Effects of different land use on soil chemical properties, decomposition rate and earthworm communities in tropical Mexico

The effects of land use on soil chemical properties were evaluated, and earthworm communities and the decomposition rate of three typical land use systems in tropical Mexico, namely banana plantations (B), agroforestry systems (AF) and a successional forest (S) were compared. The study was carried out from November 2005 to April 2006. A completely randomized sampling design was established in six sites (B1, B2, AF1, AF2, S1 and S2). Soil properties and chemical characteristics (texture, pH, organic carbon (Corg), nutrients, and available Zn and Mn), earthworm communities and the decomposition of Bravaisia integerrima and Musa acuminata litter were analyzed over a period of 8 weeks.All soils were loamy clays with a medium to high content of nutrients. Three principal clusters were generated with the soil chemical properties: a first cluster for forest soils with high Corg and Ntot and low available Zn content, a second cluster for AF1 and a third cluster for B1, B2 and A2. The decomposition of B. integerrima litter was significantly faster (half-life time: 1.8 (AF2)–3.1 (B1) weeks) than that of M. acuminata (4.1 (AF2)–5.8 (S2) weeks). However, the decomposition rates did not differ significantly among the different sites. The greatest earthworm diversities were observed in AF2 and B1. Native species were dominant in the forest soils, whereas exotic species dominated in AF and in the banana plantations. The abundance and biomass of certain earthworm species were correlated to physical and chemical soil parameters. However, litter decomposition rates were not correlated with any of the soil physical–chemical parameters. While none of the land use systems studied led to a decrease in nutrient status, earthworm biodiversity and abundance, or in litter decomposition rate, they did result in a change in earthworm species composition.