DOI: 10.5061/dryad.g4f4qrfqn
title: Large-scale drivers of relationships between soil microbial properties and organic carbon across Europe

description: The aim of this study was to quantify direct and indirect relationships
 between soil microbial community properties (potential basal respiration,
 microbial biomass) and abiotic factors (soil, climate) in three major
 land-cover types. Location: Europe Time period: 2018 Major taxa studied:
 Microbial community (fungi and bacteria) We collected 881 soil samples
 from across Europe in the framework of the Land Use/Land Cover Area Frame
 Survey (LUCAS). We measured potential soil basal respiration at 20ºC and
 microbial biomass (substrate-induced respiration) using an
 O2-microcompensation apparatus. Climate and soil data were obtained from
 previous LUCAS surveys and online databases. Structural equation modeling
 (SEM) was used to quantify relationships between variables, and equations
 extracted from SEMs were used to create predictive maps. Fatty acid methyl
 esters were measured in a subset of samples to distinguish fungal from
 bacterial biomass. Soil microbial properties in croplands were more
 heavily affected by climate variables than those in forests. Potential
 soil basal respiration and microbial biomass were correlated in forests
 but decoupled in grasslands and croplands, where microbial biomass
 depended on soil carbon. Forests had a higher ratio of fungi to bacteria
 than grasslands or croplands. Soil microbial communities in grasslands and
 croplands are likely carbon-limited in comparison with those in forests,
 and forests have a higher dominance of fungi indicating differences in
 microbial community composition. Notably, the often already-degraded soils
 of croplands could be more vulnerable to climate change than more natural
 soils. The provided maps show potentially vulnerable areas that should be
 explicitly accounted for in coming management plans to protect soil carbon
 and slow the increasing vulnerability of European soils to climate change.
description: Soil samples were collected during the 2018 LUCAS soil sampling
 campaign. Soil chemical and physical properties were measured at the Joint
 Research Centre in Ispra, Italy (Orgiazzi et al., 2018). Soil microbial
 respiration and biomass, as well as water content and water holding
 capacity, were measured in the Eisenhauer lab of the German Centre for
 Integrative Biodiversity Research. Fungi/Bacteria was measured by fatty
 acid analysis by Felipe Bastida at CEBAS CSIC. Climate and geographical
 data were harvested from various databases, which are listed in Appendix 1
 (data sources) of the associated paper. For more
 details on the soil sampling and physical and chemical properties,
 see: Orgiazzi, A., Ballabio, C., Panagos, P., Jones, A., & Fernández-Ugalde, O. (2018). LUCAS Soil, the largest expandable soil dataset for Europe: a review. <i>European Journal of Soil Science,</i> 69(1), 140-153.<br> https://doi.org/10.1111/ejss.12499 For more details on the measurements of soil microbial respiration and biomass, fatty acids, and water holding capacity, see the supplementary methods of the associated paper (Appendix 2).
description: Fatty acid analysis was performed for a subset of 267 samples.
 Water holding capacity and associated measurements of basal respiration
 was analyzed in a subset of 100 samples. The samples that were not in
 these subsets have NA values for the columns associated with these
 measurements. In order to protect the precise locations
 of the LUCAS sampling sites, latitude and longitude values could not be
 given. The approximate location of each sampling site is instead described
 by the NUTS3 region. If you wish to replicate the structural equation
 modeling described in the paper, for which latitude is required, please
 get in touch. A description of each column is available
 in the associated metadata file.