28 FOREST RESOURCES OF TEXAS. 



activities, this will become a region in which timbered tracts will be 

 maintained as adjuncts to farms, furnishing local fuel and construction 

 supplies and at the same time protecting against soil erosion and deteri- 

 oration. It will then be well worth while to try what the pine will do. 



TIMBERED AKEA OF THE EDWARDS 1'LATEAU AND OF HILLS AND 

 BLUFFS NORTHWARD FROM IT. 



Next to the forest area of east Texas, this is the most important 

 timbered region of the State. The Edwards Plateau is the rough, 

 deeply eroded southern margin of the Great Plains, which end abruptly 

 in this part of Texas at the vast fault line, or downthrow, known geo- 

 logically as the Balconcs Escarpment. This escarpment is very promi- 

 nent along the southeast and south from Austin to San Antonio, and 

 westward to the mouth of Devils River. The body of the plains in 

 this region has been so deeply eroded as to present a picturesque 

 mountainous country, with all the diversities arising from erosion and 

 weathering of limestone strata of various degrees of hardness and dif- 

 ferences of texture. Thus there arc steep bluffs and deep gorges, 

 isolated buttes, long, even slopes covered with talus debris, or flatter 

 upland covered with coarse fragments of hard limestone bowlders the 

 " hardscrabble " countiy. Again, there arc small valleys and lower 

 flats upon which a fair amount of rich soil lias accumulated, thus offer- 

 ing limited agricultural opportunities. The area embraces perhaps 

 15,000 square miles, with considerable additions in the hills and bluffs 

 along the stream ways in north middle Texas, where similar physio- 

 graphic conditions occur. 



The region lies mostly to the west of the ninct3 T -eighth meridian, 

 and consequently in a rainfall zone of under 30 inches annually. This 

 amount of rainfall, especially with its very irregular seasonal distribu- 

 tion, is too low.to maintain a forest cover, except under conditions 

 where the rock strata are broken up sufficiently to retain and give up 

 gradually the precipitated moisture. Jt is interesting to note this close 

 dependence of a certain type of vegetation upon a particular phase 

 in the history of a geological formation. Thus, climatic conditions 

 remaining the same, if the Edwards Plateau were an uneroded highland, 

 its vegetation would, under natural conditions, be open grass prairie. 

 As a matter of fact it is being cut down to the coast level as fast as 

 erosion can do it, and coincident with this it is in process of transfor- 

 mation from a grass prairie to timberland. This transformation is 

 being hastened by the interference of man. Both agriculture and 

 grazing have operated to prevent the recurrence of prairie fires, which, 

 so long as they were periodic, kept the field swept clean of woody vege- 

 tation. The grass throve under this burning; seedlings of trees were 

 killed. Again, both have resulted in breaking up the heavy sod cov- 



