The Amphibians and Reptiles of Sinaloa, Mexico - Smithsonian ...

AMPHIBIANS AND REPTILES OF SINALOA, MEXICO 57
tropical evergreen forest. Interspersed throughout the lower vegetation
are trees, Enterolobium, Ficus, and Taxodium mucronatum,
that often reach a height of 30 meters or more. Many trees and
shrubs carry epiphytes and parasites. Orchids are abundant along
many of the waterways in southern Sinaloa and northern Nayarit.
Plants common in the semiarid forest (e.g., Pachycereus pectenarboriginum)
are much less abundant in the more moist dry forest.
The flat coastal plain of extreme southern Sinaloa supports a
savanna type vegetation (Leopold, 1959:33). This formation is
not a climatic climax but rather a result of the edaphic conditions
of high water-table and poor drainage. In some regions, as near
Teacapan, the plants utilize the subsurface water and remain leaved
and green throughout the year; however, the high water-table prevents
this forest from attaining the stature characteristic of the
dry forest farther inland (Scott, 1962:8). Where forest is absent,
the dominant plants of the savanna are coarse tropical grasses.
Scattered trees may occur irregularly in the grassland. Palms and
jicaros (Crescentia alata) are characteristic of the savanna in
northern Nayarit.
Some of the common plants found in the dry forest of Sinaloa are:
Haematoxylum brasdetto, Erythrina occidentalis, Bursera grandifolia,
Ceiba aesculifolia, Sapium lateriflorum, Castillo elastica, Cordida
sonorae, Jatropha cinerea, Sideroxylon capiri, and Ficus petiolaris.
Subtropical Dry Forest
The subtropical Dry Forest occupies the central elevations along
the western slope of the Sierra Madre Occidental between 1000 and
1500 meters (Fig. 7). This vegetation, equivalent to the Tropical
Montane Forest of Gentry (1946a: 359; 1946b: 462), lies in about
the same belt as the oak forest but has a different physiognomy and
consists of different species. The presence of subtropical dry forest
is attributed to conditions of exposure, soil, and local climate as
affected by terrain.
This vegetation is generally limited to canyons and slopes where
the greater amount of precipitation is retained by good soil and
evaporation is reduced by cloud-cover. Gentry (1946b:453) credits
the rain clouds and fog as a chief factor in supporting the abundant
epiphytic growth and the varied forest of tropical nature. Shrubs
are more dense than in the semiarid or dry forests at lower elevations
(Plate 7, Fig, 2), Nearly all of the commonest species in the