Reflections on Buckthorn in the Intervale
This summer, the Burlington Wildways Interns joined Duncan Murdoch and Trail Stewardship program volunteers to remove non-native invasive plant populations throughout the Intervale and Intervale Center. Common non-native species found in the Intervale, common and glossy buckthorn, grow throughout the under story of the forest where they form dense colonies, and suppress habitat and native plants.
Buckthorn is a difficult plant to manage and often times, when faced with a colony, a treatment with roundup is the solution. Our method of removal is manual and takes a few years to complete- let me tell you why. The silver maple floodplain forest natural community type that we work in is sensitive. The seasonal flooding means that any land practices also impact the river ecosystem including fish, micro and macroinvertebrates and eventually land dwellers such as ourselves. Agricultural practices within the Intervale are strictly organic for just this reason. Therefore, even when diluted, a buildup of glyphosate in our environment could have damaging effects. Someone recently mentioned to me that there may even be an impact to the mycelia fugal networks as plants exchange nutrients and communicate. All that in consideration, we've decided to use the power of saws, clippers and girdling wire to do the job instead.
Buckthorn management in the Intervale has been a several year process, working different areas, revisiting sites and looking for emergent plants. Upon cutting down the oldest trees and counting their annual growth rings, it suggests that these plants have been in the areas for around 30 years.
In doing this work, I've noticed that perhaps 1 in 10 trees that gets cut back ends up either sickly or not coming back in some of these sites. It cutting the tree, it becomes susceptible to pathogens, insects and it's health degrades. Though much of the work is still a process over a number of years, it's interesting to see nature doing some of the work for us.
What might it mean for the forests of this area if management did not occur? I can only speculate, but, I do know that these silver maple floodplain forests lack a substantial under story. The name of the game for trees here is grow tall, make seeds to establish a seed bank, and then, wait for disturbance. When a tree falls in the forest, making a hole in the canopy, light is let in and the seed bank awakens. Those young trees can grow up and fill the place of their predecessors. The presence of invasives complicates this relationship. Invasive plants such as buckthorn are opportunists and will thrive best in disturbed areas such as the space made by a recent tree-fall, they may have the upper hand in this scenario. I could imagine that after generations of trees falling and being replaced by these competitors, there may not be much room for the lofty silver maple canopy and it might be much more common to find dense, dark, colonies of buckthorn.