High Quality Content by WIKIPEDIA articles! High Quality Content by WIKIPEDIA articles! Temperate broadleaf and mixed forests are a temperate and humid biome. The typical structure of these forests include four layers. The upper most layer is the canopy which is composed of tall mature trees ranging from 100 to 200 feet high. Below the canopy is the three-layered, shade tolerant understory which is roughly about 30 to 50 feet shorter than the canopy. The top layer of the understory is the sub-canopy which is composed of smaller mature trees, saplings, and suppressed juveniles canopy layer trees awaiting an opening in the canopy. Below the sub-canopy is the shrub layer, composed of low growing woody plants. Typically the lowest growing (and most diverse) layer is the ground cover or herbaceous layer.