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Restoration Planting Design

A Snapshot of River Partners’ New Science Webpage

A restoration planting design in action on the Bear River. Photo by River Partners staff.

River Partners works with over 50 tree, shrub and herbaceous plants in their restoration designs. Each species offers unique resources for wildlife because of its structure, nutritional quality (leaves, flowers, stems, bark etc.) and invertebrate assemblage it attracts. Planting designs can incorporate a mix of species that will attract a high diversity of wildlife because of the multiple cover, nesting, and foraging habitats that are provided.

The structures of trees, shrubs and vines vary in obvious ways such as the height, width and diameters of the main stems. Among trees, shrubs or vines there are more subtle differences, such as the number of main stems and the angle of branching. Wildlife cue into these subtle differences and select optimal locations for nesting, foraging and cover habitat. You can visit River Partners’ science webpage to read more about the structure and wildlife value of each individual plant listed below.

In restoration design, different plant communities are formed by varying the densities and species used, and by changing the ratio of trees, shrubs, and herbaceous species. This gives River Partners the flexibility to create a range of structural features by incorporating multiple canopy layers. Tall trees form the highest canopy layer – the overstory. In riparian plant communities, this layer is formed by mature valley oaks, cottonwoods, sycamores, and black willows. The midstory In fact, following what botanical science tells us about root development, tree and shrub root growth would improve levee integrity, not compromise it. Roots are respiring organs. To grow and develop, they require oxygen, moisture, nutrients, and space. Nutrients and soil moisture are required for internal physiological processes and for physical growth. Space within the soil matrix (between soil particles) is essential for the root to grow. Where all four of these conditions—oxygen, moisture, nutrients, space—are met, roots proliferate. When any one of the four is not available, such as in the interior of levees, root growth stops.

In perennial woody plants, root growth develops over the years into a characteristic architecture that must physically support the tree and meet its needs for moisture and nutrients. Most (90 percent) of the root biomass is located in the upper two feet of the soil profile. It is in the upper two feet of the soil profile that the four requirements for root growth are met: the soil is mixed and loosened by invertebrates allowing oxygen and water to percolate into it and the roots to easily grow through it. A decades old tree can have horizontal surface roots many feet beyond its dripline. is created by immature tall tree species, mid-size trees, and large shrubs. Common midstory riparian plants are box elder, arroyo willow, and oregon ash. Shrubs and vines make up the woody understory, such as coyote brush, elderberry, blackberry, rose and grape. The herbaceous layer is the lowest ground cover and is made up of grasses and nonwoody broad leafed plants.

The ratio of trees to shrubs will determine the complexity of the forest canopies. A design with mostly tall trees will create a closed overstory, but this can be broken with clusters of shrubs to create openings in the forest and introduce a diversity of foliage, fruits and seeds to the habitat.

The density, spacing and type of plants used in restoration design will determine the kind of structures created, and which wildlife will use them for cover and nesting. Shrubs with multiple stems for instance, such as rose and willow, can form dense thickets when several are planted together. Elderberry, which also tends to grow with multiple stems, is a trellising species, and can grow over smaller shrubs when planted close together. The combination of rose and elderberry create a more densely covered thicket. Vines can take on several growth forms and make connections between different plants and different canopy layers. Both blackberry and grape can spread throughout the forest, climbing over and through plants. Grape often climbs into the upper canopies and forms an overstory. The lateral branching of vines are preferred nesting substrates of many birds, and the dense layers of cover offer protection from predators. The variety of stem sizes, textures and foliage, attract a greater suite of insects which are a basic food source for wildlife.

The above article originally appeared in the Fall 2009 issue of the River Partners Journal.