By Lizzie Wilson
Last month, a three-acre field in Mt. Cuba Center’s natural lands became home to 3,000 new native trees and shrubs. More than 60 volunteers worked tirelessly over two weeks to get all of the plants in the ground. Three thousand plants may seem like a lot, but this is actually part of a much larger, 100-year-long reforestation experiment in partnership with West Chester University and University of Delaware. Once completed, approximately 12,000 trees and shrubs will be planted across 12 acres of land.
The experiment is designed to fill knowledge gaps and identify the most successful reforestation techniques for our region. In simple terms, reforestation is a type of habitat restoration that involves regenerating or replanting destroyed or damaged forest areas. Despite a great need to establish more forest habitats throughout the Mid-Atlantic and beyond, there is surprisingly little data on which reforestation techniques work best to help land managers make informed decisions.
The Benefits of Native Forests
Forests filled with native plants are critical because they help sustain not only wildlife, but also human life. Here are some services they provide, to name a few:
- Native forests provide shelter and food for many species of insects, birds, and mammals.
- Through photosynthesis, trees capture and store carbon and release oxygen that we breathe.
- Deep, interconnected roots hold soil in place and absorb water, preventing erosion and minimizing flood damage.
- Forests support biodiversity and create more stable, healthy ecosystems.
Native trees and shrubs have deep roots that help hold soil in place.
Reforestation Research
Reforestation strategies often differ in two main ways. First, the types of plants used, and second, the density at which they are planted. Within Mt. Cuba’s reforestation experiment, six reforestation methods are represented across six different plots, including:
- Sparsely planted trees: plants are placed at ten-foot intervals
- Sparsely planted trees and shrubs: plants are placed at ten-foot intervals
- Densely planted trees: plants are placed at five-foot intervals
- Densely planted trees and shrubs: plants are placed at five-foot intervals
- Natural succession: no trees or shrubs are planted in the natural succession plot; rather, it is left untouched and succession is allowed to run its course.
- Control: the control plot is planted like the sparsely planted trees plot, but will be maintained differently in the coming years.
Plots 1-4 will be mowed for three to five years following planting, while plot 6, the control plot, will be mowed for ten to fifteen years.
The graphic above shows how the experimental plots are laid out within the field. Each box represents one plot/one unique reforestation method. In the densely planted plots, there are approximately 700 trees/shrubs and in the sparsely planted plots, there are approximately 500 trees/shrubs.
The experimental design calls for four replicates, meaning that four fields will be planted the same way (all including the six reforestation methods) over the course of 10 years. The replicates serve to strengthen any results derived from the fields. Two replicate fields were planted in the natural lands in 2015 and 2018. One final replicate will be planted in the fall of 2024.
This aerial image reveals the unique plots within one of Mt. Cuba’s reforestation sites. Notice how some plots are planted more densely and some more sparsely.
Creating a Forest
Biodiversity, or the presence of many unique plants, is an important part of forest health. Mt. Cuba’s experimental plots are planted with 28 species of native trees and shrubs, including oak, maple, hickory, dogwood, viburnum, and sumac. Shrubs are used in addition to trees in some plots to create multiple layers within the forest. A forest with multiple layers often supports a greater diversity of wildlife.
Mt. Cuba sourced plants from several local nurseries to increase genetic diversity within the plots and improve their ability to survive disease. In 2021, Mt. Cuba ordered plants from Pinelands Nursery in New Jersey as well as Octoraro Native Plant Nursery and Go Native Tree Farm in Pennsylvania, all of which specialize in producing plants for habitat restoration.
Plants were delivered to Mt. Cuba’s natural lands in one- to three-gallon pots, stacked high in large trucks. They were unloaded and organized into groups of fast- and slow-growing trees or shrubs. To mimic natural processes that occur when an area of land returns to forest, Mt. Cuba included 70 percent fast-growing plants and 30 percent slow-growing plants in each of the plots. Each plant was placed in a designated hole, marked by a corresponding flag color, and before long, the field began to look like a young forest.
Once in the ground, the trees and shrubs were watered once then left on their own. These native plants are hardy and well-adapted to local conditions, thus they will not be given supplemental water unless we experience severe weather. Approximately 95 percent of the plants are expected to survive. To help their chances of survival, grass between the plants will be mowed to keep meadow voles out of the plots. A ten-foot fence was also installed around the plots to prevent deer damage. It will be removed once the trees are well-established.
In the coming years, researchers from West Chester University and University of Delaware will visit the experimental plots to collect data on tree growth rates, light infiltration, photosynthetic rates, and soil composition. Additionally, Mt. Cuba will track the amount of time spent on maintenance for each of the six plots. This data will shed light on best practices for reforestation and help us better understand how to restore forest habitats for native wildlife.
We expect preliminary results from the experiment ten years after trees and shrubs are planted. Beyond that, scientists will continue to monitor and collect data from each of the four replicate fields.
Mt. Cuba thanks everyone who came out this October to help us create the beginnings of a forest. Many hands truly make for light work!
