Such sites will often have some special biodiversity characteristics associated with the particular substrate, microclimate or growth conditions offered by such features. Overall, higher species diversity is associated with temperate broadleaved deciduous trees (particularly oaks), than for boreal deciduous trees (particularly high for aspen and willows, less so for birches), which again tend to have higher associated species diversity than pine or spruce (Figure 4.1). These patterns are also partly reflected in the forest composition (Figure 4.2).