Solar irradiation (5 states)
1 in very shaded situations, e.g. deep gorges, closed evergreen forests
2 in shaded situations, such as on the northern side of boles in close-canopied deciduous forests
3 in sites with plenty of diffuse light but scarce direct solar irradiation, such as in rather open-canopied deciduous woodlands
4 in sun-exposed sites, but avoiding extreme solar irradiation
5 in sites with very high direct solar irradiation, e.g. on the southern side of isolated boles