[APWG] Percentage cover of each species to find constants

[tyju at xmission.com]

I think that the Petri dish analogy is quite apt.  The complex  
interactions between species which determine dominance as the macro  
scale are almost as obscure as those at the microscale, if not more  
so.  I agree that detailed canopy cover data are critical for  
documenting and assessing plant ecology dynamics in the face of  
disturbance, invasion and restoration.  Ty Harrison

Quoting Craig Dremann - Redwood City Seed Company <Craig at astreet.com>:

> Dear Wayne and All,
>
> I apologize if you thought I was not answering your questions-- I will try
> and elaborate further in this email.
>
> WAYNE: I do think of the whole earth as a huge Petri dish, but I cannot
> understand
> what you are talking about. I asked "What ecological condition(s) are
> revealed by cover?"
>
> CRAIG:  The whole world is a giant petri dish, because all teresstrial
> life is closely confined in an extremely thin layer on the planet.  If we
> shrank the planet to the size of a petri dish, all life would be a layer
> about 30 millionths of an inch thick.
>
> In terms of plant interactions, if you think of the local ecosystem you
> are working within, as one big giant petri dish, then the plant
> interactions become more readily evident.   The ecological conditions
> revealed by cover--cover is what shows you the interactions between the
> two species of native plants, or between the native plants and the weeds.
>
> What is seen on a regular petri dish is the battle between a pathogen and
> an antibiotic, and this battle is played out on a macroscopic scale in the
> ecosystem cover interactions.  Every terrestrial non-riparian plant as it
> grows, gives off natural herbicides in greater or lesser amounts and
> potencies, that act like antibiotics.
>
> You can do experiments by adding native seeds as an antibiotic to a weed
> patch, such as California poppy seeds.  Or add fertilizers to benefit your
> preferred antibiotic/herbicide/allelopathy-producing plants, to change the
> species composition of the weed cover.  You can then use cover to measure
> the changes you made by adding the natives or the fertilizers, and you can
> see some of those results  at http://www.ecoseeds.com/arastradero.html
>
> I am translating from the microscopic scale--what I have been working on
> for almost 20 years--to the macroscopic scale.  In my petri dishes that my
> lab cultures pathogens and then uses to discover new plant antibiotics
> against pathogens like MRSA, we measure the zone diameters of the
> antibiotics killing the pathogens, that you can see at
> http://www.ecoseeds.com/mrsa.html.
>
> The same thing happens on the macroscopic scale, where one plant inhibits
> another--we just have not gone out yet to measure the battle that is going
> on out there each year, just like the pathogens and the antibiotics in the
> petri dish.
>
> WAYNE: Do you think that ecological conditions that give rise to
> ecological phenomena are not important to the subject at hand?
>
> CRAIG: Cover measurements, especially when done on a very fine scale, is
> your very best tool to measure plant interactions.  When I do a transect,
> I measure every single species, even if it is only a single plant within a
> 100 foot long transect.
>
> WAYNE:  Please preserve the string of relevant emails in the future; I'll
> greatly appreciate not having to hunt up previous emails to recall the
> context and issues under discussion. Thank you.
>
> CRAIG: Sure.
>
> Sincerely,  Craig Dremann (650) 325-7333
>
>
>
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