converted your work to grayscale to make a point...
there isn't a lot of range in your values...
and the circled tree in the distance isn't really all that much different in values from the nearby trees as indicated.
John F. Carlson (1929- Landscape painting) teacher and painter taught that darks are their darkest nearer to the viewer's eye...and lighten going back into space. Colors are their purest, and warm colors their warmest nearer the eye, beginning to lose intensity going back and cooling in color temperature.
Edgar Payne taught us that the eye can detect roughly 400 values, that we are lucky to paint and represent 40 values at best. He also taught that nature's light presents color 200 to 300 times more intense than what earth pigments can possibly imitate.
Arguably, that means we are all abstract painters...attempting at whatever level to paint realistically...but starting off with serious deficits. Thus...with our limitations, it is important at times to overstate and push certain things to make our work "feel" right.
Picasso said, "art is a lie that tells the truth"...and in this sense I believe he is right. We push even what perhaps we don't see...so that in the work all can see.
Another problem is that often artists work primarily from photographs and not from life. The camera favors light, and pushes darks to lifeless colorless areas...and we get a skewed idea.
the circled (reddish) areas in the foreground are your opportunity to push the darks darker...and the area purer in color to push the illusion of depth.
hope this gives you some ideas...
I was a moderator at Wetcanvas for about 12 years, last of the original staffers, but retired of it this past year to focus more on my painting, writing, teaching...travels...so I am not around nearly so much. I would like to help more...for everyone...but time and managing time is in and of itself an art...
keep at it...don't hold work too sacred to play, push, experiment...for there is where we grow quickest.
peace