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permaculture - Re: [permaculture] Edge Effect

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  • From: "Scott Pittman" <scott@permaculture.org>
  • To: "'permaculture'" <permaculture@lists.ibiblio.org>
  • Subject: Re: [permaculture] Edge Effect
  • Date: Sat, 3 Feb 2007 19:32:06 -0700

When I first learned of edge in was in the context of strip cropping
different pulses to increase yield. Planting Oats in alternative strips
with wheat increasing the yield significantly more(up to 20%)than does
either crop planted alone.

Edge effect was a problem with agronomists when they tried to calculate
yield of a given field and took their samples from the edge (lazy research)
only to find that their predictions were consistently wrong. The edges of
fields have higher yields.

So where the pavement meets the field, is an edge just as the meadow/forest
edge.

There are some great papers on "edge effects" or "boundary effects" on
wikipedia.


Scott Pittman
Director
Permaculture Institute
-----Original Message-----
From: Rich Blaha [mailto:rich@mossbackfarm.com]
Sent: Saturday, February 03, 2007 12:57 PM
To: permaculture@lists.ibiblio.org
Subject: Re: [permaculture] Edges - Re: permaculture and science

As Robyn mentions, the 'Edge Effect' is a long standing ecological term.
Interestingly enough, many in the conservation biology field have a negative
view of this phenomenon in its effect upon sensitive species.

In my work in both Tallgrass Prairie and northwestern US Old growth forests,
the fragmentation of habitat allows for invasion of these habitats by
'generalist' species, generally to the detriment of a habitat specialist
species. In forests, increased edge increases the habitat for Marbled
Murrelet nest predators, such as Crows, Ravens, and Jays. In prairies, the
edge increases habitat for nest parasites like Cowbirds.

An edge is considered ecologically productive because it is a location that
can tap into the resources of 2 different environments. The shade,
coolness, fungal diversity, and biomass of the forest; and the sunlight,
fossorial rodents, and nitrogen fixation of the meadow, for example.

Or to use the shoreline example, the coastal headlands, with their moisture
and milder climate than inland locations; and the nearshore ocean, with its
seawood and plankton production. Add the destructive power of waves, which
bring forth a bounty of dead and dying flotsam with each tidal cycle, and
sloughs and brackish water (an edge habitat unto itself), which harbor an
entirely different, and very productive, ecosystem.

As habitat generalists, humans' preference for edges allows us to tap into
the productive capacity of ecotonal environments (a la the forest garden).
It's just nice to have options....

Cheers

Rich
Mossback Farm






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