Figure 4.

Classification and regression tree (CART) analysis to describe the effect of temperature (4 and 14°C) and aeration (anoxic and oxic) on average CO₂ production rates (mg CO₂ g drymass⁻¹ day⁻¹) after 270 h (n = 3) in a microcosm experiment using peat soil collected at three depths (0–10, 50–60, and 100–110 cm) from peatlands in the James Bay Lowlands, Canada. At each split the following information is given: the variable that splits the observation into “daughter” nodes, the classification criterion (e.g., peatland, depth, aeration, or temperature), the average potential CO₂ production rate and the number of observations in each group (n_i).