Posted: Sat Apr 01, 2017 5:31 pm
by AndrewJoslin
Lucas wrote:I find it incredible that jays (maybe passenger pigeons) that spread oak seed far and wide would still produce the restricted pattern seen. These trees will grow outside their range when planted so there has to be more to this.

Something to think about is that many species will grow out of range and will grow in habitat where they are not found "normally" when planted and cared for by humans. When you look at species composition in a tract of relatively undisturbed forest you'll find that many species locations are very specific to micro habitats. One question to ask is will a given species germinate on its own out of range and/or in unfavorable habitat? Taking that further a tree species may germinate and start to grow in unfavorable habitat and eventually not survive. Clearly there are more adaptive species that germinate and survive in a variety of habitats but many are specialists. Thinking Nyssa sylvatica which has very predictable habitat dependent locations where it grows in eastern Massachusetts. Quercus rubra, Pinus strobus or Acer rubrum for example are quite versatile, I can imagine them moving rapidly back into glaciated landscape.

Perhaps each of the 19 species mentioned are meeting one or more criteria for NOT moving back into glaciated areas: 1. Don't compete as well on assisted seed movement (jays etc) 2. Have more narrow germination/growth habitat requirements 3. Are more cold intolerant during germination and early growth phases.

That's just three limiting variables off the top of my head, some more learned forest ecologists could probably come up with more.