Dl2 datalogger

Soil respiration rates were measured with a field-portable infrared gas analyzer (IRGA; LiCor 8100-A, Lincoln, Nebraska, USA) in PVC collars, randomly placed within each plot. There were 2 collars per plot permanently inserted into the soil (5 cm deep) 1 day before treatments started, and collars were open to rainfall and litterfall, except during measurements (Taneva and Gonzalez-Meler, 2011 (link)). The chosen measurement times were 12:00 h (11:00–13:00 h) and 18:00 h for all plots (18:00–20:00 h). Measurements were carried out at the beginning and at the end of the 30-day warming period for three consecutive days. Soil temperature and moisture were continuously monitored using the sensors Theta Probe ML2x for moisture Theta Probe ST2 for temperature coupled to a DL2 datalogger (Delta-T Devices, UK).

Air temperature (T_a) and RH (relative humidity) were continuously measured using EHT sensors with radiation shields (Decagon Devices Inc., Pullman, WA). Water VPD (vapor pressure deficit) was calculated from the temperature and humidity data according to Goudriaan and van Laar (1994). PPFD (Photosynthetic photon flux density) was continuously measured using a QSO‐S PAR sensor (Decagon Devices Inc.). Volumetric soil water content (θ_v), at a depth of 5 cm, was continuously measured in each of the experimental plots using EC‐5 soil moisture sensors (Decagon Devices Inc.). All above‐mentioned sensors were connected to EM‐50 data loggers (Decagon Devices Inc.), recording half‐hourly means. Precipitation was measured with a RG2 rain gauge (Delta‐T Devices, Burwell, Cambridge, U.K.), and stored as half‐hourly means on a DL2 data logger (Delta‐T Devices).