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PostPosted: Tue Jan 14, 2014 2:07 pm 
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Location: Germany
Dear bamboo friends,

You may be interested in my theoretical considerations about competition in a bamboo stand. Comments and first hand reports are welcome.

Regards,
Raimund


Reduction of intraspecific competition in "moso" bamboo forests of South China?

The "moso" bamboo species can be very invasive in South China and even suppress other forest vegetation. "Moso" takes advantage over trees, when it comes to interspecific competition, meaning the competition among different species. But "moso" plants also compete with each other. In this case the term intraspecific competition is used.
When the intraspecific competition is stronger than the interspecific competition, the expansion capacities of invasive species should be consequently reduced. Therefore it is important to understand how invasive species are able to lower the intraspecific competition to a point, where individual plants will not weaken each other too much.
A new research in this field was just published¹. With the aid of sophisticated statistical methods, four groups of bamboo culms, with different ages, were studied and it was concluded, that younger culms were found more frequently in the neighborhood of trees (interspecific competition) than of older culms (intraspecific competition). According to this study, the strategy bamboo plants use to reduce intraspecific competition consists in maintaining distance from each other, but at the same time advancing against trees.
This research certainly deserves much credit, because of all the statistical methods employed, but from a biological perspective, several questions remain unaddressed. It is confusing, for instance, that the study always mentions bamboo plants of different ages, when in fact only culms of different ages were considered.
The careful distinction of terms between "bamboo plants" and "bamboo culms" is of importance, because otherwise it's impossible to distinguish between intraspecific competition and the competition of the culms of one individual plant. It's certainly reasonable to suppose, in relation to competition of culms of an individual plant, that in the course of evolution the ideal distance between culms has been developed. And that has nothing to do with intraspecific competition and could be regulated by the bamboo plant in the same way as trees regulate the ideal distance between their branches and leaves.
Unfortunately we have no possibility to find out, with justifiable resources, how many individual plants constitute a bamboo plantation. If it turned out, in the study case, to involve only a few large individual plants advancing against the trees, then the result of the statistical calculations would not have shown us the reduction of intraspecific competition, but rather only the big average distance between culms, characteristic for "moso" plants.
The study doesn't mention, how the supposed bigger distance between culms of different bamboo plants would be regulated. It may be worth to have a look on a plant native to North America called "pale jewelweed" (Impatiens pallida). This weed behaves altruistically towards kin, avoiding any attempt to overgrow them. The recognition of related plants happens through the rootsystem². It may be possible, that also in the case of "moso" bamboo a reduction of intraspecific competition occurs through altruism towards closely related plants or even genetically identical bamboo plants. Considering evolutionary biology this would make sense, because when a plant cares for the survival of kin, it passes on to the next generation a large number of its "own" genes, not only through the direct descendants, but also through the descendants of their relatives. So, a lot of items remain to be studied.
As bamboo gardeners, we are constantly dealing with the three phenomena: interspecific competition, intraspecific competition and culm competition of the same plant. According to some testimonials in the forum of EBS - Germany, culm competition and intraspecific competition, which occur in the unnatural environment of a rhizome barrier, can be so severe as to compromise the vitality of the whole plantation.
Even planting only one single plantlet inside a barrier, to avoid a clogging with rhizomes before the dreamed large culms sprout, sooner or later the intraspecific competition will occur. The bamboo plant can decay into competing individual plants, caused by dying of old rhizome connections or by damages caused by winter, root voles or the actions of the gardener.
One can interfere in different ways into the so established intraspecific competition relations between plant fragments. A gardener would prefer to spare the larger culms and eliminate the thinner ones. As a consequence, smaller fragments with thinner culms would enter a downward spiral and would disappear sometime from the rhizome barrier. So the tendency of the plantation to decay into fragments would meet the opposing tendency to remain only one fragment.
For bamboo farmers the situation looks different. Also a "moso" grove in its natural environment will decay into fragments, caused by dying of old rhizome connections. But in this case the larger culms would be removed on a regular basis to be used. Supposing, that larger culms are produced in the larger fragments, the intraspecific competition in relation to smaller fragments would be reduced, resulting in the survival of a large number of smaller individual plants. Since we don't know of how many individual plants a bamboo forest is composed of, one can't judge if such a dynamic could lead to a yield reduction for larger culms.
As a gardener, one has to deal with interspecific competition, for instance, in the case of planting together, inside a common barrier, two different bamboo species or a ground cover plant and a bamboo. Two species of Phyllostachys have supposedly very similar environmental requirements. They occupy the same ecological niche and therefore they compete even more. In many cases the gardener will have to act in a regulating manner, to avoid that the weaker species is eliminated inside the barrier. On the other hand, a ground cover plant and a Phyllostachys occupy quite different ecological niches. This reduces the interspecific competition and there are good chances to find a suitable ground cover plant to coexist with a Phyllostachys, provided that sufficient light reaches the ground.

Original title:
DÜKING, R.: Minderung der innerartlichen Konkurrenz in südchinesischen Mosobeständen? Bambus Journal, Ausgabe 4/2013, 24. Jahrgang, S. 18-19

Translation: Hans-Jürgen Kleine, Florianopolis

References:
1. H.S. Sandhu, P. Shi, Q. Yang: Intraspecific spatial niche differentiation: Evidence from Phyllostachys edulis. Acta Ecologica Sinica, Volume 33, Issue 5, October 2013, Pages 287-292
2. Murphy et al. Kin recognition: Competition and cooperation in Impatiens (Balsaminaceae). American Journal of Botany, 2009; 96 (11): 1990


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PostPosted: Thu Jan 16, 2014 1:14 am 
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Rai - I have pondered your posting and wonder how they can make a conclusion with so many variables not dealt with. How do feel about the science there?

I assume we know little to nothing of where the various Phyllostachys species were once native. Is that your understanding? Therefore can we conclude much on the "intent" of rhizomes outside there native haunts? Or are these adaptives reactions? Excuse me I am no science expert, just the puzzlings of an interested observer.

I think of a programme I saw a few months ago where they - if I remember correctly - tested the uptake of rotting salmon on trees in forests adjacent to salmon rivers in the Pacific northwest. They left dead salmon with measureable radioactive isotopes under trees and found the tree nearby not only absorbed the nutrients from the salmon but shared it through root grafts with neighboring trees. I wonder if these isotopes could be used to "see" what is happening underground with bamboos? I suppose it could very well degrade too quickly (?).

johnw - an incredible day here at +10c. More rain tomorrow, Friday and Saturday. More mild weather like this and we will be in big trouble.

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PostPosted: Thu Jan 16, 2014 3:35 am 
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Quote:
How do feel about the science there?


Hi John,

The cited study seems to be very valuable concerning the applied statistical method. But I’m not a mathematician and I’m not able to judge this method.

Quote:
They left dead salmon with measureable radioactive isotopes under trees and found the tree nearby not only absorbed the nutrients from the salmon but shared it through root grafts with neighboring trees. I wonder if these isotopes could be used to "see" what is happening underground with bamboos?


The Japanese Koichira Ueda excavated about 30 bamboo plants and found out that the life span of Phyllostachys rhizomes is approximately 10 years. Thus after this time span the rhizomes cannot conduct nutrients anymore. There are studies with radioactive isotopes, but I don’t know if the nutrients are conducted about the whole length of 10 rhizome generations.

I personally am interested in the issue „regulation of culm density“ because I want to keep a Phyllostachys in a rhizome barrier long-lasting vital without cutting off rhizomes.

For a bamboo farmer this issue may be interesting regarding the harvesting method.

Rai

PS.: In Hannover minimum temperature this so-called winter -5°C. More mild weather like this in Gearmany and we will be here in big trouble too.


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PostPosted: Thu Jan 16, 2014 1:52 pm 
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Rai - Maybe you can explain how Phyllos stay in such good shape when in a barrier "bed". I presume those stunning clumps at Kimmei are in these too. I see this enclosure as similar to a Phyllo in a pot and here a Phyllo in a pot needs to be potted up anually to stay vigourous and healthy. Do feeding roots travel down and under the barrier into uncontained soil? What kind of fertilizing regime is necessary for such enclosed Phyllos.

Vigorous Sasas and Indolacalmus spp. must be even trickier to keep in perfect health; at least here they are not at all happy in pots.

johnw - +5c, drizzle.

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PostPosted: Thu Jan 16, 2014 4:08 pm 
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John – I cannot answer your questions. May be that Jos van der Palen has a high groundwater level. In my garden (sandy soil) I found very few roots travelling down under the barrier of 70 cm into the uncontained soil.

In the Internet forum of the EBS-Germany a majority is of the opinion that it is not possible to keep a Phyllostachys in a barrier „bed“ in the long term without cutting and removing rhizomes.

I myself am experimenting with the following barrier „bed“. I imagine that the rizomes are directed inside the barrier „bed“ where they find conditions like in a natural bamboo forest.

Rai


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PostPosted: Fri Jan 17, 2014 11:34 pm 
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Location: Landisburg,PA USDA zone 6b
Rai,
how deep is your barrier? I would think that leaning it outward slightly from the bed would also keep the rhizomes from going under it. And if it gets filled I would imagine removing some culms and rhizomes would not hurt to keep it healthy and looking clean. This is going to be very nice in a few years. Nice job.


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PostPosted: Sat Jan 18, 2014 5:17 am 
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The barrier is 70 centimeter (27,6 inches) deep. I never had problems with rhizomes going under my barriers. My intention is to direct the rhizomes inside. I hope that the rhizomes inside the barrier „bed“ reduce their competition like in a natural bamboo forest.
Cutting the rhizomes only would induce an unnatural intense branching oft he rhizomes. If the barrier „bed“ gets filled I intent to remove culms, but I don’t want to remove rhizomes (I’m too old for this kind of work :) ).
This is the aim of my experiment. May be that my method also can prevent rhizomes from going under the barrier.

By the way it is not possible to lean the stiff barrier outward because the developed view of cone is not a rectangle.

Rai


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PostPosted: Sat Jan 18, 2014 7:40 am 
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The problem I see with barriers is that rhizomes will eventually end up wrapping around the edges of the barrier creating a situation where lots of culms are produced right on the perimeter where the barrier is, and the continual build up of root/rhizome mass inside the barrier will eventually lead to root bound conditions. It's just like in a pot where the rhizomes will push on the outsides, and it will become tough to keep the bamboo well irrigated once it establishes.

I believe bamboos are much happier without any barriers.

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PostPosted: Sat Jan 18, 2014 10:29 am 
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Quote:
I believe bamboos are much happier without any barriers.

I agree with you.

Quote:
The problem I see with barriers is that rhizomes will eventually end up wrapping around the edges of the barrier creating a situation where lots of culms are produced right on the perimeter where the barrier is

I hope to avoid this by the special construction of my barrier.

Quote:
and the continual build up of root/rhizome mass inside the barrier will eventually lead to root bound conditions.

In a natural bamboo forest there is no harmful accumulation of rhizomes (see my article above). I hope that I can imitate the natural situation. It’s only an experiment and may be that you are right.

Rai


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PostPosted: Sat Jan 18, 2014 11:09 am 
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That kind of flexible barrier that can easily change form could work if the area is large enough for the bamboo not to get overcrowded. I guess each of bamboos has specific rhizome spread and density in 10 year cycle. If planned correctly, this thing should work. There might be other factors, like nutrients and water availability, growing location,... that would also affect the 'rhizome mass factor'. I think if you would take 10 years old bamboo, check the diameter of it's spread and divide it with 3 or 4, you might get size of enclosed area in which bamboo should grow without overcrowding issue.

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PostPosted: Sat Jan 18, 2014 4:21 pm 
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I wonder if the culm density is more important than the size of the area. I suppose that each area can get overcrowded. Large areas should get overcrowded later than small areas.
In my experiment I want to imitate the culm density of a natural bamboo forest.

Rai


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PostPosted: Sun Jan 19, 2014 4:05 pm 
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Rai - By roots I mean to say exactly that as opposed to rhizomes. Surely some roots can grow long enough to penetrate deep down below the barrier depth and find extra moisture and nutrients don't you think? Or is the oxygen supply so bad at such depths that that is a limitation.

That is a fantastic amount of work you have done constructing that bed. Here we would need a good quantity of TNT!

johnw

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PostPosted: Sun Jan 19, 2014 4:43 pm 
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John - In my garden (sandy soil) I found very few roots travelling down under the barrier of 70 cm into the uncontained soil. I'm in doubt whether this is sufficient to supply the bamboo with enough water and nutrients. Lucky who has a high groundwater level!

By the way my barrier is aged 6 years. I hope that I can report the results of the experiment in several years :) .

Rai


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