Coniferous forest have a rather neutral slightly acidic soil. It probably has to do something with the worm population in those soils also worms reduce the density in the soil and air is transported in the holes they create. read more
The soil in a coniferous forest tends to be young and nutrient-poor. The "thinness" of the soil is usually because of the cold, that hinders the development of soil and the ease, which plants can use its nutrients. read more