DOI: 10.5281/zenodo.15335784
title: Environmental drivers of microbial communities composition following the retreat of an Alpine glacier: Microbial community composition, soil physical characterisation and biogeochemistry

description: The retreat of glaciers and ice sheets in response to the increase of temperature creates proglacial margins, leading to emergence of new ecosystems. Despite an increasing knowledge of microbial communities in glacier forefields through next-generation sequencing, the links between microbes (e.g. Bacteria, Archaea) and their environment remain yet poorly understood. We investigated these relationships by conducting a field campaign to the Bricola glacier (Southwestern Swiss Alps) between June and October 2023 sampling proglacial sediments following a chronosequence approach. We then analysed the samples for both soil microbiology (DNA extraction, quantification, 16S Illumina sequencing) and soil physical and biogeochemical characterisation (e.g. pH, TOC, granulometry). These two datasets contain the data used in Lardet et al (submitted in May 2025 to Arctic, Antarctic and Alpine Research) and were the base of the analyses proceeded to characterise soil microbiology and investigate the relationships with soil development and topography using multivariate statistics.

The file JMF-2312-01_16S_refined_min1000_Bricola_2023.xlsx. contains the counts of Amplicon Sequence Variants (ASVs) obtained DNA extration and 16S Illumina performed at the Joint Microbiome Facility of Vienna following the protocol of Pjevac et al (2021). The ASVs were identified based on the DADA2 package (Callahan et al, 2016) and the corresponding phylogenetic table is also provided in this file. The file Data_Bricola_AAAR_2023.xlsx contains the information concerning the sampling locations (name, sampling date,time since glacier retreat, coordinates expressed in the CH1903+ LV95 Swiss coordinates system), as well as the data monitored in-situ and in laboratory.

References: 







Callahan, B. J., Sankaran, K., Fukuyama, J. A., McMurdie, P . J., & Holmes, S. P . (2016). Bioconductor workflow for microbiome data analysis: From raw reads to community analyses. F1000Research, 5, 1492. https://doi.org/10.12688/f1000research.8986.1







Pjevac, P., Hausmann, B., Schwarz, J., Kohl, G., Herbold, C. W., Loy, A., & Berry, D. (2021). An Economical and Flexible Dual Barcoding, Two- Step PCR Approach for Highly Multiplexed Amplicon Sequencing. Frontiers in Microbiology, 12, 669776. https://doi.org/10.3389/fmicb.2021.669776
description: The Data_Bricola_AAAR_2023.xlsx file is structed with samples (varying in space and time) as rows and their characteristics as columns. We provide hereafter a description of the columns:



Site: Name of the sites sampled

Transect: Number of the transect on which this sample was collected

Site number: Site number along the transect from low to high elevation

Space for time index: Inverse of the site number colummn to have increasing values with increasing time since glacier retreat

Sampling date: Date of sediment collection

Month: Sampling month

Deglaciation date classes: Date of soil exposure after glacier retreat obtained by analysing images from the Swiss Federal Office of Topography (2023)

Distance from the glacier front: The distance of the sampling sites compared to the position of the Bricola glacier front in 2023

Calculated soil age: Approximation of the exposure age of the sediments based  on the analyis of the images from the Swiss Federal Office of Topography (2023), in years

Uncertainty of soil age: Uncertainty due to to the fact that age is calculated based on deglaciation date classes.

x coordinates: x coordinates of the sampling sites using the CH1903+ LV95 Swiss coordinates system, in meters

y coordinates: y coordinates of the sampling sites using the CH1903+ LV95 Swiss coordinates system, in meters

 Elevation: Elevation of the sampling sites using the CH1903+ LV95 Swiss coordinates system, in meters above sea level

Plant coverage: Plant coverage, in %, estimated visually

Precipitation: Summed precipitations in mm during the 30 days prior sampling measured by the Swiss Federal Office of Meteorology at the Bricola weather station and assumed as constant over the catchment.

Slope: slope of each sampling site in degrees, calculated by averaging a 0.5 m resolution Digital Elevation Model provided by the Swiss Federal Office of Topography (2023) over the 2 x 2 meters of the sampling plot

Aspect: aspect of each sampling site in degrees, calculated by averaging a 0.5 m resolution Digital Elevation Model provided by the Swiss Federal Office of Topography (2023) over the 2 x 2 meters of the sampling plot

Curvature: curvature of each sampling site, calculated by averaging a 0.5 m resolution Digital Elevation Model provided by the Swiss Federal Office of Topography (2023) over the 2 x 2 meters of the sampling plot

SPI: Stream Power Index, calcutated based on the average slope and average flow accumulation area of each sampling location

Flow accumulation surface: Flow accumulation area of each sampling point, calculated by averaging a 0.5 m resolution Digital Elevation Model provided by the Swiss Federal Office of Topography (2023) over the 2 x 2 meters of the sampling plot

ISR_Pot: Potential incoming solar radiation, in w·m-2 averaged for each sampling location and each sampling month using the solarradiation.m function develped by Kumar et al (1997). The input was the 2023 DEM of the Swiss Federal Office of Topography

Initial sample weight: Initial mass of sediments sampled on the field, in [g]

Final sample weight: Final mass of sediments sampled on the field after 4 days in an oven at 35°C, in [g]

water content: Gravitational water content, in [g], measured by subtracting final sample weight to initial sample weight

T: soil temperature measured at each sampling location and averaged over the 30 days before sampling

pH_CaCl2: pH of the sediments measured in a solution of CaCl2

granulo_coarse: Weight of particle > 2 mm after having sieved the samples, in [g]

granulo_fine: Weight of particle < 2 mm after having sieved the samples, in [g]

prop_coarse: Proportion of coarse particles, in [%]

prop_fine: Proportion of fine particles, in [%]

TOC: Total Organic Carbone obtained by combustion using a RockEval sensor, in [%] of sample mass

TIC: Total Organic Carbone obtained by combustion using a RockEval sensor, in [%] of sample mass

Total_Carbon: TOC + TIC, in [%]

Total_Nitrogen: Total Nitrogen content obtained by chromatrography, in [%] of sample mass

Grainsize: Weighted by proportion grainsize of each sample, obtained through laser granulometry, in [um]

Exchangeable acidity: Exchangeable acidity obtained by titration, in [cmol·kg-1]

P: Total Phosphorus, in [mg·kg-1]

DNA, [ng·uL-1]: DNA concentration, in [ng·uL-1] of extracting solution

DNA-sample mass, [g]: Mass of sediments used for DNA extraction, [g]

DNA_content, [ng·g-1]: DNA content, in [ng·g-1] 

DNA_content_corrected: DNA content corrected for water content, [ng·g-1]

Notes: Remark concerning the samples


References







Kumar, L., Skidmore, A. K., & Knowles, E. (1997). Modelling topographic variation in solar radiation in a GIS environment. International Journal of Geographical Information Science, 11(5), 475–497. https://doi.org/10.1080/136588197242266