permaculture

[Rain Tenaqiya <raincascadia@yahoo.com>]

Well, I've been trying to figure out how frost works for awhile, and I still 
have a lot to learn, but here's my understanding of how trees reduce frost.  
 
There are two kinds of frost.  One kind results from loss of heat to space, 
by direct radiation.  The other kind results from cold air moving downhill, 
collecting in basins, and piling up in low areas.  Trees can help prevent 
both.  
 
In the first case, trees act as a thermal umbrella, blocking heat from 
leaving the area under the tree.  This effect is reduced when deciduous trees 
have lost their leaves, but the trees still help hold in some heat.  Trees 
also hold a lot of water, and increase the ability of soil to hold water 
through the addition of organic matter.  This water also holds heat.  During 
the Winter, the ground is always warmer than the night air (at least around 
here), so blocking its release of heat to the air will keep the area above it 
warmer.
 
In the second case, trees hold warm air underneath their canopies and 
(especially if they have low branches) can prevent cold air from above or 
piling up from below from pushing the warm air out.  Trees can also form dams 
that block cold air from continuing downhill.  This means that the area below 
a forest or belt of trees can stay warmer.  However, the uphill side will 
become a frost pocket.  When cold air piles up in valleys during the night 
and eventually reaches trees further up, I am not sure how much the trees 
help to retain the warm air beneath them.  Wind conditions are an important 
factor.  Cold air supposedly behaves as a liquid more viscous than water.  
Therefore, even an open mesh of trees can divert its flow.  I have seen 
guidelines (maybe in the design manual) for how wide clearings in forest can 
be before they lose the benefits of the trees' heat retention.  Clearings 
that are too large can become frost pockets, as well.
 
I do not know how much it is possible to moderate the temperature using 
trees.  In my experience, it only seems like a couple of degrees.  However, 
plants underneath trees (or other protection) seem to respond 
disproportionately to what the thermometer says, depending on the species and 
their growth stage.  I am often amazed at how much better plants survive 
frost under trees.
 
If anyone has anything to add, I would love to hear it.
 
Rain
 



>From jnazak@yahoo.com  Wed Aug 13 14:18:42 2008
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Subject: [permaculture] Permaculture/sustainable life skills internship at
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Hi All,

I'm pretty sure there are still spaces available in
this nine-week internship. It strikes me as an
extremely good value, and I say jump on it! For about
the same as a person might typically pay for food and
a place to live, you get that, plus expert instruction
and hands-on experience in permaculture
design/sustainable living, not to mention the
opportunity to experience life in an eco-village. (I
stayed at Earthaven during the Bioregional Congress of
2005 and really got a lot out of it.)

The lead instructor is Patricia Allison, who in my
opinion is a phenomenal teacher, all-around wise
woman, and lovely spirit. It seems to me that this
nine-week internship will not only give the
participants a firm grounding in permaculture design
principles and practice, but also equip them to
jump-start and lead sustainability efforts in their
communities.

The following is from the course flyer put out by
Earthaven:

Sustainable Life Skills Permaculture Internship
at Earthaven Ecovillage (North Carolina, USA)

Sept 1 through Nov 8

Learn Permaculture by living it! This 9-week intensive
teaches the practical and cultural skills of
sustainable living, in the context of a collective
neighborhood in a developing ecovillage. Consensus,
conflict resolution, Tantra, and natural healing
complement the basic  Permaculture curriculum.
Participants form a tightly knit learning community,
combining classwork with active participation in
Earthaven life. Students receive a Permaculture Design
Certificate.

Tuition $1,900 including food, housing, and materials

*******************


Contact: permaculture@earthaven.org, 828-669-7632





*   *   *   *   *   *   *

Permaculture Design Course in Austin - 10 selected weekend days Sept 27-Nov 22
Other classes and events throughout the year

Austin Permaculture Guild
512-619-5363 / austinperm@permie.us
www.permie.us