Hidden Engineers and Service Providers: Earthworms in Agricultural Land-Use Types of South Tyrol, Italy

Earthworm activities affect the provision of many ecosystem services. Land use can strongly influence earthworm communities and, hence related soil functions. We assessed earthworm biomass, abundance, and species composition on grasslands, apple orchards, and vineyards in the context of an existing sustainability assessment tool in South Tyrol, Italy. A stratified sampling campaign revealed significant differences in earthworm distribution. We found 21 to 700 individuals m−2 in grasslands and surprisingly abundant earthworm communities in apple orchards (14 to 382 individuals m−2). Results for vineyards were ambiguous with no or very low abundance in 47% of the vineyards and a maximum of 396 individuals m−2. Mesohumic endogeic species were the most abundant functional group observed (75% of the biomass in grasslands, 50% in apple orchards and vineyards). Aporrectodea caliginosa was the most abundant endogeic species, Lumbricus rubellus the dominant polyhumic endogeic species in all land-use types. We estimated a total of 34,900 t of earthworm biomass on agricultural areas in South Tyrol corresponding to a total value of EUR 872 million. Although soil quality is a complex concept that cannot be captured with a single indicator, earthworms are suitable and feasible indicators for sustainable soil use at the landscape scale.