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Table of Contents
Foreword
Preface
Glossary

Chapter 5: Vegetation

5.6: Riverine Gallery Forest in the Pembina Valley East of Snowflake

The misfit Pembina River 1 occupies the floor of a glacial spillway that carried water from glacial Lake Hind, to the west, into glacial Lake Agassiz. Here the spillway has an asymmetrical cross-profile because the channel slid off to the southwest cutting a steep bank 2 and leaving behind a gentle slope on the northeast 3. Several small lakes 4 exist on the south wall of the spillway in low-lying land between slumped blocks.

Almost all the southwest side is covered by riverine gallery forest 5, including in this area cottonwood (Populus deltoides), Manitoba maple (Acer negundo), green ash (Fraxinus pennsylvanica), willow (Salix spp), and basswood (Tilia americana). Elms (Ulmus americana) that used to exist here are dying because of Dutch elm disease. Similar forest exists on the northeast wall 6, but here on southwest-facing slopes the microclimate is drier leading to patches of grassland 7. Forest also exists along the course of the Pembina River 8.

As in previous figures the main criterion for identifying forest is its dark tone, but in this case the scale is large enough that, using a magnifying lens with the original photo, the rounded crowns of the deciduous trees can be identified; they produce a mottled texture 9.

The Pembina River with numerous cutoffs 10 meanders southeastward through the area. Some land has been cleared for agriculture along the valley floor 11 and on flatland south of the valley 12. Clusters of farm buildings 13 can be seen in both locations. Only one road 14 crosses the Pembina, but numerous forest trails 15 exist on both sides of this valley.

Figure 5.6: Riverine Gallery Forest in the Pembina Valley East of Snowflake

Figure 5.6: Riverine Gallery Forest in the Pembina Valley East of Snowflake

Figure 5.6

Vertical air photograph: A16181-184

Flight height: 10,150 feet a.s.l.; lens focal length: 152.4 mm

Date: July 20, 1958

Scale: 1:18,400 (approx.)

Location: Township 1; Range 9 WI

Map sheets: 1:250,000 62G Brandon

1:50,000 62G/2 Pilot Mound