Soil Slope Exposure Affects Physico-Chemical and Microbiological Properties in Soil Aggregate Size Fractions
Tommaso Bardelli,
Shamina Imran Pathan,
Paola Arfaioli,
Nadia Vignozzi,
Sergio Pellegrini,
Flavio Fornasier,
Markus Egli,
María Gómez-Brandón,
Heribert Insam,
Giacomo Pietramellara,
Judith Ascher-Jenull
Affiliations
Tommaso Bardelli
Dipartimento di Scienze e Tecnologie Agrarie, Alimentari, Ambientali e Forestali (DAGRI), University of Florence, Piazzale delle Cascine 18, 50144 Firenze, Italy
Shamina Imran Pathan
Dipartimento di Scienze e Tecnologie Agrarie, Alimentari, Ambientali e Forestali (DAGRI), University of Florence, Piazzale delle Cascine 18, 50144 Firenze, Italy
Paola Arfaioli
Dipartimento di Scienze e Tecnologie Agrarie, Alimentari, Ambientali e Forestali (DAGRI), University of Florence, Piazzale delle Cascine 18, 50144 Firenze, Italy
Nadia Vignozzi
Council for Agricultural Research and Economics (CREA-AA), Via Lanciola 12/A, 50125 Firenze, Italy
Sergio Pellegrini
Council for Agricultural Research and Economics (CREA-AA), Via Lanciola 12/A, 50125 Firenze, Italy
Flavio Fornasier
Council for Agricultural Research and Economics (CREA-VE), Via Trieste 23, 34170 Gorizia, Italy
Markus Egli
Department of Geography, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland
María Gómez-Brandón
Department of Microbiology, University of Innsbruck, Technikerstraße 25d, 6020 Innsbruck, Austria
Heribert Insam
Department of Microbiology, University of Innsbruck, Technikerstraße 25d, 6020 Innsbruck, Austria
Giacomo Pietramellara
Dipartimento di Scienze e Tecnologie Agrarie, Alimentari, Ambientali e Forestali (DAGRI), University of Florence, Piazzale delle Cascine 18, 50144 Firenze, Italy
Judith Ascher-Jenull
Department of Microbiology, University of Innsbruck, Technikerstraße 25d, 6020 Innsbruck, Austria
Slope exposure is known to affect soil biogeochemical processes in mountainous forest ecosystems, but little attention has yet been paid to its influence at a soil aggregate scale. Therefore, we evaluated the effects of slope exposure (north- vs south-facing slope) on the physico-chemical and microbiological properties of bulk soil and dry-sieved and water-stable aggregate size fractions in both organic (OF) and mineral (AE) horizons in an Italian alpine forest. The changes in organic carbon (OC) and nitrogen (ON) fractions were assessed together with a battery of thirteen enzyme activities involved in the main nutrient cycles. In addition, soil biological properties including microbial biomass (estimated as double-stranded DNA content), and microbial activity (assessed as the ratio between the extra-(exDNA) and intracellular (iDNA) fractions of the total soil DNA pool) were determined. The OF horizon at the north-facing slope was enriched in recalcitrant and insoluble OC and ON fractions and characterized by a lower microbial activity, as indicated by the higher exDNA/iDNA ratio with respect to the south-facing slope. On the contrary, exDNA and iDNA contents, microbial biomass, as well as most of the enzyme activities, reached higher levels at the southern exposure in the AE horizon. These exposure-effects were bulk soil- and aggregate size fraction-specific. Overall, lower values of the chemical and microbiological parameters were found in the water-stable fraction. Our findings indicate that slope exposure (and thus topography), soil horizon, and aggregate size distinctly influence soil OC dynamics in mountain ecosystems.
