18 BULLETIX 367, U. S. DEPAETMEXT OF AGKICULTUEE. 



Along the ai'royos several grasses have taken possession, and the 

 crop of feed they put on the margins of these dry watercourses is 

 probably sufficient to render this broken land as productive of feed 

 as the smoother areas (PL VI, fig. 1). 



There is no doubt that the prediction made by Griffiths, that the 

 mesquites and other shrubs would increase in size and number, is 

 slowly coming true within the protected area (PL VI, fig. 2, and PL 

 VIII, fig. 1) . The only retardation they have received has been from 

 the occasional fires, some of which have been severe enough to com- 

 pletely kill plants 10 to 12 feet high, though usually onlj^ the smaller 

 bushes are killed back to the ground. 



Along with the information relative to the general character of 

 the changes taking place on a protected area, some data have been 

 obtained as to the rate at which these changes take place. 



The spring annuals and the six-weeks grasses occupy the bare land 

 at once wherever there is sufficient rainfall. The recovery of the 

 short-lived perennials was cjuite well advanced on this reserve after 

 about three years' complete protection, and the area covered by them 

 has certainly doubled in size in seven years' time. It has taken at 

 least seven or eight years to bring about a condition favorable for 

 the increase of the black grama, and this increase will doubtless con- 

 tinue for another 10 years before reaching its maximum. Yet much 

 of the land, where this plant normally grows, would doubtless pro- 

 duce a crop of this grass where practically no forage grows now if 

 it were given a period of complete rest for a few j^ears and very 

 light stocking for a number of years more. On the areas that have 

 been carrying stock the recovery has been much less rapid, though 

 very noticeable improvement has occurred. 



CARRYING CAPACITY. 



The method of making quadrat measurements, established by 

 Griffiths,^ has been continued by the writer since he has been con- 

 nected with the work. The detailed reports of these records for the 

 years 1903 to 1908 and 1912 to 1914, inclusive, are on file in the 

 Office of Farm Management. 



There is good reason to think that the areas now occupied by the 

 crowfoot-grama and needle-grass associations, at least in that part 

 of the reserve wdiere these associations meet, has about reached its 

 normal productivity under complete protection. Some further re- 

 placement and substitution of species may take place, but no marked 

 change in the total productivity is to be looked for. As nearly as 

 the writer is able to judge, this condition has existed, on the area 

 mentioned, for the past three or four years. 



1 Reported in detail in Bureau of Plant Industry Bulletin 67, p. 25 et seq. 



