That final render had a touch of post work. Partly because my PC monitor was not calibrated properly and I edited the trees as I will explain.
Below are non post worked crops showing different render settings of the ground. The top one was detail 1 the bottom was detail 5! I hope you can distinguish that there are 2 renders pasted together here. I's not very clear. The top also had a lower anti-aliasing setting. I think AA 2 and the bottom was 4. Possibly I should have balanced it with more AA and less detail but I found it didn't completely correct the noisy look. I should definitely have reduced GI because that was way too high at setting 2 with detail 5 because I presume it is relative to detail. There is not much point in showing other cropped tests of this area because they are basically between these settings but you can see the difference. The ground textures are made with 4 Power Fractals. Two on flatter lower ground and two on slopes which you can't really see here. The larger one is stretched on 1 axis and there is a smaller one that provides some sand like grain at very close view. It was a problematic POV. When I initially worked on these textures I was at a totally different planet location so they were not as stretched but then I ran into populations problems being away from position 0,0,0. I didn't want to increase anti-aliasing too much and create a blurry image. This was actually my first proper render with TG2 Deep. It ended up taking several days but I won't be using these settings again. Detail 5 is extreme but I am just testing.
Another problem shown below is that trees in a detail 1 render looked like the top picture and at detail 5 they looked like the bottom. I also increased the trees own rendering quality one step to top level but I don't think this caused the effect:
Probably connected with relative increase of GI but I don't understand this. I hope you can see the problem here to do with darkness of colours. I have a 24 inch Eizo monitor which shows every single deficiency. These are awesome monitors by the way. I tried an Apple Monitor but it was so bad I sent it back. Pink shades down one side. Not even close to the quality of the Eizo.
The final image was post worked to change this tree problem because I thought some trees were too dark. I also actually had to initially completely edit the textures on the tree because otherwise they would have turned out very dark but it turned out that at detail 5 they were dark anyway and it was the same file taking the same edited tree textures. At first I though I had somehow got the original textures back but this was not so. Trees all seem to end up very dark in TG. When you use GI this is further exemplified. Maybe because the leaves would need to be transparent and reflective to look right even at distance.
