What is a dynamic accumulator?

I’ve been working on my literature review this week and I gotta say it is one of the hardest papers I have ever written.  The chosen topic, dynamic accumulators, is term that is thrown around quite often in permaculture texts and I have yet to find the origin of the term.  I have gone down paths of hyperaccumulation of metals, of geobotany and of biogeochemistry. Of plant nutrition and plant physiology, agroecology and agroforestry.  All very interesting disciplines.  I have been searching through the primary sources (Hemenway’s Gaia’s Garden, Jacke and Toensmeier’s Edible Forest Gardens, Martin Crawford’s Creating a Forest Garden and Robert Kourik’s Designing and Maintaining your Edible Landscape Naturally) and into their bibliographies to find secondary sources which may prove useful for the review.  Part of the trouble, is that there are many definitions, all similar, and all fairly vague, to explain dynamic accumulators.  Now, these guys were not writing for an academic audience, so that is why they are vague, though Hemenway is a professor in Portland which is pretty cool.  Maybe I will ask him to be on my committee 🙂  I digress.  

So, the idea is that there are plants which bring up minerals (both metals and non-metals….Ca, Mg, N, P, K, and so forth) into their tissues and then can be “chopped and dropped” onto the topsoil, releasing these metals and nutrients into the soil for other plants to access.  Digging further into the academic literature, I have found some interesting papers on “nutrient uplift” and “nutrient pumping” by trees like Cornus florida (aka dogwood).  Incidentally, a Clemson grad, Dr. TH Nation wrote a paper on dogwoods and land snail diversity and looked at how calcium levels under these trees might be linked to snail populations (due to the need for calcium in their shells).  I am interested in not only the chemistry of the plants but also the morphology.  Many times, plants like chicory or comfrey are listed as dynamic accumulators because they have a long taproot.  Are these plants all similar in a protein they possess or a chelation mechanism that is bringing these elements into their tissues? Are they in similar genera?  Do they even accumulate these minerals at all? All plants accumulate Ca, Mg, P and K, what sets these apart?  These are some of the questions I have set out to try and answer.  Another field came to the fore this afternoon, as I was researching, which is biodynamics.  This is a school of thought/philosophy/cosmic framework/movement from Germany by a guy named Rudolf Steiner.  It is not quite scientific, in the same way that permaculture is questioned about being a science, so I feel like I am dancing on this line of what is scientific and what is not. Sometimes I feel like I’m reading more about the philosophy of science and not about plant or environmental science 🙂   (See these links from Washington State for more information about science and pseudoscience or the origins of biodynamics.)

I am ready to get this lit review done with and move into doing some experiments in the greenhouses, growing out some of the dynamic accumulators and measuring the levels of Ca, Mg, N, P, K and so forth.  Another idea I am working on is to visit permaculture sites in South Carolina, and collect soil samples from them, especially if they have some of these plants growing already. That way I will also have a diversity of soil types to compare, since the soil in the Upstate is more clayey and Lowcountry soil is more sandy.  Eventually, I’d like to grow out dynamic accumulator plants (should i put that in air quotes, I don’t know) and then use them as top dressing on vegetable crops with a control plot and measure differences in soil, leaf and vegetable concentrations.  Some other “dynamic accumulators” are tree species, such as maples, hickories and walnut, so a soil collection under these trees might show elevated levels of these accumulated minerals?  We will see.

Another permaculture researcher, Rafter Ferguson, has a nice website called Liberation Ecology and he has just completed a site visit of a lot of permaculture sites in the Midwest and Northeast.  He published two new articles in the most recent Permaculture Activist. One is “People’s Science or Pseudoscience” where he argues for a People’s Science, bringing more science-based research into permaculture.  The other is “Critical Questions, Early Answers”.  Both can be downloaded here. Another article that he published in Agronomy for Sustainable Agriculture (that I referenced in an earlier post) cites a source where the label “pseudoscience” has been applied to permaculture.  He makes a convincing argument for why we, who consider ourselves permaculturists, should care, in the People’s Science article. 

An interesting thread that I found recently is on a garden blog hosted by the Washington State Extension.  Dr. Linda Chalker-Scott wrote a series of articles on permaculture and they (and the comments sections) are especially telling.  The first post is “Beginning a Discussion” about invasive species.  The next presents a critical review of Hemenway’s Gaia’s Garden and is one example of where the notion of “dynamic accumulators” has been chalked up to “pseudoscience”. In the next post, she critiques sheet mulching and in the final post, she challenges someone to write a new book on permaculture in collaboration with a scientist. I (of course) have more to say on this, but will save my laptop battery and try to wrap this up. 

(Note: Dr. Chalker-Scott writes about other horticultural “myths” on her blog The Informed Gardener.)

If you don’t have enough to read yet, check out Chelsea Green Publishing House. They have an amazing collection of books on permaculture, organic gardening, natural building, homesteading, energy and water conservation and so much more. 

I still owe ya’ll a run down of the SAEA conference, so I’ll muse on that next time. 

Til then, peace and parakeets.

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