permaculture

[loren luyendyk <loren@sborganics.com>]

Very interesting thread.  From an economical perspective, the issue of 
alternate bearing is indeed important to fruit farmers, as it seems that all 
trees of the same variety in a certain area will follow the same pattern 
seasonally.  In my experience, avocados (Hass) typically have "on" and "off" 
years which is represented regionally, and this trend can affect market price 
significantly.  An "on" year creates a glut and low market prices, as 
everyone has a bumper crop that year.  (this trend is more complicated now 
with the importation of foreign fruit)  Alternate bearing can be pretty 
extreme with avos, with harvests ranging from 15,000 lbs/acre to 2,000 
lbs/acre. 

However, if you had Hass avocado trees (the variety is important in a 
commodity market) that were unaffected by alternate bearing, you would be a 
happy farmer.  You would have above average harvests during "off" years and 
your crop would demand a higher price, as a result of limited supply.  I 
imagine plant breeders have tried to get around this one, but I am not sure 
(anyone know?).

The process of "thinning"- removing small fruit- is very common with most 
stone and pomme fruits, mainly because if you remove 1/2 to 2/3 of the fruit 
you will get larger fruit (and we all know that bigger is better :)  Thinning 
is not feasible with avocados as the trees are usually too tall, and they 
tend to drop excess fruit during the year on their own accord.  I have never 
heard that thinning was an attempt to disrupt alternate bearing.  Also, in my 
experience thinning is mainly practiced on deciduous trees. 

>From and evolutionary biology perspective, I am not too convinced of the 
>predator satiation hypothesis- this appears to be a Darwinian approach based 
>on competition.  I agree that the more fruit a tree produces the more the 
>animals will plant it (not just squirrels but birds), and it would be a 
>"reproductive advantage" to have more fruit every year.  

I think alternate bearing (in some trees at least) is based more on weather 
(and possibly that the tree simply needs rest after a big year).  Here in 
Southern California we can tell if we are going to have good winter rains if 
the coast live oaks set lots of acorns.  The trees seem to know that there 
will be good conditions for their fruit to grow into new trees and they pump 
them out.

Loren Luyendyk
805-452-8249
Permaculture Design and Education
ISA Certified Arborist #WE-7805A
www.sborganics.com
www.globalpermaculture.com
www.surferswithoutborders.com


> Date: Sun, 23 Dec 2012 14:19:01 -0800
> From: ben.martinhorst@gmail.com
> To: permaculture@lists.ibiblio.org
> Subject: Re: [permaculture] fruit trees
> 
> >
> > OK, Ben - I'll go along with that (although a reference to a study
> > confirming the specific relationship you describe would make the thesis
> > even more convincing).
> >
> 
> Sure. In general, you can look up the Predator Satiation Hypothesis. For a
> brief account in the mainstream press, see
> http://www.nytimes.com/2011/12/03/nyregion/boom-and-bust-in-acorns-will-affect-many-creatures-including-humans.html?_r=0,
> regarding last years low acorn crop in the US northeast.
> 
> For a more technical discussion, see "The evolutionary ecology of mast
> seeding in 
> trees"<http://www.jonathansilvertown.com/Site/Research_publications_files/Biolog%20Jour14(1980)%20.pdf>
> by
> Silvertown, "Predator satiation and recruitment in a mast fruiting
> monocarpic herb" <http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3043937/> by
> Tsvuura et al, or the more nuanced "Prolonged diapause of specialist
> seed-feeders makes predator satiation unstable in masting of Quercus
> crispula"<http://link.springer.com/article/10.1007/s00442-003-1381-6/fulltext.html>
> by
> Maeto and Ozaki.
> 
> I should note that it does look from a quick review of the literature that
> irregular cycling of mast production is a fair bit more complicated than
> I've presented it, with factors like hormonal variability, annual climate
> variation, and insect predation playing major roles (although it looks like
> evidence for the predator satiation hypothesis is stronger for oaks and
> weevils than it is for oaks and rodents).
> 
> Moreover, it's still far from clear to me that irregular fruiting cycles in
> apples, etc, are affected by predator satiation dynamics. I haven't yet
> found anything to suggest that it's even been researched, but since I'm
> looking through some of the literature anyway, here's a review of what
> general consensus is about alternate bearing in a number of crops,
> including apples: "Alternate bearing in fruit
> trees"<http://www.crec.ifas.ufl.edu/academics/classes/HOS6546/materials/Hort_Reviews.pdf>,
> by Monselise and Goldschmidt.
> 
> Fun stuff.
> 
> -Ben
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