message from Ewen

Tony Travis ajt at
Thu Sep 16 05:29:34 EST 1993

I'm forwarding this message to bionet.plants for Ewen McPherson.
(please reply to him as: EWEN at

> Dear plantnetters,
> As I only have infrequent access to the net these days (annual office
> upheaval, nobody knows whos moving where, when, why or if there's a
> server connection there), it's been gratifying to see that people are
> in fact posting a few paras about their work to the group. So
> gratifying that I thought I'ld better do it myself as I did suggest
> this round.
> Oops.
> Anyway, I'm just entering the final year of my PhD with Jim Harris
> at the University (sic) of East London (AKA Poly of East London AKA
> North East London Poly AKA Essex Technical College. Are we
> cynical...YES!) on the Application of Plant Strategy Theory to the
> processes of microbial succession. So what's it all about ?
> Yes, it is all a bit theoretical, and I spent most of last year
> bandying semantics between r-K theory and Grime's rCS theory, which,
> at the moment, seems to be the most promising paradigm. Initial
> results, from a fairly simple Stress/Disturbance matrix, show that,
> generally,
>     I) bacteria correspond to what in plant terms could be
> called the r- (ruderal) and S- (stress-tolerant) strategies.
>     II) fungi correspond to the C-strategy (competitors)
>     III) There may be a fourth strategy, the Survivalist-Escaper,
> which under conditions of extreme stress and disturbance, either a)
> causes the organism to go "dormant" but still live (i.e. NOT
> sporulate) or b) Sporulate. ( a) therefore becomes a survivalist and
> b) an Escaper). Why Therefore call it one strategy ? The reason that
> I choose at the moment (until I can get the bigger, more advanced
> matrix up and running and look at some biomass C and N figures), it
> seems impossible to determine simply by plating out,although
> something like Lipid Phosphate may have been useful. Anybody else any
> ideas...?)
>     (Incidentally, here's a quick Plug for a paper coming out in Soil
> Biology and Biochemistry Soon, we've just had the proofs back. Hill,
> TCJ, McPherson, E., Harris, J. and Birch, P.... Microbial Biomass
> estimated by Phsopholipid phosphate in soils with diverse microbial
> Communties, in which Myself and Tom actually try to answer that
> question. As we were developing the technique at the same time as I
> was carrying out this first experiment, we couldn't really apply it
> until we'd ironed the  bugs out)
>     (Sorry, did go on a bit there.. still young and enthusiastic
> enough about getting my name in print....)
>     IV) that there may be, to differing degrees, a possible
> Interchange of strategy. Imagine, if you will, a basic circular set
> diagram ( algebra, c.5th grade), which, if you come back to Grime's
> basic triangle, add a side to make it Pugh's strategy square and
> start ordinating everything in terms of "degrees of adaptation"
> starts to look rather nice.
>     However, consider the nature of the soil Microbial Biomass and
> what's actually there; bacteria, fungi,actinomycetes;
> Virtually Infinite Diversity if Torsvik's work is to be believed. And
> within that diversity there may exist the possibility of, for
> example, mutation caused by stress, uptake of free plasmids/fragments
> of DNA, straightforward "evolution", if you will, then, it may be the
> case that it's possible for a species to change "strategy", or be
> capable of a multi-strategy approach.
>     With me so far ? . Now, this all starts to tie in with the recent
> postings re: Do Plants have Free Will etc. To what extent can we then
> apply this question to the SMB re. Change/Interchange/Interlocking of
> Strategies. Just on first sight, and without really having a chance
> to think about it, lets ask the question this way... Is it possible
> for a plant that characterises one of the Classic Strategies (either
> r-K or rCS depending on who's model you choose) to actively change
> it's strategy (i.e. not just to survive but to flourish), and if so,
> what "motivates" this change ? What I'm saying is that, in the SMB,
> where we have generation times in terms of millionths of plant, this
> interchange is possible, that it is driven by a simple "need" for
> survival, that, simplistically, we have the organism frantically
> trying every bit of DNA it can lay its enzymes on to see if anything
> works;- trying unexpressed bits of the genome, incorporating new
> plasmids/DNA, trying to survive;- There must be a name for this sort
> of "behaviour" (and I use the term advisedly !) but it escapes me at
> the moment.
>     Now, lets go back to the basic rCS (-SE) Triangle (square), and
> examine a different model, which I have called the Model of Cyclical
> Strategy, which, may be expressed more in terms of thermodynamics, I
> think.
>     If we assume that the natural state of any community is one of
> Competition, i.e. all members of any community in competition for
> nutrients/energy, this will (eventually) reach some sort of
> equilibrium, and (given regular inputs of nutrient i.e.
> fertilisation) will be stable. Apply then a "killing event" to that
> community, either a) a Discrete, punctuated Killing (After Rykiel)
> i.e. a "disturbance" (After Grime) or b) a continuous killing event
> (i.e. "stress"), either of which will then release the nutrient tied
> up in that portion of the SMB that does not survive into the
> environment.
>     Under a), "ruderal" strategists will dominate the community, in
> this new, nutrient-rich, competition-free, environment. As ruderals
> are characterised by fast-growth fast-resproduction, the nutrients are
> soon all "utilised", which, by "evolution", will then select for
> those organisms capable at first of using the less-available
> nutrients (e.g. High MW C-cpds), which, eventually, leads back to a
> state of competition in the community, ALTHOUGH the environment has
> been changed by the action of the organisms, and may indeed resemble
> the "initial" environment.
>     Under b), "stress-tolerators" will dominate the community. Now we
> delve into semantics. What is a stress ? I've described it as this
> "continuous" killing event, which I take as a manifestation of some
> sort of alteration to the environment, which, indeed, may also
> characterise the "ruderal" event. (a "ruderal" event i.e. one-off
> physical change in the environment e.g. ploughing a field; a "stress"
> event i.e. physico-chemical alteration to the environment e.g. salt-
> flooding, severe repeated frost, etc).
>             So, these stress-tolerators i.e. those capable of
> ACTIVITY under a stressed condition dominate the community. Let's
> characterise them by such things as extreme halophiles. There, again,
> is no competition, we're in a nutrient-rich environment, and off we
> go. Chew, Chew, grow, grow, albeit a bit slower than a ruderal.
> Again, were going to have an eventual change in the environment (due
> to the usage of free nutrients and, to a certain degree, (possibly),
> mineralisation or immobilisation of nutrients. Eventually, again,
> it's all going to come back to there having to be a state of
> Competition, in this new, changed environment.
>     Big question:- Is therefore the strategy that an organism adopts
> a function of its environment, or, is environment a function of
> strategy?
>         (Aside Question ? Do stress-tolerators actually promote
> themselves by "allowing" the environment to remain stressed ? We culd
> take stress to mean some form of nutrient limitation, and, If stress
> tolerators are slow-growing,allowing some form of immobilisation of
> free nutrients, are they in fact maintaining this stressed condition
> by allowing the "environment" itself to act as some form of storage
> body  to which only these Stress-tolerant organisms are going to have
> some form of access by dint of larger genome/more capability for
> expression of constitutive enzymes/greater capability for plasmid
> incorporation/?/. Is this a manifestation of "free will" by bacteria,
> actively excluding competition ?).
>         And that's about it so far. The next stage of the experiment
> (which will be as soon as I get our autoclave fixed;- It's only been
> u/s for 6 weeks now, but, of course, the chap to sign the forms is ON
> HOLIDAY) will be following four actual species, 2 bacterial 2 fungal
> through two stress/disturbance matrices, stress being C-availability
> and Disturbance being NPK availability and seeing what happens.
>     OK, Plantland, let me have it. Am I adoptingthe wrong strategy in
> my environment ? Am I altering this environment (sic) by posting this
> diatribe to bionet.plants ? Is there anybody out there ?
>     Now, Tony, about that after-hours 80/-......
> ***************************************************
> *         "Beam Me Up, Scotty,                    *
> *               This Planet Sucks !"              *
> ***************************************************
> * Ewen McPherson, Research Assistant              *
> * e-Mail: EWEN at                   *
> * Snail : Environment and Industry Research Unit  *
> *         Department of Environmental Sciences    *
> *         University of East London               *
> *         Romford Road, Stratford,                *
> *         London E15 4LZ                          *
> *         United Kingdom                          *
> ***************************************************

Dr. A.J.Travis,                       |  JANET: <ajt at>
Rowett Research Institute,            |  other: <ajt at>
Greenburn Road, Bucksburn,            |  phone: +44 (0)224 712751
Aberdeen, AB2 9SB. UK.                |    fax: +44 (0)224 715349

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