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, 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 20 ºC and microbial biomass (substrate-induced respiration) using an O2-microcompensation apparatus. Soil and climate data were obtained from the same LUCAS survey and online databases. Structural equation models (SEMs) were 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 future management plans to protect soil carbon and slow the increasing vulnerability of European soils to climate change.
Title: Large-scale drivers of relationships between soil microbial properties and organic carbon across Europe.
Description: Maps of potential soil microbial basal respiration (bas), microbial biomass (Cmic), and respiratory quotient (qO2) predicted across Europe for the year 2018. Maps with “LC” in the file name were predicted with regard to land-cover type (forest, grassland, cropland) in the predictions; maps with “gen” were predicted without considering land-cover type.
Spatial coverage: European Union
Pixel size: 1000 m
Measurement Unit: Potential basal respiration: µL O2/(g soil dry weight⋅hr) Microbial biomass: µg Cmic/g soil dry weight Respiratory quotient: µL O2/(µg Cmic⋅hr)
Projection: ETRS89 Lambert Azimuthal Equal Area
Temporal coverage: 2018
Maps predicting, for the year 2018, potential soil basal respiration at 20°C, soil microbial biomass as estimated by substrate-induced respiration, and soil microbial respiratory quotient (the ratio between potential basal respiration and microbial biomass) across Europe. Predictions were performed with structural equation models fit using the following predictive variables: mean annual temperature, annual precipitation, mean temperature in the past month, annual precipitation in the last month, soil sand content, soil water content, pH, soil organic carbon content, elevation, and latitude. Maps with “LC” in the file name also included land-cover type (forest, grassland, cropland) in the predictions; maps with “gen” were predicted without regard for land-cover type.
As two of the climate variables (Bas, Cmic) are on a monthly basis, predictions were made for every month in the year 2018. The provided maps are the average of these twelve monthly maps. For the individual monthly maps, please contact email@example.com or firstname.lastname@example.org . Soil water content was also predicted using structural equation models.