Tra suolo e foresta

The urban forest is among the most widely adopted metaphors for the transformation of the city. To explore its potential, the ‘3-30-300’ rule induce more attention to urban tree planting, but also suggest the option of not increasing trees. The sole reference to what is above – tree component – is questioned. What is below – the soil – as- sumes a central position to analyse the forest-city relationship. This contribution explores the role of open spaces with organic soil but no measures to protect it assuming the city of Pistoia as a context for investigation. On a sample of three open spaces of this type the variation in canopy surface area is investigated with simulations based on three growth scenarios. The results are discussed in light of a projection on the scale of the urban agglomeration and a comparison with the tree cover of three existing parks. The modelling shows margins for increasing the tree component provision not in conflict with giving open spaces appreciable levels of morphological. The contribution highlights that the conservation and improvement of the soil of vulnerable open spaces has a strategic value for an urban forestry policy.