Healthy Hemlocks, Healthy Watersheds
The Eastern hemlock (Tsuga canadensis) is an icon of northern forests. Tsuga canadensis is considered a foundation species and creates many soil and water conditions that are essential for the health of our watersheds. Ranging from Northern Georgia to the Northwoods of Maine, this species of evergreen thrives in moist soils present in much of the Adirondacks. The eastern hemlock is a shade tolerant species that can grow in slightly acidic soil; however, their shallow root systems make them susceptible to erosion or drought. Tsuga canadensis is the only species of hemlock native to the Adirondack mountains. Although it might take 250-300 years for this tree to reach maturity, it has the capability to live well over 500 years – making it one of the longest-lived species in Adirondack forests. blackburnian warblers, black-throated green warblers, and other seasonal birds frequent the hemlock for habitat, and deer often browse the needles or use the area under the canopy for a bed site.
How do you identify a hemlock tree?
The eastern hemlock has flat, short needles that are roughly ½ inch long. The needles are rounded at the tip, dark green in color, with a lighter green or silver coloration on the underside of each leaf. The tree produces small cones, much smaller than the Eastern White Pine or Red Spruce. Each cone is about ¾ inch long and hangs from the end of the twig. The bark of the tree is dark, thick, and rigid. Eastern hemlock can easily be distinguished from a few other northeastern evergreens. The hemlock has flat needles, while red spruce has four sided needles, and much larger cones. Tamaracks can be commonly confused with hemlocks, although tamarack needles are produced in clusters of ten to twenty, as opposed to the single needles of the hemlock. The hemlock might also be confused with the Balsam Fir. The balsam fir has longer needles, much larger cones, and has a smoother, lighter colored bark, with a growth pattern that tends to be more conical.
What is the role of hemlocks in our watersheds?
Tsuga canadensis provides shading, sheltering and temperature regulating services in aquatic ecosystems. Although most evergreens aren’t considered efficient shade producing species, the hemlock canopy tends to be more of a silhouette than a conical shape. The more shading that is provided by hemlocks, the cooler, and more oxygenated the local waters are likely to be. In smaller rivers or streams, this relationship is critical for cold water dwelling species such as brook trout. During the winter months when hardwood trees are dormant, the hemlock absorbs excess groundwater. The shallow root systems of the hemlock are surprisingly efficient at retaining water, - providing more groundwater to the watershed, which minimizes flood events. Streamflow is directly affected by the concentration or availability of groundwater. Without the soil stabilizing, water retaining root systems that the hemlock offers, it’s likely that a watershed would experience higher fluctuation in water levels throughout the year. Additionally, these root systems are filtering out pollutants that would otherwise enter our rivers, stream, and lakes.
What are the threats to the eastern hemlock?
If you’re familiar with the eastern hemlock you’re likely familiar with the Hemlock Wooly Adelgid. The Hemlock Wooly Adelgid (HWA) was first observed in the eastern United States in the 1950’s, arriving in New York State sometime around 1985. The hemlock serves as host to the insect, which feeds on the tree’s stored starches in the xylem by using their long, specialized mouthparts. This invasive pest has the capability to produce two generations of offspring each year, with up to 150 eggs in each generation. Its rapid reproduction leads to additional damage to the hemlock, killing the tree buds and eventually the needles. The Hemlock Wooly Adelgid eventually causes a deterioration of the tree’s crown, making photosynthesis difficult, as well as slowing down the tree’s ability to transport nutrients. After an infestation of HWA, hemlock trees are only able to survive for another 5-10 years. Following the loss of hemlock, primary succession tree species begin to establish. In the Adirondacks this would likely lead to more paper birch (Betula papyrifera), as well as understory plant species such as hobblebush, or the invasive knotweed. Oaks, maples, birch, and white pine could begin to move into new territories. These changes could lead to altered riparian zones, reduced habitat for birds or mammals, and warmer waters that would negatively impact native fish populations that are sensitive to temperature and dissolved oxygen changes.
What can you do to help protect the eastern hemlock and our watersheds?
Native trees such as the hemlock are vital to the health of our streams, lakes, and surrounding watersheds. Become a trained community scientist by becoming a Forest Pest Hunter with the Adirondack Park Invasive Plant Program (APIPP). APIPP recruits and trains volunteers to survey for Hemlock Wolly Adelgid. These surveys are vital to minimizing the spread of this invasive species. Additionally, the Adirondack Watershed Institute is recruiting landowners with streamside property to participate in Stream Wise, a new voluntary program that promotes and recognizes good stream stewardship. AWI is offering free Stream Wise assessments in the Saranac River watershed that uses a protocol based on research conducted on riparian buffer programs, regulations and guidelines for Vermont, New York and Quebec under a grant sponsored by the Lake Champlain Basin Program. If you have streamside, riverside, or brookside property, get in contact for a free assessment today to learn more about the hemlocks or other species on your property!
To learn more and get involved, visit our Stream Wise webpage.