Do Extensively Managed Semi-Natural Grasslands or Regularly Re-Seeded Multi-Species Grasslands Increase Soil Biodiversity Compared to Intensively Managed Permanent Grasslands?

Abstract

Intensification of agriculture has reduced aboveground and belowground biodiversity, and its ecosystem services. Regenerative or nature-inclusive agricultural systems are supposed to enhance functional agro-biodiversity and create more resilient systems. For dairy or beef farming, essential components of these agricultural systems are extensification towards semi-natural grasslands and/or establishing multi-species grasslands in which specific functional grassland plant species are sown while maintaining productivity. Both grassland types differ from each other in terms of plant diversity (i) and management (ii), but it is unclear whether and how these differences will translate into soil quality and soil biodiversity. Therefore an on-farm trial was set up in which the abundance and diversity of soil biota was compared between  intensively managed species-poor permanent grasslands, intensively managed frequently re-seeded multi-species grasslands, and extensively managed species-rich semi-natural grasslands. Total abundance and biomass of nematodes, micro-arthropods and earthworms did not differ between grassland types. Bacterial PLFA was higher in semi-natural grasslands than in multi-species grasslands, and intermediate in permanent grasslands. Protozoan PLFA was higher in permanent grasslands than in multi-species grasslands, while semi-natural grasslands took an intermediate position. The grassland management types only had an effect on alpha and gamma diversity in case of micro-arthropods, with a higher taxonomic richness in semi-natural grasslands. Nematode, micro-arthropod and earthworm taxonomic community structure differed between grassland management types. Differences in abundance and diversity of soil biota between multi-species grasslands and permanent and semi-natural grasslands were thought to be particularly related to disturbances caused by tillage and its direct and indirect effects on soil biota and its living conditions. So for the transition to grassland systems that simultaneously utilise and support soil biodiversity and their ecosystem services, longevity of particularly multispecies grasslands without regular soil disturbance is considered important. However, decisions on transitioning from current grassland management to future farming systems must also consider impacts on aboveground biodiversity including insects (Visser et al., 2024) and birds (Visser et al., 2024) and ecosystem services such as agricultural production (Zetterlind et al., 2024).

Keywords: Soil biota, microbial, nematodes, micro-arthropods, earthworms, taxonomic diversity