Figure 3

Regression tree predicting distribution of Qinghai spruce forests (and non-forest vegetation) from limiting factors (PRE = 0.659). Each node (square) is labeled with average forested ratio (mean), standard deviation (S.D.) and the number (n) of spatial units in that group. The model is read from top down until terminal nodes appear. Partial PRE values are presented in parentheses at each root node to split. This map was generated using SYSTAT 13 (Systat Software, San Jose, CA).