Biotic and abiotic controls on carbon storage in aggregates in calcareous alpine and prealpine grassland soils

Ingrid Kögel-Knabner,Bernd Josef Berauer,Noelia Garcia-Franco,Ralf Kiese,Vincent Buness,Marcus Zistl-Schlingmann,Michael Dannenmann,Roswitha Walter,Luis Carlos Colocho Hurtarte,Martin Wiesmeier

doi:10.1007/s00374-020-01518-0

Abstract

Alpine and prealpine grasslands provide various ecosystem services and are hotspots for the storage of soil organic C (SOC) in Central Europe. Yet, information about aggregate-related SOC storage and its controlling factors in alpine and prealpine grassland soils is limited. In this study, the SOC distribution according to the aggregate size classes large macroaggregates (> 2000 μm), small macroaggregates (250–2000 μm), microaggregates (63–250 μm), and silt-/clay-sized particles (< 63 μm) was studied in grassland soils along an elevation gradient in the Northern Limestone Alps of Germany. This was accompanied by an analysis of earthworm abundance and biomass according to different ecological niches. The SOC and N stocks increased with elevation and were associated with relatively high proportions of water-stable macroaggregates due to high contents of exchangeable Ca2+ and Mg2+. At lower elevations, earthworms appeared to act as catalyzers for a higher microaggregate formation. Thus, SOC stabilization by aggregate formation in the studied soils is a result of a joined interaction of organic matter and Ca2+ as binding agents for soil aggregates (higher elevations), and the earthworms that act as promoters of aggregate formation through the secretion of biogenic carbonates (low elevation). Our study highlights the importance of aggregate-related factors as potential indices to evaluate the SOC storage potential in other mountainous grassland soils.Graphical abstract

Highlights

We could not identify which ecological group of earthworms was more relevant in aggregate formation, we suggest that the earthworms have direct and indirect influences on soil structure and soil organic C (SOC) (Brown et al 2000; Jégou et al 2001) because they seem to play a relevant role in promoting soil microaggregate formation in Fendt
The results of our study showed that alpine and prealpine grassland soils in the Northern Limestone Alps have a naturally high aggregate stability associated with a high stabilizing capacity for SOC and N storage in aggregates
In prealpine grassland soils at lower elevation, earthworms act as promoters of aggregate formation through the secretion of biogenic carbonates

Summary

Introduction

One of the largest grassland regions (> 1 Mio ha) in Central Europe is the grassland belt in alpine and prealpine regions along the Northern Limestone Alps of Germany This grassland region, and similar areas in Austria, Switzerland, and Italy provide various ecosystem services that regulate, support and underpin the environment we live in (Kremen 2005; Chan et al 2006; Soussana and Lüscher 2007). Besides their importance as biological hotspots, these grasslands store large amounts of SOC and represent one of the largest C reservoirs in Central Europe (Vidal et al 2020; Wiesmeier et al 2013; Zistl-Schlingmann et al 2019)

Methods

Results

Conclusion