CULTURAL GEOGRAPHY OF THE MODERN TARASCAN AREA—-WEST 9 
covered with pine and oak within the memory of 
living inhabitants. Increased cultivation of slopes 
and constant cutting for firewood and charcoal 
will soon destroy the greater part of the pine-oak 
remnants in the northern plateau. 
The escarpment zone.—South of the Sierra lies 
a series of climatic types arranged in altitudinal 
sequence. The upper part of the escarpment 
(5,600 to 3,600 ft.) is characterized by a narrow 
belt of Cwa (tierra templada) climate, which is 
followed abruptly by the subhumid tierra caliente 
(below 3,600 feet), or Aw. Below 2,000 feet with- 
in the Tepaleatepec and Balsas Basins, a semiarid 
tropical climate (BSh) prevails. 
The pine-oak association of the Sierra spills 
over onto the upper escarpment, but the sub- 
tropical Pinus oocarpus becomes the dominant 
pine. Between 4,600 and 3,600 feet, pines disap- 
pear, leaving an open oak forest mixed with sub- 
tropical and tropical plants of southern Mexico. 
At lower elevations the latter plants become 
dominant." 
SOILS 
Three soil types, which tend to coincide with 
climate and vegetation, predominate in the Taras- 
can area: (1) a yellowish-brown leached soil of 
the upper mountain slopes (Cwb to Cwe, pine-fir 
cover); (2) a dark, fine sandy loam (t‘uptiri) of the 
lower slopes and basins in the Sierra (Cwhb, oak- 
pine, probably grass vegetation); and (3) the 
reddish-brown clay soil (¢ar4nda) of the lower 
altitudes (warm phase of Cwb, Cwa, broadleaf 
vegetation) around Lake PAatzcuaro, in the lower 
elevations of the northern plateau, and in the 
escarpment zone (map 6). Transitional and special 
soil types also occur; for instance, many of the 
Sierra soils are termed “charandosas,”’ having a 
; gees 
higher clay content than the t‘uptri loams. 
Yellowish-brown soil.—This soil develops in 
high altitudes under seasonally humid conditions 
“The tropical vegetation of the escarpment is characterized by a great 
variety of genera and species. The most common plants include the 
milky-sapped trees and shrubs of the family Moraceae—comuchin (Ficus 
padifolia), siranda (F. petiolaris), saruma (Ceropia mexicana); the pod-bearing 
Mimoaceae—timbin (Mimosa stipitata), guaje (Leucaena sp.), huisache 
(Acasia sp.), tepehuaje (Lysiloma sp.), parota (Enterolobium cyclocarpum), 
timuche (Pithecellobium lanceolatum), guamuchil (Pithecellobium dulce), 
Calliandra sp.; the pod-bearing Caesalpiniaceae—habilla (Cassia occidentalis), 
easacalote (Caesalpinia coriaria), etc.; the edible fruit-bearing plants of the 
Annonaceae—chirimoya (Annona cherimolia); of the Lauraceae—ahuacate 
(Persea americana); of the Sapotaceae—chicozapote (Achras sapota), mamey 
(Calocarpum mammosum); of the Anacardiaceae—circuela, cupu (Spondias 
mombin); of the Mirtaceae—guayaba (Psidiwm quayaba); and the copal- 
bearing Burseraceae—copal ( Elaphrium jorullense). 
and fir-pine vegetation. It is the soil of the higher 
hillside maize plots in the Sierra; leached and 
infertile, it will produce crops for no longer than 
4 or 5 years, after which the field is abandoned. 
The fine, sandy topsoil, however, is moisture 
retentive, and is therefore known as “‘tierra de 
humedad,” in which crops can be p'anted 2 months 
before the rains. Podzolic soils (uncultivated) 
probably occur above 10,000 feet in the fir forest. 
T‘uptri.—The most productive of the highland 
“humedad” soils is t‘uptri. Like the yellowish- 
brown soil, the texture of the topsoil is extremely 
fine. (Analyzed as fine sandy loam: 56 percent 
fine sand, 23 percent silt, 21 percent clay, 1 per- 
cent coarse gravel.) The surface drys to a fine 
powder and acts as an insulator, preventing the 
evaporation of moisture from the soil beneath. 
Consequently, in April and May near the end of 
the dry season the t'uptri soil is well moist 3 
inches below the surface. T’uptiri usually occurs 
between 6,500 and 8,600 feet on both the lower 
slopes and in the basin plains. Being porous, the 
soil soaks up moisture rapidly, preventing serious 
sheet or guily erosion even on the steeper slopes. 
Generally, the basin t‘uptiri is more fertile than 
the yellowish-brown, the topsoil of the former 
having a high humus content (6 percent), a fair 
content of critical elements (e. g. 0.09 percent N), 
but a deficiency of lime (0.31 percent). Various 
subtypes of t‘uptiri occur, differences being based 
mainly on soil texture. At the base of slopes or 
on alluvial fans the topsoil is often partially com- 
posed of coarse voleanic cinder. Such soil is 
locally called ‘‘cascajo,” or gravel. Other sub- 
types are characterized by an increase in clay con- 
tent. These eecur on the lower slopes, and are 
sometimes referred to as “tierra charandosa.”’ 
Caranda.—This is a reddish-brown clay soil, 
which prevails below 6,500 feet and develops trom 
the spheroidal weathering of volcanic rock under 
warm summer and mild winter temperatures and 
a cover of broadleaf plants. (Textural content: 
39 perceat sand, 26 percent silt, 35 percent clay.) 
15 Surface soil samples (to a depth of 25 em. below surface) were taken by 
the writer in the Sierra and Lake areas and were analyzed by the Comisién 
Nacional de Irrigaci6n, Direccién General de Agroeconémica, México, D. F. 
‘Texturally the highland yellow-brown soils are sandy loams, (60 percent fine 
sand, 20 percent clay, 20 percent silt, are highly water-retentive (30 percent), 
and are low in hummus (4to 10 percent). All soils analyzed (including t‘uptri 
and ¢aranda types) were low in lime content (0.24 to 0.34 percent), and 
slightly alkaline to alkaline (pH values: yellow-brown mountain soils, 7.22 
to 7.24; t‘upuri, 7.44 to 7.71; ¢aranda, 7.21 to 7.42; uirds, 8.05 to 8.13). Since 
profiles were not determined, classification according to world soil groups is 
not possible at this time. 
