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CIRCULAR 912, TJ. S. DEPARTMENT OF AGRICULTURE 



Figure 7. — These trees of Pinus ponderosa are 33 years old. Although the 

 species frequently is difficult to establish, it is excellent for windbreaks either 

 under irrigation or in dry-land conditions. 



trees lost most of their needles during the severe drought years of 

 1934 and 1936. The species makes an excellent dry-land or irrigated 

 windbreak tree (fig. 7), but is frequently difficult to establish. 



Pinus resinosa. — This species was tested throughout the area. The 

 trees killed back severely and losses were heavy during the severe 

 drought years of 1934 and 1936. The species is not recommended for 

 dry-land planting. 



Pinus sylvestris (1174). — This species was tested throughout the 

 region. Heavy killing back and losses in stand occurred during the 

 severe drought years of 1934 and 1936. P. I. 65796, tested at the 

 Mandan station only, appears to be much more hardy. The species 

 can be recommended only for planting on the more favorable moisture 

 sites and under irrigation. 



Pinus tabulaejormis. — Testing of this species was confined to the 

 Mandan station. Of six plantings made during the drought years, 

 only one tree became established. This tree made fair progress. The 

 species may have some promise for planting in the area. 



Populus acuminata. — This species is native to the western part of 

 the area. The trees suffered variable winter injury each year. Sixty 

 percent of the trees died by the sixth season and all were dead at the 

 end of the eleventh season. P. acuminata is not suitable for dry-land 

 planting, but is recommended for planting under irrigation. 



Populus alba var. nivea. — This species has been planted for orna- 

 mental and windbreak purposes on many dry-land and irrigated 

 farms throughout the area. It is not satisfactory under dry-land 



