Ecological processes at large scales are studied in complex ecosystems that are shaped by multiple factors at various scales. Moreover, many fundamental (macro)ecological questions become difficult when applied to microorganisms, due to the complexity and dynamics of their communities. As a result, microbial macroecology is still in its infancy. This project aims to overcome these problems by using a simple model ecosystem – the surface of the Greenland Ice Sheet (GrIS). We have gathered a unique microbial community data set from the surface of the GrIS and use this data set to test key macroecological hypotheses concerning assembly rules of microbial communities and spatial patterns in the distribution and diversity of phylogenetic vs. functional groups of microorganisms at different taxonomical levels. We expect this research will bring novel insights into two fields of ecology – macroecology and microbial ecology – by combining the expertise and methodologies of both disciplines. The project is unique by its synergy between approaches of glacial microbial ecology (provided by Jakub and Marek at CryoEco) and theoretical ecology (Arnošt Šizling at the Centre for Theoretical Study, Charles University).