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Thinning Hartley’s pines will keep forest healthy

Hartley Park, one of many beloved and heavily used parks in Duluth, is set to see some changes. A master plan was completed in July 2014 with the help of many public meetings, public input and expert advice. The master plan established a framewor...

Students in Hartley
A group of Piedmont Elementary 5th graders walk along a path at Hartley Park in September 2014 on their way to the next forestry station. (File / News Tribune)

Hartley Park, one of many beloved and heavily used parks in Duluth, is set to see some changes. A master plan was completed in July 2014 with the help of many public meetings, public input and expert advice. The master plan established a framework for implementing improvements and managing resources over the next five to 10 years.
One item in the master plan calls for selective thinning of several red pine and Norway pine plantations within the park. The city of Duluth Tree Commission has studied this proposed thinning process and agrees that it is the right action at this time.
Selective thinning is a standard forestry-management practice designed to create openings in the overhead canopy, which enhances wildlife habitat and woodland diversity. Thinning helps to create better tree spacing and reduces competition, which improves individual tree and overall forest health. Selective thinning encourages diverse natural plant regeneration, optimum tree growth and health, and canopy layering, which enhances both woodland and wildlife habitat diversity. It reduces tree stress due to competition and, in the pine stands, will reduce the potential for mortality due to pine bark beetles.
The pine plantations in Hartley Park were planted about 60 years ago and have never been thinned. Therefore, the trees today are tall with very thin trunks and only at the very top is there leaf and needle growth.  A live crown ratio is a measurement commonly used by foresters to determine tree and overall forest health, and this ratio is considered to be very poor in the Hartley pine plantations. These trees are stressed due to crowding, and stressed trees are more vulnerable to diseases and pest infestations.  
The purpose of pine management in Hartley Park is to increase the species and age diversity of the pine plantations in a manner that also contributes to the survival of mature pines and the stand’s cathedral-like feeling. It is recommended to thin the pine stands that have not been thinned to date by removing approximately one-fourth to no more than one-third of the stand and, if possible, by snaking rows to create a more natural appearance with randomly selected trees from each side of the rows removed to create gaps for planting.
After thinning, a variety of seedlings will be planted in the openings in order to increase forest diversity and sustainability and to protect forest health. Suggested species for planting include white pine, white spruce, paper birch, balsam fir, northern white cedar (in moister areas), and native berry- or nut-producing shrubs. Due to browse pressure from deer, all the newly planted trees will need to be protected.
These stands will be selectively thinned two more times, approximately five to seven years apart, again removing approximately one-third of each stand in each of the thinning sequences.
Tree thinning in Hartley Park will be noticeable. It will require equipment, create noise and cause temporary disruption in certain areas. Yet thinning of these planted trees is long overdue; and if nothing is done, we risk losing all of or at least many more of Hartley’s trees.
With the future health of Hartley Park in mind, the director and staff of Hartley Nature Center are in full agreement with these actions, as is the city of Duluth Tree Commission.
 
Barbara Stark is a member of the city of Duluth Tree Commission and wrote this on behalf of the commission.

Weigh in
The city of Duluth Planning Commission is accepting written comments through Wednesday on the Environmental Assessment Worksheet for the Hartley Park Mini Master Plan. The plan can be found on the city’s website at duluthmn.gov. Written comments can be directed to the Planning Commission - Keith Hamre, Duluth City Hall, Room 208, 411 W. First St., Duluth MN 55802.

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