Soil and fungus

Below is the set of documents I have found while investigating here and there relation between:

Temperature (in North European cold climate) ⇒ Fertilizer and soil type

Why that came to my mind was an interview with Walter Pall where he talks about fertilizers and bacterias being efficient only above 12 degrees C (at 05:40). The summers here are very mild and way too many nights drop below 12C. Having pots soil temperature drop so much would mean or:

  • using artificial fertilizer only (where nourishment is already available to the plant to be absorbed)
  • find another way to improve decomposition on lower temperatures

So here is what I found. Half of it I didn’t understand 😀 but it does gave me the direction on what to try. This will serve more as a memo for myself when I forget about all these facts…in case I am interested again to find them. And it was fun looking for these things 🙂


I started by asking myself a question:

Q: What is the relation between soil temperature and tree growth/survival?

The document getting my attention was:

Seasonal Changes in Soil Temperature and in the Frost Hardiness of Scots pine Roots under Subarctic Conditions: Comparison with Soil Temperature and Snow-Cover under Different Simulated Winter Conditions

I consider “mineral soil” in below sentences being bonsai soil.

During most of the sampling time, the frost hardiness of the roots in the humus layer was greater than in the mineral soil. There was a clear relationship between the soil temperature and the frost hardiness of roots. The temperature in the humus layer was after late August continuously lower than in the mineral soil. The results obtained in this study indicate that cold acclimation of the roots is much slower than that of the shoots. The needles survived temperatures of -20 °C even though they had not experienced air temperatures of below 5 °C. Roots attained a similar frost hardiness level only after experiencing temperatures of 0 °C or below for a period lasting many weeks.
This suggests that during winter with exceptionally fast decrease in soil temperature the roots of Scots pine may be damaged.

Some kind of conclusion/answer I extracted from this is:

A: Trees should get milder frosts before the full winter hits for several weeks before full winter hardiness for roots is obtained

Nothing new.

Tony Tickle mentions it, also in Nigel Saunders video is similar information. I am sure more of the same can be found on internet.

In case I ever wonder what is relation between temperature and soil depth in these areas here it is: Annual variation of soil temperature at different depths

Next question:

Q: Is there/What is the difference between Forest/Organic and Agricultural/Mineral soil?

I consider “agricultural/arable soil” here being bonsai soil, in need of constant fertilizing.

Properties of humus of natural forest soil and arable soil

The content of organic carbon in agriculturally used soil was 68.8% lower, as compared with the average content of total organic carbon in the layers from 0 to 30 cm of the forest soil. Arable soil also demonstrated a definitely lower content of nitrogen than the forest soil. In forests soils a constant supply of fresh organic matter (quantitatively higher than in arable soils) significantly modifies properties of humic acids. In arable soils oxidization processes are more intensive than
in forest soils.


Organic matter, Humus, Humate, Humic Acid, Fulvic Acid and Humin: Their importance in soil fertility and plant health
A fertile soil should contain from 2-8% organic matter, most soils contain less than 2%. Humus is the major soil organic matter component, making up 65% to 75% of the total. The availability of trace minerals is a requirement for the formation of humic substance. Some of the main functions of humins within the soil are to improve the soil’s water holding capacity, to improve soil structure, to maintain soil stability, to function as an cation exchange system, and to generally improve soil fertility.

Because of the relatively small size of fulvic acid (FA) molecules they can readily enter plant roots, stems, and leaves. As they enter these plant parts they carry trace minerals from plant surfaces into plant tissues. Fulvic acids (FAs) are key ingredients of high quality foliar fertilizers. Foliar spray applications containing fulvic acid (FA) mineral chelates, at specific plant growth stages, can be used as a primary production technique for maximizing the plants productive capacity.

Many of the organic compounds released by fungi aid in forming humus and soil crumbs. When Humic acids (HAs) and fulvic acids (FAs) are applied to plant leaves the chlorophyll content of those leaves increases. As the chlorophyll concentration increases there is a correlated increase in the uptake of oxygen. Chlorophyll development within plant leaves is more pronounced when fulvic adds (FAs) are present in the foliar fertilizer.

Well, this gave me lots of data with which I can hardly do anything 😀 Nothing new again. No breakthrough though none of it I expected either.

Fungi does appear as the agent for soil conditioning.

Coming back to the original questions version:

Q: What is relation between decomposition and soil temperature?

Comparison of temperature effects on soil respiration and bacterial and fungal growth rates

Soil bacterial and fungal growth rates in cold climates usually have optimum temperatures below 30 °C, with activity values decreasing at higher temperatures.

Fungi as a group are more adapted to low soil moisture conditions than bacteria and would therefore be more important in dry soil.
Persson et al.[18] found a difference in temperature dependence of respiration in a forest and an agricultural soil, in that a lower minimum temperature for respiration (tmin) was found in the former soil. One proposed explanation is that fungi are more important in the forest soil and are more active at low temperatures than bacteria [18–21].
One was an agricultural soil with a dry weight of 88% of the wet weight, a pH of 7.8 and an organic matter content of 5%. The other was a humus soil (the A01/A02 horizon) from a forest with mainly spruce, with a dry weight of 29% of the wet weight, a pH of 4.1 and an organic matter content of 82%. A temperature of 45 °C was not included in the fungal activity measurements, since it was assumed to be too high a temperature for fungal activity. The respiration rate increased with increasing temperature over the whole temperature range in the agricultural soil (Fig. 1(a)) and up to 40 °C in the humus soil.

The calculated apparent minimum temperature for bacterial growth (tmin) was −8.4 °C for the bacterial community from the agricultural soil and −12.1 °C for that from the humus soil.
The calculated apparent minimum temperature for fungal activity (tmin) was estimated to be −12.3 and −17.5 °C for the fungal community from the agricultural and humus soil, respectively.

The temperature dependence of fungal and bacterial growth differed in that the former group was less inhibited by low temperatures and the latter less inhibited by higher temperatures

The advantage of fungi at low temperatures is in accordance with the finding that fungi dominated in high-altitude soils during winter and spring, when the soil was covered with snow, whereas bacteria appeared to dominate during summer under snow-free conditions [20,21,26].

The advantage of fungi at low temperatures may also explain the high amounts of fungal biomass found in forest soils during cold periods.

Graph shows that below 12C in Humus soil fungis are more active

Aaha! 12 degrees C again mentioned for bacterias. But now the new player appearing even clearer: fungi.

A: Fungi is better decomposing agent than bacterias in colder climates! In lower temperatures, fungi operates better in humus/organic soil than agricultural soil.

Organic soil + fungi looks to be a new direction.

A simpler document about bacteria vs. fungi: Fungi vs. bacteria

Q: What kind of fungi, what are main characteristics and roles?


Overall, the relationship between plants and mycorrhizal fungi depend mainly on the availability of nitrogen, phosphorus, carbon, and water (1). Since areas within the environment vary in nutrient and water availability, this can have a major effect on whether or not a mycorrhizal relationship can form between a plant and the fungus.

If an environment’s soil does not contain much nitrogen and phosphorus, it is likely that a mycorrhizal relationship will occur and a plant is more likely to allocate its carbon to the roots (4). This is because the plant needs nitrogen and phosphorus in order to prosper. This can also be true in areas where water is not easily accessible. As noted earlier, mycorrhizae expand the surface area of roots and therefore aid in the uptake of water. If an environment is lacking in moisture available to plants, it is likely that a mycorrhizal symbiosis will occur to aid in the uptake of water. Also, the environment where mycorrhizae will be found change depending on the type of mycorrhizae.

Mycorrhizal Fungi in Hydroponics – Questions and Answers

Should I feed mycorrhizae carbs? (e.g. molasses?)

Molasses and other carbs are good for feeding bacteria and other types of fungi. But you don’t need to feed the mycorrhizae. The plant feeds them! You are better off adding products which contain humic acids (organic growers can use high quality organic inputs such as North Atlantic sea kelp) to promote more root exudates (food for the mycorrhizae).

Q: How to attract/activate more fungi in the soil?

Interactions between needles of Pinus resinosa and ectomycorrhizal fungi

In comparison with mineral soil, forest litter contains large concentrations of leachable organic compounds with potentially strong effects on mycorrhizal fungi.

The pine needles increased density of all species of mycorrhizal fungi used in experiments. We used a needle concentration of 0.5% in the first experiment, resulting in a total watersoluble phenolic concentration of approx. 126 µg tannic acid equivalents g−” solution. The concentration we used seems to be relevant, as it lies between the concentrations provided by fresh litter and humus.

The experiments of this study were performed in the absence of saprotrophic fungi and bacteria. Bending & Read (1996, 1997) have shown that, whereas many ectomycorrhizal fungi have difficulty in hydrolysing polyphenolic molecules, some saprotrophic fungi have none. Thus, the presence of saprotrophs in the forest floor might have a strong influence on the interaction between mycorrhizal fungi and litter. 

Succession of fungi and fauna during decomposition of needles in a small area of Scots pine litter

When the fine root system of pine developed through accumulated old needles (F1 layer), mycorrhizal fungi penetrated the needles and seemed to impede any further bacterial development.

Faunal activity led to the presence of holes in all pine needles in the F1 layer, thus allowing the dominant fungi to enter the pine material.

Colonization of decomposing Sphagnum moss litter by mycorrhizal roots in two types of peatland ecosystems

Some mycorrhizal fungi were shown also to possess the capability to degrade more complicated and resistant molecules present in plant cuticle or secondary cell walls, and this occurred owing to the secretion of e.g. esterases, polygalacturonases, xylanases, cellulases, thyrosinases, peroxidases, poly- and monophenol oxidases, laccases, and even ligninases. Thus, the saprotrophic role of ectomycorrhizal fungi in ecosystems is also recently considered.

The chemical composition of needle and leaf litter from Scots pine, Norway spruce and white birch in Scandinavian forests

Concerning organic chemical components, the spruce needle litter had significantly higher concentrations of lignin and mannan than all the other litters and lower levels of ethanol-soluble substances, cellulose and galactan than the pine needle litter. Further, it had lower concentrations of water solubles, rhamnan and xylan than the birch litter.

A: Pine needles/Sphagnum moss to be incorporated into the soil.

Sphagnum moss is also favored by Colin Lewis. No bark, no leafs, no coconut fibers. Just sphagnum moss. Those and pine needles can be found in any sqaure meter of Finish forest! 🙂 Back to the basics. The best solution usually IS in front of your nose 😀

Some more documents on different aspects on what fungi needs in the soil to operate:

Root Fungus Stores a Surprising Amount of the Carbon Sequestered in Soil: Unlike bacterias who needs more nitrogen fungi needs more carbon to grow and function.

FertilizerInorganic fertilizers exclude carbon-containing materials except ureas.

This would mean that by using inorganic fertilizers fungi has nothing to eat. So, if fungi is to be encouraged inorganic fertilizer is not a correct choice or at least not sufficient.

Plant Structure & Function: What plant parts contain celulose/lignin which is important for saprotrophic fungi to digest.

Q: What is relation of saprotrophic and mycorrhizal fungi, do I need both?

Mycorrhizal and saprotrophic fungal guilds compete for the same organic substrates but affect decomposition differently

Through competitive interactions, mycorrhizal fungi can thus indirectly regulate litter decomposition rates by restraining activities of more efficient litter saprotrophs.

What I understood is that:

A: Saprotrophic produce nourishment by decomposing organic material to be absorbed by mycorrhizal and plant.

Both needed.


Cold climate of Northern Europe

⇒ Low temperature

⇒ Fungi

⇒ Organic soil components (as addition/conditioner to mineral soil)

Pine needles & Sphagnum moss


I am very happy with the investigation. Did it ring the new bells, found extremely new information, not logical or not expected? No! These are already used by others. What I did not know nor found directly related is colder climate vs. soil components through “activating” fungi as the main decomposer.

Some care must be taken considering acidity of soil when these are added. Needles in different stage of decomposition might be a good idea. I got PH testing paper strips so I can get some idea how it works before I put the first victim into it.

Is pine needles/sphagnum moss necessary? I am positive Kaizen Bonsai’s detailed information is really truth that it is better to add just humus via specific soil additions than play with degradable organic compounds. I don’t think anyway pine needles/sphagnum moss combination should be the only source of nourishment to be used. I plan to use Tibolar RS with which I have some results already but about that will produce another post sometimes.

But I think for experienced grower it is easy to estimate the moment and amount of special fertilizer/soil conditioner/humus for trees to make thrive. For a beginner like me I somehow believe it is not that simple and that plain mineral soil will too easily leave the plant with zero nourishment if not enough given. Also, most of my trees are not fully established ⇒ more organic material in soil could help…perhaps…maybe 🙂

Cat litter water retention properties experiment

Bonsai soil is often a discussion topic and controversy and it is so also in our local bonsai society. My knowledge and experience about the subject is low to brag anything about it. Nevertheless due to one of the discussions I decided to do an experiment.

It is found on many different places that on the bottom of bonsai pot should be put a more coarse akadama (or whatever soil is in use) due to water column which is to be shorter. In one of the books though it was mentioned (can’t remember the book’s name) that there is no use to do that as already small space in the pot is even more reduced for useful fine roots because the coarser the soil the less fine roots can find space and thus the water consumption is reduced. Sounds logical.

I wanted to know, how much the water column really depends on the soil grain coarseness and what height is the water column.


I decided to simulate a bonsai pot with a transparent plastic fruit “box” into which I would put different cat litter grains and will check what water column it produces but first I wanted to know how much water each grain keeps in.

Test 1

I measured 200 ml of 2-3 mm cat litter, 3-5 mm and >8 mm (should be 8-11mm).

Photos of the first 2 grain sizes but I did the same for the third one too










Then I put it into 250 ml of water to soak properly:








and after the free dripping of water back I would have the difference of water levels to conclude what amount of water remained inside the grains:


The photo shows that water was lower around 75 ml. So, I can conclude that cat litter keeps water equal to its ~35% of volume.

The test showed same values for all grains which is logical. The difference of volume space of each grain sizes doesn’t differ that much.

This test doesn’t bring me much value for the next test nor for the question I asked above but I wanted to know.

Test 2

Now is the time to check water columns. I created the simulated transparent bonsai pot with screen on the bottom which I filled with different grain sizes. I watered the “pot” thoroughly and let the water leak out freely without any pressure. When the dripping stopped I made a photo of the end result. After that I would put the pot under angle, let it drip and make a photo of the end situation too.

Notice: Measuring is not extremely accurate but I rather wanted to know comparison between grain sizes than having perfect measuring “devices”.

Grain size 2-3 mm
Before watering
After dripping stopped
After “forced” dripping under angle

In the second photo is visible that the water is visible even above half of the depth of the grains. Water column was around 2-3 cm.

Setting the “pot” under angle didn’t reduce water column much. Yes, the water did drip away to some extent but the water column still remained even on the side which is higher.

Grain size 3-5 mm

Same test:

After, under angle







Expected result, water column was lower 2-3 times, around 1 cm for this grain size.

Setting “pot” under angle here did make the difference, the water column remained only in the lower part of the pot, in the corner, again, around 1 cm.

Grain size >8 mm

Same test:








The photos don’t reveal much to be honest but I did not find any water column. After setting the “pot” to the side some small amount of water did leak out but nothing so substantial like in 2-3 mm gran size test.

After all of this, it is visible that the coarser grain does have lower water column. Not a big deal, that was expected. It looks that after 5 mm the water column is almost non-existent. The small particle grains of 2-3 mm have quite a high water column, around 2 cm. For bonsai pot of 5-8 cm that is pretty much.

Test 3

Now came the moment to try the “soil” with mixed grains. Coarser to the bottom and finer to the top. I put one layer of >8 mm cat litter grains (so it is around 8-10 mm on the bottom) and then finest I have, 2-3 mm over it.

Same test:









I repeated this test several times. I never managed to see any water column!


What value the final conclusion can bring is questionable 🙂

Nevertheless, I will do it for myself.

My experiments showed that coarser grain to the bottom does remove water column. I didn’t expect it to be removed so substantially but it did. One layer of  very coarse grain and the water didn’t stay anymore. That gives at least to me trust into the advice to keep coarser grains on the bottom.

Now, that it reduces the space for finer roots it does. Nevertheless, the lack of water column in my opinion (I repeat this is only my opinion) means to me more than slightly reduced space for fine roots. That can also mean that I just don’t know the subject well and/or I don’t maintain bonsai’s well and I can agree with that 😉

Perhaps this experiment is lacking a mixture of different soil types (like pumice for an example) test. I avoided doing such a “fine” experiment because there are so many different mixtures that it wouldn’t make much difference. I assumed that cat litter, as the most retention-wise soil type, is the most important for keeping the water column.

The water columns is existent because the bonsai pot has the bottom and only holes on some places. If the bottom would be the full screen mesh the water would leak out freely, I guess. BUT, then the pot wouldn’t be a pot anymore wouldn’t it 🙂