Go to the pictures tab in the terrain editor, have your mountain loaded in one frame and your desert in the other and select blend. (I'm at work without Bryce, or I'd show a screen shot).

Hi! You have two sets of problems here! One is the texture, second is the placement of the mountain. The texture on the ground seem to be the same as the one on the mountain (i.e. in the same setting!). This spoils the illusion of depth. If you were to tile the texture less and increase the bump map in the ground terrain the terxture would start differing. Secondly in crease the size of the mountain and take it further back and away from the camera! Also in the atmosphere setting in crease the haze by about 2-3 points. Lower the camera a bit so that its nearer to the ground level and tilt it up. That should give you a more realistic image. My bryce is busy rendering right now. I'll try and post an image later about what I mean! Hope this is clear to you. Do let me know in case you require any further clarifications.