Tropical Deciduous Forest, commonly called TDF for short, represent the most tropical parts of our region in the warm and protected canyons and slopes of southern Sonora. Although closely related and with a similar assemblage of tree species as thorn-scrub, TDF hosts more species of tropical origin. These species are generally sensitive to frost or need better and more consistent rainfall patterns to survive. TDF has a taller and more robust structure.
The floras of the tropical vegetation in the Sky Island Sierra la Madera (SMA) near Moctezuma in northeastern Sonora (30°00’N 109°18’W) and the Yécora (YEC) area in the Sierra Madre Occidental (SMO) in eastern Sonora (28°25’N 109°15”W) were compared. The areas are 175 km apart. Tropical vegetation includes foothills thornscrub (FTS) in both areas and tropical deciduous forest (TDF) in the Yécora area. A total of 893 vascular plant taxa are known from these areas with 433 taxa in FTS and 793 in TDF.
TDF and thorn-scrub are often cleared to make way for planting of non-native buffelgrass (Pennisetum ciliare) for cattle forage. Calumnar cactus are often left, but do not always survive. Generally there will not be recovery to TDF. Sometimes a monoculture of Acacia cochliacantha can eventually invade cleared areas if it can outcompete beffelgrass and the area isn't burned or re-cleared.
