100 mmand 1 mm) filled with 8 g of S. sphacelata litter. At the same time, we sampled the soilsurrounding litterbags to estimate microbial dehydrogenase activity and the abundance ofnematodes and mesofauna. Soil microbial activity was greater outside the nests, mesofaunawere significantly more abundant inside the nests, and nematodes had similar abundanceinside and outside the nests. Throughout all seasons, there was a greater proportion ofProstigmata and Mesostigmata in the nests, whereas Oribatida and Collembola were moreabundant outside. Oribatid species composition differed between microsites. In the nests,there were two periods of higher decomposition (spring and summer) while outside themaximum occurred in spring, but only in litterbags of 7 and 2 mm mesh. The lack of macroand mesofauna (litterbags with 100-mm mesh) decreased organic matter decomposition inthe nests in summer and induced phosphorus immobilization in winter. Ant activity andfeeding preference, nest architecture and the plant community on C. punctulatus nests aresuggested as plausible factors that modify soil organism abundance and decomposition.