Pedodiversity, biodiversity, and SOC storage in an alpine pasture

Mountain soils provide a variety of ecosystem services (ES) that are increasingly threatened by anthropogenic impacts and climate change.

We present here the results of a study on the pedodiversity, biodiversity, and soil organic carbon (SOC) sequestration of alpine soils in a pasture of the central Alps, that took into account the effect of morphology and vegetation. The study area was the Andossi plateau (350 ha) in Valchiavenna (Lombardy Region), between 1800 and 2000 m elevation.

As part of the PascolAndo project, whose goal was to promote sustainable pasture management, at 160 georeferenced points we characterized soils (down to bedrock or a maximum of 50 cm) and carried out the floristic survey to define the vegetation type; soil samples were collected by horizons and analyzed for the main soil properties.

The main soil types were Leptosols, Regosols, Cambisols, Umbrisols, Podzols, Gleysols and Histosols, strongly related to geomorphology and vegetation type (peat bogs, earth hummocks, and poor, calcareous, shrub and rich pastures).

Histosols and Gleysols of peatland and wet areas showed the highest SOC stock with an average of 31.8±2.6 kg m^-2 and 23.3±2.7 kg m^-2 respectively, followed by Umbrisols, distributed all over (17.2±6.2 kg m^-2), and Podzols (16.6±4.6 kg m^-2), typical of poor pastures and shrub areas. The most prevalent soils on the plateau were Cambisols (average SOC stock of 13.6±2.7 kg m^-2): Eutric Cambisols were primarily in rich pasture and Dystric Cambisols in poor pasture. Among poorly developed soils, Regosols stored on average 10.8±4.2 kg m^-2, while Leptosols, widespread on steep slopes in calcareous pastures and shrub areas, showed the lowest SOC stock (9.6±4.9 kg m^-2).

Soil types, vegetation types, and SOC were first modeled using geomorphometric variables (27 variables extracted from a 4-m resolution DTM) and vegetation indices (NDVI, NDWI, NDRE, for 3 dates of the growing season, extracted from Sentinel 2 images) and then spatially estimated, allowing quantification of the pedodiversity, biodiversity, and SOC sequestration in the study area.

The study showed that the plateau has a high level of biodiversity and pedodiversity, with OC-rich soils that are important for regulating the global climate. There was evidence that grazing and livestock loading affected soil ES by acting on biodiversity, soil fertility, and erosion.