FOREST PLANTING IN EASTERN NEBRASKA. 



117 



average velocity is high. The southerly winds of summer frequently 

 come as hot waves, which, by causing excessive transpiration, injure 

 tree growth. Moreover, the strong northwest winds of winter are more 

 injurious to trees than is commonly supposed. Transpiration goes on 

 at all seasons, and since the northerly winds blow when the ground is 

 frozen, the trees are unable to secure the soil water and suffer or even 

 die from drought as certainly as in summer. 



Occasionally prolonged hot or cold periods occur, which are a very 

 severe test to trees, and species which have been introduced from other 

 localities sometimes die. In the unusually cold winter of 1898-99, for 

 example, a large percentage of the Osage Orange hedges were killed, 

 not only in Nebraska, but throughout the central Mississippi valley. 



PRECIPITATION. 



The following table shows for eastern Nebraska the total annual pre- 

 cipitation, the total for the growing season, and the ratio of the seasonal 

 to the annual rainfall: 



STATION 



Omaha 



Desoto 



Genoa 



North Platte 



Yankton, S. Dak. 



Elevation 



Feet 



l,OiO 

 1,100 

 1.585 

 2,809 

 1,206 



Period of 

 Observa- 

 tion 



Years 



27 

 24 

 21 



29 

 20 



Average 

 Annual 



Precipi- 

 tation 



Inches 



31.4 

 29.6 

 26.8 

 18.1 

 25.8 



Prenir itation During 

 Growing Season 



April to 

 August, 

 Inclusive 



Inches 



20.8 

 19.3 

 17.9 

 13.4 

 17.9 



Ratio to 

 Annual 



Precipi- 

 tation 



Per Cent 



66 

 65 

 67 

 74 

 69 



Although the average annual precipitation for Nebraska for the period 

 from 1876 to 1904 was but 23.27 inches, the above table shows that more 

 than two-thirds of the total falls during the growing season, thus giving 

 the state a very favorable showing against states farther east, where the 

 total annual rainfall is considerably greater but more equally distributed 

 through the different seasons. This fact explains, in large measure, the 

 success which has attended tree planting. 



On the other hand, the wide deviation in the amount of precipitation 

 from year to year is a factor which tends to restrict the number of 

 species that can safely be recommended. For example, the precipitation 

 in 1881 was 30.91 inches. In 1893 the precipitation was only 16.18 inches, 

 and the years 1894 and 1895 also experienced a shortage in rainfall, 

 making three consecutive dry years. This period was very severe on 

 planted timber, and some species proved unadapted to certain localities 

 or situations where they hitherto had been successful. Much of the 

 Cottonwood and willow, for example, which had done well for several 

 years on the upland, was either badly injured or killed. Thus it is clear 

 that in selecting a species for a given locality, not only the average but 

 the extremes of weather conditions must be taken into account. 



