Don: You mean a positive reinforcement of negative effects. There are plenty of those involving shade and an allelopathic chemical, or changing the chemistry of the litter layer, say to a lower pH and then throwing in an allelopathic chemical and shade (i.e. black walnut). Or making the litter layer poor in nitrogen plus an allelopathic chemical and shade (Bracken fern), and all of the above smothering competition with litterfall (e.g. sugar maple, the latter reinforces chemical and resource changes with a physical effect). Trees keep out their competition with multiple strategies.
Lee DON BERTOLETTE wrote: > Lee- > Can you suggest an allelopathically positive effect (chemical > combinations that turn out to be synergistic come to mind)? > -Don > > > Date: Thu, 24 Sep 2009 14:18:13 -0500 > > From: [email protected] > > To: [email protected] > > Subject: [ENTS] Re: Marion Brooks Natural Area, Elk County, PA > > > > > > Don: > > > > Most ecologists take allelopathic to mean negative effects on other > > plant species. The plants that benefit could be either directly and > > positively affected by the allelopathic chemical (but this is > unlikely), > > or benefit indirectly by being insensitive to the allelopathic > chemical, > > but being freed from competition by removal of other species sensitive > > to the allelopathic chemicals (this is the most likely case, but no > proof). > > > > Lee > > > > DON BERTOLETTE wrote: > > > Lee/Mike- > > > In my time wandering through Kentucky woods, black walnut trees were > > > the only thing I saw that could alter the advance of a field of poke > > > salat! > > > My question? What would negative allelopathic refer to? I can see > > > that it would be positive in this case for black walnut and negative > > > to most anything else, but I suspect it may refer to something else > > > entirely? > > > -Don > > > > > > > Date: Thu, 24 Sep 2009 07:50:26 -0500 > > > > From: [email protected] > > > > To: [email protected] > > > > Subject: [ENTS] Re: Marion Brooks Natural Area, Elk County, PA > > > > > > > > > > > > Mike: > > > > > > > > We had a discussion a while ago on this topic, probably before > you were > > > > on the list. Black walnut and butternut produce the allelopathic > > > > chemical juglone, which can stunt growth or even kill certain plant > > > > species, although I have seen raspberries and a species of > coneflower > > > > (Rudbeckia triloba, the branched coneflower), growing under black > > > walnut > > > > trees. > > > > > > > > Sugar maple and bracken fern have also been found to produce > > > > allelopathic chemicals that reduce germination and growth of > competing > > > > plants. There are probably many other examples. > > > > > > > > Lee > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > --~--~---------~--~----~------------~-------~--~----~ Eastern Native Tree Society http://www.nativetreesociety.org Send email to [email protected] Visit this group at http://groups.google.com/group/entstrees?hl=en To unsubscribe send email to [email protected] -~----------~----~----~----~------~----~------~--~---
