Chemical and Biological Gradients along the Damma Glacier Soil Chronosequence, Switzerland

Abstract

Soils are the product of a complex suite of chemical, biological, and physical processes. In spite of the importance of soils for society and for sustaining life on earth, our knowledge of soil formation rates and of the influence of biological activity on mineral weathering and geochemical cycles is still limited. In this paper we provide a description of the Damma Glacier Critical Zone Observatory and present a first synthesis of our multidisciplinary studies of the 150-yr soil chronosequence. The aim of our research was to improve our understanding of ecosystem development on a barren substrate and the early evolution of soils and to evaluate the influence of biological activity on weathering rates. Soil pH, cation exchange capacity, biomass, bacterial and fungal populations, and soil organic matter show clear gradients related to soil age, in spite of the extreme heterogeneity of the ecosystem. The bulk mineralogy and inorganic geochemistry of the soils, in contrast, are independent of soil age and only in older soils (>100 yr) is incipient weathering observed, mainly as a decreasing content in albite and biotite by coincidental formation of secondary chlorites in the clay fraction. Further, we document the rapid evolution of microbial and plant munities along the chronosequence.

Potential sources of microbial colonizers in an initial soil ecosystem after retreat of an alpine glacier

“…This site was selected because it has been studied extensively in various scientific disciplines, including hydrology, botany, soil carbon dynamics and microbiology (Bernasconi et al, 2011;Menon et al, 2014), and thus detailed information about the ecosystem dynamics in this glacier forefield was available. The climate in the catchment area is characterized by annual precipitation of 2200 mm and high seasonal temperature fluctuations, ranging from − 8°C to 4°C, with an annual average temperature of 2°C (Bernasconi et al, 2011). The growing season lasts from June to September.…”

“…The growing season lasts from June to September. Before the glacier terminus, the initial soils sampled in our study are located 20 m away from the glacier tongue (deglaciated for approximately 2 years) and consist of barren sandy rocks with low carbon and nitrogen contents and are mainly characterized by lichens, algae and mosses (Bernasconi et al, 2011).…”

“…Most alpine glaciers are currently retreating leading to formation of new terrestrial ecosystems. Glacier ecosystems have been used extensively to investigate dynamics of soil formation in relation to shifts in microbial communities (for example, Bernasconi et al, 2011;Zumsteg et al, 2012;Bajerski and Wagner, 2013;Rime et al, 2015). They also represent ideal ecosystems to study natural establishment of microbial communities in terrestrial environments (Edwards et al, 2014).…”

Nitrogen and phosphorus availability at early stages of soil development in the Damma glacier forefield, Switzerland; implications for establishment of N2-fixing plants

“…These sites of 4 m 2 were randomly selected in May 2007 from within each of the three stages of forefield development for the 'BigLink' project (Bernasconi et al 2011) (Fig. 1).…”

“…According to the theory of soil development, total soil P and available amounts of mineral P tend to decrease with time (Menge et al 2012;Walker and Syers 1976;Wardle et al 2004), but the Damma chronosequence is far too short to observe such decreases as the main P-containing mineral is slowly weathering fluorapatite (Bernasconi et al 2011). The absence of differences in in situ resin P along the forefield, and of a correlation between resin P and the P concentration in the vegetation, can be due to excessive P uptake by the vegetation, keeping the available amount of P in the soil low.…”