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Using Aquatic Invertebrates to Delineate Seasonal and Temporary Wetlands in the Prairie Pothole Region of North America

Results


Seasonal Wetlands

Of the wetland delineations we made along 60 transects in seasonal wetlands (six transects in each of ten wetlands), 44 of the invertebrate delineations were within 2 m of the standard delineations (Figure 3). For the five seasonal wetlands in grassland, 12 of 30 of the invertebrate delineations were at the same location as the standard delineations, and 18 were closer to the wetland's center; not a single invertebrate delineation in grassland was on the upland side of the standard delineation (Figure 4). In the five cropland wetlands, six invertebrate delineations were at the same location as the standard delineations, while eight were on the wetland side and 16 were on the upland side (Figures 3 and 5). For both groups (seasonal wetlands in cropland and seasonal wetlands in grassland), the relative elevations of the invertebrate delineations were more consistent (i.e., had lower standard deviations) within wetlands than the elevations of the standard delineations (Figure 6). Even for individual wetlands, this held true with only one exception, a seasonal wetland in cropland.

Figure 3: Four bar graphs showing distance between invertebrate and standard delineations for Seasonal and Temporary Wetlands located in Cropland or Grassland.
Figure 3.  Distance (m) between invertebrate delineations and standard delineations along six transects in each of ten seasonal and seven temporary wetlands in cropland and grassland landscapes of the glaciated plains, North Dakota, USA.

Figure 4: Radial graph showing six relative elevations of invertebrate elevations from a center midpoint.
Figure 4.  Relative elevations (m above center elevation) of invertebrate delineations and standard delineations along six transects in seasonal wetland SG5 depicting how invertebrate delineations were typically at the same locations as the standard delineations or were closer to the center of the wetland in grassland wetlands.

Temporary Wetlands

Of the ten temporary wetlands we sampled, we were able to perform standard delineations in only seven, all five grassland wetlands and two cropland wetlands. We were unable to perform standard delineations in the three cropland wetlands due to severe disturbance of indicators by tillage. In two of these three wetlands, we were also unable to perform our invertebrate delineations due to an absence of invertebrate remains in our samples.

In the seven temporary wetlands in which we were able to perform both invertebrate and standard delineations, delineations followed the same general trends we observed for seasonal wetlands. Of the wetland delineations we made along the 42 transects (six transects in each of the seven temporary wetlands), 30 of the invertebrate delineations were within 1 m of the standard delineations and 37 were within 2 m (Figure 3). Just as for seasonal wetlands in grassland, all of the invertebrate delineations in the temporary wetlands in grassland were either at the same location as the standard delineations (6 of 30) or were closer to the wetland's center (the remaining 24). Once again, not a single invertebrate delineation was on the upland side of the standard delineation in grassland wetlands. In the two cropland wetlands for which we were able to perform the standard delineations, three of the invertebrate delineations were at the same location as the standard delineations, five were on the wetland side, and four were on the upland side (Figure 3). Without exception, the relative elevations from our invertebrate delineations of temporary wetlands in cropland and grassland had lower standard deviations within wetlands than the elevations from our standard delineations (Figure 6).

Figure 5: Radial graph showing six relative elevations of invertebrate elevations from a center midpoint.
Figure 5.  Relative elevations (m above center elevation) of invertebrate delineations and standard delineations along six transects in seasonal wetland SC2 depicting how invertebrate delineations were often farther away from the wetland center in cropland wetlands.

Figure 6: Bar graph showing mean standard deviation of elevations of invertebrate delineations for Invertebrates and Plants/Soils on Seasonal and Temporary wetlands located in Cropland and Grassland.
Figure 6.  Mean standard deviation of elevations of invertebrate delineations and standard delineations for seasonal wetlands in cropland (SC), seasonal wetlands in grassland (SG), temporary wetlands in cropland (TC), and temporary wetlands in grassland (TG) in the glaciated plains of North Dakota.


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