Changes in Vegetation Structure in Seeded Nesting Cover 
in the Prairie Pothole Region 
by 
Kenneth F, Higgins 
U.S. Fish and Wildlife Service 
Northern Prairie Wildlife Research Center 
Woodworth Field Station 
Woodworth, North Dakota 58496 
and 
William T. Barker 
North Dakota State University 
Fargo, North Dakota 58102 
Abstract 
A sample of 365 stands of seeded nesting cover (mixtures of cool-season grasses and legumes) was 
studied in the glaciated prairie pothole region during 1977-79. Measurements of species composition, 
canopy cover, plant height, and visual obstruction values differed with stand age but only in a general 
way when results from over the entire region were pooled. Maximum values for plant height and visual 
obstruction occurred once per stand during the first 10 growing seasons. Although the year of maximum 
growth was variable and unpredictable, stands showed trends of degeneration in height and visual 
obstruction after the year of maximum growth, 
Seeded nesting cover grew similarly throughout the region when on soils of capability class IV or 
better and within a precipitation range of 30 to 6] cm. Precipitation was the factor that most affected 
stand growth, especially the amount received in the year before spring measurements. Height and visual 
obstruction values within a stand were also directly affected by some individual species and by the per- 
centage of grass within a stand. In 2 of the 3 study years, the height and visual obstruction values of 
residual cover were extremely reduced by ice pack, heavy snow pack, or a combination of snow pack 
and harvest by rodents. Such events, if frequent, largely negate the possibility of using minimum visual 
obstruction or plant height measurements for assessing quality of vegetation for wildlife cover and man- 
agement purposes. 
Species composition, number of species, and canopy cover varied most during the first three growing 
seasons and least during the next six, Succession toward dominance by native grasses and forbs and 
woody species was retarded by the predominance of the species of seeded nesting cover, at least during 
the first 10 growing seasons. 
All stands had at least one species present that was either a noxious weed, a problem cropland weed, 
or a nuisance weed. Weeds were usually local in distribution. Five weed species needing special man- 
agement attention on public lands are leafy spurge (Euphorbia podperae), wormwood (Artemisia 
absinthium), Canada thistle (Cirsium arvense), musk thistle (Carduus nutans), and plumeless thistle 
(Carduus acanthoides), Sites disturbed by mammal diggings or those skipped during planting operations 
became revegetated mostly with species other than those of seeded nesting cover. 
Successfully established stands on good sites provided substantial food and cover for wildlife for at 
least 6 years and retained stand composition for at least 10 years. Further study will be necessary to 
determine longevity of these stands. Except for mandatory noxious weed control, no management treat- 
ments of seeded nesting cover were necessary before the seventh growing season, at which time some 
stands needed renovation. The primary goals for management of seeded nesting cover should be stand 
quality and longevity. Guidelines to these goals are suggested. 
