create a new layer and go Filter->Render->Clouds create clouds in a bluish tone and then set the layer blending mode to color. Also if necessary using the soft mechanical eraser brush clear the bottom part of the layer
step 2 of 4
make a new layer and repeat step 1 but this time apply it to the bottom of the image with a green-cyan tone
step 3 of 4
create another clouds layer following step 1 but this time use a pink tone and then set blending mode to soft light
step 4 of 4
using the rectangle marquee tool select the tree area from source image and create layer via copy. then free transform it so it appears like the mirror of the source tree and using the soft eraser clear the edges. Blending mode: overlay