Interactive effects of altitude and exposure on soil biota in different Alpine vegetation zones.

Mountain environments harbour ecosystems that are predicted to experience a rapid warming in the future with distinct consequences for soil organic matter quality and quantity. Enchytraeids are considered a keystone group that can exhibit considerable site-specific differences, and they can be used as specific ecological indicators. However, the changes in their abundance and community structure at a species level in this type of ecosystems are still insufficiently documented. Therefore, we aimed to assess and evaluate the dominant abiotic and biotic factors shaping/regulating enchytraeid species composition and abundance along an altitudinal/climatic gradient and associated vegetation zones. Ten alpine sites were investigated in the Italian Alps (Val di Sole, Trentino). Five sites were positioned at north (N) and other five at south (S)-facing slopes. To facilitate the comparisons between soils collected on N and S slopes, the altitudes of the sites were as similar as possible (ranging from 1200 up to 2400 m a.s.l). The vegetation cover varied from different types of forests at lower elevations to alpine grasslands at higher elevations. Three plots (5x5 m) at 50 m from each other were set-up in each of the 10 study sites and soil sub-samples were randomly taken in each plot in 5 cm depth intervals (0-5, 5-10 and 10-15 cm). Microannelid extraction was performed over 48 h by a wet-funnel technique without heating and they were identified to species level under a light microscope. Soil microbial communities (bacteria, fungi and archaea) were quantitatively assessed by real-time PCR. Soil microbial biomass was estimated as double-stranded DNA yields, and the physical and chemical soil properties were also determined, together with the humus forms, which constitute the meeting point (proxy) of feedback interactions and any changes in their composition and properties is expected to affect the autochthonous soil biota.