Earthworm community structure under different land-use systems across various soil conditions

Abstract

Earthworms contribute to several soil processes and therefore influence the ecosystem services provided by soil. Land-use intensification and climate change are considered the main threats to soil health and biodiversity loss and several strategies have been proposed to address these concerns at the EU level. However, less is known about how land use affects earthworm communities across various soil conditions and how climatic conditions could affect the communities under boreal conditions. We used earthworm community data with information on land use, soil properties and climate before sampling across multiple years to understand the main factors shaping earthworm communities in Estonian agroecosystems. The land use systems included arable fields (cropland and temporary grasslands) and grasslands (transitional grasslands, semi-natural grasslands and natural grasslands). Greater earthworm Shannon's index in grasslands than in arable fields was primarily due to differences in the presence of epigeic species. We observed that the two anecic species in Estonian soils exhibited notably different tolerances to habitat conditions. Lumbricus terrestris was more sensitive to land-use intensity but less affected by soil properties, whereas Aporrectodea longa, despite being the dominant anecic species in most arable fields, showed a narrower tolerance to soil properties. Soil moisture content influenced the earthworm community positively; therefore, changes in the climatic conditions could modify the earthworm communities. Statistically significant relationships with climatic conditions on the year of sampling suggest that low precipitation and humidity during the summer can have a negative influence on earthworm species diversity and increase the proportion of the dominant species. The results of this paper indicate that land use is the main factor in selecting species composition, while soil properties mostly control the abundance of the species. While grasslands had higher biodiversity, future policy development should consider that natural grasslands on less fertile soils have a limited impact on increasing earthworm species richness and are less likely to be protected from biodiversity loss.