| 9b. "Exotics" of Marcel's Forest | ||||||||||||
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Interpretive Stops
1. Along Aptos Creek Additional Information
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"Exotics" Compete with Native PlantsThe English ivy (Hedera helix), pictured at the left of the screen, is a popular decorative plant sometimes used in floral arrangements or as a fast-growing groundcover in urban gardens. Despite its popularity, this Eurasian native can seriously impact the survival of our native redwood forest plants. Non-native plants, also referred to as "exotics," "invasives," or "introduced" plants, compete with native plants for food, sunlight, and nutrients. A non-native plant such as English ivy can adapt so well to its new environment that it can proliferate and out-compete plants that have lived in an area for centuries. Not all exotic plants pose problems for native plants, however. The introduced forget-me-nots (Myosotis latifolia), for example, are "naturalized plants," considered harmless to natives. Why Be Concerned with Exotics... Isn't it, "Survival of the Fittest"?Medicine is Derived from Knowledge of Plant Products Almost all medicine has been derived from the study of the chemical processes of one plant or another. For instance, the chemical formula for aspirin was originally derived from the willow tree (Salix spp.). Taxol, a chemical used in the majority of anti-cancer drugs, was derived from the Pacific Yew (Taxus brevifolia), a tree native to the Sierras of California. California has rich floral diversity--30 percent of its plants grow nowhere else in the world. By allowing non-natives to out-compete natives, we lose the biodiversity (the unique genetic makeup) that each native plant offers. And in losing each one-of-a-kind plant, we lose a chemical template that could mean a breakthrough for a crippling disease. Non-natives Can Cause Problems for Animals Non-native plants pose other problems. Animals that co-evolve with native plants often depend on them for food or escape cover. Studies indicate that animals sometimes suffer when non-native plants are substituted for natives. For instance, the California desert's wide-bodied lizard starved because it was unable to move through dense stands of foxtail (Bromus rubens), a plant introduced to its region. Another study, of tortoises, showed that plants that co-evolve with animals help the animal thrive. One group of tortoises was fed their normal food, the native Shredding evening primrose (Camissonia boothii). Another group was fed a non-native Mediterranean grass (Schismus barbatus). At the end of the study, the tortoises that ate non-native food averaged less in total body mass than those fed the native plant. Exotics Came with Early European SettlersExotics in Marcel's Forest were probably brought here by early settlers (including loggers) and their families. Some common plants favored by earlier generations included calla lily, hollyhock, foxglove, and periwinkle. While it was the early settler who brought non-natives to the forest, it was ultimately the sunny conditions created by canopy gaps that allowed these plants to proliferate. Logging reduces redwood canopy closure. In Marcel's Forest, gaps in the canopy created by selective logging gave these plants a chance to take root and successfully reproduce in sunnier conditions. As with any non-native in a new plant community, natural enemies that once kept them in check in their old environment are not present. The non-natives, therefore, grow and reproduce easily. English Ivy and Periwinkle Cause Concern Here and ElsewhereTwo "invasives" of concern are the English ivy and the periwinkle. Both vine plants have adapted so well in Marcel's Forest that they are slowly crowding out native ground cover and have been listed as "Exotic Pest Plants." The English ivy is on the list of "Exotic Pest Plants of Greatest Ecological Concern in California" while the periwinkle showed up on the less punitive "B" list: "Wildland Pest Plants of Lesser Invasiveness." English ivy (Hedera helix), the plant that causes the most problems, quickly establishes itself in moist, deep shade found in redwood forests. As the vine grows up the trunk of the redwood, it produces berries. Birds eat the berries and then disperse the ivy seeds to other parts of the forest. English ivy has become such a major concern in redwood forests that groups of volunteers have been organized to eradicate the plant. Since English ivy doesn't deprive nutrients from the trees but merely weighs a tree down, breaking its limbs, the large redwoods in Marcel's Forest probably aren't at risk of dying. However, the rest of the vegetation in the forest is at risk. The ivy-covered tanoak tree seen on the trail between Smiley Face and Big Stump will eventually topple with the weight of the ivy. In addition, native ground vegetation and tree seedlings (including redwood seedlings) are at risk of being choked out. English ivy has the ability to change the face of our redwood forests. How Do You Rid the Forest of English Ivy?Volunteers manually cut English ivy at the root and then pull vines off tree trunks. At the same time, stems and roots are pulled out of the ground. The area is then vigilantly watched for resprouts. If you're interested in helping rid the forest of English ivy, watch for flyers at the state park entrance kiosk about "work parties" on the trail. A Few Exotics Found in Marcel's Forest:
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