Survey of the Native and Nonnative Vascular Plant Species of Three Islands in Lake Winnipesaukee, New Hampshire

This study examined the long-term patterns in vascular plant composition on three islands in Lake Winnipesaukee, NH. It also tested the role of island biogeography in ecology as it analyzed the effectiveness of a land use plan implemented on the islands. Samplings were made on the islands in the summer of 2011 and were compared to earlier samplings in 1978, 1991, and 2001. The flora was observed and measured in 25 permanent plots that were established on the three islands in 1978. The understory flora was measured by presence and percent cover and the overstory was measured by frequency and density of individual trees and shrubs, dominance ratings, and basal areas. This study also focused on plants of interest including certain rare (Rhododendron maximum), introduced (Halesia carolina) and potentially invasive species (Poa compressa). Data from the study shows that the species richness on all the islands increased significantly from 1978 to 1991 on all three islands but remained relatively constant in the 1991, 2001, and 2011 samplings. Species evenness on all the islands remained relatively constant in all four years of sampling. The statistical analyses shothat all samplings were statistically significant across all the islands and years of sampling. The plants of interest mostly remained in the same areas that they were found in earlier samplings. In particular, the rare plants remained in the least disturbed areas of the islands while the introduced and potentially invasive species were found in the most disturbed areas of the islands