How would soil fertility likely change during the early years if primary succession

The answer is: Soil Fertility "Gradually Increase" during the early years of primary succession

Primary succession begin when an area still does not have any form of soil to begin with. Overt time, organisms such as algae,   lichen,  and fungi start to influence the environment in that area.  Gradually, rocks started to be transformed into soils and these early organisms started to gather various nutrients from around them. This will gradually increase soil fertility during early years of primary succession.

which of what? i am confused