RANGE AND CATTLE MANAGEMENT DURING DROUGHT. Zo 
stand in the tobosa type is not decreased nearly so much in time of 
continued drought as in the grama-grass type. Furthermore; im- 
provement of the tobosa type is likely to occur immediately with the 
first wet year, while in the case of the grama-grass type several years 
will probably be required for this recovery. The great reduction in 
volume of forage produced in the tobosa-grass type in a dry year 
appears to be due to a greater moisture requirement for growth than 
in the case of the grama type species. ‘The lesser reduction in den- 
sity of the stand in the tobosa type in time of prolonged drought is 
evidently due to the ability of these species to le dormant longer 
without moisture before dying than is grama-grass, and to a finer- 
textured and more compact soil which has a greater air-dry moisture 
content than the looser sandy soils of the grama-grass type. Al- 
though tobosa-grass probably has a greater drought resistance, the 
volume of forage produced is affected more directly by the amount 
of moisture that falls. 
Studies of tobosa-grass areas fully grazed during summer showed 
approximately the same depreciation on these as on areas not grazed, 
which indicates that this type of range can be grazed fully during 
the growing season without injury in time of drought as well as in 
good years. The main difficulty with this type in time of drought 
is the big decrease in foliage production rather than killing out of 
the range, as shown in figure 6. 
VARIATION DUE TO GRAZING. 
The preceding discussion is intended to bring out the amount and 
variation in forage production on certain areas of the Jornada Range 
Reserve protected against grazing. ‘This measure of natural pro- 
duction indicates the maximum forage which will probably be avail- 
able for use over a period of years under natural conditions, and is 
a standard with which to compare production on similar ranges 
under different grazing use so as to adjust grazing in a way which 
will maintain the range and support the maximum stock over a period 
of years, including drought. A comparison of this nature has been 
made for the period 1915 to 1919, inclusive. The conditions studied 
include ranges where grazing has been excessive yearlong for a period 
of years, where grazing has not been too heavy for the year as a 
whole but only during the main growing season, and where grazing 
has been heavy for the year as a whole but much lighter than average 
during the main growing season. A description of the areas and 
how they were grazed, with the results and conclusions, is here pre- 
sented. 
