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Introduced tree species in urban woodlands in Worcester, Massachusetts.
BERTIN, ROBERT1, CANTWELL, TIM1, BERSTENE, BETH1, 1
ABSTRACT- We investigated the tree species composition in urban woodlands in Worcester, Massachusetts. Worcester is a city of 9740 ha and a population of 165,000 in eastern Massachusetts. It is located near the border of the Transition Hardwoods and Central Hardwoods. Our goals were to evaluate the prevalence of introduced tree species in urban woodlands and to determine whether any of the introduced species is capable of invading intact woodlands and displacing native species. We examined a total of 20 woodlands differing in size, native species composition, land use history, and neighboring land use. At each site we sampled a minimum of 150 trees, 50 saplings and 50 seedlings. A total of 53 tree species was present, including 16 introduced species. Non-native species were especially common on disturbed sites and comprised 25% of trees, 28% of saplings and 33% of seedlings overall. The most common introduced species were Norway maple, black locust, tree-of-heaven and sycamore maple. Most of the non-natives were shade-intolerant and were rare as seedlings. However, Norway maple was common at all size classes and showed excellent regeneration in many woodlots. This species was especially prevalent on moister and richer sites, less so on drier sites dominated by black and white oaks and pignut hickory. This urban area supports a diverse array of non-native trees, including one (Norway maple) that poses a threat to native woodlands with relatively moist and rich soils. Consideration should be given to restricting the use of this species for ornamental purposes.
KEY WORDS: urban woodlands, introduced trees, Norway maple, Acer platanoides