TREE SEEDLING AND SEED FALL STUDY IN POOL 8, UPPER MISSISSIPPI RIVER
SYSTEM, 1997-2000.

Heidi Langrehr.  
Wisconsin Department of Natural Resources, Onalaska, WI 54650.

One concern for the Upper Mississippi River System (UMRS) floodplain forests is inadequate
regeneration.  A study was initiated in 1997 to describe both seed fall and seedling germination
and survival.  Two sites were established in Pool 8, UMRS.  Site 1 (located in mid-pool) was
dominated by swamp white oak, silver maple, and river birch, and site 2 (located in upper pool)
by silver maple and cottonwood.  Fifteen plots were randomly selected within a 30 meter radius
at each site.  Each plot had a bucket for collecting seeds and a 1 meter square area within which
seedlings were tagged and counted.  Seedling survival and number of seeds collected were
recorded each month (April through November).  Seedling height was recorded when first tagged
and in October of each year.  The largest seed drop occurred in 1998 for both sites.  River birch
produced the largest number of seeds at site 1 while cottonwood seeds dominated site 2. Very
few acorns were collected.  Most germination of seeds occurred in 1999 with over 95% of those
being silver maple.  The largest drop of silver maple seeds occurred in 1998.  A total of 97
seedlings were tagged at site 1 while 45 were tagged at site 2.  Survival rate was higher for site 1
(59%) than site 2 (38%).  The number of days during the growing season (April 15 through
October 15) each plot was flooded was calculated for both sites.  The total number of days
flooded by plot for the four year period varied in site 1 from 13 to 385.  Site 2 was less varied
ranging from 13 to 43 days.  Although site 2 was less frequently flooded, site 1 had more
seedlings and a higher survival rate.

Keywords: floodplain forest, seeds, seedling, monitoring, Mississippi River