Fig. 5.

Diurnal variation in a net ecosystem exchange (NEE) of CO₂ in grazed and ungrazed plots at Thiisbukta (4 year old exclosures), b photosynthetically active radiation (PAR) and c air temperature. Positive fluxes represent an efflux of CO₂ whilst negative values indicate uptake of CO₂ from the atmosphere. Significant treatment effects were between 8.00 and 20.00 h. For NEE means (two hourly) were first calculated on the treatment level and the means and standard deviations over the tree sampling periods were calculated to demonstrate the temporal (between weeks) variability in CO₂ fluxes and the abiotic conditions (PAR and air temperature)