Publication Date

2017-5

Document Type

Honors Thesis

Degree Name

Bachelor of Arts

Department

Biological Sciences

Advisors

Jesse Bellemare

Keywords

Foundation species, Eastern hemlock, Tsuga canadensis, Macrofungi, Hemlock woolly adelgid, Nutrient cycling, Community ecology, Ecological disturbances, Ecosystem change, Hemlock decline, Invasive species, Introduced organisms, Biotic communities, Eastern hemlock-Diseases and pests-Massachusetts

Abstract

The loss of foundational tree species causes major changes in ecosystem processes and communities of associated organisms. In New England, the foundational tree species Eastern Hemlock (Tsuga Canadensis) is currently being threatened by two invasive insect pests, the Hemlock Woolly Adelgid (Adelges tsugae, HWA) and the Elongate Hemlock Scale (Fiornia externa). In many parts of New England, following decline and extirpation of evergreen Hemlock, the most common replacing species is deciduous Black Birch (Betula lenta). Given the dramatic differences in litter quality, understory conditions and effects on soil chemistry between Hemlock and Birch; the shift in dominant tree species is likely to significantly alter nutrient cycling and the communities of forest floor organisms. This study aimed to assess changes in organic layer characteristics and macrofungal communities between Hemlock and Black Birch (young and mature) forest plots at two sites in Western, Massachusetts. Organic layer mass and organic layer C:N samples were collected from Hemlock and Birch forest plots to assess potential changes in nutrient cycling. Macrofungal fruiting body surveys were conducted in the same plots as organic layer sampling in order to analyze differences in the Hemlock and Birch forest fungal communities. A significant difference was found between the mean organic layer mass and C:N of Hemlock, young and mature Black Birch forest plots. Both mean organic layer mass and C:N decreased by forest type in a consistent pattern Hemlock>young Birch> mature Birch; suggesting long-term changes in nutrient dynamics. Macrofungal community ordination analyses showed homogenization of the community following the shift in dominant tree type. Community structure was also moderately correlation with C:N indicating organic layer characteristics may effect community composition. A higher proportion of rare fungal species were found in Hemlock plots indicating that rare and specialized fungi may be lost with Hemlock decline. These findings indicate that Hemlock decline may result in long-term changes in organic layer characteristics and that fungal community structure may change substantially when Hemlock forests are converted to Black Birch.

Language

English

Comments

56 pages : color illustrations. Includes bibliographical references (pages 49-56)

Share

COinS