8 FOREST RESOURCES OF TEXAS. 



NATURAL DIVISIONS OF THE STATE. 



The divisions of the State which are of significance for a discussion 

 of forest growth are physiographic rather than geological. (See fig. 

 1.) They are the following: 



1. The Coast Plain. 



2. The Fayette Prairie. 



3. The Lignitic Belt. 



4. The Rio Grande Plain. 



5. The Black Prairie, Grand Prairie, and Edwards Plateau. 



6. The Central Denuded Region. 



7. The Red Beds Prairies. 



8. The Staked Plains. 



9. The Stockton Plateau. 

 10. The Cordilleran Region. 



(1) The Coast Plain, over 15,000 square miles in extent, is the low, 

 flat plain lying along the Gulf, from which it has emerged in very 

 recent geological time. It comprises a strip 50 miles in width, more 

 or less, parallel to the Gulf and scarcely exceeding 50 feet in altitude 

 at any point. The rainfall exceeds 50 inches at the east, but decreases 

 to 30 inches soon after passing the ninety-seventh meridian. The 

 Coast Plain from 97° 30' westward may be arbitrarily included with 

 the Rio Grande Plain. The soils of the Coast Plain, thus limited, con- 

 sist of compact clays and silts, interspersed with areas haying a larger 

 proportion of sand, and therefore more porous soils. These latter are 

 more easily captured by forest, the compact soils more slowly. Thus 

 one finds alternating areas of forest and prairie. Where streamways 

 cut across the Coast Plain a line of timber follows to the Gulf. 



(2) The Fayette Prairie, containing 12,000 square miles, is a narrower 

 belt of more uneven, undulating country, lying next inland and paral- 

 lel to the Coast Plain. The rainfall conditions of the Coast Plain are 

 repeated here; but the disposition of the water is different, owing to 

 the deep beds of sandy clays and gravels which characterize the belt. 

 The soil structure is especially favorable to timber growth. The Fay- 

 ette Prairie east of the Trinity is occupied by longleaf forest. West 

 of this the timber is mainly post oak, black jack, and live oak. These 

 extend to the Nueces River, or farther; but the Fayette Prairie west 

 of 97 c 30' will be classed as Rio Grande Plain. 



(3) The Lignitic Belt, over 30,000 square miles in area, is an older 

 geological formation (Marine Eocene), lying next inland from the 

 Fayette Prairie. The altitude is greater, ranging from 200 to 500 feet, 

 and erosion has left a much more uneven country than that of the two 

 preceding divisions. Counting that portion west of 97° 30' as Rio 

 Grande Plain, the remainder comprises a large area of sandy clay 

 ridges and hills, occupying all of east Texas interior to the Fayette 



