This look is usually created more by capture technique than by Photoshop alone. Based on the answers, the most likely factors are:

• very high source resolution: either a high-quality DSLR image, a stitched multi-shot panorama, or even a medium/large-format capture
• a sharp lens, often a good prime or strong zoom at its best aperture
• a stable tripod to maximize detail
• possibly multiple exposures for tonal control

If you want to approach it with a DSLR, a practical method is to shoot several overlapping frames with a sharp lens on a tripod and stitch them into a panorama in Lightroom/Photoshop. That increases total resolution and makes distant trees render with more separation.

Good technique matters: use low ISO, careful focus, solid support, and avoid haze or poor atmospheric conditions, since distant foliage loses contrast quickly.

Post-processing can enhance the effect, but it can’t create detail that wasn’t captured. Moderate contrast, clarity/local contrast, and careful sharpening can make individual trees stand out more, but the “almost unnatural” look usually starts with an extremely detailed original file.