Macchu Picchu is not in the same biome as most major Inca sites. It sits at the border between the Andean highlands and the jungle of eastern Peru, 1000 m below Cuzco. Forestry was hardly a common Inca concern. The terrain, though, is still dramatic and sloped, so the land would have been dealt with similarly in that regard. For just about as long as their have cities in the Andes mountains, they have been surrounded by terrace fields. You can see a few terraces in the middle in this pic, but, for most inhabited slopes, that is a very small amount. Arable land is sparse in Peru and Bolivia; the flat land at high elevations is only suited to a small number of crops and much was/is used for herding rather than farming. So to imagine what it would have looked like, extrapolate those few terraces across the entire slope.