[APWG] Weeds vs. land vulnerability? perspectives on exotic plants?

[Craig Dremann]

Dear All,

I've been reading for decades about the concerns about current weed
problems and future weeds, etc., and would like to propose another
perspective that might be useful, and of interest to land managers.

In the lower 47 States (excluding Florida), perhaps the issue is of land
vulnerability and "ecosystem vacuums" rather than the weeds themselves?  

When particular elements of the original native non-riparian ecosystem
understories have been removed, perhaps that will allow any weeds to
colonize into those "ecosystem vacuums"?  

California is the perfect example of this---where 99.9% of the native
perennial grass component was removed 50-150 years ago, and now we have
over 1,000 exotic species infesting at least 50,000 square miles
solidly. 

So what if we checked each of the 47 states, to measure four things: 

1.) What percentage of the native grass understory cover is left?
2.) How much intentionally planted exotic plant cover is there?
3.) How much accidental exotic cover ("weeds") is there?
4.) What is the remaining percentage, that lacks all three: no native
grass understory, plus doesn't have the intentionally sown exotics nor
the weeds yet?

Could that reamining percentage or "ecosystem vacuum" be the vulnerable
portion that will potentially be infested by some exotic, at some time
in the near future?  

I've added some of this speculation, plus data from the Great Basin and
Rocky Mtn. states, at http://www.ecoseeds.com/megatransect.html

It would be very interesting to test this hypothesis with data from
other states, especially the NW, SE and East coast.  Any land managers
with vegetation transect data, might be a good place to start?

Sincerely,  Craig Dremann, Redwood City, CA (650) 325-7333