Invasive earthworms in Indiana old-growth and second-growth forests

Patricia Mary Quackenbush, Purdue University

Abstract

Temperate and boreal forests in Canada and the northeastern United States are susceptible to attacks by multiple invasive species, including European earthworms (family Lumbricidae) and plant species such as garlic mustard ( Alliaria petiolata [M. Bieb] Cavara & Grande) and multiflora rose (Rosa multiflora Thunb.). Old-growth forests are considered less susceptible to invasion by introduced plant species than secondary growth forests but the ability of introduced earthworms to invade old-growth forest is unclear. In a series of growth chamber experiments, I determined (1) the palatability of garlic mustard and six native herbaceous forest species (shooting star, columbine, wild geranium, sweet cicely, butterfly weed, and yellow jewelweed) to the common nightcrawler and (2) the ability of the common nightcrawler to bury and digest garlic mustard and wild geranium. I also investigated relationships among introduced earthworms, introduced plants, and native plant communities in six paired old and secondary growth forests in four Indiana natural regions along interior and edge transects positioned on either a south or west facing edge. Garlic mustard seed was readily consumed by common nightcrawlers and found to be preferred over some native plant species suggesting that common nightcrawlers may reduce the presence of the garlic mustard in the forest seed bank. In the field experiment, densities and frequencies of earthworms did not differ between forest edges and interiors or between the old- and second-growth forest stands. Differences in percent cover and frequency were not detected among forest structural stage or location of transect for introduced plant species. Ordinations of earthworm densities, soil characteristics, and plant species suggested differences between old-growth and second-growth stands for three of the six pairs. Introduced plants and earthworms appear ubiquitous in Indiana forests and appear to influence the plant species composition of Indiana forests.

Degree

M.S.

Advisors

Gibson, Purdue University.

Subject Area

Ecology|Forestry|Plant sciences|Environmental science

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