Soil temperature, moisture, pH, redox potential, and bulk density
Throughout the experiment of 2013–2019, the average monthly soil temperatures at 5 cm depth were significantly increased by 1.0±0.1°C and 2.1±0.1°C for the mid-elevation site and the low-elevation treatments (hereafter we refer to them as +1.0°C treatment and +2.1°C treatment respectively) relative to the control (19.7±0.6°C on average;P < 0.01; Fig. S2a). Compared with the control (18.9±0.3% v/v), the average monthly soil moisture at 5-cm depth was significantly decreased in the +2.1°C treatment (–3.8% v/v; P < 0.01), but was not changed in the +1.0°C treatment across the whole experiment (Fig. S2b). In-site soil redox potential at 10-cm depth was decreased by 39.1±24.9 mV in the +2.1°C treatment during 2017-2019 (P < 0.05), with no interaction between warming treatments and experimental times (Table S1). Warming had no significant effects on soil pH and soil bulk density in the topsoil (0–10 cm).