The ecosystem that usually supports thick forests of deciduous trees is the temperate deciduous forest.

Here's why:

* Climate: Temperate deciduous forests experience distinct seasons with warm summers and cold winters. This allows deciduous trees to thrive, as they shed their leaves in the fall to conserve water during the cold, dry winter months.

* Precipitation: These forests receive moderate to high rainfall, which is essential for the growth of large trees.

* Soil: Temperate deciduous forests have rich, fertile soils due to the decomposition of fallen leaves and other organic matter.

Some examples of trees found in temperate deciduous forests include oak, maple, beech, and elm.