6oo Forestry Quarterly 



The probable competition for water between the roots of trees 

 and the roots of crops was only approximated by determining" 

 the average root extent of the various species used for wind- 

 breaks. Contrary to the general opinion, it was found that the 

 Cottonwood has the least extensive roots of any of the broadleaf 

 species and hence has the least power to damage crops in dry 

 seasons. In regard to the efficiency of windbreaks in checking 

 evaporation, the author states that the area protected is pro- 

 portional to the height and density of the windbreak and the 

 distance to which protection is felt increases with the velocity of 

 the wind. The protection is appreciable to a distance equal to 

 five times the height in the windward direction and to fifteen or 

 twenty times the height to the leeward. The windbreak in 

 extreme cases, may save 70% of the moisture ordinarily lost by 

 evaporation. Portions of certain wheat fields in the protection of 

 windbreaks showed a gain in yield of 60% over the general aver- 

 age of the entire field. 



In respect to temperature, the author makes this statement: 

 "Other conditions being equal, both the highest maximum temper- 

 ture at midday and the lowest minimum temperature at night are 

 found at the same point relative to the windbreak and exceed 

 about equally (in this case about 4^° F.) the maximum and 

 minimum temperatures in the open." (p. 58.) A windbreak, ac- 

 cording to the author, produces a hot house condition on a large 

 scale, and once it reduces evaporation at the same time, its total in- 

 fluence is clearly favorable to vegetation. A cornfield in Nebraska 

 on the north side of a dense windbreak 38 feet high, made a yield 

 in the 18 rows nearest the windbreak at the rate of 18 bushels per 

 acre greater than the general average of the unprotected portions. 

 Similar results are shown in the case of orchards. In a season 

 which had been preceded by three frosts in May, twenty-eight out 

 of thirty unprotected orchards gave a yield ranging from less than 

 one to three pecks per tree. Partially protected orchards gave an 

 average yield per tree of one-half bushel to three bushels, while 

 well protected orchards in the same locality gave an average yield 

 of 4.9 bushels. The value of the windbreak in this case is given 

 as four-fifths the value of the orchard per acre over a belt ten 

 times as wide as the height of the windbreak. 



Practically all of the author's investigations point to the con- 

 clusion that windbreaks pay for themselves, without considering 



