Even though the YEW is an urban watershed, there is significant tree cover across the 5.5 acres and surrounding watershed. In 2012, students recorded the species, height, and diameter of all the trees in the YEW ≥ 4 inches (10 cm) diameter, and mapped them with GPS. Norway Maple is the most dominant tree in the YEW, making up a full 33% of the trees in the YEW. Other common species include Black Cherry and Black Walnut. The map below shows the different tree species found in the YEW.
When trees die, fall to the ground, and decay, they continue to serve as important components of the ecosystem, providing homes for animals, plants, insects, and fungi. Known as ‘coarse woody material,’ decaying wood covers about 3% of the watershed’s total area. Coarse woody material slowly releases plant nutrients and helps many different species continue to eat, live, and thrive.
As you can see in the diagram below, invasive species occupy large areas of the watershed (red bars show the stem count of invasive species for a particular size, while the green bars show the amount of native species). Invasive species can have negative effects on the environment by competing with native species for habitat and resources.
Invasive plants also may limit the nesting success of birds. Major invasive plants found in the YEW include English Ivy, Japanese Knotweed, and Multiflora Rose (pictured below). In the summer of 2014 and 2015 students from Common Ground helped to clear Japanese Knotweed from the area around the weather station. Invasive species management remains an important prospect for future activity in the YEW.
English Ivy Japanese Knotweed