Hello Jacquinot,
It is quite difficult to translate exactly those terms as light forest or brushes because they have different meanings in different countries : in the mediterranean I'ld say "maquis" with vegetation entangled from say, 3 to 6 feet and some trees 10 high. How does it look in this part of Russia , I don't know....The effect is to slow walking, prevent straight move, hide your position and sometimes make you circle like mad!
I'd found some details in dr Hourtoulle's book with authentic maps and witness illustrations : the infantry deployed and attacked in this "light green" but the formations look irregular. Also there are sketches of the redoubt and their defense in front : there was a large ditch, the abattis (whole trees cut with branches tipped and entangled and also some areas of "trous de loup" , holes about 4feet deep (enough to break horses charge and slow infantry) not on your map.
Probably you can consider (as Napoleon and Kutusov did) that the south or "vieille route de Moscou" was not the best choice as it was old, narrow and leading to wooden areas which was not suitable for a regular deployement in lines and columns for either untrained russian levies and mixed (dubiously enthusiastics ) french allies. But, good, trained and Highly spirited units may had done it...
To sum up, it was not considered clear terrain and I think you can use small spots of trees irregularly dispersed to give an idea (watch the Peninsular maps serie ).
For History, was it a good choice from both CinC to avoid the south road ????
Oster
Ps I just read Alfiere last message and I agree with his Davout's Hypothese.