PARENT SESSION
Poster Session 37: Forest Ecology.

Thursday, August 5 Presentations from 5:00 PM to 6:30 PM, Exhibit Hall A 1.

Patterns of woody plant diversity and plant-environmental relationships across three riparian corridors.

Lyon, Jonathan^*,1, Gross, Nicole^*,1, ¹ Merrimack College, North Andover, MA

ABSTRACT- High levels of species, plant community and environmental variability and heterogeneity are common among plant communities along riparian corridors. The goal of this study was to assess and characterize riparian vegetation along three forested riparian corridors that represented different disturbance histories in the southern region of the Merrimack River watershed. The study sites (Powwow River, Spicket River, Shawsheen River) were all located in the Southern New England Coastal Plains and Hills Ecoregion. Our specific project objectives were to (1) characterize and classify riparian forests across the three riparian corridors; (2) identify patterns and/or unique areas of plant diversity; (3) characterize the extent and distribution of non-native tree/shrub species; (4) determine the impact of geomorphology and soils on woody plant species assemblages. All woody vegetation on sampling plots was quantified and identified. The physical, geomorphological and soil characteristics of each plot were also analyzed. Ordination results (DCA and CCA) indicated four distinct tree layer assemblages among the three riparian systems and that tree species were responding to both underlying soil (pH, N, %Base saturation) and morphological (height above river, slope) gradients. While there were differences in species richness between the three rivers, there was no significant difference between the four tree layer assemblages. The high variability in species richness across tree layer assemblages indicates that disturbance has not eliminated forest community types, but has resulted in decreased woody species diversity. In stark contrast to the tree layer results, no clear assemblages could be distinguished for the shrub species. In addition, shrub species ordinations did not show any strong correlations with the environmental variables measured. Despite different disturbance histories, both non-native tree and shrub species were somewhat evenly distributed across the three corridors. Overall, shrub and tree layers are responding differently to the same underlying gradients. In addition, the shrub layer appears more susceptible to non-naitve species than the tree layer. Our initial assumption that more disturbed river systems would exhibit lower woody plant diversity was not supported.

Key words: vegetation, ordination, riparian, soils