The range is covered by the Talamancan montane forests to elevations of approximately 3000 m. Much of it is covered by rainforests. Above elevations of 1800 m these are dominated by huge oak trees (Quercus costaricensis). Above 3000 m, the forests transition to enclaves of sub-páramo, a sort of shrub and dwarf bamboo Chusquea dominated scrub, above 3,400 m this becomes Costa Rican páramo, a tropical alpine grassland. The sub-páramo and páramo vegetation are subject to regular frosts at night, temperatures above 3200 m can reach 0 degrees Celsius or below, the lowest recorded temperature was -9 Celsius at the Mount Chirripó base camp (the second lowest ever recorded in Central America). The region has been extensively studied by paleolimnologists to reconstruct the changes in climate, vegetation and fire frequencies (see also Sally P Horn).