Earthworm sampling   Lee E. Frelich
  Nov 02, 2006 06:43 PST 


No, I didn't examine earthworms. I was in a hurry and the worms weren't, so
I looked up at the trees and ignored underground ecology.

Let's do some earthworm samples in April. I assume your climate there is
so mild that adult earthworms will survive the winter and be ready for
identification in the spring. In MN a lot of adults die during the winter
and in the spring the eggs hatch, but can't be identified until they mature
during July.

You can always sample earthworms on your own if you want. Just mix 1/3 cup
of yellow mustard powder with a gallon of water and pour 1/2 of it on the
ground in an area of about 2 square feet, and wait for several minutes.
Then pour the rest and wait a few more minutes. Grab any worms that come up
and put them in plastic ziploc bags. You can also put them in alcohol if
you want, and that will kill them so they will sit still when you try to
identify them. Keys are available at the MN worm watch website: Most of your species will be in the key,
although you might have a few odd ones out there that aren't in the key. I
would expect to find Dendrobaena octeadra in hemlock and white pine
forests, and in areas where the duff has been stripped away, Lumbricus
rubellus and L. terrestris. You will probably also find angleworms
(Aporrectodea species), which are mostly not pigmented. There are probably
some Sparganophilus ( a North American native genus) in your area, unless
they have been displaced by the more aggressive European earthworms.


RE: earthworms   Gary A. Beluzo
  Nov 02, 2006 07:18 PST 


Thanks for posting the field method to collect worms and the worm
identification link. How late in the Fall do you think I could still do worm
sampling/ID in Robinson State Park? Also, how many representative sample
plots (and what size?) would you use for the Park or any other forest area.


Gary A. Beluzo
Professor of Environmental Science
Science, Engineering, and Mathematics Division
Holyoke Community College
RE: earthworms   Lee E. Frelich
  Nov 02, 2006 09:12 PST 


You can sample worms as long as the soil is warm enough (>50 degrees F) and
moist. During cold periods they go deeper into the soil and hibernate, and
during dry periods they estivate. If you have several days with
temperatures in the 50s or higher they will be quite active, whereas air
temps in the 30s for a few days will cause them to become inactive, because
the top few inches of the soil will be cold, and they stay deeper down.

I would try 30 samples randomly or systematically scattered throughout the
park to characterize the proportion of the park infested and the species of
earthworms present. Of course you can also look for the presence/absence
of earthworms at a number of points just by looking for middens of
Lumbricus terrestris (nightcrawler) or other castings on the surface of the
soil, without actually sampling the worms. L. terrestris is the only
species that creates middens, and each individual uses its burrow for life,
so you can use midden count density in plots of 1-2 square meters in area
as a census for that species. There were quite a few L. terrestris around
the vernal pools in the red oak stand Bob and I looked at, but I saw mostly
the castings of Aporrectodea elsewhere in the park.

A few other pointers for sampling: (1) We like to use a metal frame (made
of sheet metal about 3 inches wide) that can be pushed a half inch into the
ground before pouring the mustard solution, so that warms don't escape, the
solution doesn't run all over, and the area of every plot is equal. (2) Mix
the mustard solution just before using it. (3) alcohol will only preserve
the worms for several hours--you can ID them and throw them away. If you
want to keep worms longer, put them in the refrigerator (good for several
days) or in formalin in plastic vials, or else you will have a rotting,
smelly mess within a few days.

If you can find one or more clear fronts of invasion, you can characterize
the plant community and soil profile in front and behind the invasion and
re census the plants and soil as the front moves over the years. The annual
movement will depend on weather (they will move less during a dry summer),
and the soil types and duff types encountered (they will not move as fast
in sand; they will move faster up an ephemeral stream bed; they will not
move as fast through conifer duff as hardwood duff, except for Dendrobaena
which specializes in more acidic nutrient poor duff) That would be a great
long-term class project, since it involves above and below ground ecology,
and impacts of invasive species. There is a front of invasion in the woods
behind Monica's house, and several such fronts in Robinson.