All these areas were under ice about 10 000 years ago. It has effected nature and soil and is a good starting point to reconstruct Haaga before human. In this video you can see ice covering Finland in different ages. Video animation
Ice was very thick and heavy and land is still rising. Rising speed in Haaga is slow, 4 mm/year, but interesting phenomenom that has affected the landscape.
After ice melted away, these areas were mostly under water. All areas were washed, so in a way sorted. In this map is is show the soil types. Red is solid rock, blue is glay, orange is moraine, greys are peat land and raster means that area is filled or not investigated. Mapping is based on soil types found 1 meter under surface of the earth.
The vegetation that came after ice had melted formed slowly organic soil layers. Other plants could then find places to grow and transform this place to a forest. Among the first ones came hays, marunas, juniper and wicker.
Trees are thought to have arrived in Finland mainly from the southeast and the east. First came birch, and there were forests with only birches. Then came pine and forests consisted of both birches and pines. After that, at about same time, came alder, aspen, hazel, elm and oak. There was a warm period at that time, but about 5000 years ago climate started to cool down again and in Southern Finland, the proportion of noble hardwood trees began to decrease and the share of pine to grow. In Haaga before human there was presumably lot of pine forests, some areas with more diverse vegetation in areas that have fertile soil (glay) and some open land in peat areas.