It is an area with different plant species, whose thermal needs are known in the different phases of life (phenological phases).

These plants respond to environmental and climatic conditions of a given area and to annual climatic variations by anticipating or delaying some phases such as flowering. By monitoring the phenological phases it is possible to highlight climate changes and how these plants adapt to these changes.

The recognition of the phenological phases takes place through the use of the so-called "Phenological key or scale" which is a system designed to uniformly codify similar, observable phenological stages of development. The phenological key describes, according to specific national and international standards, the development cycle of a plant for consecutive intervals. Each interval corresponds to a precise moment of development of the plant or an organ, therefore a phenological or phenophase stage.