Correlation versus coupling

[ap.vanduijn]

Dear Anastassia, dear all,

In both Life Stability and BRE you seem to use the terms strictly, tightly or rigidly correlated (in G&M 2004 also auto-correlated) as opposed to chaotic, non- or weakly-correlated. 

I struggle to apply these terms. Charles Parrow in his book Normal Accidents (1984, p. 89) instead uses the engineering terms tight coupling and loose coupling. In table 3.2 (see attachment) he lists tendencies for tight as well as loose coupling. I first started looking into these terms because the tendencies of loose coupling seemed to link up well with somatic flexibility (sensu Bateson), which allows for the acclimatisation of motile animals to a range of 'outer' environmental conditions (e.g. temperature and altitude). Initially I thought the terms tight correlation and tight coupling and the terms weak correlation and loose coupling were interchangeable. However, after a closer examination this does not seem to be the case. Currently the application of Parrow’s terms seem to be more practical, but I may be wrong and as the terms are crucial to my understanding of the regulation of the local environment by immotile ecological communities and the regulation of the inner environment by motile ecological communities (host plus microbiome)  I would like to discuss this.

(1) You refer to higher plants as weakly correlated. However, when I try to categorise them according to tendencies mentioned in table 3.2 they seem tightly coupled with deliberately designed-in redundancies (e.g. leaves, branches, roots). That is how I currently understand the lack of correlation between respectively leaves, branches, and roots that you point out.

(2) You refer to ecological communities as rigidly correlated. When I try to categorise them according to tendencies mentioned in table 3.2 they seem tightly coupled with deliberately designed-in buffers (i.e. the biotic regulation reservoirs from figure 3 op page 5 of G&M 2020). As you point out these communities function as rigidly correlated in particularly once the biotic sensitivity threshold has been crossed. However, if the perturbation of the local environment crosses the threshold of admissible perturbations this correlated functioning will seize (i.e. the ecological community shifts from a normal community to a decay community).

(3) You refer to individual animals as strictly correlated. When I try to categorise them according to the tendencies mentioned in table 3.2 they seem loosely coupled, which would allow for somatic flexibility (sensu Bateson) or a secondary feedback system (sensu Ashby) in which feedback is linked to feedback among its various subsystems. According to Ashby this is what enables an animal to resist systemic disruptive effects rather than only local disruptions (e.g. a cat moving away from the fire).

(4) You refer to anthills and beehives as weakly coordinated (i.e. similar to true multi-cellular organism). I am a bit confused by this comparison to multi-cellular organisms as animals, which are multi-cellular are strictly correlated. When I try to categorise them according to the tendencies mentioned in table 3.2 they seem loosely coupled, which would allow for social flexibility (sensu Bateson).

I would very much like to hear your take on this.

Best,

Arie

[Anastassia Makarieva]

Dear Arie,

Anthills, beehives and plants, as well as multicellular bodies and local ecological communities, are internally correlated objects in that sense that their parts do not compete with each other but act in a coordinated manner to ensure higher competitiveness of the object as a whole.

Among these internally correlated objects, anthills, behives and big trees (with many leaves) can be characterized as weakly correlated in that sense that their multiple uniform parts function approximately independently of each other such that to their functioning the law of large numbers can approximately apply. E.g. the fact that big trees have a large number of uniform photosynthesizing units (leaves) makes it possible for the tree to stabilize its total photosynthetic flux.

The multicellular bodies of animals have a different design with just a few one-of-a-kind parts like the internal organs, legs, arms etc that are all indispensable. While a tree can lose much of its biomass and still survive (because its different parts are only weakly correlated), for an animal it is impossible.

I hope that this description, in the biotic regulation context, could be helpful for your comparisons with the available frameworks in other scientific fields. Until their relevance for solving the research tasks of BR becomes clear to me, I would prefer not to delve into addressing other frameworks and terminologies here because without very substantial time investments such a consideration would cause confusions rather than clarify anything.

Below is a photo of an old tree on the shoreline of the White Sea, which has lost most of its wood biomass but still thrives. (It is early spring so no green leaves on the upper branches but trust me they will be there.)

Best wishes,

Anastassia

пт, 8 янв. 2021 г. в 16:32, ap.vanduijn <ap.va...@gmail.com>:

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[Arie Pieter van Duijn]

Dear Anastassia,

Thank you for your explanation and the nice pictures. I'll give it some more thought and will get back to you if I think I can make the point that my line of thought has relevance for solving the research tasks of BR.

Best regards, Arie

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Arie Pieter
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"Ambulator nascitur, non fit" (Thoreau 1854)