Looks ok-ish :3

The grass could use more variation. Real world grass consists from a lot of different shapes and types. Even burnt grass from the sun.
Also, some random size for every grass stroke would improve it, since not every single one grows at the same rate.
The trees look okay at the bottom. (Sapling AddOn maybe?)
Some displacement for the bark would improve it a ton. (Unfortunately, i don't know, how to add displacement to a curve either.)

But they need more leaves.
Their shader work for this scene. But one easy way to maximise the realism is to use a green diffuse shader combined with a translucent shader via "Add Shader". This one would be the last thing you combine in the nodes, since you also used a "Transparent" Shader for the leaf texture.

The last thing, i could mention... The lack of Post-Processing. This one is a bit more complicated. But some Glare effects would be nice. The sun is directly bursting onto the grass field. This would create a lot of reflection light in this scene.

One more thing:
Never ever ever use the "Sun" lightsource. Use HDRi images for the skybox.

I hope this helps you :3
For questions, just PM me. I at least want to help others getting into 3D-Art.

blender has for some reason gotten rid of its "hair" functionality which means i used to be able to render grass as "ribbons" and the hair on creatures as "thick lines" but for some reason they took that ability away and also i am an intermediate in blender and for what i am able to do this is the best at which i can do it ... not to mention the memory constraints i am under as rendering "hair" takes up alot of memory and i will say also that if it was possible i would have made it more "varied" but if you have ever been to a field of grass you would see its not really super varied and you have to remember that the camera is set low to the ground ... if it was a few feet up it would have looked more realistic due to the fact you could see over the grass more (seeing chunks of grass like in real life instead of what seems to be an even field) also i did not use the Sapling addon i used cylinders as i have always had issues with texturing the saplings in the addon ... also i used the Principled Shader for every material and for the leaves on the trees it made more sense to not make thousands of them as that would take up even more memory .. also there is already glare effects present its subtle on purpose .. also i did use an HDRI for the Skybox and added a sun for more control and the physical sun you see is not emitting alot of light .. that is from the HDRI i used (which had to be a lower res due to memory constraints) ...


the process i used is as follows


i used the skin modifier on a cube to make the trees then subdivided them thrice ... i then took an alpha of pine tree branches and applied them to a flat plane which was then subdivided 5 times and molded into a natural(ish) shape ... i then made a plane and subdivided it 20 times in the poly editor and made it a touch uneven .. i then took to modeling the dog using the skin modifier then after a basic shape was made i then used the sculptor and made the finer details ... after doing that i used the "unsubdivider" and made it lower poly as i had used dynamic-topography when sculpting ... after that i unwrapped the fox then proceeded to texture paint at a resolution of 1024 x 1024 then after he was painted i then rigged him manually (no ik rigging as he was not needing to move much) after that i then took to adding hair to the plane which was the grass you see then i took to adding hair to the fox ... after that i added another plane and made it several times larger than the foreground plane and subdivided it about 20 times as well and then molded it into gentle hills ... after that i made another plane and applied a picture of wheat grass to it with an alpha then i subdivided it 3 times then while in edit mode i copied it and rotated it 90 degrees then i selected all faces and copied them and rotated 45 degrees .. after that i then took to applying hair to the second larger plane and then used the wheat grass object i made and used that as the dupli object for the hair .. i then added the HDRI map to it after shrinking it from a large 120 meg 8k image down to a 4k jpeg i was then able to render it out to see what it looked like ... after that i then added a sphere and gave it a "Volume scatter" material and set the density to a very low number of .002 so it would look naturally humid .. i then rendered it out in 5k and then took to the compositor and made a basic node setup with 2 glare nodes .. one was for the sun to make it "bleed" through the branches .. the other was to add the "bloom" lens flare effect .. after that it was pretty much done ... i should also mention i used some Depth of field effects to make the background blurry and to add a touch more realism ... and to despecle the render i used the de-noiser feature included in blender 2.79