Fig. 7

Lomb–Scargle periodograms of a soil CO₂ flux, b air temperature, c air relative humidity, d barometric pressure, e wind speed, f wind direction, g soil humidity, h soil temperature, and i precipitation. The dotted line in each periodogram corresponds to the level where the probability equals 0.01. The periodogram from 0.001 cph (period = 42 days) to 0.5 cph (2 h) is plotted. The arrows indicate significant diurnal and semidiurnal peaks