Plot of unbiased RE-EM tree. Each inner node (gray boxes) represents the partitioning variable, while the values for each partition are shown on the edges (lines) between the nodes. P-values in the inner nodes refer to tests of independence between the predictor and response. Mean predicted seedling abundance (mean seedling count) and sample size (n) are given in the terminal nodes (white boxes). Straw mulch had a modest benefit for lodgepole pine regeneration, but only when tree crowns were not consumed.