Table S1.
Zero curtain and spring thawing estimates in 2013 and 2014
| Year and site | Spring start | Spring end | Spring thawing days | Autumn start | Autumn end | Zero curtain days | Soil T depth, cm |
| 2013 | |||||||
| BES | — | — | — | 261 | 352 | 91 | 20 |
| ATQ | — | — | — | 260 | 343 | 83 | 15 |
| BEO | — | — | — | 259 | 314 | 55 | 10 |
| IVO | — | — | — | 259 | 360 | 101 | 15 |
| CMDL | — | — | — | — | — | — | — |
| 2014 | |||||||
| BES | 169 | 184 | 15 | 264 | 333 | 69 | 20 |
| ATQ | 154* | 174* | 20* | 264 | 319 | 55 | 15 |
| BEO | 167 | 190 | 23 | 262 | 321 | 59 | 10 |
| IVO | 135 | 158 | 23 | 245 | 340 | 95 | 15 |
| CMDL | — | — | — | — | — | — | — |
Zero curtain dates in the autumn and spring thawing dates and duration are determined from the criteria −0.75 < T < 0.75 and are shown in Fig. S1. Because of data loss in the soil temperature data, an average of BES and BEO was used for CMDL. Because spring 2013 was not consistently collected in all sites, we estimated the zero curtain periods starting from autumn 2013. Dashes indicate that no data is available.
*
ATQ spring 2013 and autumn 2014.