Bill, I'm not an expert (guy from out of town with slides), but I believe that most soils have a redundancy of bioturbaters including rodents and beetles, unlike some marine bottoms. In some northern forests in North America, the European night crawler, which takes its food from the surface, has depleted the litter layer in the extreme, exposing tree roots to harsh conditions and actually rendering soil less rather than more permeable. Some of the forest floors that formerly were thickly covered with natural mulch are bare. DMc
The source of these worm introductions is probably bait dumped when no longer needed. ---- William Silvert <cien...@silvert.org> wrote: > Perhaps Bruce could fill us in on earthworms, since not all of us are > knowledgable in this area (I'm a marine ecologist and obviously picked up on > some inaccurate ideas). I always assumed that they played the same role as > some key polychaetes do in benthic systems, where it has been shown that if > just one key species is eliminated the bottom turns to concrete. > > So please: if earthworms are absent, what keeps the soil aerated and broken > up? What are the detrimental impacts of the undesirable earthworm species? > What is the range of ecosystem functions that earthworms play? > > Bill Silvert > > ----- Original Message ----- > From: Bruce A. Snyder > To: William Silvert > Cc: ECOLOG-L@listserv.umd.edu > Sent: segunda-feira, 3 de Maio de 2010 18:41 > Subject: Re: [ECOLOG-L] State Microbes and Yucky Worms > > > Native Nearctic earthworms have not been eliminated and are quite diverse. > Pleistocene glaciations did extirpate them from the northern portion of the > continent, and the present-day ecosystems in this region developed just fine > without the presence of earthworms. This is where the detrimental impacts of > invasive earthworms are the most prominent. European earthworms are the > primary culprits in the northern forests, but Asian, African, and South > American species have all found there way to North America. > > Collective nouns are not a problem in themselves, but it is troublesome > when a collective term is applied to describe the homogeneity of something > that is far from homogeneous. E.g., not all earthworm individuals are the > same species and as such not all function the same; not all earthworm species > are beneficial in all locations. -- David McNeely
