32 BULLETIN 1170, U. S. DEPARTMENT OF AGRICULTURE. 



season contain a high percentage of water and (2) because of the 

 greater growth of the plants during the entire season. 



The clipped quadrats have clearly answered the questions in regard 

 to the period of most active growth and the effects of frequency of 

 removal of the vegetation upon the various species. In addition, 

 they furnish a basis from which to estimate the total quantity of 

 vegetation annually produced. 



PHOTOGRAPHS. 



Photographs have been taken regularly in connection with the graz- 

 ing experiment each year, beginning with 1915. The same views have 

 been taken each year, so that certain photographs are directly compar- 

 able for a series of years. One set that has been taken in each pas- 

 ture shows a general view of the quadrat area (an area 4 meters 

 square in which the mapped quadrat is located) and a closer view of 

 the quadrat that is mapped in detail. Starting in 1919, two sets of 

 photographs giving a general view of the quadrat area have been 

 taken each season. One set is taken about midsummer or early in 

 July, the other at or near the close of the grazing season. The early 

 set was added after the Artemisia frigida began to be conspicuous in 

 the 30-acre pasture. This set of photographs shows the general con- 

 dition of all pastures at the time when the vegetation is producing its 

 maximum growth. 



Photographs are of unusual value in connection with studies of 

 this nature, as they bring out points and illustrate features that do 

 not lend themselves readily to description or measurement. Photo- 

 graphs also produce a permanent record that can not be obtained in 

 any other manner or as quickly. 



GENERAL FIELD NOTES. 



General field notes have been made regarding the native vegetation, 

 beginning with the year 1915. Phenological dates are recorded for 

 27 different species of plants that are common on the prairie. These 

 notes show that the prairie during the period from 1915 to 1921, in- 

 clusive, has turned green as early as April 15 and as late as May 20 ; 

 it has started to show signs of " drying up " as early as June 15 and 

 as late as August 15. 



The points of main interest and importance in relation to the pro- 

 duction of forage for grazing are (1) the time of starting spring 

 growth and (2) the period of maximum growth. The problems of 

 pasture management depend largely upon the time (1) of flower- 

 stalk production, (2) fruiting, and (3) seed maturity. 



The data in Table 10 are presented to show the periods of growth 

 of the more important plant species. The dates in each case are the 

 earliest and the latest that have been recorded. 



It will be noted that there is considerable variation in the time the 

 plants start their annual spring growth. This is largely determined 

 by the season. 



The field notes furnish a means of ready reference in regard to the 

 periods of growth and development of the different plant species that 

 can not be obtained as clearly in any other way. 



