Composition and distribution of soil fauna in a temperate forest of Central Mexico

Background/Question/Methods

Soil fauna has an important functional role in ecosystems, it determines several physical and chemical soil characteristics, and it has clear effects on soil fertility and productivity at a large spatial scale. The objective of this study was to assess the spatial and temporal variations in composition, abundance, and distribution of soil fauna in Quercus, Abies and Pinus forests in the Río Magdalena basin, Mexico City, Mexico. Fifteen samples of litter were randomly collected in the three vegetation types by tracing a hoop of 25 cm diameter; first, soil fauna was manually extracted, and later on by using Berlesse-Tulgren funnels. Litter C/N ratio was determined and correlated with soil fauna abundance. Besides, we dug out five soil blocks of 25 cm x 25 cm x 30 cm deep at 3373, 3432 and 3491 m a.s.l. of Abies forest. Soil fauna was extracted every 10 cm depth layers, in this case sampling was carried out in dry and rainy seasons.

Results/Conclusions

Taking into account both sampling methods, we found 29 taxa in addition to larvae of holometabolous; and a total of 76,686 individuals. The most abundant taxa were Acarida, Collembola, Oligochaeta and Homoptera. In the litter, the highest abundance was found in Pinus forest with 21,633 organisms, whereas the higher number of taxa was observed in Quercus forest (25). The C/N ratio was lower in Quercus forest with 47, and the highest value was registered in Pinus (59). The correlation between litter and soil fauna abundance was significantly positive in Pinus, negative in Abies and Gaussian in Quercus. In blocks, the highest abundance of macro and mesofauna was recorded at 3,372 m a.s.l. and the lowest values were found at 3,491 m a.s.l. 0-10 cm layer showed the highest abundance, and as depth increased, abundance decreased by one-half each 10 cm layer. In litter substrate, soil fauna was more abundant in rainy season, and in soil forest was more abundant in dry season. This suggests that distribution of fauna is affected by litter mass and quality, as well as by altitude and soil depth.