The series is unified by the seasons gold/red colours. In three of the shots, the same colours are captured in the differing textures of the leaves and grasses. I feel that the second shot, and it's fine in its own right as an image, is somewhat different to the others and shouldn't be viewed in the same series. Or maybe, add more photos with similar trunk forms to round out the series?
I enjoyed the grasses in the shots as an interesting variation on Autumn leaves.