Arturo Fabiani

In permanently submerged coastal wetlands, interactions between biogeochemical processes and microbial communities strongly influence greenhouse gas (GHG) fluxes. To improve our understanding of how redox-driven processes shape GHG dynamics in these ecosystems, we investigated the relationships among iron (Fe) pools, microbial dynamics, and the potential GHG production in subaqueous soils from an interdunal wetland in San Vitale Park (Italy), permanently submerged and affected by seasonal oscillations of the saline water table. Two subaqueous soil columns (WAS-2 and WAS-4), collected from similar settings, were analyzed. Surface layers of WAS-4 showed higher salinity and carbonate content, whereas WAS-2 was characterized by overall higher Fe concentrations. Distinct vertical distributions of organic matter and sulfur (S) were shown along depth. Laboratory incubations revealed that nitrous oxide (N₂O) production was up to ten times higher in WAS-2 than in WAS-4, with peaks in the top 13–14 cm, consistent with more active nitrification-denitrification in surface layers. Methane (CH₄) and carbon dioxide (CO₂) fluxes decreased with depth, reflecting reduced availability of labile carbon. Methanomicrobiales dominated CH₄-producing layers, indicating hydrogenotrophic methanogenesis, while amoA-carrying Nitrosomonadales and Thaumarchaeota, occurred in shallow, organic-rich layers where ammonia supported nitrification and denitrification. Denitrifiers mainly belonged to α- and β-Proteobacteria, consistent with their direct contribution to N₂O peaks. Spearman’s correlations showed N₂O positively correlated to sulfur and labile carbon (C), supporting denitrification under moderately reducing conditions. CH₄ and CO₂ positively correlated with organic C (Corg), total nitrogen (TN), and reactive Fe forms, reflecting redox-mediated microbial respiration and methanogenesis. Trace elements (B, Cr, Cu, Ni) acted as micronutrients or inhibitors depending on concentration. Canonical correspondence analysis indicated depth-structured links among gas fluxes, soil chemistry (Corg, TN, S/C, CaCO₃, P), and microbial distributions: surface layers, rich in labile C and nutrients, supported active bacteria and archaea involved in decomposition, nitrification, and denitrification, whereas deeper layers hosted oligotrophic archaea adapted to inorganic substrates. Overall, Fe pools appeared to be associated with soil processes relevant to GHG dynamics, although the extent of their regulatory role remains uncertain due to potential alterations of redox-sensitive Fe fractions during sample handling. These results contribute to broader efforts to predict GHG emissions in submerged wetland soils by linking redox stratification, inorganic chemistry, and microbial functional groups.

Soil health and agricultural sustainability are primarily threatened by organic matter depletion and a decline in biodiversity. To mitigate these processes, managing set-aside systems remains a simple practice to preserve biodiversity and functions essential to soil fertility. The objective of this study was to evaluate the effectiveness of medium-term set-aside management in preventing soil degradation using changes in microbial and microarthropod communities, both of which are involved in organic matter degradation. Three different set-aside managements, with mowing (May or July) and without mowing, were compared to conventional rotation in three sites located in North, Central, and South Italy. The microbial community was analyzed through both biochemical methods, such as the assessment of soil respiration and microbial biomass, and molecular techniques, such as Denaturing Gradient Gel Electrophoresis. Soil fertility was assessed by the Biological Fertility Index, while soil biodiversity was assessed with microbial and microarthropod indicators. All set-aside management showed a statistically significant separation from conventional crop rotation for both microbial and microarthropod communities. Indicators highlighted a lower efficiency of set-aside management in organic matter use compared to conventional crop rotation, while microbial and microarthropod biodiversity increased in all set-aside managements. The QBS-ar index showed good soil quality standards in each set-aside management, benefiting the euedaphic microarthropods, whereas soil microbial respiration highlighted a higher microbial activity in the same experimental context.

The loss of organic matter and the decline of biodiversity pose significant threats to soil health and the sustainability of agriculture. Managing set-aside land through mowing remains a practical strategy to prevent land abandonment while preserving soil biodiversity and essential soil functions that support fertility. The primary objective of this study was to evaluate the effectiveness of long-term set-aside (12 years) in preventing soil degradation. In an experimental field in Vicarello (Pisa, Italy), set-aside management was compared to land abandonment and conventional crop rotation. Soil chemical and microbiological analyses were conducted, and various indicators were used to assess soil fertility conservation. Soil biodiversity was evaluated through nematode and microarthropod indices. Total organic carbon increased in abandoned fields and, to a lesser extent, in set-aside areas, following a similar trend to microbial biomass values. Nematode and microarthropod indicators revealed a more stable soil structure in set-aside areas, followed by abandoned fields, highlighting their role in regulating ecosystem services such as carbon mineralization. On the whole, the results indicate that set-aside management serves as an intermediate step in the transition from conventionally managed fields to naturalized grasslands, confirming its potential benefits for soil biological diversity and function.

Vine growing is one of the most economically important sectors of Mediterranean agriculture, but its cultivation practices are highly detrimental to the environment and the associated biota. The application of both natural products inducing endogenous plant defense mechanisms and natural soil management systems represents a potential solution for the preservation and improvement of soil health and biodiversity. The Life Green Grapes project aimed at evaluating the effects of different natural and sustainable vine protection strategies and soil management on vineyard edaphic communities. Soil TOC, TN, C:N ratio, CaCO₃ content and pH were measured. Microbial communities (bacteria and fungi) were characterized through NGS, while nematodes and microarthropods were isolated and identified. Obtained data highlighted a relationshipbetween bacteria, fungi and nematodes with soil chemistry, and an effect of the different soil management on the single and total edaphic communities. Network analysis evidenced a positive effect of the application of sustainable soil managements on the relationships among the different investigated soil trophic levels, suggesting that more natural soil managements allow a better interaction between soil organisms. In conclusion, this work confirms the importance of the application of sustainable and natural soil management practices in agricultural ecosystems, with the aim of conserving and improving soil biodiversity.

Digestate from biogas production can be recycled to the soil as conditioner/fertilizer improving the environmental sustainability of the energy supply chain. In a three-year maize-triticale rotation, we investigated the short-term effects of digestate on soil physical, chemical, and microbiological properties and evaluated its effectiveness in complementing the mineral fertilizers. Digestate soil treatments consisted of combined applications of the whole digestate and its mechanically separated solid fraction. Digestate increased soil total organic C, total N and K contents. Soil bulk density was not affected by treatments, while aggregate stability showed a transient improvement due to digestate treatments. A decrement of the transmission pores proportion and an increment of fissures was observed in digestate treated soils. Soil microbial community was only transiently affected by digestate treatments and no soil contamination from Clostridiaceae-related bacteria were observed. Digestate can significantly impair seed germination when applied at low dilution ratios. Crop yield under digestate treatment was similar to ordinary mineral-based fertilization. Overall, our experiment proved that the agronomic recycling of digestate from biogas production maintained a fair crop yield and soil quality. Digestate was confirmed as a valid resource for sustainable management of soil fertility under energy-crop farming, by combining a good attitude as a fertilizer with the ability to compensate for soil organic C loss.