Grazing intensity, soil functions and greenhouse gas emissions: a case study in Alpine pastures of the Dolomites

Alpine grasslands are crucial ecosystems for mountain livestock farming and provide a variety of non-provisioning ecosystem services. Among these services, soil microbial biodiversity and regulation of greenhouse gases fluxes can be influenced by grazing management. This study aimed to explore the relations among pasture-use intensity, the taxonomic and functional profiles of soil bacterial and fungal communities, and greenhouse gases emissions (nitrous oxide and methane) in a historical alpine pasture grazed by dairy cattle in the Dolomites, northeastern Italian Alps. Pasture-use intensity was assessed with GPS tracking to distinguish between intensively and extensively used areas. Within these areas, soil DNA and greenhouse gas emissions were sampled at three sampling times: pre-grazing, during grazing, and post-grazing. Soil bacterial and fungal taxonomic compositions and functions were inferred from DNA sequencing using the FAPROTAX and FUNGuild libraries. Soil greenhouse gases emissions were estimated using a portable FTIR gas analyzer (GASMET GT5000). These variables were analyzed as function of pasture-use intensity and sampling time. The soil bacterial and fungal taxonomic and functional profiles varied significantly with pasture-use intensity but remained stable across sampling times. Soil emissions of nitrous oxide were lower and more variable than those of methane (nitrous oxide: 5.82×10-47.61×10-4 mg m-2 h-1; methane: 1.63×10-31.28×10-3 mg m-2 h-1) and did not vary with pasture-use intensity and sampling time. No correlations were observed between greenhouse gases emissions and bacterial or fungal communities at either the taxonomic or the functional levels. These findings suggest that pasture-use intensity can influence microbial communities without remarkable effect, detectable with FTIR, on greenhouse gases emissions. Future research including in the methodological framework also the assessment of the soil nitrogen and carbon cycles, is needed to better understand the variability of greenhouse gas emissions in pasture ecosystems. However, results highlight the potential of this multidisciplinary approach to provide new insights into the influence of grazing on the complex ecosystem functions in alpine pastures in order to support their sustainable management. Research supported by the Agritech National Research Center Task 7.1.2 and the consortium iNEST (Interconnected North-East Innovation Ecosystem) Task 1.1, funding from the European Union Next-GenerationEU (Piano Nazionale di Ripresa e Resilienza (PNRR) Missione 4 Componente 2, Investimento 1.4 – D.D. 1032 17/06/2022, CN00000022 and Investimento 1.5 D.D. 1058 23/06/2022, ECS_00000043, respectively).