The reserve's flora and fauna is characteristic of four (4) life zones according to the map of life zones of Costa Rica (Bolaños, Watson and Tosi, 1999).
1. The premontane rainforest life zone takes up an area of 948 hectares and is located on the Caribbean slope, in the middle of the Peñas Blancas River.
2. The low montane rainforest life zone takes up the greatest amount of land of the reserve (2,180 ha) and it is located on both slopes, on high peaks and crests of the continental divide.
3. Low montane wet forest life zone takes up a small sector of the reserve (341.5 ha). This is the area with the greatest pressure on the resources protected by the reserve, given that this is where the reserve's administration infrastructure and the visitor sites for the thousands of visitors that come every year. Furthermore, this is the area where most of the scientific investigations have taken place during 35 years.
4. Finally, the premontane wet forest life zone is the least represented in the reserve taking up only 174.9 ha. This area is located on the pacific slope. The natural vegetation is an evergreen forest with a few deciduous species and with a variety and moderate abundance of epiphytes.