The plant species found in the North Dakota lakes described by Metcalf 
(1931) and the Minnesota lakes studied by Moyle (195) were compared with the 
species found on the study area. The distribution of the species on the study 
area did not indicate that water chemistry was an important factor since there 
were cases where species at both ends of the scale of tolerance were found in 
the same area. Apparently the Minnedosa potholes were all within the range 
of tolerance of these species, 
Ice Action -= Although this might presumably have had some effect on 
emergent vegetation, there is no reason to suppose that it was important in 
relation to species distribution. Table 2 shows that the vegetation types were 
ali distributed in potholes of nearly the same size and depth and which would 
presumably be subject to similar conditions with regard to ice, 
Grazing -- Joseph A. Calen, who owns the land on the northern third of 
the study area, was kind enough to furnish information based on detailed records 
concerning the grazing use of the study area for the past 8 years (Plate VIII). 
Since an accurate forage inventory was impracticable, the grazing use has been 
rated subjectively on the basis of entire units without attempting to 
differentiate the degrees of use of the various parts of each unit. The 
distinction between "spring and fall" and "all season" grazing is apparently 
the mest important from the standpoint of the aquatic vegetation, The "all 
season grazing" was heaviest at the time these plants were making their most 
rapid growth and producing seed. 
A comparison of Plate VIII with Plate III showing the distribution of 
the pothole types indicates that grazing may have had an important influence 
on vegetation. The sedge-whitetop potholes were in units which, for the past 
8 years, have been lightly to moderately grazed only in the spring and fall. 
All of the Type Al potholes (those with the zones of emergents intermixed or 
denuded) were in units moderately to heavily or very heavily grazed throughout 
the growing season. Most of the potholes in which cattail and bulrush were 
predominant occurred in units which were grazed to a similar extent and on 
those which had been heavily grazed in the past and protected for the last few 
years 
The effect of grazing on the vegetation can be further demonstrated by 
cases where fence lines passed through potholes, Pothole No. 2 (Plate VI) 
has the hardstembulrush and cattail cover of a Type A3 pothole to the left of 
the fence where there had been very heavy all-season grazing in alternate 
years. The cover to the right of the fence which had not been grazed is nearly 
-_pure whitetop, or Type Al. 
A striking example is furnished by potholes Nos, 11 and 12 (Plate IX). 
Apparently these were once a single pothole that had been bisected by the 
road. No. 12 had been subjected to moderate to very heavy season-long 
grazing while No. 11 had been only lightly grazed in the spring and fall, 
No. 12 was choked with water milfoil and buttercup (Ranunculus spp.), softstem 
bulrush, water plantain, cattail, spikerush, and rush, with some sparse white- 
top in the background. No. 11 had a cover of sedge and whitetop except for 
the mown area which bore spikerush, The water surface was clear of weeds, 
Plate VII (the vegetation of pothole No. ) shows the sedge and whitetop 
cover on that portion of the pothole which was protected from grazing while 
the remainder supported Type Al vegetation. Similar conditions existed in 
potholes Nos. 3, 5, 6, 10, and 25. 
Two of the ways in which grazing by livestock might have influenced 
pothole vegetation are by affecting siltation and turbidity of the potholes, 
and by actual disturbance of the vegetation, 
