this discussion has moved on an interesting tangent to the original post. There is a new book out on the number of north american species introduced to China and their impacts..its huge. i don't have the title infront of me now but north american crayfish spread a crayfish virus to Europe and wiped out nearly the entire European crayfish fauna and amphipods from Midwest have nearly wiped out native amphipods in the British Isles...the story simply points out that the exchange of species non-native to a location are happening globally, not just here...but the impacts are no less significant. Travis
On Thu, Dec 11, 2008 at 3:20 PM, DON BERTOLETTE <[email protected]> wrote: > Ed- > Your comments about invasive grasses set me to thinking...some of what you > were saying has to do with the relative periodicity of the disturbances...if > their return cycles go outside of their natural range of variation, the site > may become more susceptible to invasives...flood events are perfect vectors > for many species and are indiscriminant to the native/invasive seeds > carried. > -DonRB > > > ________________________________ > From: [email protected] > To: [email protected] > Subject: [ENTS] Re: Shrub-layer an empty niche? > Date: Thu, 11 Dec 2008 11:11:55 -0500 > > > Ryan, > > Are you saying that Rhododendron and Mountain Laurel are a native invasive > in some conditions as opposed to the "normal" forest components? If so in > what circumstances is this the case? It always struck me as a core component > of the forest rather than something that should not be there. > > The definitions you provided are useful in these types of discussions on the > list to make sure everyone is starting from the same basic perspective. The > idea of native placeholders to help prevent the establishment of non-native > invasives is interesting. > > I am wondering about what you think concerning the replacement of native > grasses by invasive ones in some settings. this is a big problem in some > patches of open prairie in the mid west. Another example is from some of > the Allegheny River Islands, portions of the islands were open grassy > areas. These have since been replaced by Japanese Stiltgrass. This may be > do to the damming of the river upstream preventing the annual or at least > frequent flooding of the islands. (The presumption being that the flooding > was more favorable to the native species than it is to the invasives.) The > same can be said for the invasive multiflora roses, the Knotweed, etc. The > only areas in portions of the island not covered by the invasives, and still > retaining a semblance of native species are areas still being flooded. The > point being that changes in the natural processes of flooding, fire, etc, > may actually result in less "disturbance" of the area and promote the rise > of invasives. Some types of disturbances are needed to maintain the natural > succession cycles and interrupting them may result in the invasion of both > exotics and atypical native species. Obviously the grassy areas do not have > shrub layer, but the process could be analogous to those affecting forest > settings. > > Ed > > Join the Primal Forests - Ancient Trees Community at: > http://primalforests.ning.com/ > > ----- Original Message ----- > From: Ryan McEwan > To: [email protected] > Sent: Thursday, December 11, 2008 10:28 AM > Subject: [ENTS] Re: Shrub-layer an empty niche? > I imagine that if you focus on life history traits, some native species are > "invasive," but, most deciduous forest shrub-layer species don't fall into > that category in my view- Smilax, Viburnum, Lindera, etc., just dont > have the same impact on biodiversity and ecosystem function as invasives > such as Lonicera or Ligustrum. What about Rhododendron, though? I think > it is an interesting case...and maybe Kalmia in some settings, I am sure > there are others I am not thinking of. > > The other really important thing to keep in mind is that native weeds should > not be considered "invasive" if they are part of an ephemeral community. > Think of poke (Phytolacca)...it has all the features of an "invasive" > species, but it does NOT form a persistent community...it is ephemeral, > holding the niche for a brief time. Ultimately, I think native weeds might > be the key for management of invasives...you need something aggressive to > hold those disturbed areas until you can get the forest floor in place and > some shade from the canopy. Native "weeds" like Phytolacca, Rubus, > Eupatorium rugosum, maybe even Acer negundo, and others, might be very > helpful in that context. > > ryan > > > On Wed, Dec 10, 2008 at 11:18 PM, Steve Galehouse <[email protected]> > wrote: > > Russ, ENTS- > > Not to be a heretic, but I think we have to realize we humans are as much > agents of dispersal of plant species as are birds, squirrels, wind patterns, > etc. Were it not native in my area, I think any of the Smilax species would > be considered invasive, as well as Viburnum acerifolium and Vaccinium > stamineum. The "alien" barberries, buckthorns, burning bushes and the rest > that have become naturalized are now effectively native species--just > because we can document how they came here from distant origins, doesn't > mean they don't belong here in the grand scheme. We don't know how "native" > species expanded their ranges, but I'm sure many did so with the help of > human influence(agriculture). I also think that observing and recording the > shrub layer of the forest, without taking in to account the herbaceaous > layer, is limiting the mix of the forest community. > > Steve > > On Wed, Dec 10, 2008 at 1:48 PM, <[email protected]> wrote: > > ENTS: > > There is no doubt that the spread of certain invasive species is accelerated > by white tail deer. In the Appalachians Microstegium vimineum, Japanese > stiltgrass is changing the condition of the "natural" hardwood forest faster > than researchers can keep up with the evolving idea of what a "natural" > forest or "natural" regeneration is likely to be defined as in the future. > > Invasive plants are showing up in tracts of woodland where nothing more than > a stream passing through the property is a part of the disturbance regime. > > In so many forested situations I have encountered, the invasive species are > not filling in a vacant niche...they are replacing a dynamic and diverse > forest understory comprised of hundreds of native plant species per acre > with a green desert that consists of a dozen or less of the most persistent > native plants fighting for space against the overwhelming assault of non > resident alien invaders that are capable of altering their adopted > environment to suit their needs while producing prodigious amounts of seed > that enjoy extremely high germination rates in the absence of fertility > depleting microorganisms that keep resident plan populations in balance. > > Again, the changes being wrought on our forests by climate change and > nonnative plants, insects and diseases is validating the ENTS historical > mission of documenting what a "natural" forest is by today's definition. > > > Russ > > > ________________________________ > One site keeps you connected to all your email: AOL Mail, Gmail, and Yahoo > Mail. The NEW AOL.com. > > > > > > > > > -- > Ryan McEwan > The University of Dayton > http://academic.udayton.edu/RyanMcEwan > > > > <BR > > > --~--~---------~--~----~------------~-------~--~----~ Eastern Native Tree Society http://www.nativetreesociety.org You are subscribed to the Google Groups "ENTSTrees" group. To post to this group, send email to [email protected] To unsubscribe send email to [email protected] For more options, visit this group at http://groups.google.com/group/entstrees?hl=en -~----------~----~----~----~------~----~------~--~---
