Don, I was thinking more along the line of periodic flooding being a controlling factor in which species survive in a niche rather than a vector for seed dispersal. Dale and I were talking about a paper on the Allegheny River Island stuff we are doing. There are several distinct zones as you move upward in elevation from the normal river level to higher grounds. on the lowest levels you find species that tolerate frequent floods sycamores, silver maples, black willow. A little higher you begin to get more black locust, hawthorn and basswood, A little higher and you get red oaks added to the mix, some hickory and butternut. This progression represents the frequency of flooding for those different elevations. Finally at the highest elevations in areas that are flooded only in the couple hundred year range you can pick up pines and hemlocks and a much wider diversity of species. The major and most noxious invasives are limited in number or absent from the areas that are flooded every year or at least every other year. At higher elevations which flood less frequent;ly, thanks to the wondrous Kinzua Dam the invasive multiflora roses and knotweed are the only species that seem to be present in the understory of trees in many areas. Certainly you are not getting any regeneration of the trees in these areas.
Ed Join the Primal Forests - Ancient Trees Community at: http://primalforests.ning.com/ ----- Original Message ----- From: DON BERTOLETTE To: [email protected] Sent: Thursday, December 11, 2008 3:20 PM Subject: [ENTS] Re: Shrub-layer an empty niche? 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 --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
