Re: those darn acorns!
david feix wrote:
>
> This same principle is now the method of choice for
> regenerating oak woodlands here in California,
> especially where they have been lost to construction
> and planning approval of construction mandates
> mitigation. It has been proven that facilitating
> natural self seeding is actually more successful long
> term than planting out nursery grown specimens. This
> method works especially well for Quercus agrifolia, Q.
> douglasii and Q. lobata. Mulch utilizes any healthy
> trees which might have been removed or trimmed as part
> of construction, and all debris is shredded by a
> chipper, and then applied as a 6 to 12" depth all
> around the perimeter of the existing tree canopy. The
> soil around these oaks is usually also fenced off
> during construction, to minimize root compaction. It
> has been found that allowing direct self seeding will
> get more, healthier and quicker growth than planting
> out 5 or 15 gallon size nursery grown trees. There is
> also an incredible mortality rate to young seedling
> oaks, as they are very attractive to rodents in
> particular.
David
There has been a considerable amount of work done here on regenerating
forest after opencast coalmining.
Among several facts which emerged was first the necessity of preserving
topsoil from the site and replacing it unmixed on top of subsoil fill.
This was naturally vastly more effective than just putting back subsoil,
but also perhaps more surprisingly a great deal more successful than
replacing a mixed layer of sub and topsoil. No doubt there was a good
deal of natural seedling growth from this replaced topsoil layer, but
this was also supplemented by adding extra seedlings from elsewhere.
In this regard (which largely equates with the findings you quote)
seedlings dug from adjacent undisturbed bush were always more successful
in establishing themselves than much larger nursery-raised seedlings
grown in standard potting mixes.
The third one was that the use of artificial fertilizers to boost growth
was only successful if exotics were being introduced. With native
species from the area it actually depressed growth.
With some knowledge of how natural soils actually work it is easy to
explain all these observations. We now know enough about their
organization (now called the Soil Foodweb) to be able to predict that
plants growing in them depend for much of their food supply on a regular
association of helpful organisms, particularly specific fungi which form
with the roots various types of mycorrhizae.
These findings suggest that this association is most successful if it
has the chance to form as soon as the seedling has emerged, and nursery
stock grown in non-soil sterile mixes are greatly disadvantaged so they
only flourish if if their food is artificially boosted. However
artificial fertilzers added to natural soils where plants already have
their associations established almost certainly produce their adverse
effect by destroying at least part of the soil flora, due to high
concentrations of ions in the cell sap which the organisms are unable
to cope with.
Your comment on the very high mortality of seedling oaks is another very
natural phenomenon. I have seen on the slopes of Mt Ruapehu the growth
of young Southern Beeches (Notofagus) in a clearing where a parent tree
had fallen and one certainly could not put a foot between them, but I
have no doubt at all if one came back ten or twenty years later these
hopeful youngsters would have been reduced to one or two winners and the
others would have perished. What would have occurred would be a
competition for light in which the tallest would be the winner and shade
out the rest - a very good example of Darwinian selection, ensuring the
survival of the best gene kit from a very large sample of material and a
sufficient root run for the winner. A most effective way of ensuring a
healthy forest.
As to your acorns, there is also another agenda operating here. Food
producing plants regularly bear far more seed than they could possibly
use, apparently as nature's means of sustaining the animal population.
And it is not only seed, I remember a TV program about the English oaks
which are known to lose a high proportion of their spring leaves to all
sorts of leaf-eating insects. Around midsummer when all these have
undergone their year's development and persumably pupated the tree
produces a second crop for its own use, which hang into Autumn virtually
undamage.
Interestingly, as I mentioned the young beech trees were growing in a
natural clearing. Breaks in the canopy are the only place one finds
seedlings in such a forest and evidently the increase in light due to
the old tree falling gave the necessary trigger for them to get going.
This of course avoids trees trying to grow beneath the shade of their
elders where they would make the planting unnecessarily crowded.
One can marvel at the complexity of the undisturbed system and regret
the mess man tends to amke of this with his lack of understanding or
callous disregard for nature's very good and long-proved arrangements.
Moira
--
Tony & Moira Ryan <theryans@xtra.co.nz>
Wainuiomata (near Wellington, capital city of New Zealand)
