INVESTIGATIONS AT ARDMORE, S. DAK. 39 



Laurel willow and boxelder in the 4 by 4 foot planting suffered only 

 partial winter killing until about 1929. From then on many trees 

 died each year, and in the winter following the dry year 1931 these 

 species were entirely eliminated. The American elm and ash sur- 

 vived fairly well, though they made little growth owing to their 

 crowded and weedy condition. Ash proved to be more hardy than 

 elm. In the spring of 1932 practically all the ash and about 60 

 percent of the elms in the original planting were still alive. 



In the section spaced 4 by 8 feet cultivation was carried on for a 

 longer period, and the trees grew more rapidly. The poplars and 

 willows, however, commenced to die following the winter of 1921, 

 and within the next few years were entirely eliminated. The box- 

 elders survived fairly well until 1929, when they had exhausted 

 the moisture in the wider area provided by the 8-foot planting. 

 During the winter of 1929 portions of many of them died, but very 

 few trees were entirely killed. During the winters of 1930 and 1931, 

 practically all the boxelders were killed outright, and by the spring 

 of 1932 the only trees left in this planting were the ash and the 

 American elm. These two species were injured but not killed dur- 

 ing the winter of 1931, and with favorable weather in the spring 

 of 1932 seemed to be again in fair growing condition. The elms 

 and ash in this planting averaged somewhat greater height and 

 diameter growth than those in the planting spaced 4 by 4 feet. The 

 elm and ash in both tests were injured by borers in 1932. 



The single row of Siberian pea-tree survived during the entire 

 period and in 1932 was one of the finest examples of a snow trap to 

 be found. The trees make a practically solid row approximately 10 

 feet in height, and each winter collect a large drift of snow that 

 not only holds much snow away from the buildings, but gives this 

 row of trees and trees situated to the east of them a surplus supply 

 of moisture. The species is perfectly hardy. 



Differences in spacing distance had little effect on survival in this 

 test. Qualities inherent in the species, rather than the closeness of 

 planting, determined their ability to survive adverse conditions. 

 Either rate of planting was thick enough to exhaust the available 

 soil water. 



Plantings of conifers were made from year to year in a strip of 

 land east of the row of Siberian pea-tree. Conifers are much more 

 difficult to transplant than deciduous trees, and only a small per- 

 centage of survival was obtained each year, but the trees seemed to 

 be hardy after becoming established. Continued plantings in spaces 

 where trees failed to survive were carried on until 1922. By that 

 time there was a fair stand of conifers and the roots of the trees 

 had become so well established that newly planted trees had little 

 chance of surviving. For the first few years the growth of these 

 conifers was slow, but during the' later years they grew rapidly and 

 in 1932 were the most showy part of the shelterbelt. 



The species of conifers used in the test were jack pine (Pinus 

 banksiana Lamb.), Scotch pine {P. sylvestris L.), and ponderosa, 

 or western yellow pine (P. ponderosa Dough). Until the winter of 

 1930, the conifers, owing to a thinner stand and to water provided 

 by trapped snow, did not experience a distinct water shortage. In 

 the summer of 1931, the jack pine showed some evidence of drought 



