Riparian (Riverbottom) Forests
Riverbottom forests grow along the edges of rivers and streams. They depend on the spring floods to deposit silt and replenish the soil with nutrients. In return, their roots stabilize stream and riverbanks, helping to reduce erosion. Riverbottom forests are very diverse habitats with a large number of plant species. This makes them attractive to many different wildlife species as they provide a variety of food and shelter, and are close to water. Habitats located along waterways are also called riparian habitats: riverbottom forest is one type of riparian habitat.
Riverbottom forests can generally be divided into three sections: the channel shelf or riverbank, the floodplain, and the terrace.
The riverbank is the gently sloping area right next to the edge of a river, stream or creek. This area of the riverbottom forest is dominated by trees such as willow and cottonwood. Few shrub species dominate in the riverbank area because of yearly flooding and damage from spring ice breakup. Instead, this part of the forest has more grasses and annual wildflowers.
Above the riverbank is the relatively flat floodplain. This part of the forest is usually dominated by trees such as green ash, basswood, American elm, and Manitoba maple. The greatest variety of species is usually found on the floodplain. Here the plant community is dominated by flood-tolerant perennial species. Common shrub species include: American hazelnut, beaked hazelnut, downy arrowwood, and chokecherry. Many flowers and grasses, as well as woody and non-woody vines also exist in the floodplain.
The terrace lies above the floodplain, on the highest elevation within the riverbottom forest, farthest from the river. As this area is not flooded as often, this part of the forest is dominated by plants which prefer a drier habitat such as bur oak. Many of the plants found in the floodplain may also grow on the terrace.
Although these three sections of riverbottom forest have distinct characteristics, it is usually difficult to tell where the boundaries are between them. Dutch Elm Disease has killed many of the American elm trees causing a shift in the dominant tree species from elm to green ash.
Reference: City of Winnipeg’s Habitat Assessment and Grading
Riparian Forest in St. Norbert
The most prominent physical characteristics of the St. Norbert area are the corridors of riparian vegetation that line its rivers, the La Salle and the Red. The riverbank environment provides not only space for plants and wildlife, but also recreation opportunites in the form of trails and walks.
St. Norbert is an enclave that harbours not only people but also a wide variety of flora and fauna, including wood duck, deer, grey herons and foxes, alongside grazing animas in fields of flax. In the heart of St. Norbert, the La Salle river corridor is home to beaver, muskrat, and several varieties of fish, reptiles, and amphibians. The diverse landscapes found in the area provide a suitable environment for a wide variety of plants, including some species that are unique to the area. By far the most diverse ecological area in St. Norbert, and indeed the prairie habitat, is the riverbottom forest.
The riverbottom forest (RBF) is home to the majority of the plant and animals species found in the area (Waters and Shay, 1995). It is beleived to have one of the highest species diversity levels of any riaprian landscape containing large numbers of plant and animal species. Dependant on silts deposited in spring flooding to replensih the soil and nutrients, the vegetation found in the forest stabilizes the river banks and decreases eriosion. (pages 92-96)
Reference: James, Andrew M. “A Holistic Approach to Dike Design: St. Norbert,
Manitoba, A Case Study and Application.” 2000. University of Manitoba
Library, Publisher.
Lemay Forest Statistics
- Approximately 18,900 trees, less the 2024 and 2025 tree removals.
- 80 species of plants (72% native).
- Two types of forest: floodplain forest and oak forest. Species include large green ash, bur oak, American elm, Manitoba maple, and American basswood.
- The shrub layers include choke cherry, saskatoon, and other introduced species.
- Environmentally sensitive grade A and B forests.
- The flood plain forest represents healthy old growth forest dominated by native species.
- The oldest trees are green ash and in one of the survey samples (in 2020), one of the trees is determined to be approximately 237 years old.
- Both forest types support provincial and federal species of concern including the Canada warbler, eastern-wood pewee, little brown bats and the federally protected barred owl, which all rely on healthy mature forest stands to survive.
- The Lemay Forest mature trees capable of providing this kind of habitat feature are difficult to replace, taking decades to reach the required size and softness.
- The pileated woodpecker nesting cavities in the Lemay Forest are federally protected. Destroying a nest cavity contravenes the Federal Migratory Bird Reg 2022.
- Local birders have recorded 124 species since 2019 including the first recorded red-bellied woodpecker nesting site in MB (April 2017). A species once rare for Manitoba.
- The ecological services are extensive such as reduction in ambient air temperature, soil stabilization, carbon sequestration, storm water retention and rich wildlife habitat.
Forest Grading
Lemay Forest is an A-B grade forest
When habitat is assessed it is assigned a grade from A-D. “A” is a very good grade while “D” is not good (just like school). The definitions for these grades follow.
“A” Quality Habitat (Maximum sensitivity to disturbance): Virtually undisturbed by man or recovered to an extent where community structure and composition is intact and reflects historical natural vegetation and wildlife habitat. Other factors include soil disturbance, a high degree of native vegetation present and conversely, a lack of weedy or non-native plant species.
“B” Quality Habitat (High sensitivity to disturbance): Light to moderate disturbance, for example, encroachment of non-native species, may have a minimal amount of weeds but maintains a more natural condition where native species are still the major vegetation community.
“C” Quality Habitat (Low sensitivity to disturbance): Moderate disturbance, a significant number of weed species which have replaced native species, few native species present. For example, an old agricultural clearing that has not been used in recent times and native plant species are slowly returning, or an area that is occasionally mowed.
“D” Quality Habitat (Minimum sensitivity to disturbance): Heavily disturbed site, the vegetation is dominated by weed species or absent all together. None or very few native species present.
Reference: City of Winnipeg’s Habitat Assessment and Grading
Forest Statistics
Tree Loss by Ward and Neighbourhood
Click here to view how the public tree canopy in St. Norbert and Seine River changed from 2015-2021. (Data courtest of Trees Please Winnipeg)
Urban Forest Advocates
The following groups are doing amazing work to protect urban forests:
Trees Please Winnipeg
Who they are:
Trees Please Winnipeg Coalition represents citizens from Winnipeg neighbourhoods, residents’ associations and various organizations working together to call attention to our urban forest crisis and the need for sustainable investment strategies for urban forests.
Save Our Seine (SOS) River Environment Inc.
Who they are:
Save our Seine River Environment Inc. is a non-profit organization in Winnipeg whose mandate is to preserve, protect, enhance, restore and repair the Seine River greenway, to raise public education & awareness of and improve public access to the Seine River greenway, and to work in partnership with governmental, business and other non-profit organizations for stewardship planning of the Seine River greenway.
OURS Winnipeg (Outdoor Urban Recreational Spaces)
Who they are:
OURS-Winnipeg (Outdoor Urban Recreational Spaces – Winnipeg) is a city-wide, community-based, green space advocate organization with a focus on urban greenspaces, river and nature corridors and the urban forest. Parks, green spaces and natural are essential to making Winnipeg an attractive place to live, work and visit. With good planning and care they will be here for generations to come.
Trees Winnipeg
Who they are:
Trees Winnipeg is a non-profit charity dedicated to promoting the benefits of and concerns about trees in Winnipeg’s urban areas, focusing on tree diversity and care.
