Results 



Germination. — Germination started about 24 May and was completed 

 by 21 September — a 4-month span. Some variation in starting dates existed 

 between plots; germination began 1 to 2 weeks earlier on the three sun- 

 niest plots than it did on the two shadiest ones. The peak of germination 

 came about 21 June (fig. 1) by which date about 50 percent of germina- 

 tion had taken place. Sixty percent of the seedlings had appeared by 1 July 

 and 85 percent by 1 August. In all, 35 yellow-poplar seeds germinated 

 per milacre the first season. This represents a rate of 35,000 per acre. 

 More seedlings appeared on the shady plots than on the sunny plots. A 

 few seedlings came up the second year, but none of them survived. We 

 observed no germination the third year. 



Survival. — In all, 40 percent of the seedlings that germinated the first 

 year survived to the end of the third growing season. A higher proportion 

 — 49 percent — survived on the three sunnier plots. On the shady plots, 

 only 33 percent survived. Mortality varied by seasons on all plots (fig. 2). 

 It was heaviest during the growing seasons; 34 percent the third summer 



100 1 1 



90 — 



80 — 



>- 



^ 70 — 



2 



| 60 



I 50 

 O 40 



a 30 

 s 



20 

 10 



1st 1st 2nd 2nd 3rd 



SUMMER WINTER SUMMER WINTER SUMMER 



Figure 2.— Seedling mor- 

 tality, by seasons. 



3 



