Microbial perspective of inhibited carbon turnover in Tangel humus of the Northern Limestone Alps.

Tangel humus primarily occurs in montane and subalpine zones of the calcareous Alps that exhibit low temperatures and high precipitation sums. This humus form is characterized by inhibited carbon turnover and accumulated organic matter, leading to the typical thick organic layers. However, the reason for this accumulation of organic matter is still unclear, and knowledge about the microbial community within Tangel humus is lacking. Therefore, we investigated the prokaryotic and fungal communities along with the physical and chemical properties within a depth gradient (0-10, 10-20, 20-30, 30-40, 40-50 cm) of a Tangel humus located in the Northern Limestone Alps. We hypothesized that humus properties and microbial activity, biomass, and diversity differ along the depth gradient and that microbial key players refer to certain humus depths. Our results give the first comprehensive information about microbiota within the Tangel humus and establish a microbial zonation of the humus. Microbial activity, biomass, as well as microbial alpha diversity significantly decreased with increasing depths. We identified microbial biomarkers for both, the top and the deepest depth, indicating different, microbial habitats. The microbial characterization together with the established nutrient deficiencies in the deeper depths might explain reduced C-turnover and Tangel humus formation.

Towards a better understanding of shallow erosion resistance of subalpine grasslands.

Shallow erosion is caused by processes such as landsliding, snow gliding, avalanches, animal trampling, or human activities and frequently occurs on high mountain grasslands. It can lead to significant long-term losses of grassland and related ecosystem services, e.g. fodder production, or water retention. Since restoration of subalpine and alpine ecosystems is difficult, prevention of shallow erosion is of vital importance for damage control. However, current knowledge on relationships between grassland ecology, management and shallow erosion resistance is very limited. In this study, we assessed relationships between the surface-mat stability of the topsoil (0-10 cm depth), vegetation cover, species diversity, growth patterns, indicator plant species for high and low tensile strength, soil texture, total nitrogen, and soil organic carbon. Vegetation composition significantly influenced the surface-mat stability of subalpine grasslands. Some key species were associated with higher reinforcement than other species. However, surface-mat stability neither depended on the vegetation type (grass or forb), nor on the root type, but rather on individual species characteristics such as roots and clonal structures as well as a certain plant and structural diversity. A balanced nutrient supply was associated with higher surface-mat stability, while soil texture had no effect. We hypothesized that stabilizing effects of plant-plant connections in tightly interwoven, dense root and clonal structure systems dominate over effects of root-soil connections. Thus, effects of soil texture may be negligible for the surface-mat stability. In general, our results show that adapted grassland management can be used as preventive erosion control measure on subalpine grasslands.