SHELTER-BELT DEMONSTRATIONS ON THE GREAT PLAINS. 25 



the results of this study is given in Table 10, which shows for each 

 species the average height attained in all plantings in each State 

 and the maximum height attained in aiiy planting in the State. 



The low average heights of willow and poplar as compared to the 

 maximum heights are due to the continual freezing back of these 

 species in most of the plantings. It will be noted that with the ex- 

 ception of green ash, all of the species made the best growth in 

 South Dakota. As the figures for green ash in that State are based 

 on three plantings only, they can not be considered adequate. Sub- 

 sequent plantings have shown the same relatively higher growth for 

 gi'een ash. The comparatively better conditions as to rainfall and 

 temperature which prevail in South Dakota will probably explain 

 this increased growth. The data given in Table 10 are shown dia- 

 gramatically in Figure 13. 



Fig. 14. — An unpruned sheltei' belt in the third summer of growth. Planting in Valley 



County, Mont. 



EXPERIMENTAL PLANTINGS. 



In addition to the shelter-belt demonstrations under actual farm 

 conditions, a number of special experimental plantings have been 

 made at the Northern Great Plains Pield Station. 



Species testing hlochs. — Since 1914 more than 80 different species 

 of trees have been planted as pure stands in blocks containing ap- 

 proximately 100 trees each. These plantings are intended to serve 

 primarily as hardiness tests. Some of the most important results 

 from this work have been embodied in the discussion under the head- 

 ing " Notes on tree species," page 6. 



Methods of care for shelter helts. — Ten blocks of identical shelter- 

 belt plantings similar to the regular demonstrations were set out in 



