The type of woodchip should not be as critical as the way it is structured. Like a plant it needs ratios of moisture, air, nutrients and a medium to grow in. If the medium, such as woodchips, is arranged in a way that allows complex interactions between nutrients, moisture and air and if climate permits a complex mushroom can grow. If one finds subs on both pine and euc then its the medium dynamics, microclimate and nutrients that are most important. Its probable certain wood mediums contain elements that favour growth