Native vs. non-native (was Re: all theory thread DESIGN PRINCIPLES).
hemenway at jeffnet.org
Fri Sep 1 11:43:23 EDT 2000
What I enjoy about threads that continue for a while is that often the areas
of disagreement between the posters becomes not as large as it originally
seemed. Much of what Barry says sounds absolutely true and reasonable to me,
and he's obviously got some experience under his belt. And he's cut some of
my too-sweeping generalizations down to size.
I don't mean to sound as though I think invasive plants aren't a problem.
They are, and only a fool would introduce them without assured means of
control. When I mentioned invaders coming to equilibrium, I'm talking about
using these observations as a way of controlling existing invaders, rather
than an excuse for introducing new invaders and assuming we can control
them. Some invaders do take an essentially infinite time to equilibrate, and
do a lot of damage.
There's a fine line between temporarily aggressive pioneers that can be used
for rehab or landscaping work and which will then self-destruct or can be
easily controlled, and rampant exotics. What I'm intrigued with is using
guilds of fast-growing native/exotic pioneer species mixes for on small
scales (backyards, small pastures, potential agroforestry sites, etc.) as a
kind of "hyper-cover crop" that can build soil, mine and concentrate
nutrients, act as nurse plants, maybe even smother unwanted vegetation
(careful!). I'd suggest using shade-intolerant species to minimize risk of
escape. These mixes would self-destruct by being shaded out or otherwise,
would work fast and in three dimensions (rather than 2 as with cover crops)
to increase light-gathering area and provide more habitat (perches, nest
sites, etc.), and might contain useful longer-lived species. Whether these
techniques could be used for restoration of pre-existing ("native") flora is
debatable, but for domestic landscape and rehab work they should be a very
useful tool. This is why I find Holmgren's recombinant ecologies so
interesting. Nature's already done the work for us by assembling these
weedscapes from natives and exotics; now we can select the assortments that
will meet our goals. And as Barry suggests, we'd want to design our
landscapes so that if humans leave them, they won't be a source of trouble.
I'm assuming that someone will stay around long enough to guide the flora
past the initial pioneer stage, say 5-10 years.
What I've seen in maturing permaculture sites is what I call the "system
pop." This is where in 5-10 years the canopy begins to close, the pioneers
die off, the cycles of mulch production, soil building, water retention, and
nutrient accumulation close and stay on-site (often right where needed if
the design is good), and the place just hums with insect, bird, and other
wild life (and the plop of falling food is deafening). The sites I've seen
have even used rampant exotics--because they are already all around them--to
help achieve this, but those exotics often die out, at least within the
site, as it matures. Some of the Russian olives at Flowering Tree, near
Santa Fe, are looking pretty sick, even though they are locally invasive.
Okay, I'm rambling, but these techniques seem so promising to me that I want
to encourage people to explore them.
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