NATURAL RESEEDING. 11 



NATURAL RESEEDING. 



Nature is normally profligate in her seed supply. It seems at 

 times, especially with desert plants, that germination will insure seed 

 production; in other words, many plants which have sufficient 

 moisture for germination seldom fail to produce some seed. Indeed, 

 in an average season the annual plants of the desert produce enough 

 seed to restock the same land and insure as large a subsequent crop 

 as the sterile soils can maintain. A small percentage of the more 

 common plants grow each year and in turn produce seed. As an 

 example we might cite Bouteloua aristidoides. A season is seldom 

 so dry that some of this grass will not grow and produce seed. The 

 plants may be a foot high and yield very little seed, or the spikes in a 

 favorable year may equal the entire length of the plant in an unfavor- 

 able one. 



It is different, however, with the perennial grasses. A season 

 which produces an abundance of seed may be followed by one 

 unsuited to the growth of seedlings, and consequently the crop of 

 seed, although it falls to the ground, may be largely lost. Since 

 the Department's operations in the Santa Rita Mountains were 

 begun there have been but two years favorable for reproduction. 

 The season of 1907, although not so prolific as the subsequent one, 

 produced an abundance of seed of Bouteloua rothrockii and Bouteloua 

 bromoides, two of the most important grasses in this region. This 

 was followed by a very favorable season in 1908. There was con- 

 sequently an exceptionally good growth of seedlings that season. It 

 is quite possible that the seedlings of these two grasses over the 

 entire areas in which they are peculiarly characteristic would average 

 from four to six to the square foot. These seedling plants were all 

 well established and in thrifty, vigorous growing condition on October 

 1, 1908. 



The condition of these seedlings the next season was not only of 

 scientific interest but of exceeding economic importance. If they 

 all grew to maturity and produced plants the next year as vigorous 

 and large as those that grew on the same area the yield ought to be 

 increased 50 per cent, other conditions being equal. This condition, 

 of course, was. beyond the range of probability, because such a yield 

 would be beyond the capacity of these desert lands to produce. As 

 a matter of fact it is doubtful whether the yield of perennials in the 

 upper portion of the field was much greater in 1909 than in 1908, in 

 spite of the large number of seedlings of 1908. Natural selective 

 influences work to thin this stand to the typical thin, scattering, 

 bunchy condition best adapted to maximum production upon arid 

 lands, a principle becoming better and better recognized in the 

 growing of farm crops with small amounts of rainfall. Thin seeding 

 is now recognized to be best under such conditions. The difference 



177 



