Effects of land-use changes on humus forms on alpine pastureland (Central Alps, Tyrol)

This study examines the effects of land-use changes on humus forms and soil properties (pH, C/N, SOM) on alpine pastureland. On 10 differently managed areas (alpine spruce forest, alpine tamarack forest, alpine meadow, alpine pasture, reforested area), humus forms were characterised morphologically, and soil properties were investigated in the laboratory and statistically analysed. Vermimull and Rhizomull were the humus forms found on intensively and lightly managed areas, while on abandoned sites and on forest floors more differentiated humus forms with varying thickness developed (Mullmoder, Leptomoder, Hemimor, Mormoder). Humus pH values ranged between 3.3 (abandoned pasture) and 5.5 (intensively managed meadow, abandoned meadow); soil pH values were generally lower and ranged between 3.0 (spruce forest) and 5.5 (intensively managed meadow). Both properties decreased from managed to abandoned areas. Humus C/N was lowest on the intensively managed meadow (21.1) and increased from managed to abandoned sites, with the highest value being 37.6 on the reforested area. Soil C/N ratios were narrow, ranging from 12.4 on the lightly managed pasture to 19.6 in the spruce forest. Soil C/N increased from managed to abandoned sites, while humus C/N showed no trend. Soil organic matter content (SOM) greatly increased from managed to abandoned areas, ranging from 12.9% (intensively managed meadow) to 41.3% (tamarack forest). In conclusion, reducing or abandoning management leads to the accumulation of litter material and the development of more differentiated humus forms. As a consequence of abandonment, the soil pH decreases, whereas humus and soil C/N and organic matter content increase from intensively managed to abandoned areas and to the forest.