20 

 me/lOOg), K* (3.11 me/lOOg and 2.37 me/lOOg), pH KCl (7.20 and 6.60), and pH HjO (7.78 

 and 7.32). 



Soil physical properties: Field edacity (52.39% and 57.23%), wilting point (21.59% and 

 22.55%), available water (30.77% and 33.54%), and bulk density (0.86 g/cm^ and 0.76 

 g/cm'). 



These results suggested that the soils of the area can support horticulture, but that the present 

 period of only a few years that Maya farmers leave the land to fallow will result in serious soil 

 degradation. A fallow period of 20 y would allow soil physical and chemical properties to return to 

 normal levels. 



Below the soils of the Yucatan Peninsula there is hard surface limestone (Wilson, 1980). 

 Widespread, especially in the north, this rock is formed by solution and precipitation of calcium 

 carbonate near the ground surface. Plant roots break up the cemented grains and shell fragments into 

 large chunks that litter the surface. 



A material called sascab occurs below the hard surface layer (Wilson, 1980). Sascab is nearly 

 pure calcium carbonate and forms as the surface limestone weathers. Friable, sascab is commonly 

 mixed with cement by Mexican workers to make roads and building foundations. 



Species Richness 



Species richness is the number of species that occur in a specific geographical area without 

 regard to their density or abundance. Among Mexican states, the species richness of Quintana Roo is 

 relatively low, containing only about 20-30% as many species as the states with greatest richness 

 (Flores-Villela and Gerez Fernandez, 1989). About 151 species of vertebrates and 1,257 species of 

 plants occur in Quintana Roo. Vertebrate endemism is low (five species), while plant endemism is 



