OK Here we go. There is nothing wrong with your .tdg I bet I named that file wrong. What was the problem as was mentioned, was that the scale setting of the trees was far too low, together with the fact that you had something in the hundreds set in the Y zone, when as was indicated it should have been 0.
Please all the Gods that I get the accompanying shots in the right order. Incidentally your trees are sitting on the ground.
OK first shot. Here I altered your Y setting to 0
Second shot. I just knew these would be in the wrong order, but this shows the cropped render, which I hope shows that the trees are sitting on the ground.