The flora of Penikese Island, Massachusetts: The fifth survey (1998-1999), with emphasis on the woody vegetation.
Five vascular plant surveys have been made between 1873 and 1999 on Penikese, one of the Elizabeth Islands (Massachusetts). The five surveys have noted a total of 326 species, the most recent survey, 218 species. Almost half of the species noted are alien on all five survey lists. Four rare (state-listed) native species were found in 1998-1999. The most significant change in the island's vegetation over 125 years is the great increase in woody vines and shrubs following cessation of the farming that stripped the island of its presettlement forest. Fifteen woody species, some of them recent introductions, are thought to be increasing. Two of the island's ponds-Tubs and South-are brackish, supratidal pools without vascular plants. Four ponds-North, Leper, Tern, and Typha-are fresh, shallow, and usually dry up annually, at which time their bottoms support a dense, diverse flora. Salt marsh species and numbers are fewer than formerly. There is evidence that the island as plant habitat is drier than in the past, perhaps as a result of the increase in woody vegetation. For instance, ferns, once common on Penikese, are now almost wholly absent. Certain species common on nearby islands are missing; for instance, no blueberries or other ericads are found on Penikese. In the absence of further disturbance, it is possible that Penikese will again become forested with red cedar (Juniperus virginiana) as a presettlement account of 1602 describes it, but island-wide burns are suggested for destroying invasive woody plants and encouraging native grasses. Such burns might also restore former tern-nesting sites to usefulness.