“…The air temperature and the temperature in the litterbags were measured from 15 November 2012 to 30 October 2013, and the following measures were calculated to clearly describe the temperature characteristics: daily mean temperature, positive accumulated temperature (sum of temperatures above 0 °C), negative accumulated temperature (sum of temperatures below 0 °C) [17,18], and the number of freeze-thaw cycles per day (one freeze-thaw cycle was completed when the threshold of 0 °C was crossed twice within at least 3 h) [34] of each critical period (Table 1). To quantify the cellulose and lignin concentrations in the litter at different critical periods, which were identified based on Olsson's period division of the cold season [35] and the field investigation of our previous To quantify the cellulose and lignin concentrations in the litter at different critical periods, which were identified based on Olsson's period division of the cold season [35] and the field investigation of our previous studies [17,18,36,37], we sampled the litterbags at the end of each critical period over the first year of litter decomposition on 26 December 2012 (snow formation period, SFP), 8 March 2013 (snow cover period, SCP), 24 April 2013 (snow melt period, SMP), and 30 October 2013 (growing season, GS). The litterbags were transported back to the laboratory for analysis.…”