permaculture

[Paul Cereghino <paul.cereghino@comcast.net>]

Hey Naomi,
Robyn Francis wrote to us about your science experiment -- some quick 
thoughts (not that I've ever done something like this before..)
Oxygen is neither created or destroyed, it just changes form.  There 
will be a finite pool of O2 in the bottle.  The task is to convert C02 
to O2 and organic matter while limiting aerobic metabolism.  The only 
available mechanism is photosynthesis.  Simultaneously, metabolism will 
be taking O2 to break down carbon compounds... most of that metabolism 
would be happening in the soil.  Since you can forcefeed nutrients to 
the system the whole 'healthy soil' thing is just a metabolic O2 drain 
for this system.  (i.e. the microcosm creates advantages for strategies 
that are not sustainable in the real world -- the length of the test and 
what you can do to prime the system pretest will be critical.)

- temperature and light levels will have a strong effect on your 
microcosm performance -- you will need to match your system to
- if you can use electricity you could circulate air through a 
aquaculture system and get photosynthesis from algae and vascular 
plants.  I wonder if you could imbed a little solar air circulator in 
there to circulate low oxygen gas layers around plant leaves - I bet 
insects could provide some air circulation service, but they'll be 
breathing oxygen too!
- if the light source is directional you'll want to reflect all light 
back into the bottle... particularly if light during the test is 
artificial and below saturation.
- for didactic purposes I would have your students construct a 
conceptual model of factors that will positively or negatively affect 
gasseous oxygen concentration.  Keep an eye out for feedback loops.
- Under elevated temperatures, plants with a C4 photosynthetic 
metabolism have higher photosynthetic rates.
- I am leaning towards a mineral soil wetland system with LOTS OF LEAF 
AREA and a nutrient soup.
  -  anaerobic metabolism in sediments may minimize aerobic metabolism 
that produces CO2.. you may get negetive feedback loops with swamp 
gasses if the experiment runs too long without gas exchange.
  -  in the saturated sediments or hydroponic system you can remove 
nutrient and water supply limits to photosynthesis.
- the degree to which plants are well established and acclimated to 
environmental conditions at the beginning of the test will count for A 
LOT!!  Transplant shock or changes in temperature or light level will 
really bog you down... you want the whole system buzzing along at full 
speed at the beginning of the test.
-fogging in the bottle may reduce light penetration

Paul Cereghino
Olympia, WA



wrote:

> I just received this request, please send any creative ideas direct to Naomi
> Thanks Robyn
>
> ------ Forwarded Message
> From: Naomi Berlin <berlinnr@hotmail.com>
> Date: Thu, 15 Feb 2007 21:46:45 -0500
> To: <permed@nor.com.au>
> Subject: terrarium
>
> Hello,
>
> I am a high school biology teacher in Toronto, Canada, and I am trying to
> help a group of students with a science competition.  The goal is to create
> a closed terrarium using a 1L pop bottle, that creates the most oxygen
> possible.  We are allowed to include any plant species, and anything
> necessary for the plant to survive.  We can use soil, insects worms...  I
> was wondering if you have any ideas for us?
>
> Thanks,
>
> Naomi Berlin
> Science Department Head
> Richmond Green S.S.
>
>
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