RANGE AND CATTLE MANAGEMENT DURING DROUGHT. ~ 33 
Plate III, illustrate the successive stages of the effects of over- 
grazing. 
FORAGE PRODUCTION CONCLUSIONS. 
Conclusions from the forage-production data obtained thus far 
may have to be changed when data from observations through an- 
other drought period are available. These tentative conclusions 
point the way, however, toward certain essentials in determining 
the grazing capacity of the range and are a basis for adjusting graz- 
ing management and use preparatory to the next drought. The 
main points indicated by the study so far are: 
(1) Grama-grass range similar to that on the Jornada Range Re- 
serve begins to die out the second year of drought, and when a 
drought lasts three years the stand of forage on ungrazed range may 
be reduced as much as 40 per cent. The volume of forage produced 
per unit of area is further reduced by decreased height growth and 
foliage production during dry years. The vigor of the grass is 
affected to such an extent that at least one good year following 
drought is necessary before the range will begin to improve in 
density. In the case of tobosa-grass range there is less dying out of 
the grass, amounting to only 30 per cent in the third year of drought, 
but the volume of forage produced per unit of area is affected more 
directly by the amount of moisture received. The actual reduction 
in the amount of forage produced at the worst of the drought, tak- 
ing into consideration both reduction in density and reduction in 
foliage production is about 50 per cent of the amount produced in 
good years on both grama-grass and tobosa-grass range. 
(2) The depreciation of grama-grass range is greater as over- 
grazing increases and especially under too. heavy grazing during the 
main growing months—July, August, and September. If grazing on 
it is reduced approximately one-half the year-long rate during July, 
August, and September, and if it 1s not too heavy the rest of the 
year, grazed range may be maintained in about the same condition as 
ungrazed and run-down range may improve to approximately the 
same condition. Apparently tobosa-grass range may be grazed heav- 
ily during the growing season, whether or not there is drought, with- 
out affecting it materially. 
(3) Overgrazing a range results in a decrease in the best forage 
species on the range and their replacement by plant species of less 
forage value. 
(4) In time of drought so great a reduction as 50 per cent of the 
volume of forage produced in more nearly average years may be ex- 
pected and should be prepared for. Grazing should be reduced on 
grama-grass range during the main growing season, July, August, 
74514°—22—Bull. 1031——_3 
