Ed, Don, Josh, and Steve, Thank you so much for so thoroughly explaining this. I was hoping to make some kind of connection between the large number of disturbances in this forest and the density - I guess there must be a lot of data somewhere in the research library, but I think I will take Ed's advice and rethink what I am trying to say about this forest.
I guess what I am trying to say is that the term "old-growth" in the NYBG forest seems bogus. Maybe it was never clear cut, but it has been soooo impacted by urbanization and human usage that how can it be defined that way? And while I guess it's good that they are planting thousands of trees (donated by New York City's Million Trees program), 500 hundred untrained volunteers are let loose to walk all over off-path undergrowth to plant saplings and I freak out. I've seen people walking over trees that had been planted the day before (I think I've walked on trees too.). Maybe I am being too cynical. Maybe I just don't like or understand urban forests. But I think it has been disrespected and it makes me sad. Josh, yeah, I forget that Aralia is native. And I didn't know about it's medicinal uses. (Is one of its medicinal uses healing all the cuts and scrapes it gives me!?) Thanks for listening to my rant...if you were able to make it through. And thanks again for the website and good information. Jenny On Mar 15, 3:50 pm, DON BERTOLETTE <[email protected]> wrote: > Jenny/Ed- > > I agree with Ed. One of the few criteria for defining old-growth forest > ecosystems that in my mind has held up the best is a summarization of one of > Jerry Franklin's criteria. Which is to say that a forest ecosystem over time > will respond to cycles of disturbance regimes, and eventually develop a > "vertical and horizontal heterogeneity of forest structure and composition". > > The vertical element here is analogous to your question of tree > heights...heterogeneity here refers to the natural variability of heights > that develop over time in response to disturbance regimes...the array of > species and their spacing would be analogous to the horizontal diversity (or > heterogeneity) that would develop in response to disturbance cycles. > > This natural variation in species spacing and composition is also often > referred to as a spatial mosaic. Here in the West, that mosaic may often be > the response to a wildfire pattern (they seldom are a continuous wall of fire > consuming everything in their path, although sadly enough the more > catastrophic fires these days are approaching that at times). It may be > elsewhere a response to a forest pathogens, or cyclic wind events, etc. > > -Don > > From: [email protected] > To: [email protected] > Subject: [ENTS] Re: Forest densities > Date: Sun, 15 Mar 2009 10:31:59 -0400 > > Jenny, > > What is the average distance between mature trees in the forest? You write: > "I know it depends on the kind of forest and what kind of disturbance there > has been," But that is the entire point. The answer is dependant on a > variety of factors, so that a single answer is not possible. We have had > similar discussions on the average height of trees. Look at how the trees > grow. Initially a patch of seedlings grow very close together with several > seedling per square foot. Over time, some of the seedlings die out and the > average spacing increases between the stems. The spacing is greater in > saplings. It increases on maturity. As trees begin to die in a mature forest > the spacing between the stems continues to increase. It increases through > time for a particular species. Beyond the initial rapid thinning phase in > which there are many trees already growing to fill the space lost by a dead > tree, there is a point at which the loss of a tree will open up a space in > the canopy and forest floor that will be filled by new growth. This is where > the period of disturbance comes into play. The shorter the period of small > disturbance the more common these denser new growth patches will be in the > forest. The size of the disturbance likewise plays a role in determining the > size of the openings and the size of the denser new growth patches. There is > the size of the species in the mix. Some trees simply grow bigger than > others. Those species that grow larger, will support a larger canopy, and > have a greater trunk spacing than small species in areas that are relatively > undisturbed. A patchwork of mixed species may have a denser packing than > those of a single or limited number of species. The species present will > also impact the number and type of trees in the understory. > > So there may be measurements made of the spacing in a particular forest, but > that does not really answer the question. It is a snapshot in time. It > tells you what the density of stems is in this particular forest, at this > particular point in time, with this particular mix of species, and this > particular disturbance history. Numbers can be generated, but are they > meaningful? A density measurement taken earlier in time, or later in time > will give you different results. The measurement is dynamic and changes with > time, so that a simple answer that can be applied broadly can't really be > found. What I suggest doing is to try to reconsider what exactly you are > trying to determine, what are you trying to accomplish, and find a different > way to approach the problem. > > Ed Frank > > _________________________________________________________________ > Hotmail® is up to 70% faster. 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