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2008 Harvard Forest REU Student Symposium Abstracts

Cassandra Rivas - University of Texas-Pan American

Forest Type Transition Directly Influences the Seed Bank


The New England forest contains a history dominated by agriculture and forest plantations which have in turn determined modern flora. The Harvard Forest is currently harvesting 80 acres of plantations in order to regenerate native species. These plantations are mainly monocultures of non-native conifers, and have lower biodiversity than most native forests. The seed bank plays an important role in forest regeneration after disturbances, such as logging, and can directly influence biodiversity. The objective of this project is to assess seed bank species composition and abundance across forest type transitions in recently harvested plantations and adjacent forests. Transects were extended from the middle of two recently logged sites (Fisher Pine and PH 25-H), to their edges, and into the adjacent forests. Soil core samples were taken every ten meters along each transect and placed in the greenhouse to evaluate the seed bank by direct germination. Overstory basal area was sampled at every plot using a Cruise Angle. In the Fisher Pine site there was apparently a smaller overall seed bank in the plantation and particularly more woodys and graminoids in the adjacent plots (Figure 1). Similarly in the PH 25-H site, an evident contrast was noted between the plantation, which had higher graminoid abundance, and the hemlock-dominated west adjacent forest, which had a lower abundance of plants, but included more woodys than the plantation (Figure 2). These trends highlight how plantations may affect future diversity and reinforce the legacy of land use history.

click for /symposium/F:Harvard Forest SummerFigure 1.pdf

click for /symposium/F:Figure 2.pdf

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