Post contributed by Brett Stolpestad and Brad Chatfield, Conservation Corps of Minnesota:
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| Great Horned Owls are one of the many species that use Saint Paul's floodplain parks to raise their young. |
The Mississippi River floodplain is Minnesota’s centerpiece. A
patchwork of cottonwood, maple, boxelder, hackberry, and ash make up the
forest ecosystem, providing critical habitat for migratory birds and other river-dependent wildlife. The
City of Saint Paul is home to a beautiful winding chain of parks along the
Mississippi and uses a variety of management practices to augment the health of
the floodplain ecosystem. One particularly useful and beneficial technique is shelterwood harvesting, the process of gradually removing mature
trees in a given area with the goal of establishing the next generation of
desirable tree species. This process has the potential to increase
biodiversity, improve wildlife habitat, and eliminate invasive species.
How does
shelterwood harvesting work?
Step one: Land managers begin by surveying
forest transects using satellite images, GPS units, and GIS software. At this
stage, typically called a forest composition survey, surveyors attempt to create
a map that clearly illustrates the distribution of tree species, the total
canopy cover, the average size of the trees and perhaps their age.
Step two: Surveyors identify potential
shelterwood harvest sites by analyzing sections of forest that may lack
diversity or contain undesirable species like buckthorn, white mulberry, or Siberian elm.
Step three: Through several gradual stages, foresters
begin removing trees that lie within the designated shelterwood harvest area. Removing
these trees helps to open the canopy, allowing sunlight to reach the forest
floor where the next generation of saplings can become established.
Step four: Native tree species can then be
planted in the newly created pockets, adding to the biodiversity of the
ecosystem and improving wildlife habitat. Trees or shrubs such as cottonwood,
silver maple, sugar maple, black willow, elderberry, and red osier dogwood
might be selected!
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| A Conservation Corps member completing a canopy survey at Hidden Falls Regional Park. |
In recent
years, prominent Saint Paul Parks including Hiddens Falls, Lilydale, and Crosby Farm Regional Parks have all been selected
as sites for shelterwood harvest. The decision to focus on these parks has
been, in part, a response to ecological threats including the encroachment of emerald ash borer. The threat of emerald ash borer has
led to the preemptive removal of ash tree throughout the floodplain, followed
by several large-scale volunteer planting events. Over the past few years,
volunteers have helped plant hundreds of trees and shrubs throughout Crosby,
Lilydale, and Hidden Falls. If you visit these parks today, you will
undoubtedly see dozens of young maple, cottonwood, and black willow standing
straight in their “tree-tubes,” along with an understory smattering of black
willow, dogwood, and elderberry.
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| Shelterwood harvest areas are replanted with native tree species. These young trees are protected with tree tubes, which facilitate growth and protect the saplings from hungry animals. |
The
Mississippi River floodplain remains a gorgeous and dynamic landscape in the
heart of our state. The floodplain parks of the Twin Cities offer the
opportunity for city-dwellers to walk the long winding paths through towering floodplain
giants, and to become immersed in the wildlife sanctuary that the floodplain provides.
