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Kenneth Parker - Plant Ecology

Old Dominion University, Virgina

Direct & Indirect Effects of Native and Invasive Earthworms on Goodyera pubescens Seed Variability and Distribution: Orchid-fungal Earthworm Interactions

This experiment will track the movement of polystyrene spheres in a 20cm deep core (4in. diameter) with 1 of four earthworm species inside:  Eisenoides loennbergi (native), Octolasion lacteum, Lumbricus rubellus, and Lumbricus friendi (non-natives).  The spheres are the same size as seeds of the orchid Goodyera pubescens, and fluoresce under black light so they can be found in the soil later.  This is an extension of the experiment that took place summer of 2007, with soils from young forests are used instead of old forest soils. One result of the summer experiment was that earthworm survival and activity were relatively low.  We think this was a result of the old forest soils we used, which normally host only native earthworms at low abundances. Huge numbers of invasive earthworms are found in young forests while they are absent from old forests, and it is suspected to be the reason so few spheres were moved in the cores taken from the old forests.  In the previous experiment, the cores were electro-shocked after they had been dug, and non-target earthworms were later found in a few.  In this experiment, we will electro-shock the ground before digging the cores, as the electrodes work best when spaced further apart than the core will allow.  Once the cores have been taken  (Oct. 5-9), different earthworm species will be added to different sets of cores, followed by spheres and one of two types of leaf litter: Liriodendron tulipifera or Quercus rubra.  Six weeks after the worms have been added to the cores, the cores will be divided into sections of different depths.  The worms will be removed and the spheres will be counted in each section.

Funding was provided by the National Science Foundation – Research Experience for Undergraduates