Epigeal invertebrate communities were sampled at three soil habitat patches on each bank of 10 geothermally heated streams in the Hengill valley, Iceland, using five pitfall traps left for 48 hours in each plot, at four time-points during the study: 19th May, 4th June, 23rd June, and 5th of July. White plastic cups of 7 cm diameter and 8.5 cm depth were filled with 10 ml of ethylene glycol and 30 ml of stream water, and left for 48 hours before collection. During collection, samples from the five traps at each habitat patch were combined into a 250-μm sieve and stored in 70% ethanol. Terrestrial invertebrates were identified to species level where possible but often to higher taxonomic groups where species-level identification was infeasible (e.g. Diptera and Hymenoptera were mostly identified to family level), using a Nikon SMZ1500 microscope at 8-100× magnification. The total number of individuals for each species found in the pitfall traps at a habitat patch was considered as the abundance of that species, while the mean dry weight of each species in milligrams was estimated from length measurements taken for each individual and published length-weight relationships.

This is a dataset of environmental variables, total invertebrate abundance, and mean invertebrate body mass, sampled at 60 soil habitat patches in the Hengill geothermal valley, Iceland, from May to July 2015. The habitat patches span a temperature gradient of 5 to 22 deg C on average over the sampling period, yet they occur within 2 km of each other and have similar soil moisture, pH, total carbon, and total nitrogen.