Fig. 3. Oxygen (a) and CO2 (b) concentrations in an unprotected control (CTL) and under winter protective covers: a commercial impermeable cover on top of either curled wood shavings mat (CW-CC), 15 cm of straw mulch (SM-CC) or a felt material (FM-CC), a clear polyethylene cover on top of a curled wood shavings mat (CW-PC) at the Royal Québec experimental golf green.