What exactly does it mean to say that a plant is a dynamic accumulator?

So I keep hearing about plants that are dynamic accumulators, but am still unclear about exactly what that means, could some kind person please educate me? =)

~Dusky

generally they either have very deep tap roots or are very good at bringing up nutrients from deep in the ground and storing them in their leaves, which then fall or are used as mulch and feed the plants..you can also plant them near things like trees and shrubs and even when the rootlets die they leave humus in the soil that feed the roots of your larger plants.

If you like figs, they will probably do well.

A long list of plants I first noticed in Robert Kourik's Designing and Maintaining your Edible... which he assembled from  Cocannouer, Easey, Gibbons, Hill, Pfeiffer, and other sources, which appears to have been revamped by Hemmenway in Gaia's Garden... I don't know anyone who really knows how much of that information is accurate or based on some kind of physical investigation.

So my opinion is that the concept and definition are somewhat imprecise and if I were the precise type I would break it down into three different phenomena...

1. The presence of a deep root system that has the potential to reach nutrients not available to plants with shallower root systems.

2. Some physiological tendancy to accumulate more nutrients than necessary for metabolism and health... (all plants tend to be dynamic accumulators of potassium - others have special fuctions they use it for like the silicon rich cell walls of horsetail - or the 'hyperaccumulators' used for heavy metal remediation).

3. Some special ability to extract nutrients otherwise inaccessable to other species without that ability (nitrogen fixation is the most obvious example - perhaps this ist he mecahsim for #2 above)

I don't konw the extent to which ay particular claim for any patrticular plant is accurate for all climates and soils, but it sure sounds good and generally is applied as a principle to capture and recycle nutrients to the extent possible by occupying fully the root zone with a variety of structurally diverse species, particularly ones that make a lot of organic matter from deep roots.

My understanding, relating to the first type that Paul C identified (deep roots), was that they were able to take up minerals from the subsoil (B horizon), which tends to accumulate some minerals and compounds that are leached from the topsoil. 

There is a really comprehensive list online, presumably obtained from Kourik, but like Paul I am unsure how reliable it is.  If you can identify minerals that are missing from your soil, or particular minerals needed by trees you are trying to grow, you can cross check which plants will accumulate it and try growing those.

http://oregonbd.org/Class/accum.htm

Thanks so much everyone! This is a huge help! I really appreciate it. =)

So... would a dynamic accumulator plant grown in poor (from a mineral perspective) soil still have a relatively high concentration of the minerals that were present?

For example, would a comfrey plant grown in  the poor soil mentioned above be similar or much lower in absolute mineral content than a comfrey plant that was grown in soil that had a more balanced/rich soil?

Will a plant that tends to accumulate high levels of say, calcium, grow well in a soil that is low, has trace levels or is entirely lacking in calcium?

Open ended questions that probably have different answers for each particular plant...

I spend more time than I probably should wondering about these kinds of questions. 

I've come across numerous references stating that soil west of the Cascades tends to be low in a number of minerals such as calcium and sulfur.  I then wonder where the animals, insects and plants that live here (and seem to thrive) find sources of these minerals?

I think when you refer to a soil lacking in calcium you would be talking about the topsoil.

If calcium is present in the subsoil due to it being leached out of the topsoil then dynamic accumulators could act as a 'nutrient pump' to cycle the calcium back to the surface layer.

I am curious as to what role deep rooted plants may play in breaking up larger chunks of bedrock (C horizon), which would be relatively rich in calcium.

So... would a dynamic accumulator plant grown in poor (from a mineral perspective) soil still have a relatively high concentration of the minerals that were present?

For example, would a comfrey plant grown in  the poor soil mentioned above be similar or much lower in absolute mineral content than a comfrey plant that was grown in soil that had a more balanced/rich soil?

yes the plant can only take up what is there, if there is no or a lack of potassium(K), its not going to pop out of thin air like N will. it will accumulate more of what K is there compared to other plants though if your doing a comparison for that particular soil.

Will a plant that tends to accumulate high levels of say, calcium, grow well in a soil that is low, has trace levels or is entirely lacking in calcium?

it will still grow, possibly not at its best, but like i said before. if there is any locked up or unavailable calcium it will make use of it in one way shape or form better than say some grass.

I've come across numerous references stating that soil west of the Cascades tends to be low in a number of minerals such as calcium and sulfur.  I then wonder where the animals, insects and plants that live here (and seem to thrive) find sources of these minerals?

this is a pretty crazy statement as the soils west of the cascades vary greatly. even a few miles from where im at now the soil may be completely different. let alone hundreds of miles. each soil will have its own nutrient profile depending on parent material and environmental effects over the years.

usually these dynamic accumulators have specific triggers which could be environmental or usually from the soil condition/chemistry. so if there is a lack of calcium, a certain weed may or may not come up while another plant may or may not come up to aid in the succession to a natural forest.

yeah, I think mining the subsoil is one of the big benefits of the deep rooted plants.  However, it seems even less common to find a profile of an areas subsoil mineral content than it is to find a detailed mineral breakdown of the topsoil.  I suspect that a lot of planting of the dynamic accumulator plants is based on the 'hope' that it is down there and the plant will find it.

HC - I agree that a plant can only take up what is available to be taken from the soil.  I've come across a few references to accumulation of other nutrients from air/rain, but I will remain skeptical for now with regards to most plants

I partially agree regarding the nature of the growth of accumulator plants in conditions where minerals are very low or absent.  I'd like to see some studies comparing plants in the same soil with ones grown in "richer" conditions.  I suspect you are likely correct, but it would be good to see the data.  I do wonder if some of these plants are accumulating out of a biochemical nececessity for a physiological function.

Regarding the broad classification for soils 'west of the Cascades', I'm guessing that it is usually in reference to Willamette valley soil.  Isn't that where everyone lives??   You are obviously right that there are many different soil types in the region, however, if there are well-controlled studies profiling a lack of certain minerals in a larger region (I am assuming this to be the case), it does bring to mind some of my earlier questions, among others.

Soils west of cascades low in nutrients?

While it can be dangerous to generalize, the 'wet side' soils do produce a suite of soils that are all exposed to winter leaching, and a vegetation with lots of nutrients stored in above ground woody biomass.

So if you cut down all the trees, burn the wood than till the glacial soils for several years, leaving it bare over winter, than all such soils would similarly suffer from the same westside syndrome--loss of cations like Calcium, Magnesium, Potassium.

On the west side somewhere around Thurston County, Washington, you start finding older soils that have developed clays.  North of there it is mostly younger post-glacial materials.  I think high Calcium and high Phosphorus parent material are rare around here. 

Any soils will develop to a state that reflects a combination of parent material, climate, and management.  Horse people I talk to prefer east side hay as it has a higher mineral content.

I must say that Willamette Valley is pretty far from the imperial mothership... even for our little far flung territory...

The upper horizon of the soil is where the most nutrients are liberated. One of the most famous deep-rooted, supposed dynamic accumulators is comfrey (Symphytum officinale). (Dynamic accumulators are those plants thought to gather more of particular minerals than other plants.) When it comes to the accumulation of NPK and silica, the anecdotal opinion is that comfrey is a dynamic accumulator plant with long roots that mine minerals and nutrients from very deep in the soil. (There are reports of comfrey roots reaching as much as ten feet into the ground.) As to comfrey being a dynamic accumulator, it’s hard to find any data. I was able to find a study that showed that the immobilized tannins prepared from lateral roots of comfrey chelated (pulled out) 3.5 times more lead from the soil than those from the taproots. Yikes—comfrey as a lead-accumulator plant! I have found no documented taproot down to 10 feet.