The study area has an annual rainfall of 55 to 60 inches and an annual 

 temperature of 48 to 50° F. Site quality is excellent: site index for yellow- 

 poplar is 90 to 100 feet. 



In the center of each of five of the openings, a 4-milacre plot was laid 

 out. Light measurements were made in each plot in the first and second 

 growing seasons. Light intensities were averages of readings taken through- 

 out the day. Readings in the three sunniest plots averaged 45 percent sun- 

 light; in the two most shaded plots, they averaged 25 percent. 



Seedling tallies and height measurements were made of yellow-poplar 

 stems at 2-week intervals from May to mid-October during the first grow- 

 ing season following logging. At each measurement new seedlings were 

 identified by a small wire stake stuck into the ground nearby; different 

 colored wires were used for each measurement period. During the second 

 and third growing seasons, only spring and fall tallies were taken. The 

 study was terminated in October 1968. 



Figure 1 .—Accumulated and periodic germination curves. 



100 1 1 1 1 1 i 1 1 1 x 1 



90 



DATES AT MIDPOINTS OF GERMINATION MEASURING PERIOD 



2 



