In the mountains of Maipo Valley, the rivers Maipo and Volcán merge. The main tributary of the Volcán is the Yeso (see photo). This area is near the capital city and it can be easily reached. Local flora and fauna have therefore been researched very well (Meigen, 1894; Hastings, 1905; Grandjot & Grandjot, 1936; Quintanilla, 1981; Faúndez et al, 1996; Muñoz-Schick, et al, 2000; Meigen, 1893; Teillier et al, 1994; Muñoz-Schick, et al, 2000; Teillier, 2003). It is worth mentioning that the river valley of the Yeso is the type of habitat for at least 27 species that were described by R. A. Philippi (Muñoz-Pizarro, C. 1960).
To preserve biodiversity in the Andean Maipo Valley, the Chilean environmental agency CONAMA has given this area priority within the national strategy to protect biodiversity.
In general, the native flora in this area can be divided according to vegetation levels (Fredericksen et al, 2011; Espinosa et al., 2011):
Sparse forest and shrub-like plants (~ 600 - 1,700 m):
Characterized by a heterogeneous layer of shrub vegetation. Dominant species are Quillaja saponaria (Quillay) and Lithraea caustic (Litre).
Other important species are Kageneckia oblonga (Bollen) and Cryptocarya alba (Peumo), the latter is mainly found in the more humid southern slopes.
Sub-Andean level (~ 1,650 - 2,000 m):
PThe dominant plant communities consist mainly of Kageneckia angustifolia (Olivillo), Guindilia trinervis and Colliguaja integerrima (Duraznillo).
Lower Andean level (~ 1,950 - 2,800 m):
Mainly shrub plants with a height of 0.5 to 1.20 m grow here. Apart from this shrub layer, there is a herbaceous layer. Typical plants are Tetraglochin alatum (Horizonte) and Mulinum spinosum (Hierba negra).
Upper Andean level (~ 2,550 – 3,250 m):
Flat plant carpets with a maximum of 0.5 m height, which can be divided into a shrub and a herbaceous layer. Typical plants are Berberis empetrifolia (Zarcilla), Laretia acaulis (Llareta), Adesmia schneideri, Nassauvia and Senecio.
In this level, wetlands are to be mentioned, which have water most of the year.
They are both important as green fodder supplier as well as for the preservation of the species, since they provide a habitat for various species of animals.
High mountain level (~ 3,250-3,600 m):
Perennial plants that are rarely more than 30 cm high grow here. There are two types of vegetation: the herbaceous steppe with the typical Poa holciformis (Coirón) and the somewhat more humid, stony gravel surfaces with flat shrubs or perennial herbs such as Nassauvia lagascae or Nassauvia pinnigera. Here, there is little vegetation, and mainly above 4,000 m there are practically no plants.
Fauna:
Fredericksen et al. (2011) identified at least 140 terrestrial vertebrates in the area of the municipality San José de Maipo. Birds represent the largest share with 58%. Mammals account for 25%. Nearly 20% of the 140 identified vertebrate species belong to endemic species of Chile. Among them, 48 species (34.3%) are listed as endangered or rare, seven are in danger of extinction (at least in the area of the municipality).
