Fig. 1: Results of the irrigation experiment.

Abiotic conditions in control (orange) and irrigated (blue) plots during irrigation (2018) and subsequent summers without irrigation (2019 and 2020). The earliest 2018 measurements were taken before irrigation started. a Average daily air temperature and b total daily precipitation recorded in Chokurdakh (WMO station code 21649). c Thaw depth (n = 90 per violin). d Water table above permafrost in plot centres (n = 10 per violin). e Volumetric soil moisture content of the topsoil (5 cm depth) (n = 90 per violin). In c–e, violin length represents data range and violin width represents the probability density of the data distribution. Horizontal bars indicate group medians. Symbols above plots represent significant Tukey contrasts between irrigation and control per measurement date (+p < 0.1, *p < 0.05, **p < 0.01, ***p < 0.001). PS indicates perfect separation (see d), in which case no p values could be derived. Model specifications and estimated marginal means are in Supplementary Results I.