Trees in the Mountain Grove biome generate with Dirt instead of Spruce Logs at the base

Summary:

In new mountains, trees are generated with a dirt block at the start. This is not logical, because if you dig out the snow, you will notice how all the trees (especially on a flat surface) are on the dirt block.

Steps to reproduce:

1. Find new mountains.
2. Find a flat surface in the mountain (at least 3 by 3 blocks with a tree in the center).
3. Remove all snow around.

Observed results:

The trees stand on a dirt block.

Expected results:

Trees will not have a block of dirt at the beginning of the trunk. Instead of this block, there must be 1 more block of the tree.

Image: