DAMAGE TO RANGE GRASSES BY THE ZlJNI PRAIRIE DOG 9 



quadrats through the season did not yield reliable results, though 

 check quadrats show that clipping reduces the forage and starves 

 out the plants far more than does grazing by cattle. Trustworthy 

 methods are now being worked out, however, which, to date, indicate 

 that growth inhibition effects have been exaggerated. Nevertheless, 

 allowing the 35 pounds of dry forage per day per cow, and estimat- 

 ing that plants weakened by average rodent grazing produce only a 

 50 per cent crop, the forage saved by extermination of rodents should 

 suffice to support 37 head of cattle additional per section if forage 

 of this type formed a continuous ground cover and if it were possible 

 to utilize the forage when in a condition such as at the time of 

 clipping. Of course, no extensive areas of western range afford such 

 forage, but the figures are indicative of the quantitative reduction 

 due to these rodents that may be expected in the best forage types, 

 which are the ones most affected. A corresponding reduction may 

 be expected in more typical forage. 



THE WILLIAMS EXPERIMENT. 



THE AREA. 



The experimental tracts at Williams, Ariz., which were installed in 

 the spring of 1918 shortly after the Coconino field test was inaugu- 

 rated, are situated near the Sweetwood Ranch, 3^ miles north of the 

 town, near the point at which the Red Lake Colony road crosses the 

 Grand Canyon Railroad. They are in typical blue grama (Boute- 

 loua gracilis) forage areas on a tract of land which slopes gradually 

 to the west. This forage type is one of the most widely distributed in 

 the country, being found in abundance from north of the Canadian 

 boundary south to the tableland of Mexico and from east of the one 

 hundredth meridian westward to the Rocky Mountains and beyond, 

 particularly across New Mexico and Arizona. Hence the results of 

 this experiment should be especially suggestive and of broad appli- 

 cability. 



A short distance from the experimental tracts is the lower edge 

 of the juniper-pinyon formation, so that they are not far from the 

 upper border of the grassland proper. Although this border is 

 more favorable than the lower areas for grass maintenance, overgraz- 

 ing has progressed so far that the grasses are more than half replaced 

 already by various shrubs, as snakeweed {Gutierrezia) and rabbit 

 brush {Chrysothamnm) . The soil is composed of a fine silt pro- 

 duced largely from the weathering and decomposition of basalt; 

 it is a deep reddish brown and very stony. The effects of washing 

 are quite noticeable, the grass tufts often having half an inch or more 

 of their roots exposed. This washing renders the grasses unusually 

 susceptible to damage by grazing. 



The Williams plots are smaller than those at Seligman and Coco- 

 nino, yet large enough for the purposes of the experiment. The 

 fenced part is 148 feet square and is divided by another fence, so 

 that two plots each 148 by 74 feet have been inclosed. The north plot 

 (planned for a prairie-dog inclosure) was first fenced with galvan- 

 ized net wire, 1 inch mesh, 3 feet high, buried about 4 inches under- 

 ground and topped with a 6-inch strip of galvanized iron, strung 



