Flora
The different geological events that have occurred in the Sierra Madre of Chiapas have encouraged the proliferation of Holartic and Neotropical ecosystems in El Triunfo Biosphere Reserve (REBITRI). The rugged terrain that ranges from 450 to 2.450 meters above sea level (MASL) contains eight vegetation types distributed among woodlands (forest) and rainforests.
RAINFORESTS
We call Selva (Rainforest) to the vegetation that grows in warm humid, sub-humid and sub-dry weathers with temperatures above 20 °C (Miranda, 1957; Miranda y Hernández, 1963). The structure and composition of the rainforests depend on the humidity perceived and the soils in which they develop.
Low and Medium Evergreen Rainforest
It corresponds to Miranda’s Medium Evergreen Rainforest, Rzedowski’s Cloud Forest and Moist Evergreen Forest of Breedlove. This type of forest is known in the region as “Nubliselva” because it has a very dense vegetation (1910 individuals/ha) regularly with a layer of thick fog (Miranda, 1957; Pérez-Farrera et al., 2004).
High Evergreen Rainforest
The vegetation map of the Reserve (CONANP, 2005) does not include this type of forest due to the vast areas of transition it has with the Low and Medium Evergreen Forests and the High and Medium semi-Evergreen Forests, between the 1,200 and 1,600 MASL in the high parts of the Sierra Madre.
High and Medium Semi-Evergreen Rainforest
The distribution of these forests in the Reserve does not generate a distribution pattern; the mosaic between canyons and plains produce humid microclimates in which these are developed. Its area of 27,299 ha represents the third major ecosystem in the Reserve and is distributed from 900 to 1800 MASL (Miranda y Hernández, 1963).
High and Medium Semi-Deciduous Rainforest
It corresponds to Miranda’s High Sub-deciduous Rainforest, partially to the Evergreen Tropical Forest of Rzedowski and the Evergreen Seasonal Forest of Breedlove. These forests are not included in the vegetation map (CONANP, 2005) due to the difficulty of separating them from the High and Medium Semi-Evergreen Rainforest in the classification image. However, it is known that these types of vegetation represent the Medium Rainforest that is in contact with the Low Deciduous Forest in the driest parts of the Reserve.
Low Deciduous Rainforest
This type of rainforest is not included in the vegetation map (CONANP, 2005) because it is difficult to identify it from the secondary vegetation that grows after High and Medium Sub-Deciduous forest have been removed. After several years of research in the REBITRI, this forest has been described at sites below 1, 000 MASL on the Pacific slope, where it gets in contact with the woodlands (Miranda, 1957).
WOODLANDS
Woodlands are located in the formations of more temperate areas in the REBITRI. This term comprises the vegetation of northern origin (holartic) that is found in mountainous places associated with temperate and cold climates (Miranda, 1957), with varying degrees of humidity (Odum, 1988) at altitudes ranging from 600 to 2000 MASL (Rzedowski, 1978).
Deciduous Woodland
This type of vegetation is found in the northeast part of the REBITRI between 1,300 and 1,700 MASL; it has an area of 96 hectares and is composed mainly by three species: pine, oak and sweetgum. This type of woodland is equivalent to the Deciduous Forest described by Miranda, partially to the Cloud Forest of Rzedowski and also partially to the Pine-Oak-Sweetgum Forest.
Pine and Oak Woodlands
These two types of vegetation in the Reserve are strongly associated as a single component (Pine-Oak Forest) and sometimes there is only one of them forming pure stands on small areas between 650 and 1,900 MASL. This association has an area of 3,703 hectares and finds its greatest development on the northwest portion of the Reserve. It is equivalent to the Conifer Forest and Quercus forest described by Rzedowski and the Pine-Oak forest by Breedlove.
Cupressus Woodland
This vegetation is distributed only on the southeastern part of the Reserve; it has an area of 1160 hectares and is surrounded by vast areas of Medium and Low Evergreen Rainforest, Pine-Oak Forests and High and Medium Semi-Evergreen Forests. The main species are Cupressus benthamii var. Lindley y Pinus oocarpa var. Ochoterenai, which form a continuous canopy between 25 and 30 m high. It is equivalent to the Forest of needle-like or sale-like leaves described by Miranda, Rzedowski’s Coniferous Forests and Pine-Oak Forest from Breedlove.
Secondary Growth
Although this term is not a vegetation type sensu lato, it is used to describe all vegetation that develops after the rainforest or woodland have been cleared. This type of vegetation covers an area of 11,023.85 hectares and does not have an order with respect to other vegetation types described.
There are other types of land use; the main three are: seasonal agriculture, permanent agriculture and pasture.