It's 65° F right now. The morning air is crisp and the skies are a gentle hue of blue. The sun rests on top of a cloud not quite ready to rise and shine. The forest is quiet as it awaits the occasional breeze to visit, ruffling its leaves and swaying its branches in motion. Soon, a dance between the tree canopies signal the critters beneath to arise from their slumber. As the critters awaken, so do the shrubs at the forest ground. The tiny branches huddle together and gaze up to admire the specks of light that seep through the canopy. A kiss of sunlight keeps them warm on the chilliest days. Today, the forest feels different. The sun hides behind a sea of grey clouds hovering over the sleeping forest. The logs stand erect with wilted leaves scattered throughout the ground, and the branches high above huddle together with their leaves seeking warmth. The branches sway and the leaves quake with great urgency. The shrubs cave in toward each other, finding comfort from the closeness of the soil beneath them in the dark world. Even the air holds its breath anticipating the downcast soon to come. The rain has arrived.
As the chorus of droplets accompany us, specks of water brush against each and every leaf before seeping into our clothes and into the ground. The leaves utter a muffled crunch with every step through the trail. In this cluster of life, we finally reach a humble shrub that awaits our presence. Almond-shaped leaves in a vibrant shade of green clutch onto wooded spines and offer us red berries. At about 3 to 6 feet tall, we meet the Japanese barberry (Berberis thunbergii), a “friend” who visits wetlands, pastures, meadows, and forests (Zouhar, 2008). Although it was first introduced to the U.S in 1875 as a decorative plant, it is now considered an invasive species that is drastically changing ecological habitats. The original intent for introducing the plant was to replace the common barberry plant (Berberis vulgaris), which was a host for a plant disease called black stem rust. Japanese barberry, while pretty and great for barberry jam, is a persistent fellow whose thorns scare away local critters and invite pests such as ticks and mice to fester a breeding ground of disease (R. Jackson & Wurzbacher, 2020). The spread of Japanese barberry is especially prominent in the northeastern United States including New York, Pennsylvania, and New Jersey (Zouhar, 2008). Japanese barberry changes the food distribution among local wildlife by taking over areas where native plants would otherwise be present. This can affect animals that already depend on the native plants for food to go find another food source.
When invasive plants such as Japanese barberry take over, they shift ecological relationships of plants and animals above and below ground by modifying their structure, function, and nutrient cycling (Ricciuti, 2019). These shrubs have multiple stems originating from the root such that if the plant stems are ripped off, they can regrow as long as the roots are present. As we have mentioned before, above ground the Japanese barberry grows in spaces where native plants could grow but its persistence allows it to thrive such that ants, spiders, and other insects have to find different food sources (Ricciuti, 2019).
Below ground, Japanese barberry continues to make new changes. When growing in large quantities in an area, Japanese barberry leaves that fall to the ground can shift the pH of the soil, making it more basic, which makes it even harder for many native plant species to grow (R. Jackson & Wurzbacher, 2020). Japanese barberry is not only good at growing, it knows how to keep away its competition. Even native plants that can survive alongside Japanese barberry, do so at a cost. For the native species that can thrive alongside Japanese barberry, their biomass is suppressed by the plant, and their recovery is slow in the first year after Japanese barberry removal (Silander & Klepeis, 1999).
Japanese barberry spreads in two ways: first, the plant can produce fruit that eventually makes its way to the ground to grow from seeds, or the second which is when one of its stems reaches the ground and the plant produces a clonal copy of itself using that stem. The berries, which are available to birds and mammals from summer through winter, are spread primarily through gravity but also through endozoochory, a process by which animals like birds and insects eat the fruit and eventually poop out the seed that then grows. On the other hand, individual plants spread horizontally through layering, a process in which roots grow when branches are in contact with the ground (Zouhar, 2008). When the plant is spread through layering, the plants are genetically identical to the parent plant (R. Jackson & Wurzbacher, 2020).
It is important to acknowledge that the consequential impacts of Japanese barberry not only pertain to the environment but also eventually affect us. When Japanese barberry is introduced into a habitat, it disrupts the ecological balance of that environment making it harder for local plants to grow and reducing the biodiversity of animals present in that area. Food webs change significantly since the animals are now struggling to find a new food source now that Japanese barberry is displacing their original ones (Ricciuti, 2019). Spider communities in habitats invaded by Japanese barberry have fewer species of spiders and fewer of them compared to those living in natural forests without the plant.
Japanese barberry also contributes greatly to the spread of Lyme disease among humans. Its dense proximity of leaves creates a favorable environment for black-legged ticks (Ixodes scapularis) which spread the disease to humans (Ricciuti, 2019). Animals, such as the white-footed mouse (Peromyscus leucopus), also find refuge under barberry, creating a higher density of Lyme-infected ticks which can use the mice as hosts and amplify the spread of disease (R. Jackson & Wurzbacher, 2020).
Like the white-footed mouse, we must be nimble and part ways with the forest. As the leaves are now nourished and the soil is content, we begin to see a ray of light entering through a crevice in the canopy, calling the shrubs to gaze upward. Not all the shrubs are keen on awakening though. The barberry is lively, stretching its branches up toward the sky while continuing to dig even deeper into the ground. The critters awaken but scurry away in the sight of the barberry, scavenging for morsels of food. While the forest is still breathing, we must take initiative to fight this foe soon for the doom of mankind is inevitable when the forest takes its last breath.
Sources
Zouhar, K. (2008). Berberis thunbergii. U.S. Department of Agriculture, Forest Service. https://www.fs.fed.us/database/feis/plants/shrub/berthu/all.html
Ricciuti, E. (2019, September 1). Impact Of Invasive Japanese barberry Cascades Through Local Food Webs. Entomology Today. https://entomologytoday.org/2019/09/13/impact-invasive-japanese-barberry-cascades-through-local-food-webs-arthropods-insects/
Silander, J. A. & Klepeis, D. M. (1999). The Invasion Ecology of Japanese barberry (Berberis thunbergii) in the New England Landscape. 1(2/3), 189–201.
Japanese barberry | National Invasive Species Information Center. (n.d.). U.S. Department of Agriculture National Invasive Species Information Center. https://www.invasivespeciesinfo.gov/terrestrial/plants/japanese-barberry
R. Jackson, D. & Wurzbacher, S. (2020, February 24). Japanese barberry. Penn State Extension . https://extension.psu.edu/japanese-barberry