Step 1
First of all, we need an image which will be our ground. I found one on sxc.hu, and You can get it from here. Open it with photoshop, then use Image > Image Size (Alt+Ctrl+I) to scale it down (I used 1600px width). Now using Rectangular Marquee Tool (M) with fixed size of 800x289 px select area which You think that it will be the best for future work. Press Ctrl+J to duplicate this part (a new layer will be created)
Step 2
Create new document (File > New) with 800x600 px size. Now drag ground layer which we just created to this document and place it at the bottom of this document (You may call this layer "ground"). Now click on this "ground" layer holding Ctrl key to make a selection. Grab Clone Stamp Tool (S), select large (~70px) brush with about 50% Hardness, create new layer (call it "ground over"). Select this new layer, and retouch ground layer (make sure, that Clone Stamp Tool Sample All Layers setting is active). All retouch result will be placed on "ground over" layer and doesn't affect "ground" layer. Our goal is clean ground.
Tip: Play around with Clone Stamp Tool until You will get what You want (image bellow is only a part of original effect, but rest of the ground looks similar).
Step 3
Grab Eraser Tool (E), and using ground brushes erase top edge of "ground" layer. Use original size of the brush (Use Sample Size) to make it as sharp as it can be (click few times in one place)
Step 4
Create new layer, place it at the top of all layers, and set blending mode to Color (you may call this layer "grass"). Click on "ground" layer holding ALT key to make a selection. Take ground (or other grunge) brush and using a green color paint on the top edge of the ground (but have "grass" layer selected). Then just use Image -> Adjustments -> Hue/Saturation (Ctrl+U), and play to get the color You want (Try to experiment with and without Colorize).
Tip: Use different brushes and try to experiment with it sizes.
Step 5
Duplicate "grass" layer, call it "grass light" and use Image -> Adjustments -> Curves (Ctrl+M) and make this layer lighter. Add Layer Mask to "grass light" and using black color "erase" bottom part of it leaving only the top edge which will be just our reflection.
Step 6
Create another layer, call it "ground darker". Click on "ground" layer holding Alt key to make a selection. Use Gradient Tool (G) and drag it over "ground darker" layer. Now the fun begins. Take Erase Tool (E) and using big, soft, round brush with different Opacity settings erase some parts of this gradient. Then take Brush Tool (B) (again big, soft) and using Opacity around 10% paint to darker some places. Feel free to improvise.
Step 7
Let's add few more things. Maybe bones? I found nice dinosaur on sxc.hu, and You can get it from here. Using any selection method You want (I used Magic Wand Tool (W)) just separate this dino from background and place it in our document. Move its layer on the top and call it "dino". Now click on this layer holding ALT key to make a selection. Create new layer, call it "dino shadow", and place it under "dino" layer. Use Select > Modify > Expand with 6px setting and fill "dino shadow" with black. Use Filter > Blur > Gausian Blur with radius about 3,5 px and lower "dino shadow" layer Opacity to about 70%.
Step 8
Dino need a little more work. Click on "dino" layer holding Alt key to make a selection. Create new layer over "dino" layer and call it "dino edges". Grab Clone Stamp Tool (S), and using ground brush thorn edges of "dino" (but paint on "dino edges" layer). After that create another layer, call it "dino dirt", set its Blending Mode to Overlay with 50% opacity and again using this same Clone Stamp Tool (S), and selection from "dino" layer make the bones look old and dirt (just paint over them).
Step 9
Place all dino layers (there should be four of them) in "dino" group, and add Layer Mask to this group. Take round, big, soft brush and using black colour just "paint" over this mask to blend dino legs with background.
Step 10
Now lets create some roots. Grab Pen Tool (P) and create a patch which will be a root. Create new layer, call it "roots" and select small (2px), soft, white round brush. In brush settings just change Shape Dynamics > Minimum Diameter to 50%, and stroke the path (make sure, that You have Simulate Pressure option selected). You may lower "roots" layer Opacity to around 70%. In this same way You may create more roots. Make new layer under "roots" layer, and call it "roots dot". Change brush color to black, increase size to around 4-5px, and just click few times making black dots under begin and end of each root (this is subtle change, and You may not notice it but in lighter background it make difference).
Step 11
Last thing we have to do is to add a nice background over the ground. I found nice one on sxc.hu, and You can get it from here. Drag it to our document, place it under all layers, use Free Transform Tool (Ctrl+T), and resize it.
Final result
In my final result I made one more thing - Filter > Blur > Gausian Blur with around 1px for background layer. Just click to enlarge.
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