I want to make a 2D architecture plan with 3D elements (like trees, ..) on them, but I don't know how exactly and in which program? AutoCad, ArchiCad, Illustrator?
Looks like a model that could've been made in anything. Autocad, Modo, Rhino or Lightwave are all viable options for something like that.
Instead of using the internal render or an advanced render they were then brought into Photoshop where some basic overlays of colors, textures, the water and such were added. Trees are hard to tell - they could've been added in the 3D package or in Photoshop.
don't know how exactly
Me neither, but for the second set of images there are a cuple of viable options.
3D using Sketchup
The internal "preview" has the look of a simple drawing. You need to hide the edges.
It is very easy to asign textures on flat surfaces, and very easy yo asign height to the sidewaks, etc.
Has a "Face Me" option. You just make a vertical square, asign a texture and that looks to the camera all the time, mantaining the vertical position.
Can have an isometric look or aperspective using a camera.
And you have a free version and big library of 3D already made objects. How cool is that?
But I must say. In the case of sketchup look, you are "limited" to the screen resolution, because you basicly bring a screen capture. But you can have a simmilar look on a lot of render engines (some again, for sketchup) you just need to use flat objects, infinite lights, and some other lights not projecting shadows.
Your image have some slight gradients. This could be prepared as a texture for the 3D model or can be added later in Photoshop.
2D using whatever program
I would use Ilustrator or CorelDraw, instead of Photoshop to make the base plan, and then aplying a deformation to simulate the isometrics of the floor, and some library of 2D objects in the correct proportion. Trees and people.
(But I would go for the 3D option it would be a lot easier and precise)
Regarding the first one, you could make first a simplified version of the plan, and after that a more detailed version of it on any 2D drawing program.