The articles in this issue are a selection of the presentations made at the 2nd International Conference of Biohydrology. This special issue ‘Biohydrology—coupling biology and soil hydrology from pores to landscapes’ contains a range of articles on biological and hydrological interactions in soil, including large-scale systems research on the influence of forests on catchments and small-scale reductionist research on processes operating at the scale of soil pores. Copyright © 2010 John Wiley & Sons, Ltd.