It's well known, that most of types of mana have cumulative effect. But some types - no. For example, Fire and Nature. The idea is to make the system more homogeneous, and add cumulative effect to all mana types. Nature Mana could increase rate (or probability) of forest growth (like Earth Mana increase a chance of resource discovering). I.e. it should make quicker all such transformations: Plain(Tundra, etc.) -> New Forest, New Forest -> Forest, Forest -> Ancient Forest (with FoL) Fire Mana, otoh, could increase rate of transformation Smoke into Flames. Maybe it's reasonable to make a little cumulative chance of spontaneous ignition. Similarly, Sun Mana could give a small cumulative chance of spontaneous drainage of marshes.