20 



BULLETIN 1031, U. S. DEPAKTMENT OF AGKICULTUBE. 



Table 6. — Amount and class of vegetation on inclosures protected from grazing 

 and percentage of maximum statid, 1915 to 1919 inclusive {grama grass 

 type). 





Good perennial 

 forage grasses'. 



Inferior perennial 

 forage grasses. 



Lonf;- 



lived 



perennial 



weeds. 



Short- 

 lived 

 weeds 



Year. 



Square 

 centi- 

 meters 1 



per 

 square 

 meter. 



Per cent- 

 age 



of maxi- 

 mum 

 stand. 



Square 

 centi- 

 meters 1 



per 

 square 

 meter. 



Per cent- 

 age 



of maxi- 

 mum 

 stand. 



and 

 annual 

 vegeta- 

 tion. 





Number 

 plants 2 



per 

 square 

 meter. 



Number 

 plants 2 



per 

 square 

 meter. 



1915 



511 



583 



3 537 



511 



347 



87.6 

 100.0 

 92.1 

 87.6 

 59.5 



7 

 8 

 7 

 9 



8 



80 

 90 

 80 

 100 

 90 



2.6 

 3.0 



17.5 

 2.0 

 0.0 



• 44 4 



1916 



33 



1917 . 



61 5 



1918 



82 5 



1919 



31.5 







1 Actual measurement of area of grass tufts in square centimeters 1 inch above the groimd on each square 

 meter. (The metric system, with area expressed in square centimeters per square meter instead of with 

 feet and inches, was used for convenience in the study because a unit of measure less than a square inch was 

 necessary. ) 



- Actual count of number of individual plants per square meter. 



3 Actual measurement showed 699 square centimeters but contained a considerable amount of dead forage 

 mixed in with the living plants. This dead forage was estimated from best method of determination to be 

 23 per cent of total stand of vegetation. 



♦ 



Change in density of the grasses did not conform immediately to 

 change in the rainfall. The main reason for this is the fact that 

 the vegetation is dependent more directly upon available soil moisture 

 than upon current precipitation, and the soil did not dry out to such 

 a degree that it affected the growth so materially the first year of 

 drought. In addition, however, the vegetation gradually decreased 

 in vigor and resistance to unfavorable conditions, and further, there 

 was difficulty in determining the percentage or total of dead grass 

 until 1919. By 1917, the second year of the drought, the soil was 

 becoming quite dry and the vigor of the grass had been considerably 

 reduced. In 1918 the soil was so dry that a more nearly average 

 rainfall occurring over a short period during the middle of the grow- 

 ing season did not materially improve growing conditions, and the 

 weakened vegetation continued to die. In 1919 soil moisture was 

 •materially increased, but in the 1919 examinations considerable grass 

 was found to be dead which had been classed as living in previous 

 examinations. There was difficulty in determining the grass actually 

 dead in 1918 on account of the absence of green growth and per- 

 sistence of dry growth from previous years. In 1919, however, the 

 dead growth had largely disappeared and the records are considered 

 a reliable index of living vegetation. 



The vegetation appeared to have reached its low point prior to 

 the 1919 examination. Comparison of the conditions in 1919 with 

 those of 1916, therefore, give the extent of range deterioration as a 

 result of the drought on grama-grass areas not grazed. This depre- 



