
Fig. 5. Example of harvest effects on plants by meadow voles dur- 
ing winter 1978-79. 
standardized precipitation, did have significant effects 
(Table 2). 
The visual obstruction increased significantly among 
stands as the percent grass increased in relation to plant 
species composition (Table 2). Visual obstruction was also 
significantly influenced by standardized precipitation. 
Differences among visual obstruction measurements 
within stands were significant from year to year. These 
differences also corresponded with changes in stand- 
ardized precipitation but not with changes of percent grass 
(Table 2). 
Attributes of Live Vegetation 
Vegetative Characteristics of All Species Within Stands 
Ten species of plants were sown in various SNC fields 
during stand establishment. Ninety-nine plant species 
were found in SNC stands in 1977, 135 in 1978, 130 in 
1979, and 159 species in all years combined (Tables 3 and 
A-3). Of the 159 plant species, 60% were of native origin, 
60% were of perennial growth habit, and 79% were of 
forb life form (Table 4). 
Vegetative Characteristics of Species Within Quadrats 
Of the 159 plant species found in 321 SNC stands, 115 
occurred in at least 1 quadrat. Frequency, canopy cover, 
and composition values for these 115 species were given by 
Higgins (1981), Alfalfa, intermediate wheatgrass, tall 
wheatgrass, and quackgrass were consistently dominant 
among the 115 species in all years. 
Aggregated values for life-forms.—A comparison of 
species frequency, canopy cover, and composition was 
made for the three major life-form groups (Table 5). Com- 
pared with grasses and forbs, shrubs and tree saplings 
) id h = = - 
- es con 
; + oS 33 
J Ss ia 
Fig. 6. Tall wheatgrass and switchgrass (left) structurally with- 
stood the effects of a winter snowpack better than intermediate 
wheatgrass and quackgrass (right) as shown in spring 1978. 
were of minor importance in all stands. Forbs appeared in 
slightly greater relative frequency than grasses (53.2 vs. 
44.6%) but grasses provided slightly more relative canopy 
cover than forbs (52.0 vs. 47.4%). Grasses made up a ma- 
jority (80.8 %) of the total species composition. 
Table 2. Analysis of covariance for repeated measures 
analysis of visual obstruction measurements. 


Mean 
Source of variation df square® F& P 
Among plots 
Soil capability class 2 0,080 1.35 0.27 
Average standardized 
precipitation 1 1.457 24.47 <0.0001 
Average percent grass 1 0.640 10.76 0,0019 
Age 1 0.009 0.16 0.69 
Error 52 0.060 
Within plots 
Year 2 1.431 43.45 <0.0001 
Year x soil capability class 4 0.013 0.38 0,82 
Standardized precipitation 1 0,658 19.97 <0.0001 
Percent grass 1 0.005 0.15 0.70 
Error 108 0.033 


’Mean square and F are for H,: Effect = 0 given all other effects 
are in the model, 
Table 3. Floristic richness in stands of seeded nesting cover 
in the glaciated prairie pothole region, 1977-79. 

Total found 


Total Plant 
seeded category 1977. 1978 1979 Years combined 
2 Families 24 32 32 36 
5 Genera 65 93 87 105 
10 = Species _99 135 130 159 

