Painting forest environments is one of the scenarios where the 'paint masses, not individual elements' principle is most important and most violated.

A forest is not a collection of individual trees. From any meaningful distance, a forest is a mass of forms with implied depth. The mass has a light side and a shadow side. The light penetrates the canopy and hits selected lower surfaces. The ground has patches of light and areas of deep shadow.

My approach: block in the entire forest mass as a single large form first. Establish where the light hits the canopy. Then add the structural elements — the major tree trunks visible in the foreground, the middle-distance tree forms visible as individual silhouettes. Finally, add the light dapple on the forest floor in the focal area.

The depth cue: atmospheric perspective applies within a forest. The trees near the viewer have full local color and high contrast. Trees even twenty meters back have begun the desaturation and contrast reduction of atmospheric haze. Forests are spacious enough that this effect is visible at relatively short distances.